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DOI: 10.1161/CIRCULATIONAHA.105.166561
2005;112;89-110; originally published online Nov 28, 2005; Circulation
Part 8: Stabilization of the Patient With Acute Coronary Syndromes
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Part 8: Stabilization of the Patient With Acute
Coronary Syndromes
A
cute myocardial infarction (AMI) and unstable angina
(UA) are part of a spectrum of clinical disease collec-
tively identified as acute coronary syndromes (ACS). The
pathophysiology common to this spectrum of disease is a
ruptured or eroded atheromatous plaque.
1–5
The electrocar-
diographic (ECG) presentation of these syndromes encom-
passes ST-segment elevation myocardial infarction (STEMI),
ST-segment depression, and nondiagnostic ST-segment and
T-wave abnormalities. A non–ST-elevation myocardial in-
farction (NSTEMI) is diagnosed if cardiac markers are
positive with ST-segment depression or with nonspecific or
normal ECGs. Sudden cardiac death may occur with any of
these conditions. ACS is the most common proximate cause
of sudden cardiac death.
6–10
Effective interventions for patients with ACS, particularly
STEMI, are extremely time-sensitive. The first healthcare
providers to encounter the ACS patient can have a big impact
on patient outcome if they provide efficient risk stratification,
initial stabilization, and referral for cardiology care. It is
critical that basic life support (BLS) and advanced cardiovas-
cular life support (ACLS) healthcare providers who care for
ACS patients in the out-of-hospital, emergency department
(ED), and hospital environments be aware of the principles
and priorities of assessment and stabilization of these
patients.
These guidelines target BLS and ACLS healthcare provid-
ers who treat patients with ACS within the first hours after
onset of symptoms, summarizing key out-of-hospital, ED,
and some initial critical-care topics that are relevant to
stabilization. They also continue to build on recommenda-
tions from the ACC/AHA Guidelines,
11,12
which are used
throughout the United States and Canada.
13
As with any
medical guidelines, these general recommendations must be
considered within the context of local resources and applica-
tion to individual patients by knowledgeable healthcare
providers.
The primary goals of therapy for patients with ACS are to
●
Reduce the amount of myocardial necrosis that occurs in
patients with MI, preserving left ventricular (LV) function
and preventing heart failure
●
Prevent major adverse cardiac events (MACE): death,
nonfatal MI, and need for urgent revascularization
●
Treat acute, life-threatening complications of ACS, such as
ventricular fibrillation (VF)/pulseless ventricular
tachycardia (VT), symptomatic bradycardias, and unstable
tachycardias (see Part 7.2: “Management of Cardiac Ar-
rest” and Part 7.3: “Management of Symptomatic Brady-
cardia and Tachycardia”)
An overview of recommended care for the ACS patient is
illustrated in Figure 1, the Acute Coronary Syndromes
Algorithm. Part 8 provides details of the care highlighted in
the numbered algorithm boxes. Box numbers in the text
correspond to the numbered boxes in the algorithm.
In this part the abbreviation AMI refers to acute myocar-
dial infarction, whether associated with STEMI or NSTEMI.
The diagnosis and treatment of AMI, however, will often
differ for patients with STEMI versus NSTEMI. Note care-
fully which is being discussed.
Out-of-Hospital Management
Recognition (Figure 1, Box 1)
Treatment offers the greatest potential benefit for myocardial
salvage in the first hours of STEMI. Thus, it is imperative that
healthcare providers evaluate, triage, and treat patients with
ACS as quickly as possible. Delays to therapy occur during 3
intervals: from onset of symptoms to patient recognition,
during out-of-hospital transport, and during in-hospital eval-
uation. Patient delay to symptom recognition often constitutes
the longest period of delay to treatment.
14
The classic symptom associated with ACS is chest discom-
fort, but symptoms may also include discomfort in other areas
of the upper body, shortness of breath, sweating, nausea, and
lightheadedness. The symptoms of AMI are characteristically
more intense than angina and last H1102215 minutes. Atypical
symptoms or unusual presentations of ACS are more com-
mon in elderly, female, and diabetic patients.
15–19
Public education campaigns increase public awareness and
knowledge of the symptoms of heart attack but have only
transient effects.
20
For patients at risk for ACS (and for their
families), physicians should discuss the appropriate use of
nitroglycerin and aspirin, activation of the emergency medi-
cal services (EMS) system, and location of the nearest
hospital that offers 24-hour emergency cardiovascular care.
Recent ACC/AHA guidelines recommend that the patient or
family members activate the EMS system rather than call
their physician or drive to the hospital if chest discomfort is
unimproved or worsening 5 minutes after taking 1 nitroglyc-
erin tablet or using nitroglycerin spray.
12
Initial EMS Care (Figure 1, Box 2)
Half of the patients who die of AMI do so before reaching the
hospital. VF or pulseless VT is the precipitating rhythm in
most of these deaths,
21–23
and it is most likely to develop
during the first 4 hours after onset of symptoms.
24–27
Com-
munities should develop programs to respond to out-of-
hospital cardiac arrest that include prompt recognition of
symptoms of ACS, early activation of the EMS system, and
(Circulation. 2005;112:IV-89-IV-110.)
? 2005 American Heart Association.
This special supplement to Circulation is freely available at
http://www.circulationaha.org
DOI: 10.1161/CIRCULATIONAHA.105.166561
IV-89
Figure 1. Acute Coronary Syndromes Algorithm.
IV-90 Circulation December 13, 2005
if needed, early CPR (see Part 4: “Adult Basic Life Support”)
and early access to an automated external defibrillator (AED)
through community AED programs (see Part 5: “Electrical
Therapies”).
28
EMS and dispatch system personnel should be
trained to respond to cardiovascular emergencies.
Dispatchers and EMS providers must be trained to recog-
nize symptoms of ACS. Dispatchers should advise patients
with no history of aspirin allergy or signs of active or recent
gastrointestinal bleeding to chew an aspirin (160 to 325 mg)
while awaiting the arrival of EMS providers (Class IIa).
29
EMS providers should be trained to determine the time of
onset of symptoms and to stabilize, triage, and transport the
patient to an appropriate facility and to provide prearrival
notification. EMS providers should monitor vital signs and
cardiac rhythm and be prepared to provide CPR and defibril-
lation if needed.
EMS providers may administer oxygen to all patients. If
the patient is hypoxemic, providers should titrate therapy
based on monitoring of oxyhemoglobin saturation (Class
I).
30–44
If the patient has not taken aspirin and has no history
of aspirin allergy and no evidence of recent gastrointestinal
bleeding, EMS providers should give the patient nonenteric
aspirin (160 to 325 mg) to chew (Class I).
45–48
EMS providers should administer up to 3 nitroglycerin
tablets (or spray) for ongoing symptoms at intervals of 3 to 5
minutes if permitted by medical control and if the patient
remains hemodynamically stable (systolic blood pressure
[SBP] H1102290 mm Hg [or no more than 30 mm Hg below
baseline], heart rate between 50 and 100 beats per minute
[bpm]).
49,50
EMS providers can administer morphine for chest
pain unresponsive to nitroglycerin if authorized by protocol
or medical control. Additional information about out-of-
hospital stabilization and care is included in the following
sections.
Out-of-Hospital ECGs
Out-of-hospital 12-lead ECGs and advance notification to the
receiving facility speed the diagnosis, shorten the time to
fibrinolysis, and may be associated with decreased mortality
rates.
51–64
The reduction in door-to–reperfusion therapy in-
terval in most studies ranges from 10 to 60 minutes. EMS
providers can efficiently acquire and transmit diagnostic-
quality ECGs to the ED
53,58,65,66
with a minimal increase (0.2
to 5.6 minutes) in the on-scene time interval.
52,56,65–68
Qualified and specially trained paramedics and prehospital
nurses can accurately identify typical ST-segment elevation
(H110221 mm in 2 or more contiguous leads) in the 12-lead ECG
with specificity ranging from 91% to 100% and sensitivity
ranging from 71% to 97% when compared with emergency
medicine physicians or cardiologists.
69,70
Using radio or cell
phone, they can also provide advance notification to the
receiving hospital of the arrival of a patient with ACS.
56,61–64
We recommend implementation of out-of-hospital 12-lead
ECG diagnostic programs in urban and suburban EMS
systems (Class I). Routine use of 12-lead out-of-hospital ECG
and advance notification is recommended for patients with
signs and symptoms of ACS (Class IIa). A 12-lead out-of-
hospital ECG with advance notification to the ED may be
beneficial for STEMI patients by reducing time to reperfusion
therapy. We recommend that out-of-hospital paramedics
acquire and transmit either diagnostic-quality ECGs or their
interpretation of them to the receiving hospital with advance
notification of the arrival of a patient with ACS (Class IIa). If
EMS providers identify STEMI on the ECG, it is reasonable
for them to begin to complete a fibrinolytic checklist (Figure
2).
Out-of-Hospital Fibrinolysis
Clinical trials have shown the benefit of initiating fibrinolysis
as soon as possible after onset of ischemic-type chest pain in
patients with STEMI or new or presumably new left bundle
branch block (LBBB).
67,71
Several prospective studies (LOE
1)
72–74
have documented reduced time to administration of
fibrinolytics and decreased mortality rates when out-of-
hospital fibrinolytics were administered to patients with
STEMI and no contraindications to fibrinolytics.
Physicians in the Grampian Region Early Anistreplase
Trial (GREAT)
73
administered fibrinolytic therapy to patients
at home 130 minutes earlier than to patients at the hospital
and noted a 50% reduction in hospital mortality rates and
greater 1-year and 5-year survival rates in those treated
earlier.
75,76
Delaying fibrinolytic treatment by 1 hour in-
creased the hazard ratio of death by 20%, which is equivalent
to the loss of 43 lives per 1000 patients over 5 years.
A meta-analysis of out-of-hospital fibrinolytic trials found
a relative improvement of 17% in outcome associated with
out-of-hospital fibrinolytic therapy, particularly when therapy
was initiated 60 to 90 minutes earlier than in the hospital.
71
A
meta-analysis of 6 trials involving 6434 patients (LOE 1)
72
documented decreased all-cause hospital mortality rates
among patients treated with out-of-hospital fibrinolysis com-
pared with in-hospital fibrinolysis (odds ratio [OR]: 0.83;
95% confidence interval [CI]: 0.70 to 0.98) with a number
needed to treat of 62 to save 1 extra life with out-of-hospital
fibrinolysis. Results were similar regardless of the training
and experience of the provider.
The ECC Guidelines 2000
77
recommended consideration
of out-of-hospital fibrinolysis for patients with a transport
time H110221 hour. But in a recent Swiss study (LOE 1),
74
prehospital administration of fibrinolytics significantly de-
creased the time to drug administration even in an urban
setting with relatively short transport intervals (H1102115
minutes).
74
In summary, out-of-hospital administration of fibrinolytics
to patients with STEMI with no contraindications is safe,
feasible, and reasonable (Class IIa). This intervention may be
performed by trained paramedics, nurses, and physicians for
patients with symptom duration of 30 minutes to 6 hours.
System requirements include protocols with fibrinolytic
checklists, ECG acquisition and interpretation, experience in
ACLS, the ability to communicate with the receiving institu-
tion, and a medical director with training/experience in
management of STEMI. A process of continuous quality
improvement is required. Given the operational challenges
required to provide out-of-hospital fibrinolytics, most EMS
systems should focus on early diagnosis with 12-lead ECG,
rapid transport, and advance notification of the ED (verbal
Part 8: Stabilization of the Patient With Acute Coronary Syndromes IV-91
interpretation or direct transmission of ECG) instead of
out-of-hospital delivery of fibrinolysis.
Triage and Transfer
Out-of-Hospital Triage
Hospital and EMS protocols should clearly identify criteria
for transfer of patients to specialty centers and conditions
under which fibrinolytics should be initiated before transfer.
When transfer is indicated, the ACC/AHA guidelines recom-
mend a door-to-departure time H1134930 minutes.
12
It may be
appropriate for the EMS medical director to institute a policy
of out-of-hospital bypass of hospitals that provide medical
therapy only, particularly for patients who require interven-
tional therapy. Patients who require interventional therapy
may include those with cardiogenic shock, pulmonary edema,
large infarctions, and contraindications to fibrinolytic
therapy.
At present no randomized studies have directly compared
triage with an experienced percutaneous coronary interven-
tion (PCI) center with medical management at the local
hospital. Extrapolation from several randomized trials on
interfacility transfer
78–80
suggests that STEMI patients tri-
aged directly to a primary PCI facility may have better
outcomes related to the potential for earlier treatment. A
cost-efficacy substudy of the Comparison of Angioplasty and
Prehospital Thrombolysis in Acute Myocardial Infarction
(CAPTIM) trial
81
suggests that direct transport to a primary
PCI facility may be more cost-effective than out-of-hospital
fibrinolysis when transport can be completed in H1134960 minutes
with a physician in a mobile intensive care unit. There is no
direct evidence, however, to suggest that these strategies are
safe or effective. Patients judged to be at highest risk for a
complicated transfer were excluded from some of these
studies.
In summary, at this time there is inadequate evidence to
recommend out-of-hospital triage to bypass non–PCI-capable
hospitals to bring patients to a PCI center (Class Indetermi-
nate). Local protocols for EMS providers are appropriate to
guide the destination of patients with suspected or confirmed
STEMI.
Interfacility Transfer
All patients with STEMI and symptom duration ofH1134912 hours
are candidates for reperfusion therapy with either fibrinolysis
or PCI (Class I). When patients present directly to a facility
capable of providing only fibrinolysis, 3 treatment options are
available: administering fibrinolytics with admission to that
hospital, transferring the patient for primary PCI, or giving
fibrinolytics and then transferring the patient to a specialized
center. The decision is guided by a risk-benefit assessment
that includes evaluation of duration of symptoms, complica-
tions, contraindications, and the time delay from patient
contact to fibrinolysis versus potential delay to PCI balloon
inflation.
In 2 prospective studies (LOE 2)
78–80
and a meta-analy-
sis,
82
patients with STEMI who presented 3 to 12 hours after
Figure 2. Fibrinolytic Checklist.
IV-92 Circulation December 13, 2005
onset of symptoms to a hospital without capability for
primary PCI had better outcome (improved 30-day combined
incidence of death, reinfarction, or stroke) when they were
transferred to a skilled PCI center (interventionalist perform-
ing H1102275 procedures per year) rather than receiving fibrino-
lytics at the presenting hospital. In these studies balloon
inflation occurred H1134993 minutes after decision to treat.
80,83–85
Thus, interfacility transfer is indicated for patients with
STEMI presenting H110223 hours from onset of symptoms from
hospitals that lack primary PCI capability to centers capable
of providing primary PCI when the transfer can be accom-
plished as soon as possible. The ACC/AHA guidelines
recommend a treatment delay of no more than 90 minutes.
12
In patients with STEMI presenting H110213 hours from onset of
symptoms, the superiority of immediate administration of
fibrinolytics in the hospital or transfer for primary PCI is not
established (Class Indeterminate).
In-Hospital Fibrinolytics and Interfacility Transfer for
PCI
Data from the 1980s to 1990s did not support a strategy of
fibrinolytic therapy combined with transfer for facilitated PCI
(LOE 1
86–88
and meta-analyses
89–91
). But all of the studies
involved in-hospital administration of fibrinolytics, and most
were completed before the era of coronary stenting and
without use of contemporary pharmacologic therapies or PCI
techniques. Three small randomized trials (LOE 1)
92–94
sup-
ported the strategy of fibrinolytics plus transfer for PCI;
however, the timing of PCI after administration of fibrinolyt-
ics, the inclusion of patients who required transfer for PCI,
the use of coronary stents, and the control group interventions
differ considerably among these trials. The most recent
study
79
was fairly small and showed a benefit of early PCI
with 1-year follow-up.
94
At present there is inadequate evidence to recommend the
routine transfer of patients for early PCI (ie, within 24 hours)
after successful administration of fibrinolytics in a commu-
nity hospital. The use of out-of-hospital administration of
fibrinolytics followed by early PCI has not been specifically
studied.
Special Transfer Considerations
Special transfer considerations are appropriate for patients
with signs of shock (pulmonary congestion, heart rate H11022100
bpm, and SBPH11021100 mm Hg). The Second National Registry
of Myocardial Infarction found that the mortality rate in
patients with AMI and shock was lower in those treated with
PCI as a primary strategy than in those treated with fibrino-
lysis.
95
In the SHOCK (Should We Emergently Revascularize
Occluded Coronaries for Cardiogenic Shock) trial, 152 pa-
tients with cardiogenic shock were randomly assigned to an
early revascularization (ERV) strategy, 150 patients were
assigned to a strategy of initial medical stabilization that
included fibrinolytics, and 25% had delayed revasculariza-
tion.
96
Although there was no difference in the 30-day
mortality rate, the mortality rate at 6 months was significantly
lower in the ERV group (50.3% versus 63.1%). In a prespeci-
fied subgroup analysis for patients H1102175 years of age, early
revascularization was associated with a 15.4% reduction in
30-day mortality and improvement in 1-year survival rates.
97
A direct comparison of the outcome of primary or early PCI
patients with patients who received fibrinolytic therapy only
was not reported.
There is inadequate evidence to recommend routine trans-
fer of stable patients for early PCI after successful adminis-
tration of fibrinolytics in community hospitals or the out-of-
hospital setting. Patients H1102175 years of age and selected
patients H1102275 years of age who develop cardiogenic shock or
persistent ischemic symptoms within 36 hours of STEMI
should be transferred to experienced facilities capable of
ERV if ERV can be performed within 18 hours of onset of
shock.
12
ED Evaluation and Risk Stratification
(Figure 1, Boxes 3 and 4)
Focused Assessment and ECG Risk Stratification
ED providers should quickly assess patients with possible
ACS. Ideally within 10 minutes of ED arrival, providers
should obtain a targeted history while a monitor is attached to
the patient and a 12-lead ECG is obtained (if not done in the
prehospital setting).
98
The evaluation should focus on chest
discomfort, associated signs and symptoms, prior cardiac
history, risk factors for ACS, and historical features that may
preclude the use of fibrinolytics or other therapies. This initial
evaluation must be efficient because if the patient has
STEMI, the goals of reperfusion are to administer fibrinolyt-
ics within 30 minutes of arrival (30-minute interval “door-to-
drug”) or to provide PCI within 90 minutes of arrival
(90-minute interval “door-to–balloon inflation” in the cathe-
terization suite).
Potential delay during the in-hospital evaluation period
may occur from door to data, from data (ECG) to decision,
and from decision to drug (or PCI). These 4 major points of
in-hospital therapy are commonly referred to as the “4 D’s.”
99
All providers must focus on minimizing delays at each of
these points. Out-of-hospital transport time constitutes only
5% of delay to treatment time; in-hospital evaluation consti-
tutes 25% to 33% of this delay.
100,101
The physical examination is performed to aid diagnosis,
rule out other causes of the patient’s symptoms, and evaluate
the patient for complications related to ACS. Although the
use of clinical signs and symptoms may increase suspicion of
ACS, evidence does not support the use of any single sign or
combination of clinical signs and symptoms alone to confirm
the diagnosis.
102–105
When the patient presents with signs of ACS, the clinician
uses ECG findings (Figure 1, Box 4) to classify the patient
into 1 of 3 groups:
1. ST-segment elevation or presumed new LBBB (Box 5) is
characterized by ST-segment elevation H110221 mm (0.1 mV) in
2 or more contiguous precordial leads or 2 or more adjacent
limb leads and is classified as ST-elevation MI (STEMI).
2. Ischemic ST-segment depression H113500.5 mm (0.05 mV) or
dynamic T-wave inversion with pain or discomfort (Box
9) is classified as high-risk UA/non–ST-elevation MI
(NSTEMI). Nonpersistent or transient ST-segment eleva-
tion H113500.5 mm for H1102120 minutes is also included in this
category.
Part 8: Stabilization of the Patient With Acute Coronary Syndromes IV-93
3. Normal or nondiagnostic changes in ST segment or T
waves (Box 13) are inconclusive and require further risk
stratification. This classification includes patients with
normal ECGs and those with ST-segment deviation of
H110210.5 mm (0.05 mV) or T-wave inversion of H113490.2 mV.
Serial cardiac studies (and functional testing) are
appropriate.
Cardiac Biomarkers
New cardiac biomarkers, which are more sensitive than the
myocardial muscle creatine kinase isoenzyme (CK-MB), are
useful in diagnosis, risk stratification, and determination of
prognosis. An elevated level of troponin correlates with an
increased risk of death, and greater elevations predict greater
risk of adverse outcome.
106
Patients with increased troponin
levels have increased thrombus burden and microvascular
embolization.
Cardiac biomarkers should be obtained during the initial
evaluation of the patient, but therapeutic decisions and
reperfusion therapy for patients with STEMI should not be
delayed pending the results of these tests. Important limita-
tions to these tests exist because they are insensitive during
the first 4 to 6 hours of presentation unless continuous
persistent pain has been present for 6 to 8 hours. For this
reason cardiac biomarkers are not useful in the prehospital
setting.
107–112
Serial marker testing (CK-MB and cardiac troponin) over
time improves sensitivity for detection of myocardial infarc-
tion but remains insensitive in the first 4 to 6 hours.
113,114
ST-Segment Elevation MI (Figure 1, Boxes 5
Through 8)
Patients with STEMI usually have complete occlusion of an
epicardial coronary vessel. The mainstay of treatment is
reperfusion therapy through administration of fibrinolytics
(pharmacologic reperfusion) or primary PCI (mechanical
reperfusion). Providers should rapidly identify patients with
STEMI and quickly screen them for indications and contra-
indications to fibrinolytic therapy and PCI.
The first physician who encounters a patient with AMI
should be able to determine the need for reperfusion therapy
and direct its administration (see Tables 1 and 2). If the
patient meets the criteria for fibrinolytic therapy, a door-to-
needle time (needle time is the beginning of infusion of a
fibrinolytic agent) H1134930 minutes is desired. Results of cardiac
biomarkers do not delay the administration of fibrinolytic
therapy or referral for PCI. They are normal in a significant
percentage of patients who present early with STEMI. Con-
sultation with a cardiologist or the patient’s personal physi-
cian delays therapy, is associated with increased hospital
mortality rates, and is recommended only in equivocal or
uncertain cases.
115
Hospitals with capabilities for angiogra-
phy and PCI should have a clear protocol directing ED triage
and initial management. Confusion about the method of
reperfusion, eg, fibrinolysis or PCI, delays definitive therapy.
UA and NSTEMI (Figure 1, Boxes 9 Through 17)
In the absence of ST-segment elevation, patients with ische-
mic-type chest pain can present with ST-segment depression
or nondiagnostic or normal ECGs. ST-segment depression
identifies a population at increased risk for MACE. Patients
with ischemic-type pain and ECGs consistent with NSTEMI
or normal or nondiagnostic ECGs do not benefit from
fibrinolytic therapy, and fibrinolysis may be harmful.
116
Although many patients will not have ACS (ie, the ECG
change is due to an alternative diagnosis, such as LV
hypertrophy), initial triage and therapy appropriately includes
antiplatelet, antithrombin, and antianginal therapy. These
patients usually have a partially or intermittently occluding
thrombus. Clinical features can correlate with the dynamic
nature of clot formation and degradation, eg, waxing and
waning clinical symptoms.
Serial cardiac markers are often obtained during evalua-
tion, including CK-MB and cardiac troponins. At any point
during evaluation, elevation of cardiac troponin places a
patient at increased risk for MACE. Studies have shown that
patients with increased troponin are best managed with a
strategy of small-molecule glycoprotein (GP) IIb/IIIa inhibi-
tor therapy and an early invasive strategy (cardiac catheter-
ization with possible revascularization). Troponin serves as
an additional and incremental adjunct to the ECG. Physicians
TABLE 1. Fibrinolytic Therapy: Contraindications and
Cautions for Fibrinolytic Use in STEMI From ACC/AHA 2004
Guideline Update*
Absolute Contraindications
? Any prior intracranial hemorrhage
? Known structural cerebral vascular lesion (eg, AVM)
? Known malignant intracranial neoplasm (primary or metastatic)
? Ischemic stroke within 3 months EXCEPT acute ischemic stroke within
3 hours
? Suspected aortic dissection
? Active bleeding or bleeding diathesis (excluding menses)
? Significant closed head trauma or facial trauma within 3 months
Relative Contraindications
? History of chronic, severe, poorly controlled hypertension
? Severe uncontrolled hypertension on presentation (SBP H11022180 mm Hg or
DBP H11022110 mm Hg)?
? History of prior ischemic stroke H110223 months, dementia, or known
intracranial pathology not covered in contraindications
? Traumatic or prolonged (H1102210 minutes) CPR or major surgery
(H110213 weeks)
? Recent (within 2 to 4 weeks) internal bleeding
? Noncompressible vascular punctures
? For streptokinase/anistreplase: prior exposure (H110225 days ago) or prior
allergic reaction to these agents
? Pregnancy
? Active peptic ulcer
? Current use of anticoagulants: the higher the INR, the higher the risk of
bleeding
AVM indicates arteriovenous malformation; SBP, systolic blood pressure;
DBP, diastolic blood pressure; and INR, International Normalized Ratio.
*Viewed as advisory for clinical decision making and may not be all-inclusive
or definitive.
?Could be an absolute contraindication in low-risk patients with myocardial
infarction.
IV-94 Circulation December 13, 2005
need to appreciate that other disorders can increase cardiac
troponin, eg, myocarditis, congestive heart failure, and pul-
monary embolism.
Risk Stratification
Braunwald Stratification
There are many ways to risk-stratify patients with chest pain.
A well-recognized approach is the one initially proposed and
later refined by Braunwald and colleagues on the ACC/AHA
Task Force on the Management of Patients With Unstable
Angina.
11,117–120
This approach is based on a combination of
historical, clinical, laboratory, and ECG variables.
Table 3 is a modified version of what has been a work in
progress by Braunwald and colleagues over several publica-
tions.
118,120,121
Patients are initially risk-stratified according to
the likelihood that symptoms are due to unstable coronary
artery disease (CAD). Patients at intermediate or high risk for
CAD are further classified by their risk of MACE. This
second classification is useful for prospectively identifying
patients at intermediate or high risk who can benefit from an
invasive strategy and more aggressive pharmacology with
antiplatelet and antithrombin agents.
TIMI Risk Score
The risk of MACE has been further studied and refined.
Researchers who derived the important Thrombolysis in
Myocardial Ischemia (TIMI) risk score used data from the
TIMI-11B and ESSENCE (Efficacy and Safety of Subcuta-
neous Enoxaparin in Non–Q-Wave Coronary Events) trials
for UA/NSTEMI
122,123
and from the In-TIME trial for
STEMI.
124
The TIMI risk score comprises 7 independent
prognostic variables (Table 4). These 7 variables were sig-
nificantly associated with the occurrence within 14 days of at
least one of the primary end points: death, new or recurrent
MI, or need for urgent revascularization. The score is derived
from complex multivariate logistic regression and includes
variables that seem counterintuitive. It is useful to note that
traditional cardiac risk factors are only weakly associated
with MACE. Use of aspirin within the previous 7 days, for
example, would not seem to be an indicator of a bad outcome.
But aspirin use was in fact found to be one of the most
powerful predictors.
122
It is possible that aspirin use identified
a subgroup of patients at higher risk or on active but failed
therapy for CAD.
The creators of the TIMI risk score validated it with 3
groups of patients, and 4 clinical trials showed a significant
interaction between the TIMI risk score and outcome.
124–128
These findings confirm the value of the TIMI risk score as a
guide to therapeutic decisions. A PDA download of this risk
assessment is available at www.TIMI.org.
By classifying patients into 1 of 3 risk strata, the Braun-
wald (Table 3) and TIMI (Table 4) risk scores serve as the
dominant clinical guides for predicting the risk of MACE in
patients with ACS. Risk stratification is applicable to patients
at intermediate or high risk of symptoms due to CAD and not
the larger general population of patients presenting with chest
pain or symptoms possibly due to anginal equivalents. Risk
stratification enables clinicians to direct therapy to those
patients at intermediate or high risk of MACE and avoids
unnecessary therapy and the potential for adverse conse-
quences in patients who are at lower risk.
The TIMI risk score has become the primary tool for
evaluating therapeutic recommendations. Incrementally
greater benefit from some of the newer therapies may be
gained for patients with higher risk scores.
One additional product of the TIMI trials is the TIMI
grading system of coronary artery blood flow. Investigators
from the TIMI study developed and validated a coronary
artery perfusion scoring system, characterizing the degree of
reperfusion of a coronary artery on a scale of 0 (no flow) to
3 (normal, brisk flow). This TIMI grading system is now used
as an outcome measure in many studies of ACS interventions.
Indicators for Early Invasive Strategies
Risk stratification (Figure 1, Box 12) helps the clinician
identify patients with NSTEMI and UA who should be
TABLE 2. ST-Segment Elevation or New or Presumably New LBBB: Evaluation for Reperfusion
Step 1: Assess time and risk
Time since onset of symptoms
Risk of STEMI
Risk of fibrinolysis
Time required to transport to skilled PCI catheterization suite
Step 2: Select reperfusion (fibrinolysis or invasive) strategy
Note: If presentation H110213 hours and no delay for PCI, then no preference for either strategy.
Fibrinolysis is generally preferred if: An invasive strategy is generally preferred if:
● Early presentation (H113493 hours from symptom onset) ● Late presentation (symptom onset H110223 hours ago)
● Invasive strategy is not an option (eg, lack of access to skilled
PCI facility or difficult vascular access) or would be delayed
● Skilled PCI facility available with surgical backup
—Medical contact-to-balloon or door-balloon H1102290 min ● Medical contact-to-balloon or door-balloon H1102190 min
—(Door-to-balloon) minus (door-to-needle) is H110221 hour ● (Door-to-balloon) minus (door-to-needle) is H110211 hour
● No contraindications to fibrinolysis ● Contraindications to fibrinolysis, including increased risk of bleeding and ICH
● High risk from STEMI (CHF, Killip class is H113503)
● Diagnosis of STEMI is in doubt
Modified from ACC/AHA 2004 Update Recommendations.
112
Part 8: Stabilization of the Patient With Acute Coronary Syndromes IV-95
TABLE 3. Likelihood of Ischemic Etiology and Short-Term Risk
Part I. Chest Pain Patients Without ST-Segment Elevation: Likelihood of Ischemic Etiology
A. High likelihood
High likelihood that chest pain is of
ischemic etiology if patient has any of
the findings in the column below:
B. Intermediate likelihood
Intermediate likelihood that chest pain
is of ischemic etiology if patient has
NO findings in column A and any of
the findings in the column below:
C. Low likelihood
Low likelihood that chest pain is of
ischemic etiology if patient has NO
findings in column A or B. Patients
may have any of the findings in the
column below:
History ? Chief symptom is chest or left arm
pain or discomfort
plus
Current pain reproduces pain of prior
documented angina and
Known CAD, including MI
? Chief symptom is chest or left arm
pain or discomfort
? Age H1102270 years
? Male sex
? Diabetes mellitus
? Probable ischemic symptoms
? Recent cocaine use
Physical
exam
? Transient mitral regurgitation
? Hypotension
? Diaphoresis
? Pulmonary edema or rales
? Extracardiac vascular disease ? Chest discomfort reproduced by
palpation
ECG ? New (or presumed new) transient ST
deviation (H113500.5 mm) or T-wave
inversion (H113502 mm) with symptoms
? Fixed Q waves
? Abnormal ST segments or T waves
that are not new
? Normal ECG or
T-wave flattening or
T-wave inversion in leads with
dominant R waves
Cardiac
markers
? Elevated troponin I or T
? Elevated CK-MB
Any finding in column B above PLUS
? Normal
? Normal
High (A) or Intermediate (B)
Likelihood of Ischemia
Part II. Risk of Death or Nonfatal MI Over the Short Term in Patients With Chest Pain With High or Intermediate Likelihood of Ischemia (Columns A
and B in Part I)
High risk:
Risk is high if patient has any of the
following findings:
Intermediate risk:
Risk is intermediate if patient has any
of the following findings:
Low risk:
Risk is low if patient has NO high- or
intermediate-risk features; may have
any of the following:
History
Character of
pain
? Accelerating tempo of ischemic
symptoms over prior 48 hours
? Prolonged, continuing (H1102220 min)
rest pain
? Prior MI or
? Peripheral-artery disease or
? Cerebrovascular disease or
? CABG, prior aspirin use
? Prolonged (H1102220 min) rest angina is
now resolved (moderate to high
likelihood of CAD)
? Rest angina (H1102120 min) or relieved
by rest or sublingual nitrates
? New-onset functional angina (Class
III or IV) in past 2 weeks without
prolonged rest pain (but with
moderate or high likelihood of CAD)
Physical
exam
? Pulmonary edema secondary to
ischemia
? New or worse mitral regurgitation
murmur
? Hypotension, bradycardia,
tachycardia
? S
3
gallop or new or worsening rales
? Age H1102275 years
? Age H1102270 years
ECG ? Transient ST-segment deviation
(H113500.5 mm) with rest angina
? New or presumably new bundle
branch block
? Sustained VT
? T-wave inversion H113502mm
? Pathologic Q waves or T waves that
are not new
? Normal or unchanged ECG during an
episode of chest discomfort
Cardiac
markers
? Elevated cardiac troponin I or T
? Elevated CK-MB
Any of the above findings PLUS
? Normal
? Normal
Modified from Braunwald et al. Circulation. 2002;106:1893–1900.
IV-96 Circulation December 13, 2005
managed with an invasive strategy. Coronary angiography
then allows the clinician to determine whether patients are
appropriate candidates for revascularization with PCI or
coronary artery bypass grafting (CABG).
The 2005 AHA Guidelines for CPR and ECC define
high-risk patients with indicators that overlap to a consider-
able degree with the more rigorously validated TIMI risk
score
122
:
●
New ST-segment depression and positive troponins
●
Persistent or recurrent symptoms
●
Hemodynamic instability or VT
●
Depressed LV function (ejection fraction H1102140%)
●
ECG or functional study that suggests multivessel CAD
Normal or Nondiagnostic ECG Changes (Boxes 13
to 17)
The majority of patients with normal or nondiagnostic ECGs
do not have ACS. Patients in this category with ACS are most
often at low or intermediate risk. The physician’s goal
involves risk stratification (see above) to provide appropriate
diagnostic or treatment strategies for an individual patient.
These strategies then target patients at increased risk for
benefit while avoiding risk (eg, anticoagulation therapy and
invasive cardiac catheterization) in patients with low or
minimal risk.
Initial General Therapy for ACS
Several initial measures are appropriate for all patients with
suspected ACS in both the out-of-hospital and ED setting.
These include immediate oxygen therapy, continuous cardiac
monitoring, establishment of intravenous (IV) access, and
several medications discussed below.
Oxygen
Administer oxygen to all patients with overt pulmonary
congestion or arterial oxygen saturationH1102190% (Class I). It is
also reasonable to administer supplementary oxygen to all
patients with ACS for the first 6 hours of therapy (Class IIa).
Supplementary oxygen limited ischemic myocardial injury in
animals,
31
and oxygen therapy in patients with STEMI
reduced the amount of ST-segment elevation.
35
Although a
human trial of supplementary oxygen versus room air failed
to show a long-term benefit of supplementary oxygen therapy
for patients with MI,
30
short-term oxygen administration is
beneficial for the patient with unrecognized hypoxemia or
unstable pulmonary function. In patients with severe chronic
obstructive pulmonary disease, as with any other patient,
monitor for hypoventilation.
Aspirin
Early administration of aspirin (acetylsalicylic acid [ASA]),
including administration in the out-of-hospital setting,
47
has
been associated with decreased mortality rates in several
clinical trials.
47,129–131
Multiple studies support the safety of
aspirin administration. Therefore, unless the patient has a
known aspirin allergy, nonenteric aspirin should be given as
soon as possible to all patients with suspected ACS.
Aspirin produces a rapid clinical antiplatelet effect with
near-total inhibition of thromboxane A
2
production. It reduces
coronary reocclusion and recurrent ischemic events after
TABLE 4. TIMI Risk Score for Patients With Unstable Angina and Non–ST-Segment Elevation MI: Predictor Variables
Predictor Variable
Point Value
of Variable Definition
Age H1135065 years 1
H113503 risk factors for CAD 1 Risk factors
? Family history of CAD
? Hypertension
? Hypercholesterolemia
? Diabetes
? Current smoker
Aspirin use in last 7 days 1
Recent, severe symptoms of angina 1 H113502 anginal events in last 24 hours
Elevated cardiac markers 1 CK-MB or cardiac-specific troponin level
ST deviation H113500.5 mm 1 ST depression H113500.5 mm is significant; transient ST elevation H110220.5 mm for H1102120 minutes
is treated as ST-segment depression and is high risk; ST elevation H113501 mm for more than
20 minutes places these patients in the STEMI treatment category
Prior coronary artery stenosis H1135050% 1 Risk predictor remains valid even if this information is unknown
Calculated TIMI Risk Score
Risk of >1 Primary End
Point* in <14 Days Risk Status
0 or 1 5% Low
28%
3 13% Intermediate
4 20%
5 26% High
6or7 41%
*Primary end points: death, new or recurrent MI, or need for urgent revascularization.
Part 8: Stabilization of the Patient With Acute Coronary Syndromes IV-97
fibrinolytic therapy. Aspirin alone reduced death from AMI
in the Second International Study of Infarct Survival (ISIS-2),
and its effect was additive to that of streptokinase.
129
In a
review of 145 trials, aspirin was found to substantially reduce
vascular events in all patients with AMI, and in high-risk
patients it reduced nonfatal AMI and vascular death.
132
Aspirin is also effective in patients with UA. The standard
dose (160 to 325 mg) is recommended, although higher doses
may be used. Chewable or soluble aspirin is absorbed more
quickly than swallowed tablets.
133,134
The early administration of a single chewed dose of aspirin
(160 to 325 mg) is recommended in either the out-of-hospital
or ED setting for patients with suspected ACS (Class I). Other
formulations of ASA (soluble, IV) may be as effective as
chewed tablets. Aspirin suppositories (300 mg) are safe and
can be considered for patients with severe nausea, vomiting,
or disorders of the upper gastrointestinal tract.
Nitroglycerin (or Glyceryl Trinitrate)
Nitroglycerin is an effective analgesic for ischemic chest
discomfort. It also has beneficial hemodynamic effects, in-
cluding dilation of the coronary arteries (particularly in the
region of plaque disruption), the peripheral arterial bed, and
venous capacitance vessels. The treatment benefits of nitro-
glycerin are limited, however, and no conclusive evidence
has been shown to support routine use of IV, oral, or topical
nitrate therapy in patients with AMI.
135
With this in mind,
these agents should be carefully considered, especially when
low blood pressure precludes the use of other agents shown to
be effective in reducing morbidity and mortality (eg,
H9252-blockers and angiotensin-converting enzyme [ACE]
inhibitors).
IV nitroglycerin is indicated in the following clinical
situations (Class I):
●
Ongoing ischemic chest discomfort
●
Management of hypertension
●
Management of pulmonary congestion
Patients with ischemic discomfort may receive up to 3
doses of sublingual or aerosol nitroglycerin at 3- to 5-minute
intervals until pain is relieved or low blood pressure limits its
use (Class I). IV nitroglycerin is indicated for ongoing chest
discomfort, control of hypertension, or management of pul-
monary congestion in patients with STEMI associated with
LV failure (Class I). In patients with recurrent ischemia,
nitrates are indicated in the first 24 to 48 hours. IV rather than
long-acting preparations should be used acutely to enable
titration.
Do not use nitrates (Class III) in patients with hypotension
(SBP H1102190 mm Hg or H1102230 mm Hg below baseline), extreme
bradycardia (H1102150 bpm), or tachycardia (H11022100 bpm). Admin-
ister nitrates with extreme caution if at all to patients with
suspected inferior wall MI with possible right ventricular
(RV) involvement because these patients require adequate
RV preload. Do not administer nitrates (Class III) to patients
who have received a phosphodiesterase inhibitor for erectile
dysfunction within the last 24 hours (longer for some
preparations).
Morphine Sulfate
Morphine sulfate is the analgesic of choice for continuing
pain unresponsive to nitrates, and it is also effective in
patients with pulmonary vascular congestion complicating
ACS. Morphine is a venodilator that reduces ventricular
preload and oxygen requirements. For this reason it should
not be used in patients who may have hypovolemia. If
hypotension develops, elevate the patient’s legs, administer
volume, and monitor for signs of worsening pulmonary
vascular congestion. Start witha2to4mgIVdose, and give
additional doses of 2 to 8 mg IV at 5- to 15-minute intervals.
Reperfusion Therapies (Figure 1, Box 8)
Perhaps the most significant advance in the treatment of
cardiovascular disease in the last decade is reperfusion
therapy for AMI. Many clinical trials have established early
fibrinolytic therapy as a standard of care for patients with
AMI who present within 12 hours of the onset of symptoms
with no contraindications.
136–140
Reperfusion reduces mortal-
ity, and the shorter the time to reperfusion, the greater the
benefit: a 47% reduction in mortality was noted when
fibrinolytic therapy was provided within the first hour after
onset of symptoms.
139,140
The major determinants of myocardial salvage and long-
term prognosis are
●
Short time to reperfusion
136,140
●
Complete and sustained patency of the infarct-related
artery with normal (TIMI grade 3) flow
141,142
●
Normal microvascular perfusion
116,143–145
Fibrinolytics
In the absence of contraindications and the presence of a
favorable risk-benefit stratification, fibrinolytic therapy is one
option for reperfusion in those STEMI patients with onset of
symptoms of H1134912 hours and ECG findings of STEMI
(elevation H110221 mm in 2 or more contiguous precordial or
adjacent limb leads or new or presumably new LBBB) (Class
I). In the absence of contraindications, it is also reasonable to
administer fibrinolytics to patients with onset of symptoms
within the prior 12 hours and ECG findings consistent with
true posterior MI (Class IIa).
The ED physician should administer fibrinolytics to eligi-
ble patients as early as possible according to a predetermined
process of care developed by the ED and cardiology staff.
The goal is a door-to-needle time of H1134930 minutes. Every
effort must be made to minimize the time to therapy. Patients
treated within the first 70 minutes of onset of symptoms have
H1102250% reduction in infarct size and 75% reduction in mor-
tality rates.
146
Pooled data from 22 randomized controlled
trials of fibrinolytic therapy documents 65 lives saved per
1000 patients treated if fibrinolytics are provided in the first
hour and pooled total of 131 lives saved per 1000 patients
treated if fibrinolytics are provided within the first 3 hours of
onset of symptoms.
147
Fibrinolytics may be beneficial H1134912
hours after onset of symptoms.
148,149
Fibrinolytic therapy is generally not recommended for
patients presenting H1102212 hours after onset of symptoms,
although it may be considered if continuing ischemic pain is
IV-98 Circulation December 13, 2005
present with ST elevation H110221 mm in 2 or more contiguous
precordial or adjacent limb leads (Class IIa).
Fibrinolytic therapy should not be administered (Class III)
to patients who present H1102224 hours after the onset of symp-
toms or to patients who show ST-segment depression (unless
a true posterior MI is suspected).
Risks of Fibrinolytic Therapy
Physicians who administer fibrinolytic agents should be
aware of the indications, contraindications, benefits, and
major risks of administration so that they may be able to
weigh the net clinical benefit for each patient (see Table
1).
150,151
This net clinical benefit requires integration of
relative and absolute contraindications versus overall poten-
tial clinical gain.
Patients who present with extensive ECG changes (consis-
tent with a large AMI) and a low risk of intracranial bleeding
receive the greatest benefit from fibrinolytic therapy.
136
Patients with symptoms highly suggestive of ACS and ECG
findings consistent with LBBB are also appropriate candi-
dates for intervention because they have the highest mortality
rate when LBBB is due to extensive AMI. Fibrinolytics have
been shown to be beneficial across a spectrum of patient
subgroups with comorbidities such as previous MI, diabetes,
cardiogenic shock, tachycardia, and hypotension.
136
The ben-
efits of fibrinolytic therapy are less impressive in inferior wall
infarction except when it is associated with RV infarction
(ST-segment elevation in lead V
4
R or anterior ST-segment
depression).
Although older patients (H1102275 years) have a higher absolute
risk of death, their absolute benefit appears to be similar to
that of younger patients. There is only a small trend for
benefit of fibrinolytic therapy administered 12 to 24 hours
following the onset of symptoms. The incidence of stroke
does increase with advancing age,
152,153
reducing the relative
benefit of fibrinolytic therapy. Older age is the most impor-
tant baseline variable predicting nonhemorrhagic stroke.
152
Although 1 large trial reported lower early and 1-year
mortality rates with accelerated administration of tissue
plasminogen activator (tPA) in patients H1102185 years of age,
154
a recent retrospective analysis found no specific survival
advantage and possible risk for patients H1102275 years of age.
155
Additional studies are needed to clarify risk-benefit parame-
ters in the elderly.
The presence of high blood pressure (SBP H11022175 mm Hg)
on presentation to the ED increases the risk of stroke after
fibrinolytic therapy.
156
Current clinical practice is directed at
lowering blood pressure before administration of fibrinolytic
agents, although this has not been shown to reduce the risk of
stroke.
156
Fibrinolytic treatment of ACS patients who present
with an SBP H11022180 mm Hg or a diastolic blood pressure
H11022110 mm Hg is relatively contraindicated. Note that this
SBP limit is slightly lower than the upper limit of 185 mm Hg
used in eligibility criteria for fibrinolytic therapy for acute
ischemic stroke; the diastolic limit of 110 mm Hg is consis-
tent with the diastolic limit for tPA administration for stroke
(see Part 9: “Adult Stroke”).
Several fibrinolytics are available for clinical use, includ-
ing streptokinase,
129,140,157
anistreplase,
158,159
various regi-
mens of alteplase,
147,160,161
reteplase,
162,163
and tenect-
eplase.
138,164
Choice of agent is typically based on ease of
administration, cost, and preferences of each institution.
Intracranial Hemorrhage
Fibrinolytic therapy is associated with a small but definite
increase in the risk of hemorrhagic stroke, which contributes
to increased mortality.
136
More intensive fibrinolytic regi-
mens using tPA (alteplase) and heparin pose a greater risk
than streptokinase and aspirin.
147,165
Clinical factors that may
help risk-stratify patients at the time of presentation are age
(H1135065 years), low body weight (H1102170 kg), initial hypertension
(H11350180/110 mm Hg), and use of tPA. The number of risk
factors can be used to estimate the frequency of stroke, which
ranges from 0.25% with no risk factors to 2.5% with 3 risk
factors.
151
Several risk factor estimates are available for use
by clinicians, including Simoons,
151
the Co-Operative Car-
diovascular Project,
166
and the In-Time 2 trial.
167
Percutaneous Coronary Intervention
Coronary angioplasty with or without stent placement is the
most common form of PCI. PCI has been shown to be
superior to fibrinolysis in combined end points of death,
stroke, and reinfarction in many studies.
78,80,82,96,168–173
These
results, however, have been achieved in experienced medical
environments with skilled providers (performing H1102275 PCIs
per year) at a skilled PCI facility (performing H11022200 PCIs
annually for STEMI, with cardiac surgery capabilities).
At this time primary PCI is preferred in patients with
STEMI and symptom duration of H110223 and H1134912 hours if
skilled personnel can ensure that door-to-balloon time isH1134990
minutes or the difference in time between administration of
fibrinolysis versus inflation of the PCI balloon is H1134960
minutes (Class I). PCI is also preferred in patients with
contraindications to fibrinolysis and is reasonable in patients
with cardiogenic shock or heart failure complicating MI.
In patients with STEMI presentingH113493 hours from onset of
symptoms, treatment is more time-sensitive, and there is
inadequate research to recommend one treatment over the
other (Class Indeterminate). In these “early presenters,” any
possible benefit from primary PCI will be lost in prolonged
transfers.
Complicated AMI
Cardiogenic Shock, LV Failure, and Congestive
Heart Failure
Infarction of H1135040% of the LV myocardium usually results in
cardiogenic shock and carries a high mortality rate. Of those
who developed shock,
174
patients with ST-segment elevation
developed shock significantly earlier than patients without
ST-segment elevation.
Cardiogenic shock and congestive heart failure are not
contraindications to fibrinolysis, but PCI is preferred if the
patient is at a facility with PCI capabilities. The ACC/AHA
guidelines note that primary PCI is reasonable in those who
develop shock within 36 hours of MI and are suitable
candidates for revascularization that can be performed within
18 hours of the onset of shock.
12
In hospitals without PCI
facilities, rapidly administer a fibrinolytic agent and transfer
Part 8: Stabilization of the Patient With Acute Coronary Syndromes IV-99
the patient to a tertiary care facility where adjunct PCI can be
performed if low-output syndromes or ischemia continues.
175
The ACC/AHA STEMI guidelines recommend a door-to-
departure time of H1134930 minutes for transfer.
12
RV Infarction
RV infarction or ischemia may occur in up to 50% of patients
with inferior wall MI. The clinician should suspect RV
infarction in patients with inferior wall infarction, hypoten-
sion, and clear lung fields. In patients with inferior wall
infarction, obtain a right-sided or 15-lead ECG; ST-segment
elevation (H110221 mm) in lead V
4
R is sensitive (sensitivity, 88%;
specificity, 78%; diagnostic accuracy, 83%) for RV infarction
and a strong predictor of increased in-hospital complications
and mortality.
176
The in-hospital mortality rate of patients
with RV dysfunction is 25% to 30%, and these patients
should be routinely considered for reperfusion therapy. Fi-
brinolytic therapy reduces the incidence of RV dysfunc-
tion.
177
Similarly PCI is an alternative for patients with RV
infarction and is preferred for patients in shock. Patients with
shock caused by RV failure have a mortality rate similar to
that for patients with shock due to LV failure.
Patients with RV dysfunction and acute infarction are
dependent on maintenance of RV “filling” pressure (RV
end-diastolic pressure) to maintain cardiac output.
178
Thus,
nitrates, diuretics, and other vasodilators (ACE inhibitors)
should be avoided because severe hypotension may result.
This hypotension is often easily treated with an IV fluid
bolus.
Adjunctive Therapies for ACS and AMI
Clopidogrel
Clopidogrel irreversibly inhibits the platelet adenosine
diphosphate receptor, resulting in a reduction in platelet
aggregation through a different mechanism than aspirin.
Since the publication of the ECC Guidelines 2000, several
important clopidogrel studies have been published that doc-
ument its efficacy for patients with both UA/NSTEMI and
STEMI.
Clopidogrel was shown to be effective in 2 in-hospital
randomized controlled trials (LOE 1)
179,180
and 4 post-hoc
analyses (LOE 7).
181–184
In these studies patients with ACS
and a rise in cardiac biomarkers or ECG changes consistent
with ischemia had reduced stroke and MACE if clopidogrel
was added to aspirin and heparin within 4 hours of hospital
presentation. One study confirmed that clopidogrel did not
increase risk of bleeding in comparison with aspirin.
185
Clopidogrel given 6 hours or more before elective PCI for
patients with ACS without ST elevation reduced adverse
ischemic events at 28 days (LOE 1).
186
In patients up to 75 years of age with STEMI who are
treated with fibrinolysis, aspirin, and heparin (low-molecular-
weight heparin [LMWH] or unfractionated heparin [UFH]), a
300-mg oral loading dose of clopidogrel given at the time of
initial management (followed by a 75-mg daily dose for up to
8 days in hospital) improved coronary artery patency and
reduced MACE.
187
The Clopidogrel in Unstable angina to prevent Recurrent
ischemic Events (CURE) trial documented an increased rate
of bleeding (but not intracranial hemorrhage) in the 2072
patients undergoing CABG within 5 to 7 days of administra-
tion of this agent.
184
In addition, a post-hoc analysis of this
trial reported a trend toward life-threatening bleeding. A
subsequent risk-to-benefit ratio analysis concluded that the
bleeding risk with clopidogrel in patients undergoing CABG
was modest.
184
One recent large prospective trial (LOE 1)
187
failed to show any increase in bleeding in 136 patients
undergoing CABG within 5 to 7 days of administration of
clopidogrel. In patients with ACS, the risk of bleeding must
be weighed against the risk of perioperative ACS events
recurring if these agents are withheld. Current ACC/AHA
guidelines, published soon after the large CURE trial, recom-
mend withholding clopidogrel for 5 to 7 days in patients for
whom CABG is anticipated.
12
Ongoing studies are evaluating
the efficacy and risk-benefit issues.
On the basis of these findings, providers should administer
a 300-mg loading dose of clopidogrel in addition to standard
care (aspirin, UFH, or LMWH and GP IIb/IIIa inhibitors if
indicated) to ED patients with ACS with elevated cardiac
markers or new ECG changes consistent with ischemia
(excluding STEMI)
184
in whom a medical approach or PCI is
planned (Class I). It is reasonable to administer a 300-mg oral
dose of clopidogrel to ED patients with suspected ACS
(without ECG or cardiac marker changes) who are unable to
take aspirin because of hypersensitivity or major gastrointes-
tinal intolerance (Class IIa). Providers should administer a
300-mg oral dose of clopidogrel to ED patients up to 75 years
of age with STEMI who receive aspirin, heparin, and
fibrinolysis.
H9252-Adrenergic Receptor Blockers
In-hospital administration of H9252-blockers reduces the size of
the infarct, incidence of cardiac rupture, and mortality in
patients who do not receive fibrinolytic therapy.
188–190
They
also reduce the incidence of ventricular ectopy and fibrilla-
tion.
191,192
In patients who do receive fibrinolytic agents, IV
H9252-blockers decrease postinfarction ischemia and nonfatal
AMI. A small but significant decrease in death and nonfatal
infarction has been observed in patients treated with
H9252-blockers soon after infarction.
193
IV H9252-blockers may also
be beneficial for NSTEMI ACS.
Oral H9252-blockers should be administered in the ED for ACS
of all types unless contraindications are present. They should
be given irrespective of the need for revascularization thera-
pies (Class I). Use IV H9252-blockers for the treatment of
tachyarrhythmias or hypertension (Class IIa).
Contraindications to H9252-blockers are moderate to severe LV
failure and pulmonary edema, bradycardia (H1102160 bpm), hy-
potension (SBP H11021100 mm Hg), signs of poor peripheral
perfusion, second-degree or third-degree heart block, or
reactive airway disease. In the presence of moderate or severe
heart failure, oral H9252-blockers are preferred. They may need to
be given in low and titrated doses after the patient is
stabilized. This permits earlier administration of ACE inhib-
itors that are documented to be efficacious in reducing 30-day
mortality rates (see below).
IV-100 Circulation December 13, 2005
Heparins
Heparin is an indirect inhibitor of thrombin that has been
widely used in ACS as adjunctive therapy for fibrinolysis and
in combination with aspirin and other platelet inhibitors for
the treatment of UA and NSTEMI. UFH is a heterogeneous
mixture of sulfated glycosaminoglycans with varying chain
lengths. UFH has several disadvantages, including an unpre-
dictable anticoagulant response in individual patients, the
need for IV administration, and the requirement for frequent
monitoring of the activated partial thromboplastin time
(aPTT). Heparin can also stimulate platelet activation, caus-
ing thrombocytopenia.
194
When UFH is used as adjunctive therapy with fibrin-
specific lytics in STEMI, the current recommendations call
for a bolus dose of 60 U/kg followed by infusion at a rate of
12 U/kg per hour (a maximum bolus of 4000 U and infusion
of 1000 U/h for patients weighingH1102270 kg).
195
An aPTT of 50
to 70 seconds is considered optimal. Because of the limita-
tions of heparin, newer preparations of LMWH have been
developed.
Unfractionated Heparin Versus Low-Molecular-Weight
Heparin in UA/NSTEMI
Six in-hospital randomized controlled trials (LOE 1
196,197
and
LOE 2
130,198,199
H1102124 hours; LOE 1
200
H1102136 hours) and
additional studies (including 7 meta-analyses [LOE 1
201–207
])
document similar or improved composite outcomes (death,
MI and/or recurrent angina, or recurrent ischemia or revas-
cularization) when LMWH is given instead of UFH to
patients with UA/NSTEMI within the first 24 to 36 hours
after onset of symptoms.
Although major bleeding events are not significantly dif-
ferent with LMWH compared with UFH, there is a consistent
increase in minor and postoperative bleeding with the use of
LMWH.
208
Omission of LMWH (enoxaparin) on the morning
of angiography resulted in vascular complication rates com-
parable to that of UFH.
209
Four trials have compared UFH and LMWH in patients
with NSTEMI who were treated with a GP IIb/IIIa inhibi-
tor.
210–213
In terms of efficacy, LMWH compared favorably
with UFH, and in terms of safety there were similar or less
frequent major bleeding events with LMWH but again an
increased frequency of minor bleeding complications.
In summary, ED administration of LMWH (specifically
enoxaparin) is beneficial compared with UFH when given in
addition to antiplatelet therapy such as aspirin for patients
with UA/NSTEMI (Class IIb). UFH should be considered if
reperfusion is planned in the first 24 to 36 hours after onset of
symptoms. Changing from one form of heparin to another
(crossover of antithrombin therapy) during an acute event is
not recommended because it may lead to an increase in
bleeding complications.
214
Unfractionated Heparin Versus Low-Molecular-Weight
Heparin in STEMI
LMWHs have been found to be superior to UFH in patients
with STEMI in terms of overall TIMI flow
215,216
and reducing
the frequency of ischemic complications,
217
with a trend to a
14% reduction in mortality rates in a meta-analysis.
218
No
superiority was found in studies in which an invasive strategy
(PCI) was used.
Two randomized controlled trials compared UFH with
LMWH as ancillary treatment with fibrinolysis in the out-of-
hospital setting.
219,220
Administration of LMWH for patients
with STEMI showed superiority in composite end points
compared with UFH. This must be balanced against an
increase in intracranial hemorrhage in patients H1102275 years of
age who received LMWH (enoxaparin) documented in one of
these randomized controlled trials (LOE 2).
220
LMWH (enoxaparin) is an acceptable alternative to UFH
in the ED as ancillary therapy for patients H1102175 years of age
who are receiving fibrinolytic therapy, provided that signifi-
cant renal dysfunction (serum creatinine H110222.5 mg/dL in men
or 2 mg/dL in women) is not present (Class IIb). UFH is
recommended for patients H1135075 years of age as ancillary
therapy to fibrinolysis (Class IIa) and for any STEMI patient
who is undergoing revascularization. In patients with STEMI
who are not receiving fibrinolysis or revascularization,
LMWH (specifically enoxaparin) may be considered an
acceptable alternative to UFH in the ED setting (Class IIb).
Glycoprotein IIb/IIIa Inhibitors
After plaque rupture in the coronary artery, tissue factor in the
lipid-rich core is exposed and forms complexes with factor
VIIa, setting in motion the coagulation cascade resulting in
platelet activation. The integrin GP IIb/IIIa receptor is con-
sidered the final common pathway to platelet aggregation. GP
IIb/IIIa inhibitors modulate this receptor activity. Three
agents are available for use: abciximab, eptifibatide, and
tirofiban.
GP IIb/IIIa Inhibitors in UA/NSTEMI
Several large studies of GP IIb/IIIa inhibitors in UA/NSTEMI
have shown a clear benefit when combined with standard
aspirin and heparin and a strategy of mechanical reperfusion
(LOE 1
221
; LOE 2
222
; and 3 meta-analyses
221,223,224
). Severe
bleeding complications (and no increase in intracranial hem-
orrhage) in the GP IIb/IIIa group were offset by the large
benefit of these agents. The benefit of GP IIb/IIIa inhibitors
extends to high-risk patients with UA/NSTEMI treated with
PCI.
223
In UA/NSTEMI patients not treated with PCI, the effect of
GP IIb/IIIa inhibitors has been mixed. In 2 studies (LOE
1)
212,221
and 3 meta-analyses (LOE 1),
223–225
GP IIb/IIIa
inhibitors produced no mortality advantage and only a slight
reduction in recurrent ischemic events in one large meta-
analysis
224
but did show a reduction in 30-day mortality in a
later, equally large meta-analysis.
225
Of note, the benefit of
GP IIb/IIIa inhibitors was dependent on coadministration of
UFH or LMWH. Interestingly abciximab appears to behave
differently from the other 2 GP IIb/IIIa inhibitors. In the
Global Utilization of Streptokinase and Tissue Plasminogen
Activator for Occluded Coronary Arteries (GUSTO) IV-ACS
trial and 1-year follow-up involving 7800 patients,
226,227
abciximab showed a lack of treatment effect compared with
placebo in patients treated medically only.
On the basis of these findings, GP IIb/IIIa inhibitors should
be used in patients with high-risk stratification UA/NSTEMI
Part 8: Stabilization of the Patient With Acute Coronary Syndromes IV-101
as soon as possible in conjunction with aspirin, heparin, and
clopidogrel and a strategy of early PCI (Class I). High-risk
features include persistent pain, hemodynamic or rhythm
instability, diabetes, acute or dynamic ECG changes, and any
elevation in cardiac troponins attributed to cardiac injury.
Extrapolation from efficacy studies suggests that this therapy
may be administered in the ED once a decision has been made
to proceed to PCI (Class IIa).
GP IIb/IIIa inhibitors tirofiban and eptifibatide may be
used in patients with high-risk stratification UA/NSTEMI in
conjunction with standard therapy if PCI is not planned
(Class IIb), although studies are not conclusive at this time.
As a result of the lack of benefit demonstrated in the GUSTO
IV ACS trial, abciximab should not be given unless PCI is
planned (Class III).
GP IIa/IIIb Inhibitors in STEMI
There is insufficient evidence to recommend for or against
GP IIb/IIIa inhibitor therapy in STEMI; studies are ongoing.
These agents have been used to facilitate antiplatelet therapy
in patients undergoing direct PCI, but relatively few patients
have been evaluated. GP IIb/IIIa inhibitors are now being
evaluated early in STEMI to “facilitate” fibrinolytic therapy
and serve as “upstream” adjuncts to planned direct PCI for
STEMI, for example, achieving some degree of infarct artery
patency during preparation or transfer. One study using
abciximab (Facilitated Intervention with Enhanced Reperfu-
sion Speed to Stop Events [FINESSE]) is ongoing. Use of
these agents in STEMI requires institutional-individualized
protocols developed in conjunction with interventional
cardiologists.
Calcium Channel Blockers
Calcium channel blocking agents may be added as an
alternative or additional therapy if H9252-blockers are contraindi-
cated or the maximum dose has been achieved.
The 1996 ACC/AHA guidelines for the management of
patients with AMI
228
make the following comment about
calcium channel blockers:
Calcium channel blocking agents have not been shown
to reduce mortality after acute MI, and in certain
patients with cardiovascular disease there is data to
suggest that they are harmful. There is concern that
these agents are still used too frequently in patients
with acute MI and that H9252-adrenergic receptor blocking
agents are a more appropriate choice across a broad
spectrum of patients with MI. In general, give calcium
antagonists only when H9252-blockers are contraindicated
or have been given at maximum clinical doses without
effect (Class Indeterminate).
ACE Inhibitor Therapy
ACE inhibitor therapy has improved survival rates in patients
with AMI, particularly when started early.
229–233
Evidence
from 7 large clinical trials,
135,232–237
2 meta-analyses,
238,239
and 10 minor trials
237,240–249
documents consistent improve-
ment in mortality when oral ACE inhibitors are administered
in the hospital setting to patients with AMI with or without
early reperfusion therapy. In these studies ACE inhibitors
were not administered in the presence of hypotension (SBP
H11021100 mm Hg or more than 30 mm Hg below baseline). The
beneficial effects are most pronounced in patients with
anterior infarction, pulmonary congestion, or LV ejection
fraction H1102140%.
Administration of an oral ACE inhibitor is recommended
within the first 24 hours after onset of symptoms in STEMI
patients with pulmonary congestion or LV ejection fraction
H1102140%, in the absence of hypotension (SBP H11021100 mm Hg or
more than 30 mm Hg below baseline) (Class I). Oral ACE
inhibitor therapy can also be recommended for all other
patients with AMI with or without early reperfusion therapy
(Class IIa). IV administration of ACE inhibitors is contrain-
dicated in the first 24 hours because of risk of hypotension
(Class III).
HMG Coenzyme A Reductase Inhibitors (Statins)
A variety of studies documented consistent reduction in
indicators of inflammation and complications such as rein-
farction, recurrent angina, and arrhythmias when statin treat-
ment is administered within a few days after onset of an
ACS.
250–253
There is little data to suggest that this therapy
should be initiated within the ED; however, early initiation
(within 24 hours of presentation) of statin therapy is safe and
feasible in patients with an ACS or AMI (Class I). If patients
are already on statin therapy, continue the therapy (Class IIb).
Glucose-Insulin-Potassium
Although glucose-insulin-potassium (GIK) therapy was for-
merly thought to reduce the chance of mortality during AMI
by several mechanisms, recent clinical trials found that GIK
did not show any benefit in STEMI.
254,255
At this time there
is little evidence to suggest that this intervention is helpful.
Management of Arrhythmias
This section discusses management of arrhythmias during
acute ischemia and infarction.
Ventricular Rhythm Disturbances
Treatment of ventricular arrhythmias during and after AMI
has been a controversial topic for 2 decades. Primary VF
accounts for the majority of early deaths during AMI.
21–23
The incidence of primary VF is highest during the first 4
hours after onset of symptoms
24–27
but remains an important
contributor to mortality during the first 24 hours. Secondary
VF occurring in the setting of CHF or cardiogenic shock can
also contribute to death from AMI. VF is a less common
cause of death in the hospital setting with the early use of
fibrinolytics in conjunction with H9252-blockers.
Although prophylaxis with lidocaine reduces the incidence
of VF, an analysis of data from ISIS-3 and a meta-analysis
suggest that lidocaine increased all-cause mortality rates.
256
Thus, the practice of prophylactic administration of lidocaine
has been largely abandoned.
Routine IV administration of H9252-blockers to patients with-
out hemodynamic or electrical contraindications is associated
with a reduced incidence of primary VF. Low serum potas-
sium but not magnesium has been associated with ventricular
IV-102 Circulation December 13, 2005
arrhythmias. It is prudent clinical practice to maintain serum
potassium H110224 mEq/L and magnesium H110222 mEq/L.
Routine administration of magnesium to patients with MI
has no significant clinical mortality benefit, particularly in
patients receiving fibrinolytic therapy. The definitive study
on the subject is the ISIS-4 study (LOE 1).
135
ISIS-4 enrolled
H1102258 000 patients and showed a trend toward increased
mortality rates when magnesium was given in-hospital for
primary prophylaxis to patients within the first 4 hours of
known or suspected AMI.
Following an episode of VF, there is no conclusive data to
support the use of lidocaine or any particular strategy for
preventing VF recurrence. H9252-Blockers are the preferred treat-
ment if not initiated before the episode of VF. If lidocaine is
used, continue it for a short time after MI but no more than 24
hours unless symptomatic VT persists. Exacerbating or modu-
lating factors should be identified and corrected. Further man-
agement of ventricular rhythm disturbances is discussed in Part
7.2: “Management of Cardiac Arrest” and Part 7.3: “Manage-
ment of Symptomatic Bradycardia and Tachycardia.”
Summary
There has been tremendous progress in reducing disability
and death from ACS. But many patients still die before
reaching the hospital because patients and family members
fail to recognize the signs of ACS and fail to activate the EMS
system. Once the patient with ACS contacts the healthcare
system, providers must focus on support of cardiorespiratory
function, rapid transport, and early classification of the
patient based on ECG characteristics. Patients with STEMI
require prompt reperfusion; the shorter the interval from
symptom onset to reperfusion, the greater the benefit. Patients
with UA/NSTEMI or nonspecific or normal ECGs require
risk stratification and appropriate monitoring and therapy.
Healthcare providers can improve survival rates and myocar-
dial function of patients with ACS by providing skilled,
efficient, and coordinated out-of-hospital and in-hospital
care.
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IV-110 Circulation December 13, 2005