- What is your job when the Step 2 exam describes a patient with chest pain?
To make sure that the chest pain is not due to any life-threatening condition. Usually you must
try to make sure that the patient has not had a heart attack. - What elements of the history and physical exam steer you away from a
diagnosis of myocardial infarction (MI)?
Wrong age: in the absence of known heart disease, strong family history, or multiple risk factors for
coronary artery disease, a patient under the age of 40 is extremely unlikely to have an MI.
Lack of risk factors: a 60-year-old marathon runner who eats well and has a high level of highdensity lipoprotein (HDL) and no cardiac risk factors (other than age) is unlikely to have a heart attack.
Physical characteristics of pain: if the pain is reproducible by palpation, it is from the
chest wall, not the heart. The pain associated with an MI is usually not sharp or well localized.
The pain should not be related to certain foods or eating.
Having said all of this, many physicians still want to make sure that a heart attack has
not occurred with at least an EKG and possibly one or more sets of cardiac enzyme levels. For
the Step 2 exam, however, these clues should steer you toward an alternative diagnosis. - What findings on EKG should make you suspect an MI?
After a heart attack you should see flipped or flattened T waves, ST-segment elevation
(depression means ischemia; elevation means injury), and/or Q waves in a segmental
distribution (e.g., leads II, III, and AVF for an inferior infarct) - Describe the classic pattern of chest pain in an MI.
The pain is classically described as a crushing or pressure sensation; it is a poorly
localized substernal pain that may radiate to the shoulder, arm, or jaw. The pain usually
is not reproducible on palpation and in patients with a heart attack often does not resolve
with nitroglycerin (as it often does in angina). The pain usually lasts at least half
an hour. - What tests are used to diagnose an MI?
Other than an EKG, the patient with a possible MI should have serial determinations
of the MB fraction of creatine kinase (CK-MB), troponin I or T, or myoglobin (usually
drawn every 8 hours 3 times before a heart attack is ruled out). Elevation of lactate
dehydrogenase (LDH) and a reversed ratio (LDH1 > LDH2) are now uncommonly used
for a late MI presentation because the troponin levels stay elevated for more than 24
hours. Aspartate aminotransferase (AST) usually is elevated, but this parameter is not
used clinically for detection of cardiac injury. Radiographs may show cardiomegaly
and/or pulmonary congestion; echocardiography may show ventricular wall motion
abnormalities. - Describe the classic physical exam findings in patients with MI.
Patients are often diaphoretic, anxious, tachycardic, tachypneic, and pale; they may have
nausea and vomiting. With large heart attacks that cause heart failure, look for bilateral
pulmonary rales in the absence of other pneumonia-like symptoms, distended neck veins,
S3 or S4 heart sound, new murmurs, hypotension, and/or shock. - What historical points should steer you toward a diagnosis of MI?
Patients often have a history of angina or previous chest pain, murmurs, arrhythmias, risk
factors for coronary artery disease, hypertension, or diabetes. They also may be taking digoxin,
furosemide, cholesterol medications, anti-hypertensives, or other medications. - Describe the treatment for an MI.
Treatment involves admission to the intensive or cardiac care unit. Several basic principles
should be kept in mind: - Early reperfusion is indicated if the time from onset of symptoms is less than 12 hours,
and choice of reperfusion therapy is determined by patient and medical center
criteria. Early reperfusion (fewer than 4 to 6 hours) is preferred to try to salvage
myocardium. Reperfusion may be accomplished by fibrinolysis or percutaneous
coronary intervention (i.e., balloon angioplasty/stent). Coronary artery bypass
grafting may be required. - EKG monitoring is essential. If ventricular tachycardia occurs, use amiodarone.
- Give oxygen by nasal cannula, and maintain an oxygen saturation > 90%.
- Control pain with morphine, which may improve pulmonary edema, if present.
- Administer aspirin.
- Administer nitroglycerin.
- Beta blockers, which patients without contraindications should take for life, reduce the
mortality rate of MI as well as the incidence of a second heart attack. - Administer clopidogrel.
- Administer unfractionated or low molecular weight heparin.
- An angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker
(ARB) should be started within 24 hours. - Administer an HMG-CoA reductase inhibitor (statin).
- True or false: With good management, patients with an MI will not die in the
hospital.
False. Even with the best of medical management, patients may die from an MI. They also may
have a second heart attack during hospitalization. Watch for sudden deterioration! - When is heparin indicated in the setting of chest pain and MI?
Heparin should be started if unstable angina is diagnosed, if the patient has a cardiac
thrombus, or if severe congestive heart failure is seen on echocardiogram. The Step 2 exam
will not ask about other indications, which are not as clear-cut. Do not give heparin to patients
with contraindications to its use (e.g., active bleeding).