Myocardial infarction represents a crossroads in the natural history of
coronary artery disease. The prognosis is determined by the severity of
coronary artery disease,
infarct size (and hence ejection fraction), and age of the patient. After
infarction, patients may remain symptomless, or suffer angina, silent
ischemia, reinfarction,
heart failure or
sudden death. Hence patient management after
infarction includes (1) estimation of risk, (2) the use of stress tests to detect
ischemia and rhythm disorders, (3) PTCA or bypass if required and (4) medical
therapy. Cardiac catheterization is indicated in patients with angina or silent
ischemia, non-Q wave
infarction or large infarctus; its use is less well established in patients without
ischemia and
left ventricular dysfunction, but this indication is nevertheless increasingly accepted. PTCA is primarily utilized in patients with single or two vessel disease, while coronary bypass surgery is indicated in patients with left main or three vessel disease. All these measures are designed to improve symptoms and prognosis. For
secondary prevention medical
therapy should be used to treat cardiovascular risk factors (
antihypertensive drugs,
lipid-lowering drugs etc.), to inhibit platelets (
aspirin,
ticlopidine) or coagulation (
coumarins), to block neurohumoral activation (betablocker,
ACE-inhibitors), for vasoconstriction (
calcium channel blockers,
nitrates) and to suppress arrhythmias. The large number of drugs requires reasoned use depending on the risk profile of the individual patient. Cardiovascular risk factors should be treated appropriately.
Platelet inhibitors should be given to all patients except those with
atrial fibrillation or large ventricles (
coumarins). Betablockers reduce mortality, reinfarction and
sudden death after
infarction and hence should be used if no
contraindications exist.
ACE-inhibitors are particularly effective in improving symptoms and prognosis in patients with impaired left ventricular function.
Calcium antagonists should be used with caution and only in patients with normal left ventricular function.
Nitrates are primarily effective in improving symptoms in patients with angina or
heart failure.
Antiarrhythmic drugs (
amiodarone) are only useful in patients with complex arrhythmias. Digitalis has been shown to improve symptoms in patients with
heart failure, while other inotropic drugs are virtually no longer used. These guidelines allow reasoned differential
therapy after
myocardial infarction to the maximum benefit of the patient and at minimum cost.