Coronary heart disease, or atherosclerotic coronary artery disease, is the commonest cause of cardiovascular disability and death in the United States. Men are more often affected than women by an overall ratio of 4:1, but before age 40 the ratio is 8:1, and after age 70 it is 1:1. In men, the peak incidence of clinical manifestations is at age 50-60; in women, at age 60-70.

Risk Factors for Coronary Artery Disease

Epidemiologic studies have identified a number of important risk factors for premature coronary artery disease. These include a positive family history (particularly when onset is before age 50), age, male gender, blood lipid abnormalities, diabetes mellitus, insulin resistance and the metabolic syndrome, hypertension, physical inactivity, cigarette smoking, elevated blood homocysteine levels, markers of inflammation such as C-reactive protein (CRP) and hyperfibrinogenemia, and hypoestrogenemia in women.

Acute coronary syndromes Acute coronary syndromes comprise the spectrum of unstable cardiac ischemia from unstable angina to acute myocardial infarction. Rather than the traditional nomenclature of unstable angina, non-Q wave and Q wave myocardial infarction, acute coronary syndromes are now classified based on the presenting electrocardiogram as either “ST elevation” or “non-ST elevation.” This allows for immediate classification and guides determination of whether patients should be considered for acute reperfusion therapy. The evolution of cardiac markers then allows determination of whether myocardial infarction has occurred. Acute coronary syndromes represent a dynamic state in which patients frequently shift from one category to another, as new ST elevation can develop after presentation and cardiac markers can become abnormal with recurrent ischemic episodes.

Arrhythmias Abnormalities of cardiac rhythm and conduction can be lethal (sudden cardiac death), symptomatic (syncope, near syncope, dizziness, or palpitations), or asymptomatic. They are dangerous to the extent that they reduce cardiac output, so that perfusion of the brain or myocardium is impaired, or tend to deteriorate into more serious arrhythmias with the same consequences. Stable supraventricular tachycardia is generally well tolerated in patients without underlying heart disease but may lead to myocardial ischemia or congestive heart failure in patients with coronary disease, valvular abnormalities, and systolic or diastolic myocardial dysfunction. Ventricular tachycardia, if prolonged (lasting more than 10-30 seconds), often results in hemodynamic compromise and is more likely to deteriorate into ventricular fibrillation.