Coronary Heart Disease - Ischemic Heart Disease

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.

Interventions to lessen some of these risk factors, such as lipid abnormalities, hypertension, and smoking, reduce the risk for subsequent coronary events.

However, the benefit of reducing homocysteine levels is less clear, and hormone replacement therapy has been associated with an early increase in coronary risk. Patients with clinical manifestations of coronary disease before age 50 often have one or more of these predisposing risk factors, though many do not. The conventional risk factors are less closely linked to the onset of coronary disease in later years.

Overwhelming evidence indicates that abnormalities of lipid metabolism play a direct role in the pathophysiology of this condition. Risk increases progressively with higher levels of LDL cholesterol and declines with higher levels of HDL cholesterol. Therefore, the ratio of LDL to HDL cholesterol provides a composite marker of risk, with ratios below 3 indicating a lower risk and ratios above 5 indicating a higher risk. Other abnormalities of lipid metabolism also play a role in the pathogenesis of coronary artery disease, and these should be sought in individuals with otherwise unexplained premature disease. Among the patterns associated with increased atherosclerosis are elevated levels of apolipoprotein(a) and of small, dense LDL lipoprotein particles. These lipoproteins and their accompanying lipids appear more likely to pass into the vessel wall and may be more difficult to clear. Accumulating evidence suggests that hypertriglyceridemia is an independent risk factor for coronary artery disease as well. Elevated triglyceride levels often occur in association with other lipid abnormalities, including low levels of HDL cholesterol and elevated concentrations of lipoprotein(a) and small, dense LDL particles. Some experts advocate the use of non-HDL cholesterol, which accounts for several atherogenic lipids, as the preferred risk indicator.