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Coronary artery disease reflects an imbalance between myocardial oxygen supply and demand. This imbalance, which represents myocar¬dial ischemia, is expressed clinically as angina or myocardial infarc¬tion. Most sudden cardiac deaths are arrhythmic secondary to coro¬nary artery disease.
Prevalence
The prevalence and severity of coronary artery disease increase dra¬matically with age. The increase is greater in men than in women and reaches a peak between the sixlh and sevenih decade, at which point it declines slightly. The increase in women continues steadily until Ihc eighth decade. The prevalence is about 60% in both sexes at the eighth decade and thereafter. Despite the high prevalence of coronary artery

disease in the elderly, symptomatic disease is noted in only 10% to 20% of this population. This discrepancy may be due to (1) decreased activ¬ity levels (work loads that would ordinarily trigger ischemic symptoms may be encountered less frequently in the elderly), (2) increased likeli¬hood of a neuropathy that alters pain sensation, or (3) age-associated myocardial and possibly pericardial changes, making dyspnea more likely to occur than chest pain when ischemia is present. The preva¬lence of disease detected on thallium stress testing also increases, from 2% in the fifth and sixth decades to > 25% in the ninth decade.
Diagnosis
(See also Ch. 34)
Coronary artery disease should be strongly suspected in persons with known coronary risk factors (see Prevention, below) and in those with signs of noncoronary atherosclerosis, such as cerebrovascular or peripheral vascular disease. The probability of disease (which is higher in an elderly person), as well as the sensitivity and specificity of a test (see TABLE 34-1), determine a test’s accuracy. Thus, a positive test result is more predictive, and a negative result less so. in an older person.
Exercise stress testing is useful for diagnosing coronary artery dis¬ease and for predicting subsequent coronary death in middle-aged per¬sons with two or more risk factors. It is probably equally useful in the elderly (see TABLE 34-2). Exercise stress testing is also used to evaluate the severity of coronary artery disease. Left main artery or triple-ves¬sel obstructions typically produce systolic hypotension (a fall in sys¬tolic blood pressure of > 15 mm Hgfrom one exercise level to the next) as well as several types of ECG changes. These include global changes (te, those occurring in both the anterior and inferior leads), marked changes (> 2 mm of ST-segment shift), prolonged changes (those per¬sisting > X min after exercise), early changes (those occurring during stage 1 or stage 2 of the standard Bruce treadmill test), and the appear¬ance of malignant ventricular arrhythmias.
Two points should be considered when evaluating a stress ECG. First. ST and T changes cannot be interpreted if a person has left bun¬dle branch block or left ventricular hypertrophy or is taking digoxin, all of which are more likely in older than in younger persons. Under these circumstances, thallium stress testing is a better alternative. Second, older patients often cannot exercise to 90% of predicted maximum heart rate because of respiratory or musculoskeletal disease. In older persons who cannot exercise to Ihe desired heart rale or work load, thallium scan or ECG testing after the administration of a pharmacologic stress such as dipyridamole or adenosine may be used to diagnose sig¬nificant coronary artery disease. Adenosine probably has a greater in¬cidence of side effects, such as impulse formation or conduction system disturbances. Pacing may also be used to increase the heart rate and soinduce ischemia in appropriate patienls. However, not only is insertion of ii pacemaker an invasive procedure, but the stress provoked by pac¬ing is often not comparable to that induced by exercise.
In addition lo scintigraphic and ECG evidence of ischemia, func¬tional evidence may be provided by echocardiography. Echocardi¬ography performed during dobutaminc infusion and then during or immediately after exercise can help diagnose, localize, and assess the seventy of ischemia-induced left ventricular dysfunction. The diag¬nostic sensitivity and specificity are similar lo those of other imaging modalities. Advantages include using less expensive technology and avoiding radiation exposure.
Prevention
The principles of coronary artery disease management are similar for all patients, and risk factor modification may be as important in older patienls as in younger ones. Measures should be taken to decrease the progression of coronary atherosclerosis in both symptomatic and asymptomatic elderly persons.
Data from the Framingham Heart Study indicate that systolic blood pressure is the strongest discriminator of coronary artery disease risk in men > 45 yr old. A study of persons > 60 yr of age with isolated systolic hypertension (systolic pressure i? 160 mm Hg without diastolic hypertension) has shown that treatment decreases the risk of major car¬diovascular outcomes.
Total cholesterol levels have been related to unfavorable cardiovascu¬lar outcomes in the elderly, although not in the Framingham data. High levels of low-density lipoprotein (LDL) cholesterol represent a significant risk factor for cardiovascular disease; conversely, high levels of high-density lipoprotein (HDL) cholesterol are associated with reduced risk. Drug and dietary interventions lo lower LDL levels have been shown to reduce cardiovascular risk in middle-aged populations. Although simi¬lar data are not available for the elderly, recommending dietary changes and pharmacotherapy for older persons with coronary artery disease and abnormal lipid levels is probably prudent (see also Ch. HI).
Many studies correlate cigarette smoking with increased cardiovas¬cular risk in the elderly. Studies also show that cessation of smoking for as little as 1 to 5 yr markedly reduces risk.
Physical inactivity is an additional risk factor fur Ihe development of coronary artery disease. The benefits of exercise may be related to maintenance of normal blood pressure, a favorable influence on the lipid profile, decreased neurohumoral activation, and improved glucose tolerance. However, since asymptomatic disease is so prevalent in the elderly, older persons should undergo a supervised exercise test before initiating, and at regular intervals while participating in, a regular exer¬cise program

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