Variable threshold exertional angina in patients with transient vasospastic myocardial ischemia. Repeat exercise test results and therapeutic implications

Thirty-five of 70 patients with vasospastic angina at rest complained of chest pain during exercise or during usual daily activity. In 22, the angina threshold was described as variable during exercise: that is, the amount of exertion that induced angina was not always the same. In 12 patients with variable threshold exertional angina, 3 exercise tests performed in the morning on different days yielded different results, because chest pain and ischemic electrocardiographic changes occurred at different work loads with a wide range in heart rate-systolic pressure product. Two patients, in whom great cardiac vein flow was measured during exercise before and after taking nifedipine, tolerated heavier work loads after receiving the drug, with a more marked increase in flow during exercise. It is concluded that variable threshold exertional angina can be objectively demonstrated by repeat exercise tests in patients with vasospastic angina. Variability of the angina threshold may be due to a functional mechanism that causes myocardial ischemia in addition to the increased myocardial metabolic requirements provoked by exercise. Because in such patients fluctuations in coronary arterial tone play an important role in determining the response to exercise, calcium antagonistic drugs, which lower coronary tone and prevent the occurrence of coronary spasm, are effective in increasing exercise capacity.