Interesting approaches to the diagnosis of angina pectoris

Twelve different approaches to laboratory diagnosis of angina pectoris are reviewed here. They employ no fewer than seven different means of intentionally provoking a disparity between myocardial requirement and supply: dynamic exercise, hypoxia, prandial stress, raised systemic vascular resistance, paced tachycardia, mental stress, and exposure to normal environment. Of these, only dynamic exercise and the diverse combinations of stresses in the normal environment are capable of altering the heart's oxygen requirement-supply ratio threefold or more, accounting for the successful results from tests using these means of stress. The reviewed tests use three different means of detecting myocardial ischemia provoked by stress: electrocardiography to indicate impaired ventricular repolarization, indirect graphic records sensitive to impairment of mechanical ventricular function, and detection of insufficient myocardial perfusion patterns by radioactive tracer. The latter approach is particularly appealing because it directly reflects the pathophysiologic anomaly of interest. It should be remembered, however, that the basic differences in these methods of detecting ischemia make them complementary to each other and encourage their use in combination for improved diagnostic sensitivity.