Exercise testing and indirect assessment of myocardial oxygen consumption in evaluation of angina pectoris

Exercise testing is an important means of evaluating the patient with angina pectoris, providing objective data not available from conventional clinical assessment. In utilizing exercise to determine functional impairment in angina, it is essential to distinguish between external stress, or the load on the skeletal muscles, and internal or cardiac stress. Evaluation of external exercise capacity alone is limited as a measure of cardiac peformance since the relationship between external function and cardiac performance is not necessarily direct. A readily applicable approach to determination of cardiac capacity in angina is afforded by indirect assessment of myocardial oxygen consumption (MVO2). This is achieved through derived indexes utilizing heart rate and blood pressure, two major determinants of MVO2, in the form of the product of heart rate and systolic blood pressure. Although this approach does not encompass all the major determinants of MVO2, changes in the heart rate-blood pressure product bear a close correlation to alterations in directly measured MVO2. Within limits and employed with caution, indirect assessment of MVO2 is useful in elucidating mechanisms of action of extracardiac and intrinsic myocardial factors in the provocation and therapy of angina pectoris.