Evaluation of isoproterenol as a method of stress testing

Thirty-five patients undergoing diagnostic coronary arteriography were evaluated before catheterization by both a standard treadmill exercise test and by the intravenous infusion of isoproterenol in a concentration of 0.2 mg. per 100 c.c. of 5 per cent dextrose/water at a rate of 1 to 2 μg per minute. S-T segment depression of 1 mm. or greater of the ischemic type was considered to be a positive test. The isoproterenol test was comparable to the treadmill exercise test in predicting the presence or absence of coronary artery disease (71 per cent correct predictions with the isoproterenol test versus 68 per cent with the treadmill test) and was administered safely and easily. The isoproterenol test had several advantages: (1) the baseline is stable and the intraprocedure ECG can be more easily monitored; (2) the test can be applied in situations where exercise is impossible, for example, when a patient had severe claudication, incapacitating pulmonary disease, etc.; (3) other monitoring such as phonocardiograms, blood pressure, etc., can be easily obtained; and (4) cardiac catheterization is not required in contrast to stress by atrial pacing. The isoproterenol test would appear to have a useful role in the clinical assessment of coronary artery disease.