Exercise capacity after acute aminophylline administration in angina pectoris

Abstract

Exercise-induced ischemia is generally attributed to an increase in myocardial demand in the presence of coronary stenosis limiting flow supply. An additional mechanism—the occurrence of coronary steal due to excessive endogenous adenosine release—has also been hypothesized. The effect of adenosine receptor blocking by aminophylline in effort ischemia was tested in 8 patients with stable effort-induced angina pectoris, reproducible positive exercise stress tests and angiographically assessed coronary artery disease. Following doubleblind, randomized intravenous infusion of aminophylline (3 mg/kg over 3 minutes) or placebo (20 ml of saline over 3 minutes), the patients underwent upright bicycle exercise stress tests on 2 consecutive days. After aminophylline, there was an increase in work tolerance (aminophylline 7.5 ± 1.8 minutes of exercise vs placebo 5.4 ± 1.5 minutes; p < 0.05). There was a parallel increase in the ischemic threshold, evaluated with the rate-pressure product (mm Hg × beats/min × 100 −2) at 0.1 mV of ST-segment depression (221 ± 35 vs 184 ± 20; p < 0.01). Thus, at a dosage that should effectively inhibit adenosine receptors, aminophylline infusion exerts a beneficial effect on exercise-induced ischemia, possibly through the prevention of myocardial flow maldistribution elicited by excessive adenosine release during effort.