Can Aminophylline Improve Exercise Capacity in Patients with Coronary Artery Disease?
Aminophylline (Am) a potent adenosine receptor blocker, may increase transmural blood flow in the ischemic myocardium by preventing the maldistribution of coronary flow, although this agent is known to elevate myocardial oxygen consumption. To determine whether aminophylline does have this action, symptom-limited ramp-fashioned treadmill stress testing, combined with gas exchange analysis, was performed in 20 patients with coronary heart disease. In the first stress testing, Am (7 mg/kg) was administered over a 20-min period just before exercise. The second stress testing, the control study, was carried out without Am. There were no significant differences in basal heart rate, systolic blood pressure, rate-pressure product or oxygen consumption (VO2) before exercise, in the two studies with without Am. After the administration of Am, heart rate increased (72 ± 13 to 80 ± 16 bpm; mean ± SD, P < 0.05), as did rate-pressure product (96 ± 28 to 108 ± 33 mmHg × bpm × 100, P < 0.05), although the systolic blood pressure and VO2 did not show significant changes. During exercise, Am effected a significant increase in exercise duration (8.9 ± 2.6 versus 10.4 ± 2.8 min, P < 0.01). The rate-pressure product recorded at peak exercise was also significantly higher after Am (212 ± 56 versus 251 ± 74 mmHg × bpm × 100, P < 0.05). However, there was no significant difference in ST segment change in ECG at the end-point of exercise between the two study groups, with and without Am. Moreover, exercise maximal VO2 (20.5 ±5.1 versus 21.6 ± 6.5 ml/min) and anaerobic threshold (14.8 ± 2.7 versus 14.8 ± 2.8 ml/min) were not significantly different in the two study groups. These findings indicate that administration of Am to patients with coronary artery disease does not induce deterioration, but rather improves exercise capacity.