Effects of bamiphylline on exercise testing in patients with syndrome X

An abnormal stimulation of adenosine A₁-receptors has been suggested to play a role in the pathogenesis of both chest pain and ischemia-like electrocardiographic changes in patients with syndrome X and a nonselective adenosine antagonist (theophylline) has been reported to be beneficial in these patients. In this study we investigated the acute effects of bamiphylline, a specific A₁-receptor antagonist, in 16 patients with syndrome X (14 women, age 57 ± 6 years), with both angina and ST-segment depression inducible during exercise testing. All patients underwent two treadmill exercise tests (Bruce modified protocol) on 2 separate days, 5 minutes after the end of randomized intravenous infusion of either placebo (saline solution) or bamiphylline (300 mg). Severity of chest pain was assessed by a 10 mm visual analogic scale. There were no significant differences in resting heart rate and blood pressure after bamiphylline or placebo. Rate-pressure product (20600 ± 5000 vs 20200 ± 5200 bpm · mmHg), time to 1 mm ST depression (549 ± 196 vs 581 ± 201 sec), time to angina (519 ± 209 vs 571 ± 196 sec), and exercise duration (717 ± 134 vs 676 ± 166 sec) were also not significantly different after bamiphylline or placebo, but there was a mild reduction of the severity of exercise-induced chest pain (30 ± 22 vs 39 ± 20 mm, p <0.05) with the active drug. Thus, in patients with syndrome X, bamiphylline does not improve exercise-induced ST changes, suggesting that A₁-receptors are not significantly involved in their appearance. In addition, bamiphylline had little effect on anginal pain, suggesting that this cannot be mediated exclusively by A₁-receptor stimulation in these patients.