Improved working capacity following theophylline infusion in patients with ischaemic heart disease

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Abstract
Summary. The effect of theophylline on the working capacity of patients with ischaemic heart disease was evaluated in a double‐blind, randomized cross‐over study. Eight patients, receiving no medication, with stable effort‐provoked angina pectoris and typical exercise‐induced ST depressions were studied. Following intravenous administration of theophylline or placebo, the patients did a supine leg exercise limited by intolerable chest pain. The workload was continuously increased by 10 W/min. Following theophylline treatment the workload at the onset of chest pain increased from 71 ± 9 to 114 ± 14 W (P< 0·002). The ST depression was less pronounced following theophylline at submaximal exercise (‐0·01 ± 0·00 vs. ‐0·09 ± 0·02 mV, P< 0·005, at 70 W). The maximum tolerable workload increased from 129 ± 15 after placebo infusion to 153 ± 12 W after theophylline infusion P<0·01).It is speculated that this beneficial effect of the adenosine receptor antagonist theophylline may possibly be due to inhibition of a pathophysiological coronary steal induced by elevated levels of adenosine during ischaemia.