ANGIOTENSIN-CONVERTING ENZYME-INHIBITION IN CHRONIC STABLE ANGINA - EFFECTS ON MYOCARDIAL-ISCHEMIA AND COMPARISON WITH NIFEDIPINE

Objectives-To determine the antiischaemic effects of a new angiotensin converting enzyme inhibitor, benazepril, compared with nifedipine, al one and in combination, in chronic stable angina caused by coronary ar tery disease. Design-Placebo controlled, double blind, latin square de sign. Setting-Regional cardiology service for a mixed urban and rural population. Subjects-40 patients with stable exertional angina produci ng at least 1 mm ST segment depression on exercise test with the Bruce protocol. 34 patients completed all four phases of the trial. Interve ntions-Each patient was treated with placebo, benazepril (10 mg twice daily), nifedipine retard (20 mg twice daily), and a combination of be nazepril and nifedipine in the same doses, in random order for periods of two weeks. Main outcome measures and results-Total duration of exe rcise was not increased by any treatment. Exercise time to the develop ment of 1 mm ST segment depression was not significantly changed with benazepril alone or in combination with nifedipine but was increased w ith nifedipine from 4.18 (1.8) min to 4.99 (1.6) min (95% confidence i nterval (95% CI) 0.28 to 1.34; p < 0.05). There was a significant rela tion between increase in duration of exercise and resting renin concen tration (r = 0.498; p < 0.01). myocardial ischaemia during daily activ ity, as assessed by ambulatory electrocardiographic monitoring, was re duced by benazepril and by the benazepril and nifedipine combination. This was significant for total ischaemic burden (451(628) min v 231(40 8) min; 95% CI -398 to -41 min; p < 0.05) and maximal depth of ST segm ent depression (-2.47(1.2) mm v -2.16 mm; 95% CI 0.04 to 0.57; p < 0.0 5) for the combination and for maximal ST segment depth for benazepril monotherapy (-2.47 (1.2) mm v -1.96(1.2) mm; 95% CI 0.18 to 0.91; p < 0.05). Benazepril significantly altered the circadian rhythm of cardi ac ischaemia, abolishing the peak ischaemic periods at 0700 to 1200 an d 1700 to 2300 (p < 0.05). Conclusions-Benazepril, an angiotensin conv erting enzyme inhibitor, had a modest anti-ischaemic effect in effort angina, but this effect was not as pronounced as with nifedipine. The anti-ischaemic action was more noticeable in asymptomatic ischaemia du ring daily activity, whereas nifedipine had little effect on this aspe ct of myocardial ischaemia. The combination of benazepril and nifedipi ne reduced ischaemia of daily activity.