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CLINICAL STUDY

Anti-ischemic effects of angiotensin- converting enzyme inhibition in hypertension

^a Cardiology Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA

Manuscript received November 15, 2000; revised manuscript received June 11, 2001, accepted June 26, 2001.

Reprint requests and correspondence: Dr. Arshed A. Quyyumi, National Institutes of Health, Cardiology Branch, NHLBI, Building 10, Room 7B15, 10 Center Drive MSC 1650, Bethesda, Maryland 20892-1650
quyyumia{at}nih.gov

OBJECTIVES

We investigated whether augmentation of bradykinin (BK) bioavailability with angiotensin-converting enzyme (ACE) inhibition is associated with reduced exercise-induced myocardial ischemia in hypertension.

BACKGROUND

Bradykinin responses are depressed in hypertension, and endothelial dysfunction contributes to myocardial ischemia by promoting abnormal coronary vasomotion during stress.

METHODS

Fourteen hypertensive (HT) and 17 normotensive (NT), mildly symptomatic patients with coronary artery disease (CAD) and ST-segment depression during exercise were studied before and after seven days of oral enalapril (EN), which was titrated from 2.5 to 20 mg daily. Patients underwent two treadmill exercise tests and determination of forearm vasodilator response to BK.

RESULTS

Despite receiving a lower dose of EN (7.8 vs. 14.8 mg, p < 0.001), NT patients had a significant reduction in blood pressure compared to HT patients. Compared to pre-EN, the ischemic threshold, defined as the rate-pressure product at the onset of 1-mm ST depression (p = 0.045), the duration of exercise to 1-mm ST depression (180 ± 54 s, p = 0.007) and the maximum exercise duration (94 ± 18 s, p < 0.001) were greater after EN in HT patients, but not in NT subjects (all p 0.3). Patients with a greater drop in blood pressure experienced no improvement in exercise-induced ischemia. Forearm blood flow responses to BK were improved with EN in all patients to a similar extent. Moreover, no correlation was observed between the basal response to BK or the magnitude of its improvement with EN and with either the dose of EN or the improvement in exercise ischemic threshold.

CONCLUSIONS

Exercise-induced myocardial ischemia is ameliorated in HT patients with CAD by ACE inhibition.

Abbreviations and Acronyms   ACE = angiotensin-converting enzyme   ANOVA = analysis of variance   BK = bradykinin   CAD = coronary artery disease   ECG = electrocardiogram   EN = enalapril   HT = hypertensive   I/D = insertion-deletion   METs = metabolic equivalents   NO = nitric oxide   NT = normotensive   RPP = rate-pressure product

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