Effects of angiotensin-converting enzyme inhibition on exercise-induced angina and ST segment depression in patients with microvascular angina.
OBJECTIVE
This study was conducted to test the hypothesis that angiotensin-converting enzyme inhibition may lessen myocardial ischemia in patients with microvascular angina.


BACKGROUND
Patients with syndrome X (angina pectoris, positive findings on exercise testing and normal coronary arteriogram) have a reduced coronary vasodilator reserve ("microvascular angina") and may show an increased sympathetic drive. Angiotensin-converting enzyme inhibition attenuates sympathetic coronary vasoconstriction in patients with coronary artery disease.


METHODS
Ten patients (seven women and three men, mean age [+/- SD] 53 +/- 6 years) with syndrome X and a reduced coronary flow reserve underwent a randomized, single-blind, crossover, placebo-controlled study of the effects of the angiotensin-converting enzyme inhibitor enalapril on angina and exercise-induced ST segment depression. Assessment was by symptom-limited treadmill exercise testing after 2 weeks of treatment with 10 mg/day of enalapril and after 2 weeks of placebo administration.


RESULTS
All patients had positive findings on exercise testing (> or = 1 mm ST segment depression and angina) while taking placebo, whereas six patients had a positive test result (four with angina) during enalapril therapy. Total exercise duration and time to 1 mm of ST segment depression were prolonged by enalapril over those obtained with placebo (mean 779 +/- 141 vs. 690 +/- 148 s, p = 0.006 and 690 +/- 204 vs. 485 +/- 241 s, p = 0.007, respectively). The magnitude of ST segment depression was also less with enalapril than with placebo (mean 1.1 +/- 0.4 vs. 1.5 +/- 0.2 mm, p = 0.004). Heart rate and blood pressure at peak exercise and at 1 mm of ST depression were not significantly different during placebo and enalapril treatment.


CONCLUSIONS
Angiotensin-converting enzyme inhibition lessens exercise-induced ischemia in patients with syndrome X and microvascular angina, probably by a direct modulation of coronary microvascular tone, which results in an increased myocardial oxygen supply.
Kaski
J C
JC
Department of Cardiological Sciences, St. George's Hospital Medical School, London, England, United Kingdom.
Rosano
G
G
Gavrielides
S
S
Chen
L
L
D003326:Coronary Circulation / Q000187:drug effects; D004562:Electrocardiography / Q000379:methods*; D004656:Enalapril / Q000627:therapeutic use*; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D006439:Hemodynamics / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008297:Male; D017566:Microvascular Angina / Q000175:diagnosis / Q000188:drug therapy* / Q000503:physiopathology; D008875:Middle Aged; D012815:Signal Processing, Computer-Assisted; D016037:Single-Blind Method
D004656:Enalapril