Vasoconstriction of stenotic coronary arteries during dynamic exercise in patients with classic angina pectoris : reversibility by nitroglycerin JONATHAN

To study the vasomotility of normal and diseased coronary arteries during dynamic exercise, symptom-limited supine bicycle exercise during cardiac catheterization was performed by 18 patients with classic angina pectoris. The cardiovascular response was assessed by hemodynamic measurements and computer-assisted determination of normal and stenotic coronary artery luminal areas from biplane coronary angiograms made before, during, and after exercise. After baseline measurements were recorded, 12 patients (group 1) performed bicycle exercise for 3.4 min (mean), reaching a maximum workload of 81 W (mean); at the end of exercise they received 1.6 mg sublingual nitroglycerin. After measurements at rest in six other patients (group 2), 0.1 mg intracoronary nitroglycerin was given, followed by exercise (3.8 min, 96 W; NS) and sublingual nitroglycerin as in group 1. During exercise in group 1, luminal area of the coronary stenosis decreased to 71% of resting levels (p < .001), while area of the normal coronary artery increased to 123% of control (p < .001). After sublingual nitroglycerin at the end of exercise, area of the normal vessel further increased to 140% of control (p < .001), while luminal area of the stenosis dilated to 112% of resting levels (p < .001 vs exercise, NS vs rest). Pretreatment with intracoronary nitroglycerin increased both normal (121%; p < .05) and stenotic (122%; p < .05) luminal areas, while preventing the previously observed narrowing of stenosis during exercise (114%; NS). Exercise resulted in a similar heart rate-systolic pressure product and caused angina pectoris in two-thirds of the patients in each group. However, patients pretreated with intracoronary nitroglycerin (group 2) had a lower mean pulmonary arterial pressure during maximum exercise (35 mm Hg) than those patients (group 1) not receiving pretreatment (47 mm Hg; p < .001). Group 2 patients reached a percentage of their predicted work capacity (65%) that was about the same as that during previous upright bicycle exercise (71 %; NS), while group 1 patients had a significantly lower work capacity (51% of predicted) than that before catheterization (82%; p < .001). Hence, narrowing of coronary artery stenosis during dynamic exercise is attributable to active vasoconstriction due to its reversibility by preexercise intracoronary nitroglycerin. Patients who did not experience narrowing of stenosis during exercise (group 2) had less evidence of myocardial ischemia (lower mean pulmonary arterial pressure) and maintained their work capacity. This indicates that vasoconstriction of coronary artery stenosis can be an important mechanism in causing myocardial ischemia during dynamic exercise in patients with classic angina pectoris. Circulation 73, No. 5, 865476, 1986. CORONARY ARTERY STENOSIS is being viewed to an increasing extent as a dynamic element in the induction of myocardial ischemia. ' The occurrence of spasm at the site of coronary artery disease has been From the Medical Policlinic, Cardiology, University Hospital, Zurich, Switzerland. Supported by a grant from the Swiss National Science Foundation. Address for correspondence: Otto M. Hess, M.D., Medical Policlinic, Cardiology, University Hospital, 100 Raemistrasse, 8091 Zurich, Switzerland. Received June 18, 1985; revision accepted Dec. 27, 1985. *Present address: Cardiology Section, Yale-New Haven Hospital, 333 Cedar St., 3 FMP, New Haven, CT 06510. Vol. 73, No. 5, May 1986 well documented at rest2' 3 and during exercise" in patients with Prinzmetal's angina pectoris accompanied by ST segment elevation. In contrast, classic angina pectoris has been presumed to be caused by an increase in myocardial oxygen demand relative to a coronary blood supply limited by a fixed stenosis.7 The ability of a coronary stenosis to change in size is predicated on the presence of an intact musculoelastic wall segment within the stenosis. Autopsy series have documented compliant tissue arcs of at least 30 degrees in over 70% of stenoses of greater than 50% severity.8' 9 Brown et al.10 have suggested that active vaso865 by gest on A ril 2, 2017 http://ciajournals.org/ D ow nladed from