Determination of coronary reserve in patients with supravalvular aortic stenosis.

Coronary reserve in patients with supravalvular aortic stenosis may be limited by coronary artery ostial obstruction or left ventricular hypertrophy. To assess the relative effect of these two factors on coronary reserve, seven patients with supravalvular aortic stenosis were studied intraoperatively before and after repair. Six patients who underwent elective cardiac surgery for conditions that did not involve the left ventricle or the left anterior ascending coronary artery served as controls (control group 1). Four patients were studied before and after cardiopulmonary bypass to determine if cardiopulmonary bypass altered coronary reserve in normal vessels perfusing normal ventricle (control group 2). Using a pulsed Doppler probe to determine coronary velocity, coronary reactive hyperemia was induced in the left anterior descending coronary artery (patients with supravalvular aortic stenosis and group 1 controls) or right ventricular branches of the right coronary artery (group 2 controls) during maximal coronary dilation produced by a 20-second coronary occlusion. All patients with supravalvular aortic stenosis underwent patch aortoplasty to relieve left coronary artery ostial obstruction and outflow tract obstruction; three patients also underwent aortic valvotomy and one patient also underwent valve replacement. Coronary reactive hyperemia was calculated as the ratio of peak to resting velocity. This ratio was 5.0 +/- 0.6 (mean +/- SEM) preoperatively and 3.6 +/- 0.3 postoperatively in control group 2. Thus, coronary reserve was only modestly reduced after cardiopulmonary bypass. Before repair, the ratio of peak to resting velocity was markedly reduced in patients with supravalvular aortic stenosis compared with control group 1 (1.8 +/- 0.3 vs 4.9 +/- 0.5, p less than 0.05) and did not change after repair (1.7 +/- 0.2), even though the aortic gradient was reduced (80 +/- 14 vs 38 +/- 6 mm Hg, p less than 0.05) and real or potential coronary ostial obstruction was eliminated by the operation. Because coronary reserve did not improve after surgery in patients with supravalvular aortic stenosis, we conclude that left ventricular hypertrophy is probably the primary determinant of decreased coronary reserve in these patients.