Demonstration of an Imbalance Between Coronary Perfusion and Excessive Load as a Mechanism of Ischemia During Stress in Patients With Aortic Stenosis

Patients with aortic stenosis are susceptible to myocardial ischemia during hemodynamic stress, which may be caused by two mechanisms. First, vascular abnormalities inherent in myocardial hypertrophy may impair coronary vasodilation, limiting the ability to increase coronary blood flow to meet increased metabolic demands. Second, aortic stenosis itself may cause an imbalance between oxygen supply and demand during hemodynamic stress by decreasing aortic pressure (decreasing coronary perfusion or oxygen supply) and increasing left ventricular pressure (increasing oxygen demand). By decreasing aortic valve gradient without immediately altering ventricular hypertrophy, aortic balloon valvuloplasty offers the opportunity to distinguish these mechanisms. We hypothesized that aortic valvuloplasty would improve the balance between myocardial oxygen supply and demand, especially during isoproterenol infusion. Nine patients undergoing aortic balloon valvuloplasty were assessed at baseline and during isoproterenol infusion (5 2 p,g/min, mean+ SD) before and after valvuloplasty. Valvuloplasty increased myocardial oxygen supply. After valvuloplasty, isoproterenol decreased diastolic pressure time index (DPTI) less and increased coronary sinus blood flow more than before valvuloplasty (- 630 367 vs.-292 224 mm Hg.sec/min, p = 0.02 and 53 137 vs. 179 145 ml/min