Stress Aortic Valve Index (SAVI) with Dobutamine for Low-Gradient Aortic Stenosis: A Pilot Study

BackgroundPotentially some patients have symptoms that arise from their low-gradient aortic valve stenosis (AS). Comprehensive valve physiology with dobutamine stress remains incompletely characterized in this population.MethodsA cohort of 18 subjects with low-gradient AS underwent graded dobutamine infusion with invasive assessment using 0.014” pressure wires. A subset of 4 subjects received thermodilution cardiac output assessment at each stage.ResultsPeak dobutamine hemodynamics could not be predicted from clinical or baseline parameters, reflecting statistically the physiologic heterogeneity of the measured pressure loss versus flow curves. While 0 subjects had a baseline aortic/left ventricular pressure ratio during ejection <0.71, 7 of 18 subjects (39%) achieved a ratio during peak dobutamine (the so-called stress aortic valve index, SAVI) below this threshold derived from a prior study of patients undergoing routine transcatheter aortic valve implantation (TAVI).ConclusionFor low-gradient AS, the hemodynamic changes from resting to peak dobutamine conditions cannot be predicted in advance due to pressure loss versus flow curve heterogeneity. A sizable minority of low-gradient AS reaches a severity during dobutamine stress equivalent to patients undergoing TAVI for established benefit. Whether this subset receives similar clinical advantage remains an unproven but natural hypothesis raised by our study.