Stress aortic valve index (SAVI) with dobutamine for low-gradient aortic stenosis: a pilot study

Background: Potentially 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. Methods: A 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. Results: Peak 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). Conclusion: For 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.