Non-invasive Assessment of the Severity of Aortic Stenosis by Doppler Derived Aortic Valve Coefficient: A Retrospective Feasibility Study in Humans

Abstract

Background: Accurate assessment of the severity of stenosis is critical in patients with aortic stenosis. The ambiguities and imprecisions of the current diagnostic parameters can result in sub-optimal clinical decisions. In this feasibility study, we investigate the functional diagnostic parameter AVC (Aortic Valve coefficient: ratio of the total transvalvular pressure drop to the proximal dynamic pressure) in the non-invasive assessment of the severity of aortic stenosis by correlating with the current diagnostic parameters. Methods and Results: AVC was calculated using Doppler measured diagnostic parameters obtained from retrospective chart reviews. A theoretical pressure recovery correction was applied to the pressure drop calculated from Doppler measurements to obtain AVC. A statistically significant and strong combined linear correlation (r = 0.93, p<0.001) of AVC with the transvalvular pressure drop and the left ventricular outflow tract velocity was observed. The mean values of AVC were shown to better delineate moderate and severe stenosis (54% difference) than the mean values of Doppler measured pressure drop and aortic valve area (22% and 25% difference, respectively), when the patients were categorized based on the catheterization measured pressure drop. Conclusion: The feasibility of using pressure and flow measurements obtained from Doppler measurements in a single combined diagnostic index for the assessment of aortic stenosis severity has been evaluated. The nondimensional clinical parameter, AVC, is expected to account for the variation in flow and pressure drop and thus improve the delineation of different grades of aortic stenosis. AVC must be further evaluated in a controlled prospective study.