A Simplified Continuity Equation Approach to the Quantification of Stenotic Bicuspid Aortic Valves using Velocity-Encoded Cardiovascular Magnetic Resonance

Objective: We aimed to compare velocity-encoded cine cardiac magnetic resonance (CMR) with an established echocardiographic method for noninvasive measurement of aortic valve area (AVA) using the continuity equation. Methods and Results: Twenty consecutive young adults with stenotic bicuspid aortic valves were examined with CMR and transthoracic echocar-diography (TTE). CMR AVA was calculated by the continuity equation, dividing stroke volume by the aortic velocity-time integral (VTIAorta), the stroke volume measured both by ventricular volume analysis and by phase contrast velocity mapping at 4 levels (1 subvalvar and 3 supraval-var). Stroke volumes measured at all levels correlated well with those from volumetric analysis. The CMR AVAs calculated using volumetric analysis and VTIAorta from jet velocity mapping cor-related and agreed well with TTE AVA measurements (R2 = 0.83). When CMR AVA was calculated more rapidly using volume flow and VTIAorta both measured from the same trans-jet velocity ac-quisition, R2 was 0.74, with a bias and limits of agreement of 0.02 (-0.44, 0.47) cm2. Conclusions: Continuity equation calculation of the AVA using CMR velocity mapping, with or without ven-tricular volumetric measurement, correlated and agreed well with the comparable and widely accepted TTE approach