Comparison of doppler-echocardiography and cardiac magnetic resonance estimation of stroke volume and aortic valve area in patients with aortic stenosis

In aortic stenosis (AS), accurate measurement of LV stroke volume (SV) is essential for the calculation of aortic valve area (AVA) by continuity equation. Furthermore, a low flow state (indexed SV≤35 ml/m2) has been shown to be a powerful predictor of adverse outcome. Underestimation of SV may lead to erroneous conclusions regarding AS severity and/or low-flow state. ASE/EACVI AS guidelines suggest that measurement of LV outflow tract (LVOT) diameter at different levels (i.e., annulus or 5-10 mm below) yield similar SV and AVA estimations. Our objectives were to examine the agreement between SV determined by several Doppler-echocardiography (DE) and cardiac magnetic resonance (CMR) methods and to evaluate its repercussion in the prevalence of severe AS and low-flow status. 106 patients with AS were prospectively recruited in the PROGRESSA study and underwent both DE and CMR. SV was estimated by DE from the product of LVOT velocity-time integral and cross-sectional area measured at the annular level and 2, 5 and 10 mm below annular level, as well as by Simpson biplane method. SV was determined by CMR using phase-contrast mapping acquired in the aorta 10 mm above the aortic valve (reference method) and volumetric method (difference between LV end-diastolic and end-systolic volumes). Comparisons were performed with Bland Altman analysis. Table 1 shows the SV and AVA by each measurement method and their bias in relation to the referent method (phase-contrast CMR). Compared to the SV measured by phase contrast CMR, DE measured at the annular level showed the best agreement, while DE 2 mm below annulus and Simpson biplane method had also very good agreement. DE measured 5 and 10 mm below annulus significantly underestimated SV and therefore AVA. CMR volumetric method overestimated both SV and AVA. Prevalence of severe AS and low flow state according to different methods is shown in figure 1. Best agreement was obtained with DE at the annulus or 2 mm below, whereas DE 5 mm and 10 mm below significantly overestimated prevalence of severe AS and low flow status. Our findings suggest that the DE method measuring LVOT diameter at (or very close to) the annulus provided the most accurate measure of SV and AVA and, thus, best estimated AS severity and low-flow status. On the other hand, measuring LVOT diameter 5 to 10 mm below the annulus significantly underestimated SV and AVA and overestimated AS severity and low-flow status.View Large Image Figure ViewerDownload Hi-res image Download (PPT)