Estimation of Stroke Volume and Aortic Valve Area in Patients with Aortic Stenosis: A Comparison of Doppler-Echocardiography and Cardiac Magnetic Resonance
Ezequiel Guzzetti, Philippe Pibarot, DVM, PhD, Marie-Annick Clavel, Lionel Tastet, MSc, Mohamed-Salah Annabi, Eric Larose, Romain Capoulade, PhD, Julio Garcia, PhD, Marie Arsenault, Elisabeth Bedard.
IUCPQ, Quebec, QC, Canada.
BACKGROUND: In aortic stenosis (AS), accurate measurement of LV stroke volume (SV) is essential for the calculation of aortic valve area by continuity equation. Furthermore, low flow state, defined as a SV index ≤ 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. The objective of this study was to examine the agreement between SV determined by several Doppler-echocardiographic (DE) and cardiac magnetic resonance (CMR) methods.METHODS: 106 AS patients underwent DE and CMR. SV was estimated by DE from the product of LVOT velocity-time integral and cross-sectional area measured: at the annulus level (SVe1), 2 mm below (SVe2), 5 mm below (SVe3) and 10 mm below annular level (SVe4) and by Simpson biplane method (SVe5). SV was determined by CMR using phase contrast sequences acquired in the aorta at 10 mm above the aortic valve annulus (SVc1; reference method) and volumetric method (difference between LV end-diastolic and end-systolic volumes in short axis cine images) (SVc2). Comparisons of SVs were performed with Bland Altman.RESULTS: Compared to the SV measured by phase contrast CMR (referent; SVc1: 83±16 ml), SVe1 showed the best agreement, while SVe2 and SVe5 had also very good agreement (Table). SVe3 and SVe4 underestimated and SVc2 overestimated SV and therefore AVA. CONCLUSION: Our findings suggest that the DE method using the LVOT diameter measured at (or very close to) the annulus provided the most accurate measure of SV and AVA. On the other hand, the methods using the LVOT diameter measured at 5 to 10 mm below the annulus underestimate, whereas CMR volumetric method overestimate SV and thus AVA.
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