P92 A novel method of correcting the left ventricular stroke volume by Doppler echocardiography: comparison with multidetector computed tomography

Background Although transthoracic Doppler echocardiography is widely used for estimating left ventricular stroke volume (SV), accelerated blood flow in the left ventricular (LV) outflow tract may lead to overestimation. SV can be calculated accurately from left ventricular end-systolic and end-diastolic volume determined by multi-detector computed tomography (MDCT). However, radiation exposure as well as the use of contrast medium hampers its routine use. Purpose The purpose of this study was to examine whether the correction of SV measured by pulsed wave Doppler echocardiography (SVdop) can accurately predicts SV obtained by MDCT (SVct). Methods： We enrolled consecutive 61 patients who underwent both MDCT and transthoracic echocardiography. Patients with moderate or severe valvular diseases and valve replacement surgery were excluded. Correction of SV was explored with SVct as a reference. Results： Univariate analysis showed that SVdop (r = 0.42, P = 0.0007) and patient age (r=-0.50, P < 0.0001) were significantly correlated with SVct. On the other hand, left ventricular ejection fraction calculated by Teicholz method (EFteich) (r = 0.19, P = 0.14), systolic blood pressure (r = 0.07, P = NS), and LV mass index (r=-0.02, P = NS) were not correlated with SVct. Multivariate analysis showed that SVdop, patient age and EFteich were the independent predictive factors for SVct (R2 = 0.49, P < 0.0001). Based on these correlations, we postulated SV as: corrected SV = SVdop × 0.40 + EFteich × 0.46 – age × 0.67 + 44.77. As expected, the correlation between corrected SV and SVct significantly improved (r = 0.70, P < 0.0001). Bland-Altman plot analysis showed that corrected SV significantly reduced the variation between SVdop and SVct, and diminished the overestimation of SVdop (Figure). Conclusion： The new correction formula of SVdop may correct the overestimation of SV obtained by pulsed wave Doppler echocardiography, although the formula remains to be validated in a separate cohort of patients. Abstract P92 Figure

P613Cardiac magnetic resonance imaging derived left ventricular mechanical function in patients with atrial fibrillation and left atrial low voltage zones

Background The relation of left atrial low voltage zones (LVZ) to left ventricular function in patients undergoing pulmonary vein isolation (PVI) is not known. Objective To explore the relationship of left atrial low voltage zones (LVZ) on left ventricular function in patients with atrial fibrillation. Methods From June to Nov. 2018, 107 (mean age 67y, 70 men, 73 persistent AF) consecutive patients with symptomatic AF underwent a PVI with LVZ mapping. Before PVI the left ventricular ejection fraction (EF) and stroke volume (SV) were measured by cardiac magnetic resonance imaging (CMR). From feature-tracking of CMR-cine images left ventricular global, systolic and diastolic longitudinal strains (GLS), circumferential strains (GCS) and radial strains (GRS) were calculated. Results Of 59 patients CMR scanning in sinus rhythm was performed, LVZ were present in 24 patients. LVEF was significantly lower in patients with left atrial LVZ (62±9% vs. 55±15%) (p=0,03). Left ventricular stroke volume was significantly decreased by the extent of LVZ (94±23 vs. 72±21ml), (p=0,03). The left ventricular diastolic strains during ventricular filling (caused by atrial contraction) of GLS (r=−0,52), GCS (r=−0,65) and GRS (r=−0,65) were highly signifcantly correlated to the occurence and extent of LVZ (each p<0,001 respectively). The only systolic ventricular strain was GLS, which decreased (r=−0,3, p=0,03) by the occurance of atrial low voltage. Conclusion The active, atrial part of diastolic left ventricular filling properties is impaired by the occurrence and extent of left atrial LVZ. In patients with left atrial LVZ the left ventricular stroke volume and ejection fraction is decreased already in sinus rhythm. It seems possible that atrial mechanical dysfunction and presence of atrial low voltage maybe predicted by LV diastolic strain analysis.

P5874D Flow cardiac magnetic resonance quantification of mitral regurgitation, comparison with transthoracic echocardiography

Background Mitral valve regurgitation (MR) is currently primarily assessed by a multiparametric approach with transthoracic echocardiography (TTE) that can be further completed by 2D Cardiac Magnetic Resonance (2D CMR) in case of doubt or poor acoustic window. TTE and 2D CMR have nevertheless imperfect agreement in terms of MR quantification. Time-resolved phase-contrast cardiac magnetic resonance imaging with flow-encoding in three spatial directions (4D Flow CMR) could help in MR quantification. Purpose Compare 4D Flow CMR quantification of MR with TTE using a multiparametric approach. Methods We conducted a monocentric, prospective study at the Institut Mutualiste Montsouris in Paris between November 2016 and 2017 including patients with chronic primitive MR. MR was evaluated with a multiparametric approach by two cardiologists with TTE and quantitatively by two radiologists with 4D Flow CMR. MR was classified as mild, moderate or severe and evaluated blindly with consensus in case of disagreement. 4D Flow CMR measurements consisted in quantifying MR regurgitant volume (RV) and MR regurgitant fraction (RF). 4D anterograde mitral flow was compared to left ventricular stroke volume using 2D-cine CMR. Results 33 patients were included. Inter-observer agreement was good in TTE (kappa= 0.75 95% CI [0.57- 0.92]) and excellent in 4D Flow CMR (ICC= 0.94 95% CI [0.79–0.95]). Agreement with TTE was excellent using optimized thresholds (Mild: RV≤20mL RF≤20%, Moderate: RV=21–39mL RF=21–36%, Severe: RV≥40mL RF≥37%): kappa= 0.93 95% CI [0.8–1] for RV and kappa= 0.90 95% CI [0.7–0.9] for RF. A validation cohort confirmed that the 4D flow thresholds as determined were accurate for MR grading. Agreement between 4D anterograde mitral flow and 2D-cine CMR left ventricular stroke volume was also excellent (ICC= 0.92 95% CI [0.85–0.96]). Conclusion 4D Flow CMR is a reliable tool for MR quantification. It provides direct quantitative evaluation of MR with low inter-observer variability. It may therefore be used as a gatekeeper before therapeutic decisions such as surgery.