Abstract 17388: Cardiac MRI Derived Forward Stroke Energy is a Better Index of Left Ventricular Pump Function over Ejection Fraction in Mitral Regurgitation

Abstract

Introduction: Mitral regurgitation (MR) into the low impedance left atrium (LA) enables a pop off valve effect and enables a false low end-diastolic volume and increased ejection fraction (EF). EF in these patients seems falsely high even though their ventricular contraction seems impaired, thus better indices that represent ventricular contraction are required in this lesion. Hypothesis: In this study we sought to investigate if forward stroke energy (FSE), which represents the forward kinetic energy of the blood through the aortic valve is a better indicator of ventricular contraction than EF. Methods: Phase-contrast MRI was performed in patients with MR (n=63; Mild MR =23; Moderate-severe MR=40), at the aortic and mitral valve planes, to compute the transvalvular through-plane flow. EF was measured as ((end-diastolic volume- end systolic volume)/end-diastolic volume), and FSE as (forward aortic stroke volume X mean arterial pressure). LV contractility was computed as the dynamic myocardial wall thickening over the cardiac cycle. Results: Regional peak wall thickening was significantly reduced in the moderate-severe MR groups - equatorial sector (5.9±0.6mm vs. 4.3±0.4mm, p=0.02) and apical sector (6.4±0.5mm vs. 4.5±0.3mm, p=0.003), indicating LV dysfunction with higher MR severity. EF did not capture this difference in LV contraction between the groups (50.1±3.7% vs. 48.3±3.2%, p=0.72). However, FSE demonstrated a significant difference between the two groups and a significant negative correlation (6527±483 mmHg.mL vs. 4895±282 mmHg.mL, p=0.002, r(MRfraction)=-0.42, p=0.0007). Conclusions: Forward stroke energy may better capture reduced myocardial contractility in the setting of MR, than EF - the current clinical gold standard.