Myocardial Contraction fraction for risk stratification in low-gradient aortic stenosis with preserved ejection fraction

Abstract

Myocardial contraction fraction(MCF), the ratio of stroke volume to myocardial volume is a volumetric measure of myocardial shortening and thickening independent of left ventricular size and geometry. The prognostic value of MCF in low-gradient severe aortic stenosis with preserved ejection fraction(LGSAS-PEF) is unknown. We included 643 patients with LGSAS-PEF in whom MCF was computed at baseline and analyzed mortality during follow-up. Throughout follow-up with medical and surgical management [median: 34.9(16.1–65.3) months], lower MCF tertiles had higher mortality than the highest tertile. 80-month survival was 56 ± 4% for MCF > 41%, 41 ± 4% for MCF 30–41%, and 40 ± 4% for MCF < 30% ( P < 0.001). After comprehensive adjustment, mortality risk remained high for MCF 30–41% [HR 1.53(1.08–2.18)] and for MCF < 30% [HR 1.82(1.24–2.66)] versus MCF > 41%. The optimal MCF cut-off point for mortality prediction was 41%. Age, body mass index, Charlson index, peak aortic jet velocity, and LVEF were independently associated with mortality. MCF (chi-square to improve 10.39; P = 0.001), provided greater additional prognostic value ( P < 0.01) over the baseline parameters than SV index (chi-square to improve 5.41; P = 0.04), left ventricular mass index (Chi 2 to improve 2.15; P = 0.14) or global longitudinal strain (chi-square to improve 3.67; P = 0.06). MCF [HR 0.97(0.96–0.98), P < 0.001 per 1% MCF increment] outperformed ejection fraction for mortality prediction. When patients were classified by SV index and MCF, mortality risk was low for the subgroup with SV index ≥ 30 ml/m 2 and MCF > 41%, higher for patients with SV index ≥ 30 ml/m 2 and MCF ≤ 41% [adjusted HR 1.47 (1.05–2.07)] and extremely high for patients with SV index < 30 ml/m 2 [adjusted HR 2.29 (1.45–3.62)] ( Fig. 1 ). MCF is a valuable risk marker in LGSAS-PEF and could improve clinical decision-making, especially for patients with normal-flow. Survival curves.