Myocardial contraction fraction predicts all-cause mortality in aortic stenosis

Background Myocardial contraction fraction (MCF) is derived from the ratio of left ventricular stroke volume to myocardial volume – it encompasses comprehensive domains of longitudinal, radial, and circumferential myocardial shortening during ventricular contraction in a single metric; and has been shown to outperform the widely-used LVEF in diagnostic accuracy and survival prediction in disease states of hypertrophic cardiomyopathy (HCM), ATTR (transthyretin) amyloidosis, hypertensive heart disease, and the heart failure spectrum. Purpose In our study, we postulate that MCF is an independent prognostic marker of mortality in moderate–severe aortic stenosis (AS). Methods Between 2011 to 2021, 312 consecutive patients with index echocardiographic diagnoses of moderate to severe aortic stenosis were stratified into 2 groups based on the median cutoff MCF value of 34.4 in our population - namely high MCF (>34.4) and low MCF (< 34.4). Baseline demographics, co-morbidities, echocardiographic findings and clinical outcomes were collected and compared, and statistical analyses performed with construction of a Kaplan-Meier curve and multivariate Cox regression model. Results 162 (51.9%) were female and 195 (62.5%) were Chinese. The mean follow-up duration was over 3.0+2.1 years. 154 (49.3%) had low MCF and 158 (50.7%) patients had high MCF. The mean MCF for the low MCF group was 25.0+7.0 vs. 42.4+6.9 in the high MCF group. The mean stroke volume and mean left ventricular end diastolic volume (LVEDV) was 58.8+21.2ml and 115.8+49.5ml in the low MCF arm vs. 75.3+19.9ml and 113.3+34.9ml in the high MCF arm respectively. The mean left ventricular ejection fraction (LVEF) in the low MCF group was 52.5+14.9% vs. 60.5+12.1% in the high MCF group. A higher proportion of low MCF patients had severe AS at 43.5% compared to a lower proportion of high MCF patients at 25.9%. The mean aortic valve area (AVA) was 0.9+0.3 cm2, mean pressure gradient (MPG) 40.9+17.5mmHg, peak velocity (Vmax) 3.89+0.91m/s and dimensionless index (DI) 0.2+0.1 in the low MCF arm, while the mean AVA was 1.0+0.3 cm2, MPG 33.7+15.2mmHg, Vmax 3.53+0.72m/s, and DI 0.3+0.1 in the high MCF arm. Majority (89.9%) of AS were of calcific or degenerative aetiology across both groups. Higher proportions of low MCF patients had co-existing coronary artery disease (CAD), previous acute myocardial infarction (AMI) and chronic kidney disease (CKD) at 50.0% vs. 27.2% vs. 43.5% and 26.0% vs. 8.2% vs. 30.8% (p<0.025) respectively. On multivariate Cox regression analysis adjusted for age, sex, and comorbidities of AMI, CKD, anaemia, malignancy, and aortic stenosis, low MCF was shown to be a significant independent predictor of worse all-cause mortality (aHR 0.81, CI: 0.68-0.97, p=0.020). Conclusion MCF is a reliable predictor of all-cause mortality for moderate-severe AS patients in our cohort.