Introduction:
Myocardial contraction fraction (MCF) is the ratio of left ventricular (LV) stroke volume to myocardial volume, and thus a measure of LV pumping capacity per unit of myocardium. We sought to determine whether MCF measured using current steady-state free precession (SSFP) cardiac magnetic resonance (CMR) sequences was an independent predictor of incident “hard” cardiovascular disease (CVD) events, defined by myocardial infarction (MI), stroke, unstable angina (UA), hospitalized heart failure (HF) or CVD death in a community dwelling cohort initially free of these CVD events.
Methods:
1794 members of the Framingham Heart Study Offspring cohort (aged 65±9 years) underwent CMR between 2002-2006 using a 1.5-Tesla system with contiguous multislice SSFP cine imaging to encompass the left ventricle. MCF was determined from the cine images by a single observer blinded to participant characteristics. We tracked incident hard CVD events over median 6.5-year follow up and used Cox proportional hazards models (adjusted for age, sex, body mass index, systolic blood pressure, diabetes, dyslipidemia, smoking, treatment for hypertension) to determine hazard of hard CVD events per increment (0.10) of MCF.
Results:
MCF was determined in 1776 (99%) Offspring (835 men). Overall, MCF was greater in women (0.92±0.14 vs. 0.78±0.15 for men), p<0.0001. There were 60 incident hard CVD events during follow up. Incident hard events included 26 MI, 2 UA, 13 stroke, 14 hospitalized HF and 5 CVD deaths. Offspring experiencing an incident event had lower MCF (0.78±0.19 vs. 0.86±0.15 for those free of events), p=0.002. On MV-adjusted Cox proportional hazards analyses, a greater MCF was protective against hard CVD events, HR [95% confidence intervals] = 0.76 [0.63 - 0.93] per 0.10 increment of MCF.
Conclusion:
Over 6.5-year follow-up, greater MCF is protective against major adverse CVD events, even after adjustment for traditional CVD risk factors in a community dwelling cohort of middle-aged and older predominantly European-descended adults. Determination of MCF requires only knowledge of LV stroke volume and myocardial volume, both of which are routinely determined in a standard CMR examination of the left ventricle, and thus imposes no additional scan-time or analysis burden. While MCF may be clinically useful for prediction of risk for incident hard CVD events, its potential value in younger age groups and other ethnicities remains to be determined.
Life-course burden of health deficits associates with later-life heart size and function in the 1946 British birth cohort
