CMR derived ventricular arterial coupling in hypertrophic cardiomyopathy

Abstract

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Ventriculoarterial coupling (VAC) is an important surrogate measurement of global cardiovascular efficiency. However, up till recently, this measurement has been rarely used in clinical practice. This could be due to its invasive nature, and the relatively complex methods required for acquisition and interpretation. We here describe a noninvasive method of measuring VA coupling using cardiac magnetic resonance (CMR) in a cohort of hypertrophic cardiomyopathy (HCM). Methods Cardiac MRI was performed in 61 patients with hypertrophic obstructive cardiomyopathy (HOCM) before and after undergoing extended surgical myectomy. Cardiac MRIs from 15 patients with non-obstructive HCM were also included for comparison. Hypertensive patients were excluded from this study. Vitals signs were recorded during each MRI study. Arterial end-systolic pressure (AESP) was determined non-invasively as previously described (0.9x brachial blood pressure). Left ventricular end-systolic pressure (LVESP) was calculated by adding the echo-derived peak systolic gradient across the left ventricular outflow tract to the arterial end-systolic pressure. Indexed stroke volume (SVI) in the ascending aorta as well as indexed end systolic volume (ESVI) were calculated from CMR. Indexed arterial (Ea) and ventricular (Ev) elastance were calculated as AESP/SVI and LVESP/ESVI. VA coupling was then calculated as Ea/Ev. Results Compared to the baseline measurements, VAC increased significantly post myectomy (mean VAC pre-myectomy and post-myectomy 0.38 vs. versus 0.62 respectively, p= 0.00001). VAC in non-obstructive HCM patients (mean = 0.64) was statistically similar to that in post-myectomy (p = 0.82) and statistically different from pre-myectomy (p = 0.00016). The mean of LVOTO gradients post- and pre-myectomy were significantly different (p = 0.00001). Significant correlation of the delta-VAC with the delta gradient in the LVOTO was found (r= 0.35, p = 0.005). Conclusion Non-invasive assessment of VA coupling using CMR is feasible and could be a useful tool in the evaluation of patients with various cardiovascular disorders. Further studies with larger numbers of patients are required to establish the utility of this method in clinical practice.