Non-invasive pressure-volume loop derived temporal elastance, contractility, and efficiency indices for assessing Duchenne muscular dystrophy patients

Abstract

Ejection fraction is commonly used to assess Duchenne muscular dystrophy-associated cardiomyopathy (DMDAC), but it may remain normal (wrongly) despite significant myocardial dysfunction in patients. Therefore, better indicators of myocardial dysfunction are needed for longitudinal (with time) assessment and treatment of DMDAC patients. This study evaluates non-invasive LV PV loop-derived elastance, contractility and efficiency in relation to EF for patients developing DMDAC. The current retrospective study includes thirty DMDAC patients who underwent two serial CMR imaging from 2014 to 2023. The patients were divided into EF < 55% and EF ≥ 55%. Brachial pressures from cuff sphygmomanometer and CMR short axis steady-state free-precession images for the LV were acquired, and a non-invasive PV loop algorithm based on temporal elastance was used to derive mean elastance, contractility, and efficiency. While mean elastance and contractility showed moderate correlations (r = 0.56, p < 0.01, and r = 0.65, p < 0.001 respectively), efficiency exhibited a strong correlation with EF (r = 0.97, p < 0.01). Importantly, mean elastance, efficiency, and contractility were significantly lower in the EF < 55% group compared to EF ≥ 55% (p < 0.001). Therefore, these indices could serve as viable diagnostic endpoints for longitudinal evaluation of DMDAC.

Keywords: Cardiovascular magnetic resonance (CMR) imaging; Contractility; Duchenne muscular dystrophy; Non-invasive pressure–volume (PV) loop; Temporal elastance; Ventricular efficiency.