Extracellular volume is an independent predictor of peak cardiac power in asymptomatic patients with moderate-to-severe aortic stenosis

Abstract

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): The PRIMID study was funded by an NIHR fellowship (Post-Doctoral Fellowship supported by the National Institute for Health Research (NIHR-PDF 2011–04–51 Gerald P McCann.) Background Cardiac power (CP) describes the cardiac work done to maintain arterial pressure in the vasculature and peak CP is the ceiling of pumping performance the heart can achieve. Mean pressure gradient adjusted CP (MPG-CP) gives a more accurate representation of afterload in patients with aortic stenosis (AS) but its association with left-ventricular remodelling parameters is unknown. Purpose To establish the determinants of peak MPG-CP in asymptomatic patients with AS. Methods In this prospective, multi-centre observational study, asymptomatic patients with moderate to severe AS underwent echocardiography, cardiovascular magnetic resonance (CMR) imaging and cardiopulmonary exercise testing. Peak MPG-CP was calculated at peak exercise during an incremental symptom-limited exercise test on semi-supine ergometer, using the formula shown (Figure-1). Clinical and imaging univariable and multivariable associations of peak MPG-CP were assessed by linear regression. Results Peak MPG-CP was measured in 86 patients (mean age 66±12 years, 77% male, mean aortic valve area (AVA) 1.08±0.33 cm^2). On univariable analysis, peak MPG-CP was directly correlated with echocardiogram-measured AVA, peak pressure gradient, max velocity, and CMR-measured myocardial perfusion reserve (MPR), LV mass index (LVMI) and LV end-diastolic volume index (LVEDVI), and inversely correlated with extracellular volume (ECV) and NT-proBNP (Table-1). ECV was the only variable independently associated with peak MPG-CP regardless of which measure of AS severity was inputted in the multivariable model. Conclusions ECV, a marker of diffuse interstitial fibrosis, is an independent predictor of peak MPG-CP in asymptomatic patients with moderate-severe AS. Given ECV's role as a prognosticator, CP parameters may be important markers of subclinical disease and serve as surrogates for fibrotic burden and risk-stratification tools in asymptomatic AS.