Abstract 15422: Diffuse Myocardial Fibrosis Predicts Outcome in Moderate and Asymptomatic Severe Aortic Stenosis

Abstract

Introduction: Patients with moderate or asymptomatic severe aortic stenosis (AS) are at increased risk of cardiovascular events, but markers to guide intervention are lacking. We investigated the use of cardiovascular magnetic resonance (CMR) to identify drivers of outcome. Methods: Moderate (aortic valve area [AVA] 1.0-1.5 cm2) or asymptomatic severe AS patients (AVA≤1.0 cm2 and NYHA functional class I-II) (n=457) were prospectively enrolled from five international sites and parameters including extracellular volume fraction (ECV%) and late gadolinium enhancement were analyzed on CMR. Clinical events were defined as all-cause mortality and admission for heart failure. Results: Moderate AS patients had smaller left ventricular (LV) mass and less diastolic dysfunction compared to asymptomatic severe AS patients, but showed no difference in the extent of myocardial fibrosis and scar. During median 5.7-years follow-up, 83 clinical events occurred. Patients with clinical events had smaller AVA, greater diastolic dysfunction, and higher ECV% (median [interquartile range] ECV% 26.3% [24.3-29.8] vs 28.2% [25.5-30.8], P=0.003). There was a stepwise increase of clinical events across ECV tertiles. ECV% was associated with clinical outcome (adjusted HR 1.05, 95% CI 1.00–1.09, P=0.035), independent of AVA and aortic valve replacement as a time-dependent covariate. The prognostic significance of ECV% was consistent when AS severity was alternatively defined using aortic peak velocity and mean pressure gradient, and also across subgroups by AS severity and symptoms, AVA, aortic peak velocity, mean pressure gradient, and left ventricular ejection fraction (Figure). Conclusions: Increased diffuse myocardial fibrosis is associated with poor outcomes in moderate and asymptomatic severe AS patients and can help identify those who require closer surveillance and possibly earlier intervention.