Abstract 4189: The Amount of Myocardial Fibrosis by Contrast-Enhanced Magnetic Resonance Imaging Predicts Mortality Late after Aortic Valve Replacement in Patients with Severe Aortic Valve Disease: Validation against Quantitative Histopathology

Abstract

INTRODUCTION: Severe aortic valve disease (AVD) is characterized by progressive accumulation of interstitial myocardial fibrosis (MF). The relationship between the amount of MF and mortality after aortic valve replacement (AVR) surgery in largely unknown. OBJECTIVES: Determine whether the quantitative assessment of MF by delayed-enhanced magnetic resonance imaging (deMRI) can predict mortality late after AVR in patients with severe AVD. METHODS: Fifty-four patients scheduled to undergo AVR surgery were examined by cine and deMRI. From the deMRI dataset, the amount of MF was automatically determined as the sum of pixels with signal intensity (SI) above a threshold value calculated as: mean SI of total myocardium + 2SD of a remote area SI + 2SD of air SI. The remote area was manually delineated in a myocardial region free of hyper-enhancement. In addition, interstitial MF was quantified by histological analysis of myocardial samples obtained during AVR surgery and stained with picrosirius red. Patients were classified in 3 groups according to the degree of MF accumulation. A second deMRI study was performed 27 ± 22 months after surgery to assess LV functional recovery and all patients were followed for 43 ± 23 months to evaluate survival after AVR. RESULTS: There was a good correlation between the values of MF measured by MRI and those obtained by histopathology (r = 0.69; y = −3.10x + 13.0; p < 0.0001). The amount of MF, either by MRI or by histopathology, exhibited a significant inverse correlation with LV ejection fraction before surgery (r = −0.63 e −0.67 respectively; p<0.0001). Additionally, the amount of MF displayed a significant inverse correlation with the degree of LV functional recovery after AVR (r = −0.42, p = 0.04 for histopathology; r = −0.47, p = 0.02 for deMRI). Most importantly, Kaplan-Meier analyses revealed that higher degrees of MF accumulation were associated with worse survival after AVR surgery (log-rank test: χ2=6.32; p=0.01 for histopathology; χ2=5.85; p=0.02 for deMRI). CONCLUSIONS: DeMRI allows for the non-invasive quantification of MF with good accuracy when compared with histopathology in patients with severe AVD. Most importantly, quantification of MF can predict LV functional recovery and all-cause mortality late after AVR surgery.