Predictors of myocardial fibrosis in aortic stenosis. Evaluation by late-enhanced MRI.

Background: Prior studies have shown that patients with severe aortic stenosis (AS) have myocardial fibrosis secondary to chronic pressure overload. The aim of the present study was to analyze the prevalence of interstitial fibrosis by gadolinium contrast late enhanced (LE) magnetic resonance imaging in a cohort of patients with severe AS, yet without coronary artery disease, and to determine which hemodynamic or echocardiographic parameters predict such LE. Methods: We studied 45 consecutive patients with severe AS (valve area 4 m/s), and clinical indication of valve replacement. Only patients without significant coronary stenosis, history of myocardial infarction or cardiac surgery were considered. All patients underwent LE-MRI and 2D transthoracic echocardiography. Presence and extent of LE, thought to represent myocardial fibrosis was evaluated using an automated detection software (Segment). Significant fibrosis was considered as LE > mean + 2SD of healthy volunteers (i.e. 1% myocardial mass). A logistic regression model was used to evaluate which clinical, hemodynamic and echocardiographic parameters correlated with presence of significant fibrosis in AS. Results: Indexed aortic valve area was 0.36±0.09cm2/m2, aortic valve resistance was 356±270 dyne/s/cm5, energy loss index was 0.42±0.12cm2/m2 and valvulo-arterial impedance was 5.2±2.0mmHg/ml/m2. Significant LE was found in 33% patients with AS (mean LE value 2.65±1.51%), and was predominantly located in inferior segments. By univariate analysis, the only predictive factors for the presence of LE in AS were indexed LV mass (80±26 versus 63±18g/m2, p=0.01) and creatinine level (1.20±0.31 versus 0.99±0.21mg%, p=0.01). In multivariate analysis, only indexed LV mass measured by MRI was found to correlate with presence of LE (p=0.002). Conclusion: Small amounts of LE, indicating diffuse myocardial fibrosis is present in one third of patients with AS without coronary artery disease. Presence of LE is predicted only by severity of hypertrophy resulting from chronic pressure overload in AS