Abstract 19115: Cardiac MR Evaluation of Diffuse Myocardial Fibrosis in Children and Young Adults with Congenital Aortic Stenosis

Abstract

Background: Diffuse myocardial fibrosis (DF) in adults with aortic stenosis (AS) is associated with heart failure, arrhythmias, and mortality; however, little is known about its role in younger patients with congenital AS. Study aims were to apply for the first time a recently validated cardiac magnetic resonance (CMR) extracellular volume fraction (Vec) measurement technique to quantify DF in children and young adults with AS and to explore associations between DF and indices of diastolic function. Methods: All pts who had a CMR with myocardial T1 measurement, were <30 yrs, and had congenital AS with a peak Doppler gradient ≥20 mm Hg at any time prior to the CMR were included. The Vec, a measure of DF, was calculated in the mid-LV by measuring T1 values for blood pool and myocardium before and after gadolinium with a modified Look-Locker technique, and adjusting for hematocrit. Vec results were compared to published values in healthy volunteers (n=14). Results: Thirty-five pts met inclusion criteria with a median age of 15 yrs (1.7-27), peak AS gradient of 36 mm Hg (0-90), and aortic regurgitation (AR) fraction by CMR of 25% (0-48). Vec was significantly greater in AS pts than volunteers (0.29 ± 0.06 (range, 0.22-0.48) vs. 0.25 ± 0.02 (range, 0.22-0.28), p<0.001) with 13 pts (37%) having an increased Vec (>0.28). Factors associated with higher Vec included any AS intervention (p=0.031), late gadolinium enhancement (p=0.028), and younger age at CMR (r=-0.37, p=0.031). Vec was not significantly associated with AS gradient, AR fraction, indexed LV mass, mass/volume ratio, or ejection fraction at the time of CMR, or a history of cardiac surgery. Increased Vec was significantly correlated with echo indices of diastolic dysfunction: E’ (r=-0.55, p=0.002), E/E’ (r=0.62, p<0.001), and indexed LA volume (r=0.56, p=0.001). In the 24 pts with contemporaneous cath data, Vec did not correlate with LV end-diastolic pressure (r=0.09, p=0.72). Conclusions: In this cohort of children and young adults with congenital AS, an elevated Vec indicating DF was present in approximately one-third. Increased Vec was associated with aortic valve interventions, late gadolinium enhancement, and echo indices of diastolic dysfunction. For congenital AS, therapies to reverse DF may be warranted.