Abstract 2241: A Novel Measure of Diffuse Myocardial Fibrosis by Cardiac Magnetic Resonance
Despite the success of cardiac magnetic resonance (CMR) for identification of cohesive scar, its utility for quantification of diffuse myocardial fibrosis is unknown. We hypothesized that delayed enhancement intensity variance (DEIV) predicts conduction system disease due to diffuse myocardial fibrosis in myotonic muscular dystrophy (MMD). Thirty seven patients with MMD underwent CMR. The DEIV of the entire left ventricle was calculated by obtaining the variance of the mean intensity of each of 20 sectors per inversion recovery prepared gradient echo image plane (120 –200 sectors/patient, Medis software). Standard (ECG) and signal averaged electrocardiography (SAECG) with frank orthogonal leads at a sampling rate of 1 kHz/channel and enough QRS complexes to reduce the noise level to <1 microvolt were performed (Norav software). After correcting for potential confounders of DEIV and conduction disease (body mass index, age and left ventricular ejection fraction), DEIV was predictive of QRS duration on ECG (0.261 ms increased QRS duration / unit increase in DEIV, 95% CI 0.153– 0.369). DEIV was also predictive of low amplitude (<40 microvolt) signal duration on SAECG (0.338 ms increased signal duration / unit increase in DEIV, 95% CI 0.049 – 0.627). Ten fold cross validation yielded a receiver operating characteristic area of 0.742 for the predictive value of DEIV on QRS > 120 ms (figure⇓). The DEIV of the entire left ventricle predicts physiologic QRS prolongation due to late depolarization of tissue within islands of patchy fibrosis and may improve the quantification of diffuse myocardial fibrosis in MMD and other cardiomyopathies.