Abstract 695: Significant Hypertrophy and Reduced Systolic Function Predict Intramyocardial Fibrosis in Patients with Hypertrophic Cardiomyopathy Undergoing Cardiac Magnetic Resonance Imaging

Abstract

Background: Contrast enhanced magnetic resonance imaging (CE-MRI) is a useful tool to define cardiac morphology, systolic function, and the presence of late gadolinium enhancement (LGE). In patients (pts) with hypertrophic cardiomyopathy (HCM), LGE may represent intra-myocardial fibrosis. We explored the association between left ventricular (LV) morphology and function to the presence and amount of LGE in pts with HCM. Methods: 424 HCM pts (age = 55 ± 16 years, 41% females), without prior history of septal ablation/myectomy, underwent CE-MRI (GE 1.5T) during a 6-year period. LV volumes, diameter, ejection fraction (EF), septal shape and thickness, and the presence of obstructive physiology were assessed from standard steady state free precession pulse sequences. The presence and amount of LGE were traced from a dynamic post contrast inversion recovery pulse sequence. Morphologic and functional findings were then compared with presence and amount of LGE. Results: Over half of the pts [239/424 (56%)] had LGE, most commonly localizing to RV insertion points [174/239 pts, (73%)]. The extent of LGE ranged from 0.4–65% of LV mass. Univariate (morphologic) predictors of LGE were: reverse curve septal shape [OR = 7.8, (95% CI, 3.9–15.6)], septal thickness ≥ 16 mm (OR = 4.5, 2.4–8.2), LV mass ≥ 150 grams (OR = 2.6, 1.7–3.8)], LVEF<50% (OR = 4.6, 1.3–16), and presence of obstructive physiology (OR = 1.8, 1.02–3). The percentage of LV mass involved with LGE increased with higher LV mass, increased septal wall thickness, and decreasing LVEF (Spearman rank = 0.2– 0.4, p<0.0001 for all). Multivariate analysis (adjusting for all morphologic and functional parameters) showed that septal thickness ≥ 16mm (p = 0.0001), LV mass ≥ 150 grams (p = 0.01) and LVEF < 50% (p = 0.02) were independent predictors of LGE on CE-MRI. Conclusions: LGE, as determined by CE-MRI, was seen in over half of the patients with HCM. Decreased LVEF, increased septal thickness, and increased LV mass were associated with the presence of LGE. The clinical and prognostic impact of these morphological features warrants further investigation.