Abstract 3208: Does Myocardial Fibrosis Differ Among Septal Morphologic Subtypes in Hypertrophic Cardiomyopathy?
Background: In hypertrophic cardiomyopathy (HCM), reverse septal curvature is strongly predictive of myofilament HCM, particularly myosin binding protein C- and beta myosin heavy chain-HCM. The aim of this study was to examine the relationship between various septal morphological subtypes and presence of myocardial fibrosis in HCM.
Methods: Cine and contrast-enhanced cardiac magnetic resonance was performed in 100 consecutive patients with HCM. The presence of myocardial fibrosis was determined from myocardial delayed enhancement (MDE) imaging. Cine imaging was used to characterize LV morphological features as follows:
Sigmoid septum; septum being concave toward the LV cavity with a pronounced basal septal bulge
Reverse curvature septum; predominant mid-septal convexity toward the LV cavity, with the cavity having a crescent shape and
Neutral septum; straight or variable septal convexity toward the LV cavity.
Results: The mean age of the patients was 53.4 ± 15.2 years. Overall, 12% had paroxysmal atrial fibrillation, 39% had hypertension and 72% had NYHA class ≥ 2. The septal morphological subtype was reverse curvature in 33%, sigmoid in 26%, and neutral in 41%. MDE was identified in 57%. MDE was present in 32/33 (97%) patients with reverse curvature-HCM, 17/41 (41%) patients with neutral septal contour, and only 8/26 (29%) patients with sigmoidal-HCM. Compared to other morphological subtypes, multivariate analysis showed that MDE-positive status was far more likely in reverse curvature-HCM, (odds ratio, 20.6; p=0.006) (table⇓).
Conclusion: Septal subtype is an independent predictor of the presence of myocardial fibrosis. Given that reverse septal curvature is a strong surrogate for myofilament mutation positive status; these findings suggest that myocardial fibrosis is an almost universal feature of genetically determined myofilament HCM. In contrast, fibrosis is much less common in sigmoidal HCM which rarely stems from a myofilament mutation.