Abstract 14941: Left Ventricular Apico-Basal Muscle Bundle Identified by Cardiovascular Magnetic Resonance Imaging in Patients with Hypertrophic Cardiomyopathy: Implications for Diagnosis and Management
Background: Cardiovascular magnetic resonance (CMR) has expanded our appreciation for the diverse myocardial phenotype of hypertrophic cardiomyopathy (HCM), including unique pattern of left ventricular (LV) hypertrophy, apical aneurysms, myocardial crypts and papillary muscle architecture. We sought to characterize the prevalence and clinical significance of a recently identified accessory LV muscle bundle extending from the apex and inserting into the basal septum or anterior wall (ie., apico-basal) in a large cohort of HCM patients.
Methods: CMR was performed on 230 genotyped HCM patients (maximal wall thickness ≥ 15mm; 48 ± 15 years, 69% male), 30 genotype positive/phenotype negative (G+/P-) HCM family members (32 ± 15 years, 30% male), 126 healthy controls (41 ± 17 years, 55% male).
Results: LV apico-basal muscle bundle was identified in: 145/230 (63%) HCM patients, 18/30 (60%) G+/P- HCM family members (p=0.96); and in 12/126 (10%) healthy controls (p<0.01 controls vs HCM patients and G+/P- HCM family members, respectively). Among HCM patients, no relationship was found between the presence of LV apico-basal muscle bundle and a number of relevant HCM disease variables including: age (49 ± 15 years vs 47 ± 15 years, p=0.28), positive genotype (32% vs 31%, p=0.88), maximal LV wall thickness (19 ± 5mm vs 20 ± 6mm, p=0.32), LV outflow tract obstruction (21% vs 18%, p=0.61) or NYHA class (p=0.32). There was no significant difference in the presence of LV apico-basal muscle bundle with respect to specific gene mutations (MYBPC3 vs MYH7; p=0.25). None of the accessory muscle bundles had late gadolinium enhancement. Preoperative CMR identified 10/18 patients (55%) in which LV apico-basal muscle bundle was judged to contribute to obstruction and were resected during myectomy.
Conclusions: LV apico-basal muscle bundle is significantly more common in HCM patients and G+/P- family members compared to healthy controls. These findings expand our appreciation of the phenotypic expression of HCM and may represent an additional morphologic marker for HCM diagnosis and genotype positive status. Identification of LV apico-basal muscle bundles may be useful in preoperative planning strategy.
- © 2012 by American Heart Association, Inc.