Significance of left ventricular apical-basal muscle bundle identified by cardiovascular magnetic resonance imaging in patients with hypertrophic cardiomyopathy

Eur Heart J. 2014 Oct 14;35(39):2706-13. doi: 10.1093/eurheartj/ehu154. Epub 2014 May 8.


Aims: Cardiovascular magnetic resonance (CMR) has improved diagnostic and management strategies in hypertrophic cardiomyopathy (HCM) by expanding our appreciation for the diverse phenotypic expression. We sought to characterize the prevalence and clinical significance of a recently identified accessory left ventricular (LV) muscle bundle extending from the apex to the basal septum or anterior wall (i.e. apical-basal).

Methods and results: CMR was performed in 230 genotyped HCM patients (48 ± 15 years, 69% male), 30 genotype-positive/phenotype-negative (G+/P-) family members (32 ± 15 years, 30% male), and 126 controls. Left ventricular apical-basal muscle bundle was identified in 145 of 230 (63%) HCM patients, 18 of 30 (60%) G+/P- family members, and 12 of 126 (10%) controls (G+/P- vs. controls; P < 0.01). In HCM patients, the prevalence of an apical-basal muscle bundle was similar among those with disease-causing sarcomere mutations compared with patients without mutation (64 vs. 62%; P = 0.88). The presence of an LV apical-basal muscle bundle was not associated with LV outflow tract obstruction (P = 0.61). In follow-up, 33 patients underwent surgical myectomy of whom 22 (67%) were identified to have an accessory LV apical-basal muscle bundle, which was resected in all patients.

Conclusion: Apical-basal muscle bundles are a unique myocardial structure commonly present in HCM patients as well as in G+/P- family members and may represent an additional morphologic marker for HCM diagnosis in genotype-positive status.

Keywords: Cardiovascular magnetic resonance; Genotype; Hypertrophic cardiomyopathy; Muscle bundle.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Analysis of Variance
  • Cardiomyopathy, Hypertrophic / genetics
  • Cardiomyopathy, Hypertrophic / pathology*
  • Case-Control Studies
  • DNA Mutational Analysis
  • Genotype
  • Heart Ventricles
  • Humans
  • Hypertrophy, Left Ventricular / genetics
  • Hypertrophy, Left Ventricular / pathology
  • Magnetic Resonance Angiography / methods
  • Magnetic Resonance Imaging, Cine / methods
  • Male
  • Middle Aged
  • Mutation / genetics
  • Myocardium / pathology*
  • Pedigree
  • Phenotype
  • Ventricular Outflow Obstruction / genetics
  • Ventricular Outflow Obstruction / pathology