Abstract 1712: Deep Myocardial Bridging is a Risk Factor for Sudden Death in Hypertrophic Cardiomyopathy
Background. Myocardial bridging (MB) of the left anterior descending (LAD) coronary artery segment has been linked with myocardial ischemia and sudden death (SD) in young patients with hypertrophic cardiomyopathy (HCM), but this association remains controversial.
Methods. The files of two pathology cardiac registries were searched for diagnosed cases of HCM. A total of 120 hearts were enrolled (34 female and 86 male; ages 1 day-90 yrs, mean 31 +/− 20). Heart weight and septal thickness were 465+/−208 g and 19+/−6 mm, respectively. Mode of death was SD in 82 (68%), heart failure (HF) in 29 (24%) (14 with heart transplantation), early post-myectomy in 2, infective endocarditis in 1 and extracardiac causes in 6.
Results. A MB of the LAD was present in 45 (37%) of 120 HCM pts, compared to 21 (21%) of 100 consecutive controls who died of causes unrelated to HCM (p=0.01). However, MB was present in 38% of SD cases vs 37% of non-SD cases (p=NS). At histology, MB most frequently consisted of a sheath of myocardial fibers totally encircling the coronary artery (71%); transversally oriented, superficial fibers were present in 29%. MB had a length of 14.8±6.6 mm and MB length was related to greater MB depth. No correlation was found between MB depth, heart weight or septal thickness. Deep MB ≥2mm was present in 25 out of 120 hearts (21%), and significantly more common in SD (21/82, 26%) than non-SD cases (4/38, 10%) (p=0.03). Deep MB was more common among SD pts aged >20 yrs (18/44, 41%) than pts ≤20 yrs (7/38, 18%, p=.02).
Conclusions. MB segments of LAD are common at autopsy in HCM, and their presence per se does not distinguish patients with SD and other modes of death. Most importantly, deep and long bridged segments are significantly more common in patients dying suddenly, suggesting a role for this anomaly in the clinical course and risk stratification of HCM.