Systematic Review and Meta-Analysis of Cardiovascular Consequences of Myocardial Bridging in Hypertrophic Cardiomyopathy.

Myocardial bridging (MB) is a congenital variant in which a segment of a coronary artery follows an atypical intramural course under a "bridge" of myocardium and is notably common in hypertrophic cardiomyopathy (HCM). This systematic review and meta-analysis explored the clinical consequences of MB in patients with HCM. A total of 3 outcome domains were investigated: cardiovascular mortality, nonfatal adverse cardiac events, and investigative indicators of myocardial ischemia. A meta-analysis was performed on 10 observational studies comparing outcomes in patients with HCM with and without MB. Studies were identified through a systematic search of 4 databases (PubMed, Scopus, Medline Complete, and Web of Science). The quality of the studies was assessed using a modified version of the Downs and Black tool, from which studies could score a maximum of 23 points. The mean score was 17.5 ± 1.3 (good). The meta-analysis showed that MB was not associated with cardiovascular mortality (odds ratio [OR] 1.70, 95% confidence interval [CI] 0.56 to 5.15, p = 0.35) or nonfatal adverse cardiac events (OR 1.80, 95% CI 0.98 to 3.28, p = 0.06) but was associated with myocardial ischemia (OR 1.89, 95% CI 1.03 to 3.44, p = 0.04). In conclusion, the potential prognostic implications of MB in HCM, especially in those with hemodynamically significant bridges and/or severe underlying disease, should not be ignored. The focus of future studies should be to establish functional and morphologic thresholds, by which MB may adversely influence prognosis by corroborating imaging findings with clinical outcome data.