The Prevalence of Myocardial Bridging Associated with Coronary Endothelial Dysfunction in Patients with Chest Pain and Non-Obstructive Coronary Artery Disease.

AIMS Myocardial bridging (MB), characterized by the epicardial coronary vessel diving into the myocardium, is present up to 1/3rd of adults and is associated with accelerated atherosclerosis, and angina. In the current study we determine the association between MB and coronary endothelial dysfunction. METHODS AND RESULTS Patients with chest pain and nonobstructive CAD (stenosis < 40%) at angiography underwent invasive assessment of endothelial function. Epicardial endothelial function was assessed by measuring the percent change in coronary artery diameter in response to intracoronary infusions of acetylcholine (%ΔCADAch). Epicardial endothelial dysfunction was defined as %ΔCADAch of < -20%. Microvascular endothelial function was assessed as the percent change in coronary blood flow in response to intracoronary infusions of acetylcholine (%ΔCBFAch), and microvascular endothelial dysfunction was defined as %ΔCBFAch of < 50%. MB was diagnosed angiographically. The frequency of epicardial and microvascular endothelial dysfunction was compared between patients with and without MB. Results Between 1993 and 2012, 1,469 patients (mean age 50.4 years, 35% male) underwent coronary angiography and invasive testing of endothelial function. Two hundred eight (14.2%) patients had MB. Patients with MB had a higher frequency of epicardial endothelial dysfunction compared to patients without MB. In multivariate analyses, MB was a significant predictor of epicardial (OR, 95% CI, 1.45, 1.05 - 2.01, p=0.026) and microvascular endothelial dysfunction (OR, 95% CI, 1.36, 1.00 - 1.85, p=0.047). CONCLUSIONS MB is significantly associated with epicardial and microvascular endothelial dysfunction in patients with non-obstructive CAD supporting its potential role as amechanism for angina in symptomatic patients with MB.