[The relationship between myocardial bridge in mural coronary artery segment and coronary atherosclerosis]

Objective: The myocardial bridging (MB) prevalence, anatomic characteristics of MB, and the relationship between characteristics of MB in mural coronary artery segment and coronary atherosclerosis were analyzed. Methods: In this perspective nonrandomized controlled study, a total of 1 132 patients who admitted to our hospital for suspected or known coronary artery disease from January 2012 to June 2013 were enrolled. All patients underwent dual-source 64-slice spiral CT coronary angiography. The general patient characteristics including gender, age, history of hypertension, diabetes, hyperlipidemia and smoking, serum level of total cholesterol (TC) and LDL-C were recorded. The length, depth and the degree of compression of myocardial bridge in systolic or diastolic phase were also analyzed in patients with MB. The relationship between MB and coronary atherosclerosis, the characteristics of MB and coronary atherosclerosis were analyzed by Spearman correlation analysis, univariate logistic regression analysis, variate logistic regression analysis and linear regression analysis. Results: Myocardial bridging was detected in 330 out of 1 132 patients, and MB was mostly located in the mural coronary artery (329/330) and at the mid-distal segment of the left anterior descending artery (LAD). Average MB length was 20.1 mm (3.3-95.5 mm) and the average depth was 2.13 mm (0.24-12.40 mm). There were 140 patients with intramyocardial MB (42.6%) and 189 patients with superficial MB (57.4%). Myocardial bridging was an independent protective factor of coronary atherosclerosis (OR=0.361, P=0.000) and the proximal segment of MB was more susceptible to atherosclerosis compared to the distal segment of MB (P=0.000). Multivariate analysis revealed that age, hypertension and the degree of compression of myocardial bridge in diastolic phase were independent factors related to the atherosclerosis (odds ratio: 1.064, 2.186 and 1.049 respectively, P value: 0.000, 0.002 and 0.000). The depth of MB was significantly correlated with systolic or diastolic narrowing(OR: 4.227, 3.398 and P value: 0.000, 0.001). Conclusions: The prevalence of myocardial bridging is 29% in this patient cohort. The proximal segment of myocardial bridging in mural coronary artery is more susceptible to atherosclerosis. In addition, the depth of myocardial bridging and the degree of compression of myocardial bridge in diastolic phase are the independent factors related to atherosclerosis.