Correlation between depth of myocardial bridging and coronary angiography findings

BACKGROUND: Myocardial bridging (MB) is a congenital anomaly in which a segment of coronary artery is surrounded by myocardium. PURPOSE: To investigate the correlation between muscle thickness over the tunneled coronary artery (depth) in MB and the presence of milking effect (ME) and systolic narrowing ratio in catheter angiography (CA). MATERIAL AND METHODS: The records of 36 patients who underwent a coronary computed tomography angiography (CTA) and following CA examination for suspicious ischemic coronary artery disease, between March 2005 and September 2007, were retrospectively evaluated. According to the depth of MB on CTA, patients were grouped into four groups: group 1, <1 mm; group 2, 1- <2 mm; group 3, 2- <4 mm; group 4, >or=4 mm. The presence of milking effect, systolic narrowing ratio, and atherosclerotic stenosis at CA were recorded. CTA and CA results were then compared to evaluate the correlation. RESULTS: In total, ME was found in 15 arteries at CA (42%). There was no ME in group 1; it was present in 11% of group 2, 67% of group 3, and 100% of group 4. Starting from group 3, the percentage of likelihood of seeing the milking effect was 77%, and the percentage of systolic narrowing was between 30 and 70%. There was a significant correlation between depth of MB and systolic narrowing (P<0.01), while no significant correlation between length of MB and systolic narrowing was found (P=0.32). In seven of the 36 patients (group 1, 0; group 2, 1; group 3, 3; group 4, 3), clinical findings were related to pure MB. CONCLUSION: The depth of MB is positively related to coronary narrowing and clinical ischemic findings.