Myocardial bridging in Taiwanese: noninvasive assessment by 64-detector row coronary computed tomographic angiography.

Background: Myocardial bridging (MB) is a congenital structural variant in which a segment of the epicardial coronary artery tunnels into and is surrounded by the myocardium. MB has been correlated to some clinical complications of cardiovascular disease (CVD). The depiction rate of MB varies significantly between catheter coronary angiography and autopsy studies. This study aimed to assess the depiction rate of MB among Taiwanese by coronary computed tomographyic angiography (CCTA), to determine the anatomical features of the tunneling vessels, and to evaluate the outcome of patients having MB.

Methods: Between September 2006 and December 2007, 425 subjects (264 men and 161 women; mean age 59.6 ± 11.7 years) underwent ECG-gated CCTA by a 64-dectector row scanner in our institution. The presence and the location of MB in CCTA images and the presence of atherosclerosis in the tunneling vessels were evaluated and recorded. Major CVD events in the cohort were tracked from the day of CCTA examination until on March 2009 termination of follow-up.

Results: The depiction rate of MB was 20.9% (89/425). A total of 122 MB were depicted by CCTA. Thirty-six tunneling segments (29.5%) were situated in the distal portion of the left anterior descending coronary artery (LAD), 23 segments (18.8%) were in the middle portion of the LAD, 19 (15.5%) were in the first obtuse marginal branch of the left circumflex artery, 18 (14.7%) in the first diagonal branch of the LAD, and 10 (8.1%) were in the ramus medianus. Nine tunneling segments (7.3%) had concomitant atherosclerotic plaques at the time of CCTA. One hundred and nine tunneled segments (89.3%) were superficially located in the myocardium, with a mean depth of 1.9 ± 0.81 mm (range, 0.9-4 mm). Twelve patients with CVD events were recorded during the mean follow-up interval of 21.91 ± 4.03 months (range, 3.08-28.82 months). All 12 patients with CVD events had no MB on CCTA.

Conclusion: The depiction rate of MB by CCTA was 20.9% in this study. The most common location of MB was in the LAD. Concomitant atherosclerotic plaques were found in 7.3% of MB cases. Eighty-nine percent of tunneling vessels were superficially situated. None of the enrolled subjects with MB developed CVD event during the follow-up period. No statistical correlation was found between the presence of MB and CVD event (p = 0.057).