[Treadmill exercise test in patients with coronary artery myocardial bridging].

Objective: To observe treadmill exercise test (TET) characteristics in patients with myocardial bridging (MB).

Methods: TET results from January 2003 to December 2010 were retrospectively analyzed in 156 patients with confirmed MB diagnosis. MB patients were divided into smoking group (68 cases) and non-smoking group (88 cases). Coronary angiography results were used to analyze the relations between MB length, myocardial ischemia and exercising duration.

Results: (1) MB was documented on two coronary arteries in 2 patients (1%), MB was detected in single artery in 154 patients (99%), of whom 146 cases were located at left anterior descending artery, 8 cases were located at right coronary artery. The degree of narrowing of MB was graded 1 (less than 50%) in 16 patients (10%), grade 2 (50% to 75%) in 108 patients (69%) and grade 3 (greater than 75%) in 32 patients (21%). The length of MB ranged between 4 to 40 mm, MB length was less than 10 mm in 40 patients (26%), between 11 to 20 mm in 48 patients (31%), between 21 to 30 mm in 44 patients (28%), greater than 31 mm in 24 patients (15%). (2) TET positive rate was 41% (64/156) and the TET positive rate was significantly higher in smoking group than in non-smoking group [57% (39/68) vs. 28% (25/88, P < 0.01)]. (3) The length of MB was positively related to the ST-segment depression (r = 0.723, P < 0.01) and negatively related to exercising duration (r = -0.828, P < 0.01). Heart rate was positively related to the ST-segment depression (r = 0.368, P < 0.01).

Conclusions: TET may serve as a good test to assess myocardial ischemia in patients with MB. The length of MB is positively related with myocardial ischemia and negatively related with exercising duration. Smoking might increase myocardial ischemic incidence in MB patients, MB patients should be advised to stop smoking.