Background: Myocardial bridging (MB) is a common, congenital coronary-abnormality that is found on average in one out of every three adults at autopsy (Moehlenkamp et al in Circulation, 106:2616-2622, 2002; Erbel et al in Circulation, 120:357-359, 2009). However, its clinical significance and impact on myocardial ischemia remains controversial and unclear. Myocardial perfusion imaging (MPI) is widely used to assess myocardial ischemia in patients with known or suspected coronary artery disease, and is frequently performed to evaluate the hemodynamic significance of MB. This study was undertaken to determine the use of MPI in evaluating MB and to identify the characteristics of MB associated with perfusion defects using MPI.
Methods and results: Thirty-nine patients with MB of the left anterior descending (LAD) artery as documented by coronary angiography (CA) were enrolled for this study. None of the patients exhibited other forms of heart disease as determined by both CA and stress-rest MPI, no later than 1 month prior to the study. Using MPI, eight patients (20.5%) were found to have perfusion defects in the corresponding myocardial areas. This frequency was significantly higher when compared with results obtained by stress electrocardiogram. The difference in the mean systolic narrowing of bridging segments was statistically significant between patients with and without ischemia. The positive rate of reversible defects in patients with severe systolic narrowing was significantly higher than in patients with mild-to-moderate systolic narrowing. However, there was no significant difference either between the mean length of the tunneled artery in patients with and without abnormal MPI or the positive rate of abnormal MPI in patients with different locations of the tunneled artery.
Conclusions: MPI is an effective, noninvasive technique for the evaluation of patients with MB. The myocardial ischemia that resulted from bridging is associated more closely with the degree of systolic narrowing than with the length of tunneled artery or the location of MB.