Figure 6 Red arrow indicates the myocardial bridge. (A) The
middle segment of the anterior descending branch is compressed by
myocardial fibers during systolic. (B) There is no compression of the
anterior descending artery during diastole and the blood flow is
unobstructed.
This study had some limitations. First, the veins that accompany the
interventricular septal branch, the anterior descending branch and the
posterior descending branch are difficult to detect by CAG when they
injured by pacing electrodes[14]. Second, the
damage to some small blood vessels of the heart is difficult to cause
changes in serum troponin, myocardial enzyme profile and ST-T segment of
the ECG[14]. It is not convenient for endurance
exercise to increase cardiac troponin[15]. Third,
because of the influence of anatomy and physiology, the distribution of
electrodes in each of the nine partition positions is not
well-proportioned, and the number of pacing electrodes in some positions
is small. Therefore, it is necessary to increase the number of cases in
further studies. Finally, in this study, the distance between the tip of
the pacing electrode and the coronary artery was a rough estimate
measured by fluoroscopy, which cannot be equivalent to the actual
spatial distance. How to measure the accurate distance between the
pacing electrode and the coronary artery is worthy of further study.