[Muscle bridges over the left anterior descending coronary artery: their influence on arterial disease (author's transl)].

A total of 711 hearts was studied and examined for coronary muscle bridges of the left anterior descending (LAD) macroscopically, angiographically and histologically. A muscular overbridging of the LAD was found in 22.9% of all hearts. The average distance from left artery bifurcation was 33.6 mm, the average length was 22.5 mm and the average thickness 2.8 mm. A thin layer of fat tissue is mostly to be found between the overbridged coronary artery and the myocardial bridge. The patient group with and without myocardial overbridging showed no difference in sex or age nor in average stature and the average heart weight. Statistically, there is significantly more atherosclerosis of the coronary artery proximal to the muscle bridge than there is under and distal to the bridge. A difference in frequency and extent of atherosclerosis in hearts with and without coronary muscle bridge could not be shown for this portion of the LAD. Nevertheless, there is a tendency for fewer anterior-wall infarctions in the patient group with a coronary muscle bridge of the LAD, because, when the whole branch is considered, there is a significantly lower incidence of atherosclerosis in hearts with myocardial overbridging of the LAD. The reason for the protective effect of a coronary muscle bridge is yet not clear.