Could increased axial wall stress be responsible for the development of atheroma in the proximal segment of myocardial bridges?

The model was adapted to the hemodynamic particularities of myocardial bridges and used to estimate by means of a numerical example the cyclic increase in axial wall stress in the vessel segment proximal to the bridge. The consistence of the results with reported observations on the presence of atheroma in the proximal, tunneled, and distal vessel segments of bridged coronary arteries was also examined.1) Axial wall stress can markedly increase in the entrance region of the bridge during the cardiac cycle. 2) This is consistent with reported observations showing that this region is particularly prone to atherosclerosis.The proposed mechanical explanation of atherosclerosis in bridged coronary arteries indicates that angioplasty and other similar interventions will not stop the development of atherosclerosis at the bridge entrance and in the proximal epicardial segment if the decrease of the lumen of the tunneled segment during systole is not considerably reduced.The existence of myocardial bridges is known since more than a century. The interest for these anatomical particularities of coronary arteries has remained, however, very modest until the development of dynamic coronary angiography in the sixties. This new imaging modality allowed for the first time to see the compression of the tunneled vessel segment during systole ("milking effect", Fig. 1). Since that time, myocardial bridges are increasingly suspected of inducing severe ischemiae in the associated myocardial territories, and even infarcts and sudden deaths [1-5].At necropsy, myocardial bridges are a common finding [6-8]. In the literature, the percentages vary, however, greatly but this is most probably due to differences between the definitions used by the investigators [6-9]. The left anterior descending coronary artery (LAD) is the most frequently concerned vessel [7,10,11], whereby the bridge is usually situated on the middle segment. Loukas et al. found that the presence of bridges in the adult hum