Objective-To assess the arrangement of myocardial bridges.Design-A necropsy study of 90 consecutive hearts (56 male, 34 female).Results-Myocardial bridges, either single or multiple, were seen in 50 (55-6%) of the 90 hearts. The left anterior descending artery was the most commonly affected artery. Thirty five of the 50 hearts which contained in total 41 muscle bridges were dissected further with a magnifying glass. Two different types of muscle bridges could be identified. Thirty one of these 41 myocardial bridges were superficial, crossing the artery transversely towards the apex of the heart at an acute angle or perpendicularly. The individual ages ranged from a stillbirth to 84 years and in none was there a history of preceding established cardiac disease and death was not referrable to cardiac causes. Myocardial bridges were identified in 50 hearts. Thirty five of these hearts were examined further by hand lens dissection. Thirteen of the remaining 15 hearts, in which the left anterior descending coronary artery was directly related to a muscle bundle, were assessed histologically. After fixation, five were embedded in paraffin and 10 gum sections were cut, and four were embedded in 8% celloidin and 100 gum sections were cut.The sections were then stained by azan and resorcin fuschin and the azan and Weigert method respectively to demonstrate connective and elastic tissue. Segments of four hearts which included muscle bridges were cut at 60 ,um in a cryostat and stained by Sudan III to assess the adipose tissue interposed between the artery and the muscle bridge. The remaining two hearts were set aside for ultrastructural investigation. STATISTICAL TESTSWe used Student's t test for paired and unpaired samples with Fisher tests for variance and multiple comparison analysis. P values < 0 05 were considered significant. ResultsThirty two of the 50 hearts that contained muscle bridges came from male subjects. In 35 hearts the bridges were single, affecting solely the left anterior descending coronary artery; 10 hearts contained two muscle bridges and five hearts contained three muscle bridges. These multiple muscle bridges affected either the same vessel or different coronary arteries or their branches. Significantly longer muscle bridges were seen in the 21-50 age group than in the hearts removed from subjects 0-20 years (table 1). There was no statistical difference between the length of myocardial bridges in male and female subjects (table 2). Shorter muscle bridges were more common (table 3 and fig 1).

No abstract

No abstract