Anatomical characteristics of myocardial loops in the adults

Abstract

Aim. To establish structural features and adjacent anatomy of myocardial loops in the adult and elderly human hearts.

Methods. We studied 100 hearts obtained from adult and elderly people who died from non-cardiac causes. We dissected subepicardial blood vessels and their intramural segments on 60 formalin-fixed hearts. The rate of the cone artery directly originating in the aorta (third coronary artery) was recorded. The number of myocardial loops, their localization and length were determined. We made histological sections from 40 heart specimens from areas of the coronary groove containing myocardial loops. The shortest distances from the coronary sinus and myocardium of the left atrium to the artery, the thickness of the loops, the cross-sectional area of the artery and perivascular space and the ratio of these parameters were measured. The statistical significance of differences was assessed by using the Mann–Whitney U-test. The relationship between the two qualitative features was identified using the Pearsons χ2 test. The Spearman’s rank correlation coefficient (R) was used for the correlation analysis.

Results. Macroscopically, myocardial loops were found in 12 (20%) hearts out of 60. More often, they were determined on specimens where the cone artery directly originating in the aorta. Histological examination revealed myocardial loops in 10 (25%) hearts out of 40. They were located above the arteries accompanying the coronary sinus. Their length varied from 8.5 to 44.53 mm (Me=16.68 mm), thickness from 0.16 to 0.58 mm (Me=0.31 mm). Two types of myocardial loops (arterial and arteriovenous), differing in thickness (p=0.045), were distinguished.

Conclusion. The myocardial loops are predominantly located on the diaphragmatic surface of the heart in the left half of the coronary groove over the arteries accompanying the coronary sinus, while the artery can pass in the myocardial loop separately from the veins or in the “sleeve” of the coronary sinus; the presence of myocardial loops is associated with the independent aortic origin of the cone artery.

Keywords

heart / coronary arteries / myocardial loops / coronary sinus / left atrium

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