Vascular Surgery

18 SAJS VOL 52 NO. 1 FEBRUARY 2014 Major coronary arteries have a subepicardial course through subepicardial fat and only dip into the myo­ cardium at or near their termination.[1­2] However, sometimes a variable segment of the epicardial artery can have a long intramural course or lie under a short band of cardiac muscle.[3­6] This anatomical arrangement has been variously described as an intramural coronary artery,[7] a submerged coronary artery,[8] a mural coronary artery,[3] a tunnelled artery[9] and, more commonly in anatomical descriptions, a coronary artery with a ‘myocardial bridge’ (MB).[8] MBs were first recognised by Rayman in 1737, then by Black in 1805 (both cited by Ferreira et al.[10]) and were first described angiographically by Portman and Iwig in 1960 (cited by Loukas et al.[11]). The MB is considered to be a congenital anomaly by some authors, while others refer to it as an anatomical variant of a coronary artery.[12­16] The first in­depth autopsy analysis of MBs was done by Geiringer.[3] Clinically, the diagnosis is made by systolic ‘milking’ of the involved epicardial artery during coronary angiography,[4] due to transient compression of the vessel during systole. However, the present report excluded the short­bridged left anterior descending (LAD) artery where no occlusive lesion was demonstrated angiographically, and patients with symptoms resulting from systolic constriction of the vessel. Myocardial infarction (MI) of the anterior cardiac wall is usually the consequence of disease in the LAD artery.[17] The LAD artery is most commonly situated intramuscularly, although other vessels may be involved.[10,11,18­20] Clinically, the LAD artery is the most important affected vessel,[10] and in view of the routine use of the left internal mammary artery (LIMA) to graft it, it presents specific challenges to the operating surgeon. In their autopsy study, Ferreira et al.[10] distinguished two types of MBs, viz. superficial and deep. The superficial variation was situated in the interventricular groove and was crossed perpendicularly by muscle fibres. The deep variation had larger muscle bundles than the superficial one and was situated deep within the inter­ ventricular septum. Geiringer[3] and Polacek[21] reported fewer atheromatous changes in the intramuscular arterial segment than in the subepicardial arterial segment. Ishii et al.[18] also observed that the intramuscular location influences the atherosclerotic disease process in the coronary artery. The MB is therefore regarded by some researchers as an uncommon cause of cardiac disease and considered as benign.[22,23] Conversely, there are reports suggesting that the myocardial bridging increases coronary artery spasm.[24] Furthermore, MBs may be a contributory factor in the development of MI,[7] cardiogenic shock after acute inferior MI,[25] unstable angina,[12] life­ threatening cardiac arrhythmias[26] and sudden cardiac death.[14] The intramyocardial left anterior descending artery: Prevalence and surgical considerations in coronary artery bypass grafting