Direct Left Main Bypass for Anomalous Left Main Origin With Interarterial Course

Anomalous origins of the coronary arteries are rare, occurring in 1-2 percent of the general population. While anomalous aortic origin of the coronary artery alone is less often problematic (for example, right coronary artery (RCA) arising cranial to the sinotubular junction (STJ)), anomalous origin with an anomalous proximal course (interarterial or intramuscular)  is more likely to be associated with ischemia.  

While RCA origin from the left coronary sinus is the most common in this category, it is usually not treated unless ischemia is demonstrated. Anomalous left coronary artery (LCA) origins from the right coronary sinus (or the RCA itself) are less common but more associated with sudden cardiac death. These arteries are often immune to atherosclerosis, and ischemia is related to compromise of the origin itself (with a slit-like orifice and intramural course) and/or by intermittent distortion or compression between the aortic and pulmonic roots, usually in the setting of exercise.  

Stenting has been utilized, but is an imperfect solution associated with failure. Because of the intermittent nature of the ischemia, intramural RCA anomalies are better treated with unroofing within the opened aortic root, as opposed to ordinary aorto-RCA bypass (which may fail due to significant competition with the native RCA circulation). Proximal RCA ligation might promote better graft patency but is concerning because of limited options for rescue if the graft goes down. 

The authors present a rare anomalous left main phenotype in a 30-year-old woman who had been seen in multiple emergency rooms (ERs) during the past decade with intermittent issues with chest discomfort. One year prior, a stress test was done that showed 1-2 mm ST segment depression inferolaterally during the recovery phase, but the echocardiogram portion of the exam did not show wall motion abnormalities (WMA), and this was not pursued further. With another presentation several months earlier, a coronary computed tomography angiography (CTA) was arranged—her first anatomic study. This showed an anomalous origin of the LCA from the medial aspect of the aortic root, just above the left-right aortic valve commissure, with a course that was compatible with dynamic compression or kinking when interacting with the pulmonic root. 

Initial options considered included relocation of the left main coronary artery to its anatomically correct left coronary sinus (with a risk of iatrogenic kinking or tension) and a 1-2-vessel bypass (left anterior descending artery (LAD)/circumflex artery (Cx)) with or without proximal left main ligation (both options having distinct and important failure modes). Dr. Soltesz described the current approach at the Cleveland Clinic, which involved a strategy that targets the “competition problem” with conventional coronary bypass. The concept was to create a short bypass directly from the left coronary sinus to the left main coronary artery using saphenous vein. The larger caliber of the vein (compared with the native left main) plus the short length of the bypass created a low-resistance conduit from the aorta to the left main. As a result, the native left main cannot out-compete the vein graft based on flow mechanics. Concerns for graft patency (due to not using an artery) were also diminished by the very short bypass length and the use of a high-quality vein segment.  

However, to access the proximal left main for a direct bypass, complete transection of the aorta and main pulmonary artery was  required. Once the left ventricular (LV) summit was exposed by reflecting the pulmonic root inferiorly, the left main was identified, released from epicardial fat, and easily bypassed. Next, the proximal saphenous vein graft (SVG) originated from the native left coronary sinus, with a final graft length of approximately 3 cm. The patient did very well and was discharged home on postoperative day four on a low-dose statin for SVG graft protection. At her 30-day postoperative visit, she reported that her symptoms appeared to have abated. 

References

1. Congenital Anomalies of Coronary Artery Origin in Adults: 64-MDCT Appearance. JD Dodd, M Ferencik, RR Liberthson, et. al. American Journal of Radiology 2007; 188:W138–W146 

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