Myocardial Ischemia Secondary to Anomalous Origin of Left Anterior Descending Coronary Artery: A Case Report and Literature Review

Introduction

Coronary artery anomalies (CAAs) carry a high risk of complications despite their rarity (0.01–0.03% incidence) [1]. Myocardial infarction, heart failure, arrhythmias, cardiomyopathy, and other complications during cardiac procedures and surgeries have all been linked to an abnormal origin of the left anterior descending (LAD) artery [1].

CAA can have either a malignant or benign course. The malignant variant has an anomalous vessel with an inter-arterial course between the pulmonary artery and the aorta, but all other variants are benign [2]. Early detection and treatment of LAD anomalies can help reduce the associated complications. We present the case of a 37-year-old man who was incidentally found to have an anomalous left anterior descending (LAD) artery originating from the right coronary artery (RCA) ostium, associated with a malignant inter-arterial course and myocardial bridging.

Case Report

A 37-year-old male patient with a history of dyslipidemia, heavy smoking, and illicit drug abuse was referred with a diagnosis of acute coronary syndrome (ACS) to our tertiary center, King Abdullah Medical City, Department of Cardiac Surgery, Makkah, Saudi Arabia, specifically ST-segment elevation myocardial infarction (STEMI) in the anteroseptal leads. He presented very early, with serial high-sensitivity troponin I values within normal limits (initial <0.015 ng/mL; reference range 0–0.045 ng/mL). Creatine kinase (CK) was 99 U/L (39–308 U/L), and creatine kinase-MB (CKMB) was mildly elevated at 43 U/L (7–25 U/L). His echocardiography findings were unremarkable, showing no regionality and normal ventricular function. Coronary angiography (Figure 1) showed an anomalous origin for the LAD from the RCA in addition to myocardial bridging at the mid-LAD, with no luminal stenosis in all territories. Given the patient’s presentation and recurrent chest pain history, CT coronaries (Figures 2, 3) were done to further evaluate and assess the course of the LAD, which revealed a dual LAD anomaly with LAD 1 (the long) originating from the proximal RCA and running a malignant course between the aorta and right ventricular outflow tract, then joining the inter-ventricular septum with evidence of moderate muscle bridge at the mid-LAD “Spindola-Franco type VI“.

The patient was reluctant to undergo surgical intervention; hence, he was discharged home on optimal medical therapy and regular follow-up. However, he still experienced symptoms, with frequent emergency department visits. At his last admission, a submaximal exercise (Bruce protocol) stress Tetrafosmin SPECT was performed. The patient achieved 77% of the target heart rate and experienced chest pain during the test. The study demonstrated a small and mild reversible perfusion defect in the anteroseptal wall, consistent with ischemia in the left anterior descending artery territory, with no evidence of fixed myocardial scarring. Eventually, on-pump coronary artery bypass grafting (CABG) was performed via median sternotomy. The left internal mammary artery (LIMA) was harvested in a pedicled fashion and anastomosed to the left anterior descending artery just beyond the myocardial bridge, which provided a suitable distal target. The bridged segment was not surgically unroofed. Cardiopulmonary bypass was established between the ascending aorta and right atrium, and myocardial protection was achieved with antegrade cold blood cardioplegia under mild hypothermia. Flowmeter assessment confirmed excellent flow with a low pulsatility index, and the patient was weaned off bypass and was decannulated uneventfully. He had an excellent and smooth postoperative recovery course.

Discussion

CAAs are complex congenital illnesses with varying symptoms and pathophysiology; these abnormalities are present at birth but typically go undetected until they are identified during coronary angiography or multi-slice computed tomography. Their prevalence is less than 1.3% according to published data. The most prevalent abnormality is the origin of the left circumflex (LCX) artery from the RCA or right sinus of Valsalva. The second most frequent cardiac abnormality is separation of the LAD coronary artery and LCX coronary artery from the left sinus of Valsalva. The third most frequent abnormality is the anomalous RCA, which originates from the left sinus of Valsalva [3].

In our case, the LAD coronary artery originated from the RCA ostium, with myocardial bridging at the mid-LAD, representing an extremely rare variant. When we reviewed the literature, we identified 12 reported examples of LAD anomalous arising from the RCA without bridging (Table 1). Unlike those cases, our patient presented with acute coronary syndrome, and the anomaly was further classified as a Group VI dual LAD with an inter-arterial (malignant) course [16]. This malignant pathway between the aorta and pulmonary artery explained the ischemic presentation and guided our decision for surgical revascularization rather than percutaneous intervention.

Most CAAs are found incidentally, with up to 81% being benign and clinically insignificant. However, malignant CAAs can cause cardiac ischemia, which can result in angina, syncope, cardiac arrhythmia, heart failure, and sudden cardiac death (SCD). It is important to note that coronary anomalies are the second leading cause of SCD in athletes (19%), following hypertrophic cardiomyopathy (36%) [17].

A CAA is malignant if it has a single coronary artery, originates from the pulmonary artery, originates from the opposite aortic sinus, passes between the aorta and pulmonary artery, has an intramural path, and has a tiny artery owing to ostial stenosis or atresia. Myocardial squeezing, vasospasm, and atherosclerosis in the aberrant artery can cause clinical symptoms [18–20].

Managing abnormal arteries requires careful consideration. Surgical intervention is the primary strategy to deal with such a pathology. Different surgical strategies have been reported, which include coronary unroofing, coronary translocation, coronary osteoplasty, CABG, and pulmonary artery translocation. Each strategy has its own reported limitations; however, there is no compelling evidence to support one strategy over the others. In our case, we thought CABG would be safer and less complex, with an optimum outcome. Based on the American and European guidelines, for patients who are symptomatic and have a malignant CAA, corrective surgery is required. The problem arises when asymptomatic people have a malignant CAA. Given the rarity of SCD, especially in those over 30–35 years old, some clinicians may advise against surgery. However, surgical intervention for such patients is considered class IIa based on the American and European guidelines. There is limited evidence to support the use of percutaneous intervention (PCI). The main indication for PCI is when an atherosclerotic lesion is coexisting with the anomalous lesion. However, PCI in anomalous coronary arteries with a malignant inter-arterial course carries significant limitations and risks. Technical challenges include difficulty in catheter engagement due to the abnormal origin, unstable guide support, and risk of vessel dissection from acute angulation. Moreover, PCI does not address the dynamic systolic compression that occurs when the vessel courses between the aorta and pulmonary artery, and thus does not eliminate the underlying risk of sudden cardiac death. For these reasons, PCI is generally not considered a definitive therapy in patients with such anomalies, and surgical revascularization is preferred as the more durable treatment option [21–23].

Conclusions

The anomaly of the LAD artery originating from the RCA ostium, along with bridging, is an exceedingly rare variant of coronary artery anomalies. In this case, the anomaly was classified as Group VI dual LAD, with an inter-arterial (malignant) course between the aorta and pulmonary artery. This anomaly is generally considered malignant, particularly when associated with an inter-arterial course. In such cases, patients are at increased risk of cardiac arrest and sudden death. Individuals with LAD anomalies may manifest symptoms of myocardial ischemia even in the absence of atherosclerotic disease, due to their abnormal course or myocardial bridging. Early detection and management of LAD anomalies are crucial for reducing mortality and morbidity. In particular, when the anomalous LAD originates from the RCA with an inter-arterial course, surgical correction should be strongly considered due to its potentially poor prognosis.