Anomalies

Stress-Induced NSTEMI Reveals Absent Left Main and Mid Left Anterior Descending Coronary Arteries

Juan A. Siordia, MD1, Christopher Angus, MD2, Sundeep Shenoy, MD2, Tushar Acharya MD2, Tom Lassar, MD2

1Banner University Medical Center – South Campus, Department of Medicine, Tucson, Arizona;2Banner University Medical Center – Tucson Campus, Department of Medicine, Division of Cardiology, Tucson, Arizona

Juan A. Siordia, MD1, Christopher Angus, MD2, Sundeep Shenoy, MD2, Tushar Acharya MD2, Tom Lassar, MD2

1Banner University Medical Center – South Campus, Department of Medicine, Tucson, Arizona;2Banner University Medical Center – Tucson Campus, Department of Medicine, Division of Cardiology, Tucson, Arizona

Abstract. Left main coronary artery atresia (LMCAA) is a rare entity that is not completely understood.  This case presents an adult patient with non-ST elevation myocardial infarction after an emotional event, with incidentally discovered LMCAA.

Presentation

A 59-year-old female presented with chest pain and syncope. On the morning of admission, she was at the hospital with her great grand-daughter who suffered a fatal accidental gunshot injury. The extreme emotional distress precipitated acute substernal chest pain, followed by syncope. When she regained consciousness, chest pain was persistent, but then abated after a few minutes. She was brought to the emergency department (ED) for evaluation.

In the ED, the patient was hemodynamically stable, with no recurrence of chest pain. Labs revealed elevated troponins at 0.43 ng/ml (normal <0.05 ng/ml) and brain natriuretic peptide elevated at 448 pg/ml. Other labs were normal. Electrocardiography showed progressive precordial and lateral T wave inversions with QT prolongation. Transthoracic echocardiography showed hypokinesis of the mid anterior and anterolateral walls, while the apical segments had normal wall motion. Non-ST segment elevation myocardial infarction (NSTEMI) and stress-induced cardiomyopathy were the initial working diagnoses. She was treated with full-dose aspirin, high-intensity statin, intravenous unfractionated heparin, and oral beta-blocker therapy, and subsequently taken to the cath lab as part of an early invasive approach. 

On invasive coronary angiography, the right coronary artery (RCA) was a large, dominant, ectatic vessel with mild disease that bifurcated into a large posterior descending artery (PDA) and posterior lateral branch artery (PLB). There was retrograde filling of what appeared to be the distal left anterior descending (LAD) artery and the left circumflex artery (LCX) from the PDA and PLB, respectively (Figure 1). Multiple attempts to engage the left main coronary artery were unsuccessful, despite the use of different catheters. A subsequent aortogram failed to identify the left main coronary ostium.  

A subsequent computed tomography coronary angiogram (CTA) showed a rudimentary hypoplqastic left main (Figure 2). The proximal LAD (not identified on the invasive angiogram) was supplied by a large conus branch from the RCA. The mid LAD was atretic as well (Figure 3). The distal LAD filled via collaterals from the PDA. Thus, the wall motion abnormalities seen on the echocardiogram correlated with the atretic mid LAD and were probably chronic. 

Past Medical History

The patient’s past medical history was significant for a 35-pack year smoking history, systemic lupus erythematosus, and fibromyalgia. She had no prior surgeries. She denied any family history of premature coronary artery disease or sudden cardiac death. She had two uncomplicated pregnancies. She had never experienced any cardiopulmonary symptoms prior to this admission. Of note, the patient mentioned she played high-intensity competitive basketball during childhood and adolescence without any issues regarding syncope, chest pain, or exertional intolerance.  

Differential Diagnosis

An anomalous origin of the left coronary artery from the pulmonary artery was high on the differential after the coronary angiography. The other differential diagnosis included congenital absence of the left coronary artery with single coronary system. Her history of smoking and chronic inflammatory disease (systemic lupus erythematosus) raised the possibility of an atherosclerotic chronic total occlusion of the left main wih collateral flow from the RCA. 

Management

A coronary CTA that was performed to further characterize her coronary anatomy confirmed the congenital atresia of the left main and mid LAD with right-to-left collateral from the PDA and PLB, as noted in the coronary angiogram. A right-to-left collateral from the conus branch to the proximal LAD with a pre pulmonary arterial course was also noted. No aortic root pathologies were noted on the CT scan. In discussion with cardiac surgery, a decision was made to quantify her ischemic burden with a nuclear stress test, with the idea to proceed with a possible two-vessel coronary artery bypass graft (CABG) if the patient had a considerable ischemic burden, not just corresponding to the area of the atretic LAD. The patient was discharged home with plans for outpatient nuclear stress testing.  

Discussion

Left main coronary artery atresia (LMCAA) is a congenital coronary artery anomaly described as a blind end of the usual connections to the proximal LAD and left circumflex coronary arteries. Perfusion to these branches is supplied in a retrograde manner via collaterals from the RCA. As of 2016, less than 60 cases had been reported in the literature.1 LMCAA is typically encountered with anatomical aortic root pathologies, including bicuspid aortic valve.1,2 Invasive and/or CT coronary angiography or cardiac magnetic resonance imaging can be used to establish the diagnosis.3,4

LMCAA must be clearly distinguished from anomalous left main coronary or single coronary ostium pathology. The latter variants tend to be more common and present with a more suitable perfusion profile than LMCAA, except when the ostium arises from the pulmonary artery; in which cases, surgery is required at birth to sustain cardiac function. 

Coronary ostia develop after truncal separation. In LMCAA, the left coronary ostia may occlude later during fetal development. For the myocardium to remain viable, the left distal coronary vascular bed forms a collateral circulation with the right coronary vascular network. The larger the collateral network, the less likely issues will present early in life.1,2,5

Adults tend to present with atypical chest pain. When they undergo coronary angiography, coronary artery disease is rare (about 11%).1,2 There are two patterns of collateral vessels: a conotruncal course and a distal RCA course. Both were noted in our patient. Patients with a distal RCA course usually present with symptoms earlier in life.1,6 Patients that present later in life have a more favorable prognosis.1 

Those patients who are symptomatic and diagnosed in the early adulthood tend to require surgical treatment. The most common procedure is a coronary bypass surgery (CABG) with the left internal mammary artery. Other modalities include bypass with a saphenous vein graft or direct reconstruction of the left main coronary artery.2,7,8 The small size of the left coronary system should not pose a contraindication to bypass surgery, as once revascularized, there is progressive increase in the diameter of the left coronary system, with gradual reduction of the collateral flow.1

Treatment in adults has to be individualized based on symptoms, age at presentation, and extent of ischemia. Revascularization strategies are used less frequently among adults, due to the presence of a large collateral circulation, often with minimal areas of ischemia. Most patients are managed medically.2 CABG is typically performed if revascularization is necessary. Rarely, adults may require left ventricular support due to global hypokinesia with symptoms of heart failure.1 

Conclusion

LMCAA is a rare subset of congenital coronary artery anomalies. Adult patients usually are managed medically unless there are areas of ischemia or significant coronary artery disease. 

Disclosures: The authors report no conflicts of interest regarding the content herein.

The authors can be contacted via Dr. Tom Lassar at tom.lassar@bannerhealth.com.

References
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