Anomalous Left Coronary Artery from the Pulmonary Artery (ALCAPA)

Definition

Anomalous left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital heart defect characterized by the abnormal origin of the left coronary artery from the pulmonary circulation instead of the aortic root. This anomaly leads to altered myocardial perfusion, with potentially fatal hemodynamic consequences in the first months of life.

Embryology and Pathogenesis

The development of the coronary arteries occurs between the fourth and eighth week of gestation, with the formation of connections between the subepicardial coronary plexus and the ascending aorta. An anomaly in this process can result in the misplacement of the left coronary artery, which arises from the pulmonary artery instead of the aortic root. At birth, pulmonary pressure is still high, and oxygenated blood from the pulmonary circulation may provide some degree of perfusion to the left coronary artery. However, as pulmonary pressure physiologically decreases in the first weeks of life, the blood flow through the left coronary artery becomes progressively insufficient, leading to ischemia and myocardial dysfunction.

Pathophysiology

ALCAPA leads to a series of hemodynamic consequences:

• Myocardial hypoperfusion: The left ventricle receives oxygen-poor blood, causing progressive ischemia.
• Coronary steal phenomenon: Collateral circulation develops between the right and left coronary arteries, but the oxygenated blood reaching the left coronary artery is drained into the pulmonary artery, worsening ischemia.
• Ischemic damage and ventricular dilation: Myocardial dysfunction reduces cardiac output and increases cardiac workload.

Clinical Presentation

Infantile ALCAPA usually manifests between the second and third month of life, when pulmonary pressure drops and coronary flow becomes critical. The most common symptoms include:

• Irritability, excessive sweating, and feeding difficulties
• Episodes of chest pain (a manifestation of neonatal ischemia)
• Signs of congestive heart failure: tachypnea, hepatomegaly, tachycardia, weak pulses
• Holosystolic heart murmur due to mitral regurgitation caused by left ventricular dilation

Patients who survive beyond infancy without a diagnosis may develop ventricular arrhythmias and sudden cardiac death in adulthood.

Diagnosis

The diagnosis of ALCAPA relies on cardiovascular imaging techniques:

• Transthoracic echocardiography with Doppler: First-line examination that shows left ventricular dilation, mitral regurgitation, and abnormal flow in the left coronary artery.
• Coronary CT angiography or cardiac magnetic resonance (CMR): Allows for a detailed characterization of the coronary anatomy.
• Cardiac catheterization with coronary angiography: Gold standard for confirming the diagnosis, revealing the coronary steal phenomenon and the abnormal connection.

Treatment

The only effective treatment is early surgical correction, which aims to restore adequate myocardial perfusion. The main surgical strategies include:

• Reimplantation of the left coronary artery onto the aortic root (reimplantation technique): The most effective technique for normalizing coronary flow.
• Creation of an intramural tunnel (Takeuchi procedure): A channel is created between the left coronary artery and the aorta within the pulmonary sinus of Valsalva.
• Left coronary artery ligation with collateral circulation development: An option only in cases where right coronary flow is sufficient.

Prognosis

Untreated ALCAPA has a high mortality rate, with approximately 90% of untreated infants dying within the first year of life due to heart failure or fatal arrhythmias. However, early surgery offers excellent outcomes, with long-term survival rates exceeding 90% in patients treated during the first months of life.

Conclusion

ALCAPA is a severe congenital coronary anomaly that requires early diagnosis and prompt surgical treatment to prevent heart failure and sudden death. The use of echocardiography and cardiac magnetic resonance has improved early diagnosis, while modern surgical techniques have significantly enhanced prognosis.

References
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2. Yau J. M., et al. "Anomalous origin of the left coronary artery from the pulmonary artery in adults: a comprehensive review of 151 adult cases and a new diagnosis in a 53-year-old woman." Clinical Cardiology, vol. 34, no. 4, 2011, pp. 204-210.
3. Hu R., et al. "Midterm surgical outcomes for ALCAPA repair in infants and children." Thoracic and Cardiovascular Surgeon, vol. 70, no. 1, 2021, pp. 2-9.
4. Kubota H., et al. "Adult ALCAPA: From histological picture to clinical features." Journal of Cardiothoracic Surgery, vol. 15, no. 1, 2020, p. 14.
5. Boutsikou M., et al. "Anomalous left coronary artery from the pulmonary artery (ALCAPA) diagnosed in adulthood: varied clinical presentation, therapeutic approach, and outcome." International Journal of Cardiology, vol. 261, 2018, pp. 49-53.
6. Angelini P., et al. "Coronary artery anomalies: an entity in search of an identity." Circulation, vol. 115, no. 10, 2007, pp. 1296-1305.
7. Alexi-Meskishvili V., et al. "Long-term results after repair of anomalous origin of the left coronary artery from the pulmonary artery." The Annals of Thoracic Surgery, vol. 83, no. 4, 2007, pp. 1463-1471.
8. Zhou Y., et al. "Midterm outcome after surgical correction of anomalous left coronary artery from the pulmonary artery." Journal of Cardiothoracic Surgery, vol. 11, no. 1, 2016, p. 50.