ALCAPA

Summary of ALCAPA

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA), also known as Bland–White–Garland syndrome, is a rare but potentially fatal congenital heart condition. It is the primary cause of myocardial ischemia in children. ALCAPA occurs when the left coronary artery (LCA) originates from the pulmonary artery (PA) instead of the aorta. The incidence is approximately 1 in 300,000 live births and it comprises between 0.24% and 0.46% of all congenital heart disease. One unit reported an incidence of about 0.35% of congenital heart diseases. ALCAPA should be suspected and excluded in any pediatric patient presenting with left ventricular dysfunction. In infants, classic presentation includes heart failure symptoms, dilated LV, low ejection fraction, and mitral regurgitation, often with a dilated RCA on echo. Early surgery is necessary for both symptomatic infants and asymptomatic children/adolescents to restore normal circulation and prevent long-term myocardial damage.

While it was first reported as a specific syndrome in 1933, it has become a standard part of routine pediatric echocardiographic screening since the 1990s. The fundamental issue in ALCAPA is not the delivery of deoxygenated blood to the heart muscle, but rather a change in pressure dynamics that occurs as an infant ages. As the pulmonary vascular resistance drops during the first few weeks of life, the pressure in the pulmonary artery becomes lower than the pressure in the coronary system, leading to a reversal of flow where blood is stolen from the myocardium and drained into the pulmonary artery. This physiological state essentially functions as a large coronary pulmonary fistula, where there is a lack of perfusion during diastole. The resulting myocardial ischemia particularly affects the endocardium and the papillary muscles, which are highly vulnerable because they are supplied by end arteries that do not allow for easy collateralization. This often leads to significant dysfunction of the mitral valve, manifesting as mitral regurgitation, along with global left ventricular dilation and profound contractile dysfunction. In many cases, clinicians will observe endocardial fibroelastosis, which appears as echo brightness or sclerosing of the endocardium and papillary muscles on imaging. Because the papillary muscles are so sensitive to ischemia, brightness in these areas can be a critical diagnostic clue even if the overall ventricular function appears normal. ALCAPA must be recognized in new onset cardiomyopathy at 4-8 weeks of life as it is a surgically addressable condition. 

Coronary Steal:

During fetal life, ALCAPA has no clinical effect because the pressures and oxygen saturations in the aorta and pulmonary artery are almost identical. However, after birth, as pulmonary vascular resistance falls and the arterial duct begins to close, the pressure in the pulmonary artery decreases significantly. AThis drop in pulmonary resistance and pressure causes the perfusion pressure of the anomalous left coronary artery (LCA) to become compromised. As the body attempts to compensate for the resulting myocardial ischemia, large collateral vessels develop on the epicardial surface, connecting the normally positioned, high-pressure right coronary artery (RCA) system to the low-pressure LCA system. The actual "steal" happens because blood entering the LCA from these collaterals follows the path of least resistance into the low-pressure pulmonary artery rather than flowing into the higher-pressure vessels that supply the myocardial capillary bed. This creates a net left-to-right shunt where oxygenated blood is diverted away from the heart muscle and into the pulmonary circulation. This retrograde flow from the left coronary system into the pulmonary artery is most prominent during diastole and is a primary driver of the severe left ventricular dysfunction and heart failure seen in affected infants. Coronary steal is dependent on the development of collateral vessels between the right and left coronary systems. If a patient has not yet developed adequate collaterals, the left coronary artery (LCA) remains dependent on the PA for its perfusion pressure. Because the PA pressure is now much lower than the aortic pressure, the perfusion pressure for the LCA becomes compromised. At this stage, the primary issue is myocardial ischemia because the heart muscle is being perfused with deoxygenated blood at a pressure that is too low to meet its metabolic demands. In this scenario, blood from the PA may reach the LCA but provides poor oxygenation and inadequate pressure, which leads to left ventricular dysfunction and potentially frank infarction. This is generally described as coronary insufficiency rather than "steal". As the body attempts to compensate for this ischemia, large collateral vessels develop on the epicardial surface, connecting the high-pressure Right Coronary Artery (RCA) system to the low-pressure LCA system. The coronary steal occurs specifically at this point: 

• Oxygenated blood from the RCA enters the LCA via these collaterals. 

• Instead of flowing into the high-resistance myocardial capillary bed to provide oxygen to the heart muscle, the blood follows the path of least resistance. 

• The path of least resistance is the low-pressure pulmonary artery. 

• Consequently, blood flows retrogradely (backward) through the LCA and "dumps" into the pulmonary artery.

1. Does steal only happen if there are collaterals? 

   • Yes. Without the "bridge" provided by collaterals, there is no source of high-pressure blood to be "stolen" by the low-pressure pulmonary circuit. Without collaterals, the LCA simply suffers from low inflow and low pressure. 

2. What if there are no collaterals? 

   • If collateral flow is initially insufficient, it results in myocardial ischemia and decreased left ventricular function because the LCA is not being adequately perfused by either the aorta or the PA. 

3. Is blood from the PA going directly to the lungs considered steal? 

   • No. Blood flowing from the PA into the lungs is the normal path of pulmonary circulation. "Coronary steal" specifically refers to blood that has already entered the coronary arterial system being diverted away from the myocardial tissue and into the pulmonary artery. This creates a left-to-right shunt, where blood that should have nourished the heart is "stolen" by the lungs.

Anatomy and Pathophysiology:

• The LCA typically arises from the main pulmonary artery (MPA), usually from the left pulmonary valve sinus, but rarely from a branch pulmonary artery.

• Embryologically, this anomaly may result from the failure of cells of the capillary plexus surrounding the pulmonary artery and aorta to reach the normal coronary origins in the aorta, with concomitant persistence of pulmonary buds.

• In utero, pulmonary and aortic pressures are similar, allowing for relatively normal coronary perfusion.

• Postpartum, as pulmonary vascular resistance (PVR) drops drastically and aortic pressure exceeds PA pressure, blood flows preferentially from the higher-pressure systemic circulation (via the Right Coronary Artery and collaterals) into the lower-pressure pulmonary circulation through the anomalous LCA. This phenomenon is called "coronary steal".

• This retrograde flow leads to reduced coronary perfusion and myocardial ischemia in the territory supplied by the LCA. The low perfusion pressure is considered the primary cause of serious problems seen in ALCAPA.

Types and Presentation: 

ALCAPA is typically classified into two types based on age of presentation, which is largely determined by the development of coronary collaterals:

• Infant Type (approximately 85%): These infants have little to no collateral development. As pulmonary artery pressure falls after birth, they develop severe myocardial ischemia. Presentation is usually around 2–3 months of age with symptoms of congestive heart failure. Symptoms may include dyspnea, tachypnea, prolonged or difficult feeding, pallor, diaphoresis, delayed development, and failure to thrive. Infants may also present with sudden, unexplained crying or screaming in the setting of heart failure. A unique hallmark in the patient history is feeding-induced colic; parents may report that the child becomes extremely distressed while eating, which is believed to be a form of angina or chest pain triggered by the increased metabolic demands of sucking and swallowing. Physical examination may reveal varying degrees of mitral regurgitation (MR) and left ventricular (LV) dysfunction. MR can be functional due to LV dilation or a result of papillary muscle ischemia. Untreated, infant mortality is reported to be as high as 90% in the first year of life. Many of these infants have bright (echogenic) papillary muscles and bright LV myocardium with ischemia on echocardiography, they can present severe LV dysfunction.

• Adult Type (approximately 15%): While many patients are diagnosed in infancy, some survive longer if they develop extensive collateral circulation between the right and left coronary arteries. These older patients might remain asymptomatic or present with a continuous heart murmur and angina during physical exertion, though they remain at risk for sudden cardiac death. These patients survive infancy due to the development of large, extensive inter-coronary collaterals, often from a dominant RCA. They may remain asymptomatic until childhood or adulthood. Symptoms in older children/adults, when present, include palpitations, syncope, dyspnea, chest pain, and fatigue. This type is a well-known cause of sudden cardiac death in adults. There is an estimated 80% to 90% incidence of sudden death at a mean age of 35 years in those who survive past childhood. Survival beyond 50 years of age without repair is very rare.

Associated Lesions: 

ALCAPA usually occurs in isolation. However, it can be associated with other congenital heart diseases such as atrial septal defect (ASD), ventricular septal defect (VSD), patent ductus arteriosus (PDA), Tetralogy of Fallot (TOF), aorto-pulmonary window, and coarctation of the aorta (CoA).

Diagnostic Evaluation: 

To confirm the diagnosis, sonographers look for the hallmark feature of retrograde or reversed color flow within the left coronary artery, where blood moves away from the myocardium and toward the pulmonary artery. Other findings include an enlarged right coronary artery, which dilates to compensate for the collateral burden, and visible color jets entering the pulmonary artery. However, a still frame image can be highly misleading because the thin aortic wall and the close proximity of the vessels can make it appear as though the coronary arises normally from the aorta when it does not. Still frame is not acceptable for evaluations of coronary arteries. Because of the diagnostic challenges, there is a need for humility regarding the fact that echocardiography may not be diagnostic, and a multi-modality approach. If a child presents with a dilated cardiomyopathy and the coronaries appear normal on echo, the diagnosis of ALCAPA must still be pursued through other means, such as CT or MRI, because it represents a potentially reversible form of heart disease. CT and MRI are particularly useful for providing a three-dimensional view and identifying the exact origin and course of the vessels, which can be obscured on ultrasound by artifacts or signal dropout. It is also important to differentiate ALCAPA from rare conditions like congenital atresia of the left main coronary artery, which mimics the clinical appearance of ALCAPA but lacks the retrograde flow into the pulmonary artery.

Prompt diagnosis is crucial for guiding surgical intervention and improving prognosis.

• Echocardiography: This is the diagnostic imaging modality of choice. It is safe, readily available, inexpensive, and portable for initial investigation. Key findings include:

  • Direct visualization of the LCA originating from the PA.

  • Retrograde flow from the LCA into the PA, particularly noted by color Doppler in diastole.

  • A dilated and often tortuous RCA.

  • Difficulty identifying the LCA arising from the aorta.

  • Significant collateral coronary arteries, sometimes seen in the interventricular septum. Pulse-wave Doppler can differentiate continuous flow in collaterals from systolic flow in VSDs.

  • Mitral regurgitation and left ventricular dysfunction.

  • Echogenic myocardium or papillary muscles.

  • Abnormal diastolic flow entering the PA.

  • The parasternal short-axis view provides the best views of the coronary origins.

  • Echocardiography can make an early diagnosis, including in asymptomatic patients. Suspect ALCAPA when echo shows a large RCA or retrograde flow in the LCA. Limitations include poor spatial resolution and difficulty visualizing the anomalous origin.

• Electrocardiogram (ECG): ECG findings suggestive of ALCAPA include abnormal deep or wide Q waves, inverted T waves, and poor R wave progression in leads I, aVL, and precordial leads V4 to V6. Left ventricular hypertrophy and myocardial injury patterns may also be present. ECG changes were observed in 77.8% of patients aged 5-16 years in one study.

• Chest X-ray (CXR): May show marked cardiomegaly and pulmonary congestion. Enlarged LA and LV may be suggested. Cardiomegaly was present in 77.8% of patients in one series.

• Cross-sectional Imaging (Computed Tomography Angiography - CTA or Magnetic Resonance Angiography - MRA): These modalities provide superior visualization of the coronary arteries compared to echo and can be used for definitive diagnosis, anatomical assessment, and postoperative follow-up. Findings include direct visualization of the LCA originating from the PA, dilated RCA with collaterals, and abnormal LV wall movement. CMR can also assess ventricular size and function. Used for older children or when echo findings are uncertain.

• Cardiac Catheterization (Angiography): While not routinely used for initial diagnosis now, angiography can corroborate the diagnosis. It shows the dilated, tortuous RCA, collaterals to the LCA, and anomalous flow into the PA. Angiography provides detailed visualization of collaterals and can quantify left-to-right shunts. Some sources still recommend corroborating echo findings with angiography. It can help differentiate ALCAPA from other lesions like a coronary fistula to the PA.

• Non-invasive Ischemic Evaluation: Tests like cardiopulmonary exercise testing, stress echocardiography, and myocardial stress perfusion can reveal ischemia.

Management: 

Surgical intervention is the recommended treatment for ALCAPA patients regardless of age and symptoms due to the lifelong risk of ischemia, ventricular dysrhythmias, and sudden cardiac death. The modern objective of surgery is to reestablish a dual coronary system that provides oxygenated blood to the heart.

• Surgical Approaches: Various techniques have been used, including direct reimplantation of the coronary artery into the aorta (coronary button transfer), transpulmonary baffling (Takeuchi technique), subclavian-LCA anastomosis, and coronary artery bypass grafting (CABG) with ligation of the anomalous LCA. Direct reimplantation and its modifications are common modern methods. The Takeuchi technique involves creating an intrapulmonary baffle. CABG is often used in older patients where direct reimplantation is difficult.

• Older Methods: Simple ligation of the anomalous artery was used in the past. While potentially used to delay more intensive surgery in severely ill infants, it is now avoided as an exclusive method due to associated complications, including persistent ischemia and sudden death risk.

• Medical Management: Medications can be used alongside surgery. Preoperative drug treatment may be used in infants with acute myocardial ischemia to help recover cardiac function. In rare high-risk adults, medication might be used instead of surgery.

• Cardiac Transplantation: This is reserved for patients with severe LV dysfunction and refractory heart failure.

In summary, the definitive treatment for ALCAPA is surgical intervention, which typically involves the re-implantation of the anomalous coronary artery into the aorta. In cases where the coronary artery is located too far from the aorta to be moved safely, surgeons may perform a Takeuchi procedure, which creates a baffle within the pulmonary artery to direct aortic blood into the coronary orifice. Following surgery, patients require close monitoring to ensure the recovery of left ventricular function and to check for complications like supravalvular pulmonary stenosis caused by the surgical baffle. While most patients show substantial improvement after repair, some may have persistent issues such as papillary muscle fibrosis or subtle myocardial perfusion defects that can be detected during long-term follow-up.

Prognosis and Outcomes: 

With surgical correction, generally positive long-term outcomes with low mortality rates are expected. Long-term survival is excellent, but depends on the recovery of ventricular function and the degree of mitral regurgitation. One study reported an 83.4% Kaplan–Meier survival rate one year post-operation in pediatric patients, with 13.8% hospital deaths. Another series reported 8.5% in-hospital mortality with no late deaths. The 10-year transplant-free survival rate is reported to be 95%. LV function typically recovers, symptoms improve, and MR often ameliorates after surgery. Complete recovery is possible if surgery is performed before irreversible myocardial damage occurs. However, some degree of MR may persist, particularly if severe pre-operatively. Residual MR and LV dysfunction may be more common in those operated on later in infancy. The type of surgical correction has not been found to significantly impact mortality, but different procedures have different complication profiles.

Complications: Potential complications after surgical repair include persistent mitral regurgitation, pulmonary artery stenosis (especially with the Takeuchi technique), baffle leaks or obstruction (Takeuchi technique), aortic regurgitation (Takeuchi technique), LCA tearing or bleeding in adults during reimplantation, and graft occlusion or stenosis (CABG). Mitral valve intervention timing is controversial as MR often improves after ALCAPA repair, but may be warranted if severe. Lifelong follow-up with a cardiologist is necessary to monitor for complications.

References

• Blickenstaff EA, Smith SD, Majdalany DE. Anomalous Left Coronary Artery from the Pulmonary Artery: How to Diagnose and Treat. Journal of Personalized Medicine. 2023;13(11):1561. DOI: 10.3390/jpm13111561. https://doi.org/10.3390/jpm13111561.

• Dipchand AI, et al., editors. Manual of Cardiac Care in Children. Springer Nature Switzerland AG; 2024. ISBN: 978-3-031-70973-9. DOI: 10.1007/978-3-031-70973-9. https://doi.org/10.1007/978-3-031-70973-9.

• Ho SY, Rigby ML, Anderson RH. Echocardiography in Congenital Heart Disease Made Simple. Imperial College Press; 2005. ISBN: 1-86094-124-9.

• Archivos de Cardiología de México. Anomalous origin of the Left Coronary Artery from the Pulmonary Artery. Echocardiographic diagnosis. ISSN: 1405-9940, e-ISSN: 1665-1731. Copyright © 2025 Elsevier España SLU. (URL inferred from publisher and journal title: https://www.elsevier.es/es-revista-archivos-cardiologia-mexico-73?bd=1).

• Jinmei Z, Yunfei L, Yongjun Q, yue W. Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) diagnosed in children and adolescents. Orphanet Journal of Rare Diseases. 2020;15:90. DOI: 10.1186/s13019-020-01116-z. https://doi.org/10.1186/s13019-020-01116-z.

• Khalid O, Awad S, editors. Pediatric Electrocardiography: An Algorithmic Approach to Interpretation. Springer International Publishing Switzerland; 2016. ISBN: 978-3-319-26256-7 (Print), 978-3-319-26258-1 (eBook). DOI: 10.1007/978-3-319-26258-1.

• Park IS, editor. An Illustrated Guide to Congenital Heart Disease: From Diagnosis to Treatment – From Fetus to Adult. Springer Nature Singapore Pte Ltd.; 2019. ISBN: 978-981-13-6977-3 (Print), 978-981-13-6978-0 (eBook). DOI: 10.1007/978-981-13-6978-0. https://doi.org/10.1007/978-981-13-6978-0.

• Rudolph AM. Congenital Diseases of the Heart: Clinical-Physiological Considerations. 3rd ed. John Wiley & Sons, Ltd. / Wiley-Blackwell; 2009. ISBN: 978-1-405-16245-6. (URL inferred from title, author, and publisher: https://onlinelibrary.wiley.com/doi/book/10.1002/9781444301549).

ARCAPA and CALM

Anomalous right coronary artery from the pulmonary artery, or ARCAPA, is a rare congenital condition where the right coronary artery arises from the pulmonary artery instead of the aorta. This diagnosis typically features a later clinical presentation than the left-sided version of the disease because the right ventricle operates at lower pressures, meaning the myocardium does not usually experience the same degree of early ischemia. While ventricular dysfunction is uncommon in these patients, there have still been reported cases of sudden death in this population. Patients with this condition often present with a continuous heart murmur and may or may not experience symptoms such as chest pain or distress during physical exertion. A defining physiological characteristic of the condition is the presence of a significant collateral burden. Because the right side of the coronary system is being supplied through connections from the left side, the left coronary artery often becomes very dilated as it takes on the burden of providing flow to the entire heart. On an echocardiogram, these changes can be visualized through specific imaging windows. In the parasternal short axis view, the dilation of the left coronary artery is often a prominent finding. Furthermore, a parasternal long axis view may allow for the visualization of the right coronary artery as it makes its way into the proximal portion of the main pulmonary artery. However, echocardiography has limitations, such as the inability to always distinguish the aortic wall from a coronary orifice or the difficulty of identifying an intramural course. Because of these diagnostic challenges, while coronary anomalies can be ruled in by ultrasound, they cannot always be completely ruled out. If clinical signs such as a continuous murmur or a dilated left coronary artery are present but the origins appear normal on echo, other modalities like CT or MRI should be used to provide a definitive three-dimensional view. These advanced imaging techniques are highly effective for confirming the exact origin and course of the vessels, which is critical for planning surgical intervention.

CALM syndrome, which is the acronym for congenital atresia of the left main coronary artery, is an extremely rare anomaly where the left coronary artery ends blindly because the patient has no left coronary ostium. Anatomically, the left coronary artery fails to connect to the aorta, forcing the heart to rely entirely on collateral flow from an enlarged right coronary artery to perfuse the left side of the heart. Because of this reliance on collaterals and the resulting myocardial ischemia, CALM syndrome closely mimics the clinical presentation of ALCAPA, often featuring a massively dilated left ventricle and echo brightness or sclerosing of the endocardium and papillary muscles. While the echocardiographic findings of a poorly contractile, enlarged heart and subtle retrograde color flow in the left anterior descending artery are common to both conditions, a critical diagnostic difference is that unlike ALCAPA, CALM syndrome does not exhibit retrograde flow into the pulmonary artery. Due to these similarities and the subtle nature of the imaging findings, this condition usually requires additional imaging, such as CT or MRI, to definitively confirm the atresia and rule out an anomalous origin from the pulmonary artery.

ECG in ALCAPA

Q waves: 

• Pathologic Qs in I, aVL, V5, V6 Suggest anterolateral infarction pattern (see ECG below).

• Abnormal Qs in infants should raise red flags. These Q waves are deep and wide, supporting anterolateral myocardial injury or infarction, which is common in ALCAPA due to poor perfusion of the left ventricle.

• Deep, narrow, dagger-like Q waves are typically seen in leads I, aVL, and the left precordial leads (V4–V6), often much deeper than physiologic Q waves of healthy infants, with Q waves in V5–V6 and aVL >3 mm considered highly suggestive of ALCAPA.

Chest radiography

Case 1

Case 2

Case 3

In this case, one may observe a neonate who presented at two weeks of life with diaphoresis, difficulty feeding, tachypnea and failure to thrive. The patient was found to have ischemic changes on electrocardiogram and severe LV failure by echocardiography. The coronary artery was found to be attached to the pulmonary artery. Here, you will appreciate by colour Doppler the abnormal implantation of the left coronary artery.