What is the medical significance of ARCAPA?

ARCAPA: Anomalous Right Coronary Artery from the Pulmonary Artery

Definition and Clinical Significance

ARCAPA is a rare congenital coronary anomaly where the right coronary artery originates from the pulmonary artery instead of the aorta, occurring in approximately 0.002% of patients undergoing coronary angiography. 1 This malformation carries significant risk for myocardial ischemia, left ventricular dysfunction, myocardial infarction, and sudden cardiac death, even in asymptomatic patients. 2, 3, 1

Pathophysiology

• Adult survivors typically develop extensive collateral networks from the left coronary artery to the anomalous right coronary artery, which contributes to dilation of both vessels. 4
• This collateral development explains why many patients remain asymptomatic or paucisymptomatic until later in life (typically around 40-60 years). 2
• The anomalous RCA receives deoxygenated blood from the pulmonary artery, creating a chronic ischemic state. 3
• Retrograde flow from the RCA to the main pulmonary trunk can occur, creating a left-to-right shunt. 1

Clinical Presentation

Patients present along a wide spectrum from completely asymptomatic to sudden cardiac death. 2, 5

Common presentations include:

• Asymptomatic with incidental discovery (most common in adults). 5
• Intermittent chest pain or angina. 3
• Dyspnea on exertion. 2
• Heart murmur (continuous murmur may be audible). 2
• Fatigue and exercise intolerance. 3
• Congestive heart failure symptoms. 3
• Myocardial infarction. 3, 1
• Sudden cardiac arrest or death. 3, 1

Isolated ARCAPA (without other structural cardiac defects) is typically diagnosed later in life compared to cases with associated cardiac anomalies. 2

Diagnostic Evaluation

Initial Imaging

Coronary CT angiography has become the gold standard for assessment of anomalous coronary origin and course in adults. 4 The American Heart Association recommends CT or magnetic resonance angiography as the initial screening method in centers with expertise in such imaging. 4

Echocardiography

• Echocardiography can identify dilated coronary arteries in children and young adults but has limitations in older adults. 4
• Key echocardiographic findings include: dilated coronary arteries (32.1% of cases), coronary collaterals (28.6%), and retrograde flow from RCA to main pulmonary trunk (25%). 1
• Echocardiography serves as a convenient, non-invasive, and reliable primary screening method when ARCAPA is suspected. 1

Coronary Angiography

• Invasive coronary angiography remains the definitive diagnostic test and is valuable for delineating arterial course, branches, and assessing for atherosclerosis. 4, 2
• Angiography typically demonstrates the anomalous origin of the RCA from the pulmonary artery and extensive collateral vessels from the left coronary system. 2, 3

Additional Testing

• Stress testing (dobutamine stress echo or exercise stress test) to evaluate for inducible ischemia. 6, 3
• Myocardial perfusion imaging with dipyridamole to quantify ischemic burden. 6
• Electrocardiogram may show ischemic changes during stress or at rest. 3
• Troponin levels if acute coronary syndrome is suspected. 3

Management Recommendations

Surgical Intervention

The American College of Cardiology/American Heart Association guidelines recommend reconstruction of a dual coronary artery supply in patients with ARCAPA, with surgery performed by surgeons with training and expertise in congenital heart disease at centers with expertise in managing anomalous coronary artery origins. 7, 4

General recommendations suggest early corrective intervention to prevent complications such as myocardial ischemia and cardiac dysfunction, even in asymptomatic patients. 2

Surgical options include:

• Reimplantation of the RCA into the aorta (most commonly performed, 53.6% of cases). 1
• Coronary artery bypass grafting in selected cases. 1

Conservative Medical Management

After complete imaging assessment and thorough clinical evaluation, medical management could be regarded as a valid alternative to surgery for paucisymptomatic ARCAPA patients with evidence of limited ischemia. 6

Medical therapy includes:

• Aspirin for antiplatelet effect. 3
• Beta-blockers to reduce myocardial oxygen demand. 3
• Statins for cardiovascular risk reduction. 3

A case report demonstrated successful 2-year event-free follow-up with medical therapy alone in a patient with mild ischemia at stress testing. 6

Critical Decision Point

The decision between surgical and conservative management should be based on:

• Extent of ischemia on stress testing (limited vs. significant). 6
• Symptom burden (asymptomatic vs. symptomatic). 6, 3
• Left ventricular function. 3
• Patient preference and surgical risk. 3

Long-term Follow-up

For adult survivors of ARCAPA repair, clinical evaluation with echocardiography and noninvasive stress testing is indicated every 3 to 5 years. 7, 4

• Even after successful repair, residual coronary abnormalities may persist, including proximal, midvessel, and distal coronary artery obstructions. 4
• Patients may have residual myocardial fibrosis from preoperative ischemia, requiring ongoing surveillance. 4

Important Clinical Pitfalls

• Do not dismiss asymptomatic patients – ARCAPA carries risk of sudden cardiac death even without symptoms. 2, 1
• Recognize the anomaly during cardiac catheterization – failure to identify the anomalous origin can lead to missed diagnosis and delayed treatment. 3
• Do not rely solely on standard echocardiography in older adults – CT or MR angiography is more sensitive. 4
• Consider ARCAPA in young to middle-aged adults with unexplained chest pain or ischemic changes, especially if standard coronary angiography shows extensive collaterals. 3