Anomalous Right Coronary Artery from the Pulmonary Artery

Anomalous right coronary artery from the pulmonary artery (ARCAPA) is a rare congenital anomaly (about 0.002% of the population, under 0.1% of congenital heart disease) in which the right coronary artery arises from the main pulmonary trunk, less often from the right pulmonary artery.

It is about one tenth as common as ALCAPA and is usually isolated, though it may accompany aortopulmonary window, tetralogy of Fallot, patent ductus arteriosus, ventricular septal defect, bicuspid aortic valve or truncus arteriosus.

Many patients are asymptomatic into adult life and the diagnosis is made incidentally, but myocardial ischaemia, ventricular arrhythmia and sudden death occur.

Pathophysiology. The right ventricle has lower pressure and oxygen demand than the left, and abundant collaterals from the left coronary system usually perfuse the right coronary territory in retrograde fashion. The collateral flow ends in the pulmonary artery as a small left-to-right shunt (coronary steal).

The left coronary artery becomes dilated and tortuous. Steal and a reduced diastolic perfusion pressure produce ischaemia of the right ventricle and inferior wall, particularly with exertion, and ventricular arrhythmia from scar.

• Often asymptomatic, with an incidental continuous murmur at the left sternal border.
• Angina, exertional dyspnoea, palpitations, syncope, right ventricular or inferior wall infarction, heart failure and sudden death.
• Infants rarely present with heart failure, usually when another lesion coexists.
• ECG is often normal, or shows inferior Q waves and ST-T changes.

Red flags.

• Exertional chest pain or syncope
• Ventricular arrhythmia or resuscitated arrest
• Right ventricular dysfunction
• Reversible perfusion defect in the right coronary territory
• Rising troponin

• Echocardiography: dilated, tortuous left coronary artery, septal collaterals, right coronary flow entering the pulmonary artery (diastolic colour jet), no right coronary ostium on the aortic root, and right ventricular function.
• CT coronary angiography: the best test; origin, course, collateral anatomy and associated lesions.
• Cardiac MRI: right ventricular volumes and function, perfusion and scar.
• Stress imaging (nuclear, echocardiographic or MRI perfusion): shows inducible ischaemia and directs the timing of surgery.
• Cardiac catheterisation with selective coronary angiography and shunt measurement: when non-invasive imaging is unclear.
• Ambulatory ECG: for ventricular arrhythmia.

Differential diagnosis.

• Coronary artery fistula draining to the pulmonary artery
• ALCAPA
• Aortopulmonary window with coronary involvement
• Patent ductus arteriosus
• Ruptured sinus of Valsalva aneurysm
• Atherosclerotic coronary disease
• Anomalous aortic origin of a coronary artery
• Right coronary artery to pulmonary artery collateral flow in chronic occlusion

• Surgery is advised for symptoms, ischaemia, right ventricular dysfunction or arrhythmia. Many centres also repair asymptomatic patients on diagnosis, because sudden death has been reported in apparently silent cases. Operative risk is low.
• Operation: direct reimplantation of the right coronary artery into the aorta (preferred), or ligation of the origin with bypass grafting (saphenous vein, radial artery or right internal mammary artery) when reimplantation is not feasible. Ligation alone is not enough when the territory is at risk.
• After bypass grafting: aspirin 75 to 100 mg orally once daily indefinitely (usual maximum 325 mg daily); graft patency is checked by CT angiography.
• Pending surgery, for angina or ventricular ectopy: bisoprolol 5 mg orally once daily, increased to 10 mg once daily as needed, maximum 20 mg daily, with heart rate, blood pressure and ECG monitoring. Do not exceed 10 mg daily at creatinine clearance under 20 mL/min or in severe liver impairment. Contraindicated in sinus node disease, second or third degree atrioventricular block without a pacemaker, and severe asthma. Beta blockade is a bridge only.
• Ventricular arrhythmia or cardiac arrest: revascularisation, and an implantable cardioverter defibrillator when arrhythmia persists.

Special groups. Pregnancy is high risk with unrepaired disease and ischaemia. Repair before conception.

Monitoring. Echocardiography, ECG and symptom review at 3 and 12 months after repair, then every 1 to 2 years. Stress imaging or CT angiography at 6 to 12 months to confirm graft or reimplanted vessel patency. Ambulatory ECG yearly with a history of arrhythmia.

Referral and escalation. Refer to a congenital heart disease centre with coronary surgical experience. Urgent for ischaemic symptoms, arrhythmia or right ventricular dysfunction.