Coronary artery fistula (CAF) is an abnormal connection between the coronary artery and a cardiac chamber, coronary vein, pulmonary artery, or other structures. It is a rare congenital heart disease with an incidence of approximately 1.3%.
Pathological Anatomy
CAF can involve any part of the heart or great vessels. The right coronary artery is most commonly affected (about 50%-60%), and the majority of fistulas drain into the right heart system (90%). The most common drainage sites are the right ventricle (40%), right atrium (25%), pulmonary artery (17%), and coronary sinus (7%). Fistulas draining into the left atrium or left ventricle are less common.
Pathophysiology
Blood from the coronary artery flows directly into a cardiac chamber, leading to increased volume load on the right or left heart. Over time, this may result in congestive heart failure. Additionally, reduced blood supply to the distal coronary artery can cause localized myocardial ischemia.
Clinical Manifestations
Most CAF cases are asymptomatic and are often discovered incidentally during physical examination due to a heart murmur. CAF with significant shunting may cause symptoms of angina. Approximately 75% of patients with CAF develop heart failure symptoms by the age of 40-50.
Key Findings:
- A continuous murmur with a palpable thrill is characteristic.
- For fistulas draining into the right ventricle, the murmur is loudest at the 4th or 5th intercostal space along the left sternal border during diastole.
- For fistulas draining into the right atrium, the murmur is loudest at the 2nd intercostal space along the right sternal border during systole.
- For fistulas draining into the pulmonary artery or left atrium, the murmur is loudest at the 2nd intercostal space along the left sternal border.
Auxiliary Examinations
Electrocardiography (ECG)
ECG may show signs of biventricular hypertrophy. Some patients may have atrial fibrillation.
Chest X-ray
In cases with significant shunting, mild enlargement of the pulmonary vasculature and cardiac silhouette may be observed.
Echocardiography
It can clearly visualize dilated coronary arteries and trace their course. Color Doppler imaging can help identify the location of the fistula opening.
Coronary CTA
It provides detailed information on the origin, course, and termination of the fistula. Magnetic resonance imaging (MRI) can also provide data on blood flow through the fistula, cardiac function, and myocardial thickness.
Cardiac Catheterization
Coronary angiography remains the gold standard for diagnosing CAF.
Diagnosis and Differential Diagnosis
Diagnosis is typically straightforward based on symptoms, precordial murmurs, chest X-ray, ECG, and echocardiography findings. However, CAF should be differentiated from conditions such as patent ductus arteriosus, aortic sinus aneurysm, aortopulmonary septal defect, and ventricular septal defect with aortic regurgitation.
Treatment
Treatment options include interventional therapy and surgical therapy.
Conventional surgical treatments include fistula ligation. Other options include transcatheter embolization of the fistula and surgical repair of the fistula.
Prognosis
Most patients with successfully embolized CAF have a favorable prognosis.