When to treat a coronary artery fistula and what is its clinical significance?

Management and Clinical Significance of Coronary Artery Fistulas

Treatment of coronary artery fistulas should be based on symptoms, size, and potential complications, with large fistulas requiring closure regardless of symptoms, while small asymptomatic fistulas can be monitored with periodic follow-up. 1

Definition and Epidemiology

• Coronary artery fistulas (CAFs) are abnormal communications between coronary arteries and cardiac chambers or vessels, bypassing the myocardial capillary network 2
• CAFs have an incidence of 0.1% to 0.2% of all catheterized patients and represent the second most common coronary artery anomaly after anomalous coronary artery origins 1
• These fistulas typically arise from either the right coronary artery or left anterior descending artery, with drainage most commonly to the right atrium, right ventricle, or pulmonary artery 1

Clinical Significance

• Most patients with CAFs are asymptomatic, particularly in childhood, with increasing symptoms developing in adulthood 1
• Clinical manifestations can include:
  • Myocardial ischemia due to coronary steal phenomenon 3
  • Congestive heart failure from volume overload 2
  • Thrombosis within the fistula (rare) potentially causing myocardial infarction 1
  • Paroxysmal atrial fibrillation and ventricular arrhythmias 1
  • Endarteritis 1
  • Risk of rupture, particularly with increasing age and fistula size 1
• Small fistulas may increase in size over time with advancing age and changes in systemic blood pressure and aortic compliance 1

Diagnostic Evaluation

• A continuous murmur is often present and highly suggestive of CAF; its origin should be defined by imaging 1
• Recommended imaging includes:
  • Echocardiography with color Doppler as initial assessment 3
  • CT angiography or MRI for detailed anatomical evaluation 1
  • Coronary angiography for precise delineation of coronary anatomy and hemodynamic assessment, especially for treatment planning 2
• Transcatheter delineation of the CAF course and access to distal drainage should be performed in all patients with audible continuous murmur 1

Treatment Indications

Class I Recommendations (Definite Indications)

• Large CAFs should be closed via transcatheter or surgical approach regardless of symptomatology 1
• Small to moderate CAFs with documented:
  • Myocardial ischemia
  • Arrhythmia
  • Unexplained ventricular dysfunction or enlargement
  • Endarteritis
  • Should be closed via transcatheter or surgical approach 1
• Symptomatic coronary artery fistulae require transcatheter occlusion 1

Class IIa Recommendations (Reasonable Indications)

• Transcatheter occlusion is reasonable for moderate or large coronary artery fistulae without clinical symptoms 1
• Clinical follow-up with echocardiography every 3 to 5 years is useful for patients with small, asymptomatic CAFs to monitor for:
  • Development of symptoms
  • Arrhythmias
  • Progression of size
  • Chamber enlargement that might alter management 1

Class III Recommendations (Not Indicated)

• Transcatheter device occlusion is not indicated for clinically insignificant coronary arteriovenous fistulae (e.g., normal-sized cardiac chambers) 1

Treatment Options

Transcatheter Closure

• Preferred for suitable anatomy due to less invasiveness 4
• Can be performed with coils or other occluding devices 1
• Should only be performed in centers with expertise in such procedures 1
• Potential complications include:
  • Incomplete occlusion with residual shunting
  • Myocardial ischemia if a more distal coronary artery is inadvertently occluded
  • Distal embolization of a coil requiring retrieval 1

Surgical Intervention

• Indicated when transcatheter closure is not feasible or has failed 5
• Should be performed by surgeons with training and expertise in congenital heart disease 1
• Surgical fistula closure can be successful if CAF is well defined and clear surgical access is technically achievable 1
• Potential complications include recurrence if anatomic definition is suboptimal 1

Follow-up Recommendations

• Patients with small, asymptomatic CAFs should have clinical follow-up with echocardiography every 3 to 5 years 1
• Life-long follow-up is essential for all patients with CAFs to monitor for progression of disease or cardiac complications 3
• Antibiotic prophylaxis is recommended for all patients with CAFs undergoing dental, gastrointestinal, or urological procedures 3
• Patients with treated CAFs should have intermediate and long-term follow-up, as these patients may still have large, patulous epicardial conduits 1

Clinical Pitfalls and Caveats

• Differential diagnosis of a continuous murmur includes persistent ductus arteriosus, pulmonary arteriovenous fistula, ruptured sinus of Valsalva aneurysm, and other conditions 1, 2
• Late recanalization or endarteritis has not been reported after coil embolization of coronary artery fistulae 1
• Small fistulas are increasingly detected incidentally with improved imaging techniques, particularly Doppler echocardiography 1
• Spontaneous regression of CAFs has been reported, particularly in small fistulas 1, 4