A coronary fistula (or coronary arteriovenous fistula) is a rare, typically congenital, abnormal connection between a coronary artery and a cardiac chamber, systemic vein, pulmonary artery, or the coronary sinus.
Because the blood bypasses the normal myocardial capillary bed and flows directly into a low-pressure target, it can create a “steal” phenomenon — myocardium downstream of the fistula is underperfused.
1 CCTA imaging findings
- A markedly enlarged, tortuous feeding coronary artery that terminates into an abnormal drainage site.
- Aneurysmal dilatation of the vessel immediately proximal to the drainage site is often present.
The contrast shunt sign. On CCTA, imagers can frequently visualize a distinct jet of high-density arterial contrast spilling into the lower-attenuation blood of the receiving chamber (e.g. the right ventricle) or the coronary sinus.
2 Clinical significance
- Small fistulas are often asymptomatic and found incidentally.
- Larger fistulas can cause severe complications due to blood shunting:
- Angina pectoris (from the steal phenomenon)
- Congestive heart failure
- Pulmonary hypertension
- Endocarditis
Larger or symptomatic fistulas require surgical ligation or transcatheter closure.