Discussion
A CAF affects communication between one of the coronary arteries and a cardiac chamber or vein. CAFs are present in 0.2% of patients undergoing diagnostic cardiac catheterization. (8)
The right and left coronary arteries are involved in 55 and 35% of cases, respectively, with involvement of both vessels in just 5% of cases. (2) The arteries serve as a shunt between the coronary system and the cardiac chamber into which they drain. The most common drainage sites are at the right ventricle ventricular fistulae and are exceedingly rare with the incidence being reported as 1.2% of all coronary artery fistulae. (9) Large shunts may present with pulmonary edema, pulmonary hypertension, infective endocarditis, rupture, or thrombosis of the fistula, and associated arterial aneurysm or myocardial ischemia distal to the fistula (‘myocardial steal phenomenon’.) (9)
There are several possible reasons why CAF cannot be visualized directly using transthoracic echocardiography. The CAF may be distally positioned in the coronary circulation, and could be of smaller caliber. This can make them much more difficult to detect, particularly during ventricular systole. However, it is possible to visualize them with contrast when a higher MI (Mechanical Index) is used. This supports visualization of both the myocardial tissue and the contrast agent simultaneously.
The safety of contrast agents (including SonoVue) has been reported previously. It has been used safely during septal ablation in patients with hypertrophic obstructive cardiomyopathy (14). These agents have a good safety profile for use in both cardiac and abdominal ultrasound applications. The incidence of severe adverse reactions to ultrasound contrast agents is no greater, and may be lower than that reported for the contrast agents commonly used in other cardiac imaging tests. (8)
Previously, CAF have been diagnosed with aortography, (10) coronary angiography, (11) and coronary CT. (13) Although there has been a case of color Doppler assessment of a CAF, (12) we cannot readily confirm them with echocardiography. In this study, we employed a new and simple diagnostic approach for CAF using a contrast agent. This assisted with the diagnosis, because it clarifies typical turbulence flow, as it appears in the left ventricle. The use of intraprocedural contrast echocardiography results in an improved procedure and thereby patient outcomes, by shortening the procedure and fluoroscopy time. Contrast echocardiography at the time of aortography proves extremely valuable in both opacifying the coronary arteries and determining which chambers the fistula connects to.
The value of localizing the site of drainage of the fistula is high to the interventional cardiologist, when attempting to close it.