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.