Discussion
Congenital CAFs occur with equal frequency in both sexes, there is no
research to suggest a correlation to ethnicity. In the general
population, the occurrence of coronary anomalies ranges from 0.2% to
1.2%, with CAFs constituting 0.002% of these cases. Among CAFs,
solitary fistulas are more prevalent, and approximately 75% of
incidentally discovered CAFs exhibit no clinical symptoms. (1)
The RV serves as the most common drainage site for CAFs, representing
34.9% of reported cases. The RA and the PA rank as the second most
frequent drainage sites, each comprising 27% of cases, followed by the
left ventricle at 6.3%. The coronary sinus accounts for 3.2% of cases,
and lastly, the left atrium makes up 1.6% of occurrences. (7)
The most common types of CAFs have a congenital etiology. Anomalies in
the coronary arteries can arise from various sources, including the
persistence of rudimentary embryonic coronary arterial structures,
disruptions in normal development or atrophy processes, and misplacement
of connections within an otherwise typical coronary artery. (1,8)
CAFs can be classified based on their size: small, medium, or large,
depending on whether the fistula diameter is < 1, between 1 to
2, or > 2 times the largest diameter of the coronary vessel
that does not supply the coronary fistula. They can also be categorized
according to the drainage site: coronary-cameral fistula (the most
common), coronary-to-pulmonary artery fistula, coronary
artery-to-coronary sinus, and coronary artery-to-bronchial artery
fistula. (2,9) A shunt from left to right (coronary artery to right
vessels or chambers) leads to an ongoing flow throughout the entire
cardiac cycle, driven by the lower pressure within the right structure
(vessel or chamber) in comparison to the myocardial capillaries or
arterioles. This often gives rise to a volume overload on the right
side, although this pathophysiological mechanism can also involve
chambers on the left side. (1)
Symptoms typically arise around age 18, with dyspnea being the primary
symptom, accompanied by fatigue, congestive heart failure and pulmonary
hypertension. Possible complications encompass coronary artery dilation,
aneurysm formation, intimal ulceration, medial degeneration, intimal
rupture, atherosclerotic deposition, calcification, side-branch
obstruction, mural thrombosis, and rupture. Notably, angina pectoris is
rare without arteriosclerotic coronary artery disease. (3,4)
A characteristic physical finding in patients with CAFs is the presence
of a gentle, continuous murmur. This murmur typically follows a
crescendo-decrescendo pattern in both systole and diastole, with its
intensity being more pronounced during diastole. (3) Depending on the
location where the fistula connects to the heart, the murmur will be
most audible at certain points on the chest wall. (4)
Diagnosing CAFs can be challenging. Initial assessment includes an
electrocardiogram, with findings based on the fistula’s location and
flow. Selective invasive coronary angiography used to be the reference
standard. It enables precise visualization of the anatomy of the CAF,
including fine vessels, with high temporal and spatial resolution and
yields hemodynamic information. In addition, it facilitates the
diagnosis and therapeutic embolization. However, conventional coronary
angiography is invasive and involves risks of procedure related
complications. Furthermore, it yields two-dimensional projection images,
which are often limited in the delineation of the complex anatomy of
abnormal communications, with reported correct diagnosis rates of
35%–50%. (5).
Selective invasive coronary angiography has been replaced by TTE, the
now preferred initial assessment method. TTE can show dilated coronary
arteries (coronary artery fistulas that are large and/or have a diameter
greater than 3 mm) and distal drainage via color flow mapping in CAF
cases. (9) However, it’s less effective for small shunts and pulmonary
artery fistulas. Microbubbles enhance color Doppler signals to pinpoint
CAF locations. (7) Two-dimensional echocardiography displays heart
enlargement and function, but not fistula function. (4)
MDCT is a valuable alternative to echocardiography and catheter
angiography for evaluating anomalies, with its increased use leading to
enhanced anomaly recognition due to improved sensitivity in volumetric
data acquisition and pre-procedural planning for patients with larger
communications to specific heart chambers, defining fistula
characteristics and assisting in treatment approach decisions, device
selection, embolization predictions, and optimal fluoroscopic angle
identification. (7,10)
DSCT with ECG gating provides high-resolution images in a shorter time
frame through a single breath-hold, with superior temporal and spatial
resolution compared to MRI. Volume-rendered images from
three-dimensional CT data sets offer comprehensive views of cardiac and
vascular anatomy, aiding surgical planning by clarifying anatomical
complexities. The primary downside of CT lies in radiation exposure
risk, which can be mitigated by modern DSCT scanners and advanced dose
reduction techniques. (7,10)
The updated 2018 American College of Cardiology/American Heart
Association guidelines underscore the significance of a collaborative
heart team approach to assess the suitability and feasibility of CAFs
closure at centers proficient in both percutaneous and surgical closure
techniques. (11)
Common clinical scenarios warranting consideration for CAFs closure
encompass evidence of ischemia in the feeder artery territory,
arrhythmias suspected to be linked to CAFs, endarteritis, vessel
rupture, cardiac chamber enlargement, and ventricular dysfunction. It’s
crucial to highlight that small CAFs tend to close spontaneously over
time, allowing for monitoring without intervention. In contrast, medium
to large sized fistulas can expand, particularly in pediatric and young
adult patients, often associated with proximal coronary artery dilation
signifying prolonged high shunt flow. Medium-sized fistulas are ideally
closed early to prevent further growth, as closing larger fistulas
carries a heightened risk of myocardial infarction. (2)
Hyun Woo Goo’s 2021 review outlined the following as contraindications
(9) for percutaneous transcatheter closure: fistulas draining near the
atrioventricular annulus, extreme tortuosity, a very small patient size
that complicates the procedure, as well as multiple communications and
drainage sites.