History

A 65-year-old gentleman with hypertension and hyperlipidemia, an idiopathic left bundle branch block and new dyspnea on exertion had a pharmacologic nuclear stress test that showed anteroseptal and distal lateral ischemia. Coronary angiography demonstrated a tangle of dilated vessels off of the right coronary artery with a potential fistula to a cardiac chamber or to the pulmonary artery, and an approximately 50% mid LAD stenosis with a fractional flow reserve of 0.78, and a 90% stenosis in the mid circumflex coronary artery. Intravascular ultrasound of the LAD showed a minimum luminal area of 2.1 mm2. Shunt fraction calculated in the right pulmonary artery was estimated at 1.4 by oximetry. CT coronary angiography was requested to further evaluate for a potential coronary artery fistula and determine the site of communication. The Cardiac CT demonstrated a coronary artery fistula off the distal RCA that demonstrated a small narrowed communication with the right pulmonary artery. The chamber sizes were normal. The CT also confirmed a significant stenosis in the mid circumflex and a moderate stenosis in the mid LAD. Based on the anatomic findings from the cardiac CTA and the physiologic information from the interventional coronary angiogram that included, a lack of chamber enlargement, normal pulmonary pressures, and relatively low shunt fraction, a decision was made to treat the stenosis found in the LAD and Circumflex coronary arteries with drug-eluting stents, which was performed without complications. The patient's symptoms have resolved and the coronary artery fistula will be followed both clinically and with a possible follow-up Cardiac CT angiogram should the patient later become symptomatic. 

Findings

The coronary angiogram revealed marked enlargement of the RCA with a large tortuous SA Nodal branch and markedly tortuous vessel from the distal RCA with an unclear distal attachment site (Figures 1 and 2). Chamber sizes and pressures were normal.  Subsequent cardiac CTA imaging revealed a large RCA and dilated sinoatrial nodal artery with a tortuous fistula from the distal RCA to the right pulmonary artery (Figure 3, 4,5).   The fistula insertion into the right pulmonary artery was quite small however easily demonstrated on CT (Figure 6).  The moderate stenosis of the LAD and obstructive lesion of the circumflex coronary artery were also confirmed (images not shown).   

Fig 1.	Fig 2.

Early and late RCA injection demonstrates a markedly enlarged SA nodal branch (arrow Fig 1) and tortuous dilated distal RCA with a presumed fistula from the distal RCA (large arrow Fig 2) connecting to an unclear vessel or chamber (small arrow Fig 2).  

Fig 3.
Fig 3. demonstrates the enlarged RCA origin with an enlarged and tortuous SA nodal branch.
Fig 4.	Fig 5.
Figs 4 & 5 demonstrate the tortuous dilated distal RCA with a fistula (black arrow fig 4) off the distal RCA that then extends posterior to the left atrium and ending in a narrowed short insertion into the right pulmonary artery (yellow arrow Fig 6).
Fig 6.
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Discussion  Coronary artery fistulas are defined as abnormal communications bypassing the capillary bed that occurs between a coronary artery to a cardiac chamber or large intra-thoracic vessel.  Coronary artery fistulas comprise 14% of congenital coronary artery anomalies and may be seen in approximately 0.1 to 0.2% of patients undergoing selective coronary angiography.  The majority of patients, in a review by Rittenhouse, found 59% of patients were asymptomatic1.  The most common symptoms when symptomatic were dyspnea at rest or with exertion (19%), angina pectoris or chest pain (10%), and congestive heart failure (9%)2.   Coronary artery fistulas are more commonly congenital but may be acquired from various causes often associated with atherosclerosis or prior myocardial infarction 3.  The factors that determine the hemodynamic significance of the fistulous connection include the size of the communication and the resistance of the recipient chamber.  The larger fistulas may become symptomatic by causing a coronary artery steal phenomenon that leads to ischemia by reducing the myocardial blood flow distal to the site of the fistula by reducing the diastolic flow due to a pressure gradient from the coronary vasulature to a low-pressure receiving chamber or vessel.  Cardiac CTA is a very useful tool in the assessment of complex congenital anomalies of the heart such as in this case by determining the site of chamber or intra-thoracic great vessel communication and determine the size of the coronary fistula.  Back to Top
References RittenhouseEA, Doty DB, Ehrenhaft JL. Congenital coronary artery-chamber fistula: review of operative management. Ann Thorac Surg1975; 20(4): 468-485. Vavuranakis M, Bush CA, Boudoulas H. Coronary artery fistulas in adults: Incidence, angiographic characteristics, natural history. Cathet Cardiovasc Diagn 1995; 35:116-120. Yamanaka O, Hobbs RE. Coronary artery anomalies in 126,595 patients undergoing coronary arteriography. Cathet Cariovasc Diagn 1990; 21:28-40.