coronary artery fistula ( caf ) is an abnormality in the termination of coronary artery and it was first described in 1865 by krause ( 1 ) .
it is a communication between one or more coronary arteries and a cardiac chamber or great vessel resulting in a left to right shunt .
caf is rare with an estimated prevalence of 0.002% in the general population and 0.05 - 0.25% among patients who undergo coronary angiography ( 2 ) .
the majority of the caf originate from the right coronary artery and drain into the right ventricle ( 3 ) .
herein , we report a rare case of caf from the left circumflex artery to the coronary sinus .
a 35-year - old woman with no co - morbidity was referred to the cardiology unit for palpitations that she had been experiencing since childhood .
the episode occurred at rest , lasting for less than 10 minutes and happened 2 - 3 times a week .
she denied having any chest pain or symptoms of heart failure . on examination , her hemodynamic status was stable .
there was a soft pan - systolic murmur at the precordial area and grade-1 continuous murmur at the left sternal border .
transthoracic 2-dimensional echocardiography demonstrated dilation of both the atrium and left circumflex artery with a maximum diameter of 15 mm color doppler echocardiography showed the course of the left circumflex artery emptying into the coronary sinus ( figure 1 a ) .
continuous turbulence flow on color doppler at the level of coronary artery - coronary sinus connection as well as in the coronary sinus indicated left - to - right shunt flow ( figure 1 b )   for further delineation of the fistulous communication , ecg - gated contrast - enhanced coronary ct angiography was performed .
the patient subsequently underwent an ecg - gated contrast - enhanced coronary ct angiography study using a dual - tube 64-slice multi - detector ct ( siemens , erlangen germany ) .
as per standard protocol in our institution , to achieve a resting heart rate of not more than 70 beats / minute , she was given oral metoprolol 50 mg , and lorazepam 1 mg . in addition , sublingual glyceryltrinitrate 0.5 mg was given immediately before the scan to improve visualization of the coronary artery .
electrocardiographically ( ecg)-gated ct coronary angiogram was performed by intravenous injection of 50 ml of non - ionic low osmolar contrast medium ( iopromide 370 mg / ml ) via 18 gaugebranula at a rate of 5 ml / s .
the ct scan revealed a tortuous fistulous communication between the left circumflex artery and the coronary sinus 13.6 mm in diameter for the left circumflex artery and 11.8 mm ( axial ) and 24 mm ( coronal ) diameter for the coronary sinus ( figures 2 and 3 ) .
the circumflex artery was remarkably large and originated directly from the left coronary cusp of the aorta . left anterior descending artery originated from the left circumflex artery .
the coronary sinus was bulky in size draining into the right atrium causing right atrial enlargement due to volume overload .
the patient was referred for cardiac catheterization , which confirmed a giant coronary arterial - venous ( a - v ) fistula arising from a dilated and mildly tortuous circumflex artery ( figure 4 ) .
the vessel course could not be well delineated because of its poor contrast opacification . at present
coronary artery fistulas ( caf ) are anomalous terminations of the coronary arteries and are considered a major congenital anomaly ( 4 ) . caf is a rare abnormality and usually occurs alone ( 5 ) .
congenital cafs are thought to arise as a result of incomplete embryonic development ; normally the coronary arteries communicate with the great vessels and chambers of the heart via sinusoids and during development , these sinusoids transform into a normally calibrated capillary network .
it has been postulated that incomplete closure of these sinusoids can result in caf ( 4 ) .
acquired caf can occur as a result of inflammation , atherosclerosis , trauma and collagen vascular disease . in our case ,
the patient had no significant previous surgical or medical history to suggest that the caf is acquired .
the main difference between congenital and acquired caf is mainly based on history . in terms of vessels
involvement and symptoms , the congenital and acquired forms can appear identical ( 6 ) .
caf originates from the right coronary artery in 52% of cases followed by left anterior descending artery in 30% and left circumflex in 18% of cases ( 5 ) .
more than 90% of cafs drain into the right side of the heart ( 5 ) .
the most common drainage sites in order of decreasing frequency are the right ventricle ( 41% ) , right atrium ( 26% ) , pulmonary artery ( 17% ) , coronary sinus ( 7% ) , left atrium ( 5% ) , left ventricle ( 3% ) and the superior vena cava ( 1% ) ( 4 , 7 ) .
most cafs are single communication , but multiple fistulae have been reported too ( 8) . the clinical symptoms of caf depend on their anatomy , the relative size of the fistula and their flow reserve ( 9 , 10 ) .
the majority of patients with caf are asymptomatic especially during the first two decades of life ( 5 , 11 , 12 ) .
the most common clinical finding in this group of patients is continuous heart murmur that leads to further evaluation and diagnosis of caf ( 8) . this murmur is usually heard at the middle left or right sternal border or even at the lower sternal border ( 9 ) .
however , symptoms can develop later in life due to gradual enlargement of the fistula leading to an increase in the left to right shunt ( 8) . at this stage ,
the patient can present with symptoms of congestive heart failure that presents as reduced effort tolerance and paroxysmal nocturnal dyspnea .
apart from that , they can also present with myocardial ischemic symptoms such as angina due to coronary artery steal ( 5 , 8 , 11 ) .
rare complications include stroke , endocarditis , endarteritis , fistula thrombosis that may cause acute myocardial infarction , atrial and ventricular arrhythmia ( 5 , 12 ) . in this case ,
our patient presented with palpitation and blackout that are rare presentations of caf , but may happen as a result of atrial or ventricular arrhythmia .
tortuous and ectatic coronary artery is an important clue of caf ; however , the tortuous vascular course also makes the detailed anatomy difficult with echocardiogram .
cardiac catheterization and angiography has traditionally been the main diagnostic technique in the assessment of caf .
the precise course of the coronary artery and its relation to the surrounding structure is not shown .
in addition , this modality is invasive with a small but not negligible procedure - related morbidity and mortality .
most of cafs are small and are found incidentally during coronary angiography . however , with more frequent use of multidetector computed tomography ( mdct ) in cardiac imaging , the number of incidental findings of caf has been increasing .
in contrast to catheter angiography , ct coronary angiography is noninvasive and has multiplanar capability to evaluate caf . with the introduction of mdct and the development of ecg - gated scanning and reconstruction technique ,
ct coronary angiography has emerged as a new opportunity for noninvasive cardiac imaging ( 13 , 14 ) .
the high spatial and temporal resolution of mdct with faster volume coverage permits direct visualization and analysis of the coronary artery system to detect any enlarged fistula ( 13 ) .
it allows systematic evaluation of the aorta , pulmonary vessels , cardiac chamber and ventriculoatrial connection as well as evaluation of aneurysmal dilatation or thrombus formation .
in addition , ct via volume rendering enables 3-dimensional ct data evaluation of the heart and coronary arteries and gives an excellent overview of the complex cardiovascular anatomy for pre - operative planning ( 14 ) . furthermore , multiplanar reconstruction ( mpr ) analysis permits specification of the drainage site in a patient with caf ( 13 , 14 ) . in congenital caf , the involved coronary artery is usually tortuous and dilated , as in this case .
true aneurysm formation can also be seen along the fistulous tract in the congenital form .
magnetic resonance imaging ( mri ) is another noninvasive technique that can be used in the assessment of caf to evaluate anatomy , flow and function .
cine mri sequence has the advantage of demonstrating dynamics and turbulence flow at the fistula entry site ( 9 ) .
black blood imaging allows better visualization of the coronary lumen and wall over conventional spin echo sequence by improving the image quality ( 9 ) . besides that , mri has the superiority of not using ionizing radiation .
however , it is not as widely available as ct and requires longer scanning time .
spontaneous closure of the fistula is uncommon and may occur due to spontaneous thrombosis especially in small cafs ( 4 ) .
most cafs will eventually enlarge and warrant intervention by either trans catheter closure or surgical ligation .
indication of treatment includes symptoms attributable to caf , multiple fistula connection , myocardial ischemia and fistula rupture with cardiac tamponade ( 11 , 15 ) .
trans catheter closure is usually indicated for proximal location of the fistulous vessel , single drain site , extra anatomic termination of fistula away from the normal coronary artery and older age group ( 10 ) . on the other hand , surgical ligation
is indicated for large cafs , multiple communications , multiple terminations , very tortuous pathway , significant aneurysm formation and presence of large vascular branches ( 10 ) .
trans catheter occlusion is associated with lower morbidity and mortality rate as compared with surgical ligation ( 15 ) .
long - term follow - up is recommended due to possible post - operative recanalization , persistent dilatation of the involved artery , thrombus formation and myocardial infarction ( 16 ) .
management of caf ( either congenital or acquired ) mainly depends on the symptoms and size of the fistula .
small caf in an asymptomatic patient does not require immediate intervention but a regular follow up and reassessment of the fistula are indicated ( 15 ) .
however , asymptomatic caf should be repaired as symptoms and fistula related complications increase with age ( 8 , 12 ) .
for this reason , our patient was planned for surgical ligation . in conclusion , even though cardiac catheterization and angiogram is the gold standard diagnostic method , mdct is a noninvasive and useful alternative in determining the accurate anatomic relationship in caf .
therefore , in addition to evaluation of the coronary arteries for stenosis and plaques , special attention should be paid to their courses and terminations in every ct study of the heart to detect these potentially fatal anomalies .
the choice between embolization and surgical ligation should depend on anatomical and functional characteristics of the fistula .
 coronary artery fistula ( caf ) is a rare anomaly of the coronary artery . 
 patients with this condition are usually asymptomatic 
 . however , cardiac failure may occur later in life due to progressive enlargement of the fistula . 
 diagnosis is traditionally made by echocardiogram and conventional angiogram . 
 however with the advantage of new technologies such as computed tomography ( ct ) coronary angiography , the course and communications of these fistulae can be delineated non - invasively and with greater accuracy . 
 we report a case of a left circumflex artery fistula to the coronary sinus which was suspected on echocardiogram and the diagnosis was clinched on ecg - gated ct . 
1. Introduction
2. Case Presentation
3. Discussion