Left circumflex coronary artery to coronary sinus fistula diagnosed in infancy

Abstract

Coronary artery fistulas are rare anomalies, their incidence range from 0.1 to 0.2% of congenital heart defects. The left circumflex coronary artery (LCX) fistula draining into the coronary sinus (CS) is a less common form, and most cases described in the literature were adult cases. We are describing this type of fistula in an 8-month-old asymptomatic female presenting with a continuous murmur over the pericordium. Electrocardiogram was normal. Echocardiography revealed a dilated LCX and CS with turbulent flow in CS; 2-D speckle tracking echocardiography revealed normal left ventricular strain with no regional wall abnormalities. Multidetector computed tomography demonstrated the fistula. As the patient was asymptomatic, with no ventricular dilatation or dysfunction, we decided conservatively.

<Learning objective: Coronary artery fistulas are rare anomalies that require complementary diagnostic modalities. 2D echocardiography, color flow Doppler, 2D speckle tracking, and multidetector computed tomography are needed to delineate the anomaly and to conclude the prognosis and long-term follow-up plans.>

Introduction

Coronary artery fistulas are rare cardiac anomalies; left circumflex coronary artery (LCX) to coronary sinus (CS) fistula is an uncommon form, and most cases were described in adult populations. These fistulas may be asymptomatic and may be discovered accidently during routine clinical examination by auscultating continuous cardiac murmurs [1]. They may also present with high cardiac output congestive heart failure, or myocardial ischemia. The presentation depends mainly on the size of the fistula and occurrence of complications such as aneurysmal formation, intimal degeneration, and thrombosis. Diagnosis of these fistulas requires multiple diagnostic imaging modalities namely echocardiography, multi detector computed tomography (MDCT), and coronary angiography. The treatment of these anomalies may be conservative, transcatheter, or surgical closure according to the clinical condition and imaging status [2].

Case report

An asymptomatic eight-month-old female was referred to us due to a cardiac murmur accidently discovered during routine examination. There was no history of dyspnea, sweating with feeding, or failure to gain weight. The patient's weight was 8 kg (50th percentile), height 70 cm (75th percentile), no respiratory distress, heart rate was around 135/beats per minute, auscultation revealed a continuous murmur all over the pericordium with maximum intensity at the lower left sternum, normal chest examination, no hepatomegaly. Chest X ray revealed no abnormality. Electrocardiography (ECG) revealed relative sinus tachycardia, no ST segment or T wave changes. Echocardiography revealed a dilated CS with turbulent flow inside in the parasternal long-axis view (Fig. 1), in parasternal short-axis view the main coronary and circumflex coronary arteries were dilated (Fig. 2), the left ventricular diastolic diameter measured by M-mode at parasternal long axis was 2.7 cm (Z-score 1.89) [3].

Fig. 1.

(A) Parasternal long-axis view showing a dilated coronary sinus (CS). (B) Parasternal long-axis view with zooming on CS combined with color flow Doppler showing mosaic turbulent flow inside a dilated CS (arrow).

Fig. 2.

Modified parasternal short-axis view was used to show a long course of left circumflex (LCX) coronary artery, 2D imaging (A) and color flow Doppler (B) with increasing color gain to show blood flow inside LCX adequately. Note the dilated left main coronary trunk (LMT), left circumflex (LCX), the LAD is not dilated (arrow). AO, aorta; LA, left atrium; MPA, main pulmonary artery; RA, right atrium.

2D-speckle tracking echocardiography (2D-STE) was done for left ventricle using General Electric (GE, Vivid-5, Little Chalfont, UK) system with probe 6 MHz (multi frequency transducer). The ECG cable was connected to the ultrasound machine to define and to time the cardiac cycle events; the beginning of QRS complexes was used as a reference point. 2D images were obtained in the apical four chambers, apical long-axis, and apical 2 chamber views for measurement of longitudinal deformation. Parasternal short-axis views at mitral valve, papillary muscles, and apical levels were obtained for assessment of both radial and circumferential strains. Frame rates 60–90 Hz were used, because these rates are thought to be optimal for 2D-STE [4]. Data were stored; acceptable images from three cardiac cycles were digitally saved in cine loop format on the hard disc of the echo machine then exported to a DVD (digital versatile disc) then imported to a software installed on the computer (Echo PAC version 11, GE) for offline speckle-tracking analysis. Cardiac cycles with length more than 10% different from the mean length of the three cardiac cycles were excluded from further analysis, manual tracking of the endocardial borders have been done. The timing of aortic valve closure was also manually determined. Care was taken to keep the heart rate in the same range in the stored loops. Tracking was accepted not only if the EchoPAC software showed adequate tracking, but also if the examiner's inspection revealed good tracking throughout the cardiac cycle. Q analysis -2D strain was used. Global longitudinal strain was measured using 18 segments Bull's eye and was 21%. Global circumferential strain (GCS) was calculated as the average strain measured at mitral, papillary muscle, and apical levels; GCS was -23%. Like circumferential strain, global radial strain measured at mitral, papillary muscle, and apical levels was +46%, all strain values were within normal range [5]. MDCT angiography revealed a fistulous communication between the LCX and CS with dilated LCX and CS (Fig. 3).

Fig. 3.

Multidetector computed tomography of the heart (A): showing dilated left main trunk, left circumflex (LCX) that drains to coronary sinus (CS) then to the right atrium. (B) 3D volume rendering showing dilated LCX draining into a dilated CS, left anterior descending is not dilated (arrow).

Discussion

Coronary artery fistulas are communications between coronary artery and either chamber of the heart (coronary-cameral fistula) or great vessel (coronary arterio-venous fistula) bypassing the myocardium. Coronary fistulas are rare, their incidence is about 0.1–0.2% of congenital heart diseases [1]. They usually occur in isolation from other defects [6], the majority of them are congenital but may also be acquired following cardiac surgery. Fifty percent of fistulas arise from the right coronary artery, 42% from the left coronary artery, and 5% from both coronaries, rarely from the LCX. Regarding drainage site, they included right ventricle (41%), right atrium (26%), pulmonary artery (17%), CS (7%), left ventricle (3%), and superior vena cava (1%) [7], [8]. Coronary fistulas lead to steal of blood from the coronary artery to the low pressure cardiac chamber or vein causing ischemia distal to the site of the fistula [9], moreover decrease of coronary perfusing pressure due to distal run off will compensate over time by progressive dilatation of the fistulous tract that may lead to aneurysmal formation and thrombosis [9], [10]. Sometimes patients with coronary arterio-venous fistula present with high cardiac output congestive heart failure. These pathophysiological effects depend mainly on the size of the fistulous communication. More than 90% of the coronary fistulas drain in the right sided cardiac structures (right ventricle, right atrium, and pulmonary artery) [2]. Coronary arterio-venous fistula to the coronary sinus is extremely rare; in most literature, this type of fistula is diagnosed in adults [1], [8], [9], [10]. 2D-STE is an echocardiographic modality that allows assessment of the global and regional myocardial deformation [2], it may have a value in the evaluation of the systolic function of myocardial segments supplied by the coronary artery involved in the arterio-venous fistula. Regarding our patient: she was asymptomatic, gaining weight, moreover the ECG has no ST segment–T wave changes, echocardiography combined with 2D-STE revealed normal longitudinal, circumferential, and radial strains with no regional wall abnormalities, the condition that could be explained that myocardial perfusion is mainly dependent on the patency of the distal coronary bed, such as the proximal one which is widely patent in these cases, and physiology of coronary steal does not differ from that of a large PDA or a surgical systemic-to-pulmonary artery shunt [11], so the decision of management was conservative management until the baby grows, planning for future transcatheter closure.

We conclude that fistulous communication between LCX artery and CS is a rare cardiac anomaly that may present only with cardiac murmurs. MDCT is a conclusive non-invasive study for diagnosis of such anomaly once suspected by echocardiography. Asymptomatic cases can be managed conservatively while being regularly monitored by ECG, echocardiography combined with 2D-STE for assessment of regional and global ventricular systolic function, symptomatic cases should be closed either by interventional catheterization or surgery.

Conflict of interest

There are no conflicts of interest to declare.