Left Circumflex Coronary Artery to Bronchial Arterial Fistula Associated with Tetralogy of Fallot: A Case Report and Review of Literature

Zunping Ke1, Chao Li2, Qiang Liu3, Gang Bai4, Junfeng Wang5, Ming Zhou5 and Xiao Dong5,* 1School of Public Health, Hubei University of Medicine, 442000, China 2Children’s Medical Center, Affiliated Taihe Hospital of Hubei University of Medicine, 442000, China 3Department of Cardiothoracic Surgery, Affiliated Taihe Hospital of Hubei University of Medicine, 442000, China 4Department of Ultrasonics, Affiliated Taihe Hospital of Hubei University of Medicine, 442000, China 5Cardiovascular Center, Affiliated Taihe Hospital of Hubei University of Medicine, 442000, China Article Information Received 02 February 2021 Revised 23 February 2021 Accepted 28 February 2021 Available online 12 August 2021


INTRODUCTION
C oronary artery to pulmonary arterial fistula is a rare variant in patients with tetralogy of Fallot. Dabizzi et al. (1980) and Haworth and Macartney (1980) reported one-tenth of their large series of patients studied angiocardiographically had such fistulous communications from the coronary arteries, but all the identified fistulas were small. As an extra communication in systemic-topulmonary system, it has hemodynamic and physiologic significance during correction surgery. In most of reported cases, the fistula arose from the anterior interventricular artery, followed by the main stem of the left coronary artery, and less frequently from the circumflex artery. In this report, O n l i n e F i r s t A r t i c l e the right parasternal area over the third intercostal space.
The baseline systemic arterial oxygen saturation (SaO2) was 88%. Blood test showed elevated red blood cells quantity with HGB 198g/L, indicated of chronic hypoxia, no signs of dyslipidemia or diabetes mellitus were found.
BNP was mild elevated (422Pg/ml), while liver function, renal function, CTnI, D-dimer, PCT were all in the normal range, HIV antibody, hepatitis markers, syphilis antibody were all negative.

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Electrocardiogram revealed normal sinus rhythm with features of pulmonary p wave, right ventricular hypertrophy (RVH) and right axis deviation. T wave was flat or inverted in leads II, III, avF and V1 to V6. Transthoracic and transesophageal echocardiography revealed a large (17mm) subaortic ventricular septal defect (VSD) with 50% aortic override, increased supraventricular ridge bundle and parietal band caused severe infundibular stenosis. A diaphragm like structure as well as thickened pulmonary valve bulged into pulmonary trunk caused its stenosis. Left atrium and ventricular were in normal size, whereas right atrium and ventricular were enlarged and thickened. The ejection fraction of left ventricle was in normal range, no collateral vessel or fistula could be appreciated on color Doppler imaging (Fig. 1).
Enhanced cardiac computed tomography (CT) scan showed enlarged pulmonary trunk(diameter of 3.3cm), as well as both pulmonary arteries, especially the left one of 5.1cm in diameter. MGoon index was 3.1, crosssectional area of left pulmonary artery was 2073.2mm 2 , right one was 181.1mm 2 , Nakata index was 1454mm 2 /m 2 . Obstruction of right ventricular outflow tract, right-sided aortic arch, aortic overriding and RVH were also showed, thickened pulmonary valves bulged into pulmonary trunk like discovered by echocardiography (Fig. 2).
Subsequent catheterization and angiographic study confirmed the diagnosis of TOF with large VSD, RVH, and aortic override. Pulmonary artery pressure was not obtained because the guide wire could not pass through the narrowed pulmonary valve during right cardiac catheterization, only right ventricle pressure was obtained (117/14 mmHg). Selective coronary angiography showed no stenosis of coronary arteries but the presence of a fistulous communication arising from the proximal left circum flex coronary artery to bronchial artery (Fig. 3).  Considering the significance of the fistula in the corrective surgery, it should be find out and ligated prior to cardioplegic arrest. During exploration, pulmonary trunk was dilated seriously while three pulmonary valves infused in the centra caused the valve almost atretic. The MPA (main pulmonary artery) was opened longitudinally and no fistula opening was seen in MPA, left and right pulmonary arteries on careful inspection. Increased supraventricular ridge bundle and parietal band caused severe infundibular stenosis. The originations of left and right coronary arteries were normal and no abnormal communication was seen from LCX. To avoid systemic hypoperfusion on bypass through loss of volume to pulmonary circulation and shunting of cardioplegic solution to pulmonary circulation through the fistula, the volume of cardioplegic solution was increased a little under cardiopulmonary bypass. Intracardiac repair of TOF was performed, closure of the VSD, pulmonary valvotomy, pulmonary arterioplasty, and right ventricular outflow tract (RVOT) augmentation were completed using a patch of autologous pericardium. Tricuspid valve regurgitation was solved by contract tricuspid ring using an autopericardial ring. The patient recovered uneventfully after surgery, postoperative echocardiography showed no residual VSD, no RVOT gradient, and normal biventricular function (Fig. 1). Twelve months after surgery, the patient is asymptomatic, he was asked to close the coronary artery to bronchial arterial fistula by further transcatheter procedure.

DISCUSSION
TOF is the most common cause of a right-to-left shunt in individuals who survive infancy, it usually need to be corrected by surgery in early stage. Before surgical management, other anomalies like coronary artery fistulas (CAFs) should be explored extensively because surgical strategy may differ according to its presence. Congenital CAFs are characterized by a normal aortic origin of the coronary artery involved but with a fistulous communication with the atria, the ventricles or with the pulmonary artery, coronary sinus, or the superior vena cava. CAFs are rare anomalies, the incidence in the overall population is estimated 0.002%. The true prevalence of these fistulas in patients with VSD and pulmonary atresia is unknown, however, they can occur in as many as 10% of these patients (Talwar et al., 2009;Angeli et al., 2008). Many of these CAF anomalies are difficult to detect intraoperatively by surgical teams, hence carefully examination of the coronary arteries by angiographic studies prior to surgical treatment should be performed.
The fistulous communication itself can arise from either the left or right coronary artery. According to Talwar et al. (2014) review, three-quarters cases had the fistulas arising from the left coronary artery, in most cases involving the left coronary arterial system, the fistulas arose from the anterior interventricular artery, followed by the main stem of the left coronary artery, and less frequently from the circumflex artery. Most frequently, the fistula itself terminates in the pulmonary trunk, then other structures. Many cases of coronary to pulmonary artery fistulas were also reported in patients with TOF (Chowdhury et al., 2015;Lee et al., 2014;Witters et al., 2014;Mc-Mahon et al., 2014;Kim et al., 2017;Kajihara et al., 2009;Trehan et al., 2004). In Dabizzi et al. (1980) investigation, fistulas between coronary artery and bronchial arteries is the most common anastomoses in TOF. But we are aware that few coronary-to-bronchial fistulas were reported in patients with TOF. In our case, an obvious fistulous communication arose from LCX artery was discovered by angiography, but the distribution and termination of the fistula could not be shown very clearly, the fistula seemed more likely drained into bronchial artery rather than pulmonary artery. Subsequent enhanced cardiac CT scan confirmed it was a communication between LCX and bronchial artery. The fistula arose from the proximal portion of the LCX, then divided into two branches, one of the branch terminated at tracheal carina and the other one at right main bronchus. Talwar et al. (2009) reported an accidental transection of RCA when opening the main pulmonary artery because of a missed diagnosis of anomalous originated right coronary artery in TOF before procedure. Recently, computed tomography had proven to be an useful tool in coronary artery fistulas detection and morphological assessment by other studies (Punzo et al., 2019;Czekajska-Chehab et al., 2020;Butt et al., 2019;Al-Umairi et al., 2019;Li et al., 2019). In our patient, the morphological distribution and termination of the CAF was revealed much more clearly by coronary artery angiography combined with enhanced cardiac CT scan, hence different image methods should be used together for CAF evaluation especially in the complicated cases like TOF to accurately delineate the anatomy and avoid the accidental destruction of the anomalies during surgery.
The occurrence of coronary artery fistulas in TOF have several surgical implications. The fistulous communication should be identified and ligated prior to the institution of cardiopulmonary bypass in order to prevent systemic hypoperfusion on bypass through loss of volume to pulmonary circulation. And it is also important to close the fistulas prior to aortic cross-clamping because shunting of cardioplegic solution to pulmonary circulation through the communication will result in incomplete myocardial protection and excessive left heart return. In those patients where there is an additional source of blood supply to a lung segment, they are treated just like any other collateral artery by ligation or division immediately upon institution of CPB. Unfortunately, we could not find the coronary artery to bronchial artery fistula under cardiopulmonary bypass, maybe because of the fistula's opening buried deeply inside of the cardiac muscles. We chose to increase the cardioplegic solution to avoid insufficient protection caused by the fistula. The patient recovered uneventfully and biventricular function was reserved after surgery, which means increase the cardioplegic solution is an alternative choice in the circumstance when have difficulties to find out the abnormal communication by surgeons.
Only a few patients with TOF reach adulthood without surgical correction, the prognosis is relevant to the severity of the abnormalities. Stanescu and Branidou (2008) had reported a 75-year-old survivor of unrepaired tetralogy of Fallot with quadricuspid aortic valve. Hussain et al. (2012) reported a successful surgical repair of TOF for a patient at age 83. In the present case, the patient survived to undertake surgery until 53 years old. Considering the patient's career is tailor and have limited daily activities, we believed that this is the reason why he can survive with cyanosis for so many years before surgical correction. The patient is doing well after surgical correction, but attempt to close the coronary artery fistula by transcatheter procedure is still recommended.

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Coronary Artery to Bronchial Arterial Fistula Associated with Tetralogy of Fallot