Discussion

This study makes an original contribution to the literature by presenting a surgical procedure for the first patient with persistent left superior vena cava, unroofed coronary sinus, intact atrial septum, coronary sinus orifice atresia, and tetralogy of Fallot. When the literature is reviewed, there are five cases with tetralogy of Fallot, unroofed coronary sinus, and persistent left superior vena cava. ^{Reference Nomura, Kurosawa, Morita, Miyamoto, Tatara and Hanai2,Reference Ueno, Sakata and Iguro3,Reference Jian, Li and Xiao4,Reference Muthialu, Rao and Balakrishnan5,Reference Mallula, Patel, Abdulla and Bokowski6} In these cases, the authors described some surgical techniques for directing of persistent left superior vena cava to the right atrium. These techniques are tunnelling with interatrial patch, reposition of interatrial septum, extracardiac mobilisation, and anastomosis of persistent left superior vena cava.

In particular, the studies designed by Caballero ^{Reference Caballero, Izquierdo and Jaurena1} and Ueno ^{Reference Ueno, Sakata and Iguro3} are similar to our case with detailed explanation of the extracardiac directing of persistent left superior vena cava to the right atrium. In these studies, the authors noted that the extracardiac anastomosis is more effective than intracardiac repair in the presence of complete unroofed coronary sinus. But Ueno and his colleagues preferred the intra-atrial rerouting technique for their patient due to the presence of incomplete unroofed coronary sinus and a history of previous cardiac surgery. ^{Reference Ueno, Sakata and Iguro3}

In the preoperative echocardiography of our patient, persistent left superior vena cava, unroofed coronary sinus and coronary sinus orifice atresia could not be detected. This missed diagnosis was due to the absence of coronary sinus dilatation. ^{Reference Hahm, Park, Lee, Choi, Sul and Lee7} In addition, the probable cyanosis of unroofed coronary sinus and persistent left superior vena cava were concealed due to cyanosis caused by tetralogy of Fallot.

In a study of 20 patients, Xie and his colleagues pointed out that transthoracic echocardiography is 65% successful in the diagnosis of unroofed coronary sinus. ^{Reference Xie, Yang and Cheng8} The failure to diagnose unroofed coronary sinus and persistent left superior vena cava can cause postoperative persistent arterial desaturation.

If the innominate vein is wide enough in a patient with persistent left superior vena cava drained into the left atrium, persistent left superior vena cava can be ligated. However, 65% of patients with persistent left superior vena cava do not have an innominate vein or have small ones. ^{Reference Webb, Gamsu, Speckman, Kaiser, Federle and Lipton9} In this instance, persistent left superior vena cava should be directed to the right atrium or any systemic vein. For this purpose, the intra-cardiac rerouting technique can be used. However, this technique may cause impaired pulmonary venous drainage, supramitral gradient or atrial arrhythmia if not performed correctly. ^{Reference Van Son, Hambsch and Mohr10} Because of its close proximity to the roof of the left atrium, the interatrial conduction pathways may be injured during intra-atrial rerouting, causing atrial arrhythmia. For our patients, we preferred the extracardiac anastomosis technique so as not to extend aortic cross-clamp time. Furthermore, with this extracardiac technique, the growth potential of tissues is preserved with the use of native tissue.

In the extracardiac approach, mobilising persistent left superior vena cava is important for surgical success. If necessary, the hemiazygos vein should be ligated and divided from persistent left superior vena cava. The anastomosis side should be chosen carefully. Otherwise, persistent left superior vena cava might be obstructed under ascending aorta or kinked during the procedure.