Discussion

In the embryological period, the 6th left aortic artery – one of the symmetrical aortic arteries arising from the dorsal aorta – remains unchanged and functions as a “ductus arteriosus”. ^{Reference İrdem, Kervancıoğlu and Başpınar3} Prostaglandins, nitric oxide, and relative hypoxic environment prevent closure of ductus arteriosus during the intrauterine period. After birth, ductus arteriosus closes due to increase in blood oxygen saturation and decrease in prostaglandin levels (since the placenta is disabled). Prostaglandin synthetase inhibitors such as indomethacin, ibuprofen, and paracetamol may be used with the aim of medical closure of haemodynamically significant patent ductus arteriosus, which did not close spontaneously. ^{Reference Bardanzellu, Neroni and Dessì4} In case of medical closure failure, percutaneous or surgical closure of patent ductus arteriosus are the treatment options. Closure of patent ductus arteriosus with percutaneous technique involves some technical difficulties (vascular injury and embolism) in the neonatal period. Surgical treatment is often the preferred method for closure of patent ductus arteriosus in the neonatal period. The most common surgical complications are bleeding, recanalization, aneurysm, wound infection, pneumothorax, vocal cord paralysis, phrenic nerve injury, and chylothorax. Other extremely rare surgical complications are ligation or clipping of left pulmonary artery, left main bronchus, and aorta. The incidence of inadvertent left pulmonary artery ligation is estimated to be almost about 1 in 1000 cases. ^{Reference Panagopoulos, Tatooles and Aberdeen5} However, the fact that there is no post-operative routine echocardiographic examination for these patients in many centres suggests that this rate may be much higher than expected. In the early post-operative period, patients with the following findings should be suspected to ligate the left pulmonary artery instead of patent ductus arteriosus: decreased pulmonary vascular markings of left lung on chest X-ray, continuous murmur and persisting necessity to mechanical ventilation without improvement of pulmonary function. Echocardiography should be done immediately for these patients. If echocardiography determines that patent ductus arteriosus flow continuing and there is no flow in the left pulmonary artery, computed tomography angiography should be done to the patient immediately. Kim et al published a case report that left pulmonary artery was ligated instead of patent ductus arteriosus. In this publication, they emphasised that performing control echocardiography and computed tomography scan is important for early detection of this complication in patients whose expected signs of improvement in the early post-operative period are not observed. They treated this complication successfully by performing emergency reoperation to their patient on the 2nd post-operative day. ^{Reference Kim, Kim and Shin6} Orzel et al published a case report in which they used pulmonary perfusion scintigraphy to diagnose this complication. The authors emphasised that this diagnostic method is non-invasive and portable. ^{Reference Orzel and Monaco7} The patient should be reoperated as soon as possible after the ligation of the left pulmonary artery and continuing patent ductus arteriosus are clearly defined. Delay of the reoperation leads to further impairment of the patient’s pulmonary functions. In addition, in a delayed reoperation, the possibility of recanalisation of the left pulmonary artery decreases and the risk of mortality increases. Because irreversible wall damage occurs at the ligated segment of the left pulmonary artery, hypoplasia and dysplasia develop in the patient’s left lung. There are some important issues to be kept in mind during the operation in order to avoid this complication in the neonatal period: In patients with patent ductus arteriosus larger than 4–5 mm, the aortic arch and other vascular structures must be carefully distinguished. It should be avoided to retract the left lung inferiorly during the operation. Because, this manoeuvre can cause confusion of the patent ductus arteriosus and left pulmonary artery. ^{Reference Pontius, Danielson and Noonan8,Reference Tefera, Bermudez-Cañete and van Doorn9} In patients whose vascular anatomy is suspected to be abnormal, intraoperative echocardiography should be planned and performed to avoid this complication. The right lateral decubitus positioning during the surgical procedure allows echocardiography examination on the right side of the patient under the sterile surgical area.