Case report
The patient was a 34-year-old woman (weight, 38.3 kg; height, 150 cm; BSA, 1.29) who had been diagnosed at birth with tetralogy of Fallot on the basis of severe cyanosis. The original m-BT shunt on the left was performed at the age of 2 years. During outpatient follow-up, the patient fell down the stairs and suffered a cervical spinal injury. Recently, however, cyanosis has progressed rapidly during physical movement, and we decided to treat her with surgery. The patient’s physical activities of daily living had decreased significantly, and there was concern about pulmonary artery hypoplasia; therefore, it was thought that the patient would not tolerate radical surgery. Preoperative contrast-enhanced computed tomography (CT) revealed stenosis of the subclavian artery at the anastomosis to the pulmonary artery and complete occlusion of the right ventricular outflow tract. (Figure 1 a) In surgery, dissection was performed through a midline incision approach as usual, and after establishing an artificial heart-lung machine with ascending aortic blood supply and right atrial debridement, a short circuit was created from the ascending aorta to the main pulmonary artery using a 6 mm artificial vessel. (Figure 2) The patient was easily weaned from cardiopulmonary bypass and had a good course of postoperative ICU management. The patient was weaned from the ventilator on the first postoperative day, and subsequent rehabilitation progressed smoothly despite the paralysis. Postoperatively, her SpO2 increased to 80% and her preoperative symptoms, such as decreased SpO2 with light exertion, improved. Postoperative contrast-enhanced CT showed that blood flow to the shunt and pulmonary artery was maintained. (Figure 1 b)
Discussion
The BT shunt was originally designed and performed to improve cyanosis in the tetralogy of Fallot, but it is not curative, and the pulmonary artery blood flow rate decreases as the body grows. In fact, the survival rate at 25 years after surgery of patients with tetralogy of Fallot who underwent palliative surgery only is approximately 50%. [2] There have been almost no case reports of palliative central shunting in adulthood, [3] and we report here another case in which cyanosis was improved in adulthood after central shunting.
The concerns in this case were the development of postoperative congestive heart failure and hypercapnic lung injury. [4] Shunt reduces blood flow to the body and increases pulmonary blood flow, thereby increasing Qp/Qs as a surgical procedure. Although it is difficult to accurately evaluate preoperatively whether the patient’s heart tolerates congestive heart failure, the 6 mm artificial vessel used in this study did not progress to heart failure due to low blood flow, although the postoperative lungs showed temporary lung damage due to high pulmonary blood flow.
The second concern is the patency of artificial blood vessels. In general, there are many reports on the patency of artificial vessels in FP bypass, but there are no reports on the patency of the central shunts in adulthood. The shorter distance of the artificial vessel and its higher blood flow rate in this procedure may be expected to result in a higher patency rate than that of FP bypass; however, this has not been clearly confirmed.
Central shunting was effective in improving SpO2 in adult patients; however, there are many uncertainties regarding postoperative hemodynamics.