Retraining the left ventricle after arterial switch operation: Emerging uses for the left ventricular assist device in pediatric cardiac surgery

ECHANICAL ASSIST DEVICES for the left ventricle (LVAD) are used in adult cardiac patients with increasing success. The application of this technology is emerging in the pediatric population. A case presentation and review of the literature show a unique indication for LVAD, the anesthetic considerations, complications, and outcomes in the pediatric patient. CASE REPORT A 4.5-month-old, 6.5-kg boy presented for repair of congenital transposition of the great arteries (d-TGA). He was born at 37 weeks’ gestation by Cesarean section, with Apgar scores of 6 and 10 at 1 and 5 minutes. Shortly after birth, respiratory distress and cyanosis occurred. Echocardiography revealed d-TGA with an intact atrial and ventricular septum. A balloon atrial septostomy was performed to allow mixing between the pulmonary and systemic circulations. The infant was referred to this institution from another country for possible complete surgical repair with an arterial switch operation (ASO). The patient’s preoperative echocardiogram showed the atrial septum was intact again. The study revealed bowing of the interventricular septum to the left with a thinned left ventricular wall and insufficient myocardial mass to accommodate systemic pressures once the ASO was performed (Fig 1). For the ASO to be successful, the left ventricle required retraining to tolerate systemic arterial pressures. A decision was made to perform the ASO and to insert an LVAD electively to assist weaning from cardiopulmonary bypass (CPB) and to retrain the left ventricle to function as the systemic ventricle in the postoperative period. Anesthesia was induced and maintained using incremental doses of fentanyl, 15 µg/kg; midazolam, 0.1 mg/kg; and pancuronium, 0.1 mg/kg. Inhalation agents were not administered to avoid their negative inotropic effects. Routine monitors were applied and transesophageal echocardiography was used to follow left ventricular function and to assist in device placement. Phenoxybenzamine, 1 mg/kg, was administered intravenously in divided doses at aortic cannulation and at the start of CPB. Once the arterial switch was performed, the LVAD (Bio-Medicus, Eden Prairie, MN) was introduced surgically, using left atrial and aortic cannulae for device inflow and return (Fig 2). Infusions of dopamine, 5 µg/kg/min; nitroglycerin, 2 µg/kg/ min; and milrinone, 0.25 µg/kg/min, were initiated for inotropic support during weaning from CPB and in combination with phenoxybenzamine to reduce afterload and systemic vascular resistance to the left ventricle. Blood flow rates through the LVAD were adjusted as indicated by hemodynamic parameters, acid-base status, and echocardiography. On arrival in the intensive care unit (ICU), flow through the LVAD was 160 mL/kg/min, producing stable parameters of cardiac output with an acceptable mean arterial blood pressure of 45 mmHg, central venous pressure of 12 mmHg, and left atrial pressure of 2 mmHg. After surgery, the patient required continuous active warming. Heparin was administered to maintain an activated coagulation time of 150 seconds. Fresh frozen plasma and platelets were administered for evidence of bleeding from mediastinal chest drains and abnormal coagulation profiles. Peritoneal dialysis was used electively for fluid balance and renal replacement therapy. Evidence of renal dysfunction included transient oliguria and a rising plasma creatinine (baseline, 0.6 mg/dL; peak, 1.7 mg/dL on postoperative day 5). The patient’s left ventricle was stressed each day by reducing flow rates through the LVAD gradually and allowing for left ventricular ejection. Throughout the weaning period, left atrial pressure was maintained at 10 mmHg. As flow rates were reduced, evidence of a positive response along Starling’s curve was sought using the arterial waveform (increase in pulsatile pressure with increase in left ventricular volume) and echocardiography (improved left ventricular fractional area shortening). Flow rates were reduced in increments of 20% daily. By postoperative day 7, blood flow rates through the LVAD had been weaned to 20% of initial values. The device was removed in the operating room with full monitoring and CPB circuit on standby. The patient remained in ICU for a prolonged period because of sepsis and pneumonia and was later discharged with stable hemodynamics. Echocardiography performed before discharge indicated normal ventricular function.