EFFECT OF LATE POSTOPERATIVE ATRIAL SEPTAL-DEFECT CLOSURE ON HEMODYNAMIC FUNCTION IN PATIENTS WITH A LATERAL TUNNEL FONTAN PROCEDURE

Objectives. The aim of this study was to evaluate prospectively the ef fect of late atrial septal defect closure on cardiac output and oxygen delivery in patients who have undergone the Fontan procedure. Backgro und. An adjustable atrial septal defect is incorporated in patients un dergoing the Fontan procedure who have increased pulmonary vascular re sistance or poor ventricular function, or both. After the Fontan proce dure, the atrial septal defect is test occluded. Patients with mean ri ght atrial and pulmonary artery pressures > 15 mm Hg are discharged wi th the atrial septal defect open.Methods. Twelve patients (20 months t o 12 years old) underwent evaluation and closure of the atrial septal defect at a mean interval of 3.8 months (range 1 to 18) after the Font an procedure. Each patient underwent full right and left heart cathete rization. Cardiac output was obtained using the cine-volume method. Th e study included six patients with a high transpulmonary gradient or p oor ventricular function preoperatively, or both (high risk group) and six who had only borderline increased pulmonary vascular resistance ( low risk group). Patients in both groups had a mean right atrial press ure > 15 mm Hg when the atrial defect was test occluded in the first w eek after the Fontan procedure. Results. All results are given as mean value +/- SD. Ventricular end-diastolic pressure was significantly lo wer (p = 0.03) with the atrial septal defect open in low risk patients (6 +/- 3 mm Hg) than in high risk patients (10 +/- 3 mm Hg). With the atrial septal defect open, low risk patients had a significantly high er (p = 0.04) cardiac index (4.87 +/- 0.81 liters/min per m(2)) than t he high risk patients (3.96 +/- 0.47 liters/min per m(2)). There was n o significant difference (p = 0.14) in cardiac index between the two g roups with occlusion of the atrial septal defect. Oxygen delivery was also significantly higher (p < 0.05) with the atrial septal defect ope n in low risk patients (836 +/- 99 ml/min per m(2)) than in high risk patients (704 +/- 106 ml/min per m(2)). There was no significant diffe rence (p = 0.89) in oxygen delivery between the two groups with occlus ion of the atrial septal defect. With the atrial septal defect open, t he interatrial gradient was not significantly different in low risk pa tients (4 +/- 1 mm Hg) from that in high risk patients (4 +/- 1 mm Hg) . Conclusions. These data show that an interatrial communication resul ts in increased postoperative systemic perfusion and oxygen delivery i n patients with good diastolic ventricular function after the Fontan p rocedure.