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 effect of late atrial septal defect closure on cardiac output and oxygen delivery in patients who have undergone the Fontan procedure.

BACKGROUND

An adjustable atrial septal defect is incorporated in patients undergoing the Fontan procedure who have increased pulmonary vascular resistance or poor ventricular function, or both. After the Fontan procedure, the atrial septal defect is test occluded. Patients with mean right atrial and pulmonary artery pressures > 15 mm Hg are discharged with the atrial septal defect open.

METHODS

Twelve patients (20 months to 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 Fontan procedure. Each patient underwent full right and left heart catheterization. Cardiac output was obtained using the cine-volume method. The study included six patients with a high transpulmonary gradient or poor 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 pressure > 15 mm Hg when the atrial defect was test occluded in the first week after the Fontan procedure.

RESULTS

All results are given as mean value +/- SD. Ventricular end-diastolic pressure was significantly lower (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 higher (p = 0.04) cardiac index (4.87 +/- 0.81 liters/min per m2) than the high risk patients (3.96 +/- 0.47 liters/min per m2). There was no significant difference (p = 0.14) in cardiac index between the two groups with occlusion of the atrial septal defect. Oxygen delivery was also significantly higher (p < 0.05) with the atrial septal defect open in low risk patients (836 +/- 99 ml/min per m2) than in high risk patients (704 +/- 106 ml/min per m2). There was no significant difference (p = 0.89) in oxygen delivery between the two groups with occlusion of the atrial septal defect. With the atrial septal defect open, the interatrial gradient was not significantly different in low risk patients (4 +/- 1 mm Hg) from that in high risk patients (4 +/- 1 mm Hg).

CONCLUSIONS

These data show that an interatrial communication results in increased postoperative systemic perfusion and oxygen delivery in patients with good diastolic ventricular function after the Fontan procedure.