Restrictive interatrial communication after reconstructive surgery for hypoplastic left heart syndrome.

S reconstructive surgery for hypoplastic left heart syndrome (HLHS) requires unobstructed flow from the pulmonary veins to the right atrium. This is achieved at the time of a Norwood stage I procedure by performing an atrial septectomy. Previous series have reported that the atrial septum can become “restrictive” in some patients months after initial reconstruction. This phenomenon, however, has not been well characterized. This study determines the incidence of and risk factors for development of restrictive interatrial communication (IAC) after stage I surgery. In addition, we report our experience with transcatheter and surgical interventions to relieve obstruction at the IAC. • • • We reviewed the database at our institution to identify all patients with HLHS who underwent stage I reconstruction between January 1984 and December 2000 and were discharged home. Patients with unbalanced atrioventricular canal or total anomalous pulmonary venous connection were not included in this series. Follow-up of this patient cohort has been reported elsewhere. Restrictive IAC was defined as a transatrial gradient of 5 mm Hg determined at catheterization or an IAC measuring 3 mm in diameter at autopsy. We reviewed surgical notes and postoperative echocardiographic studies to identify risk factors for the development of restrictive IAC. A control group of hospital survivors of stage I surgery (2 controls:1 case) was randomly selected to perform a nested case-control study. Among the patientand procedure-related factors included in the analysis were presence of an intact or restrictive atrial septum before stage I surgery, a dilated coronary sinus, deviation of septum primum, mitral valve anatomy, weight at surgery, and year of surgery. In addition, echocardiographic data from the immediate postoperative period were reviewed to determine the initial diameter of the IAC. Interventions to relieve restrictive IAC were also examined. Data are expressed as mean SD or median and range, where appropriate. Univariate comparison of characteristics between patient groups was performed with Fisher’s exact test for categorical variables and the Mann-Whitney U statistic test for continuous variables. Significance was determined at a p value 0.05. All p values are 2-sided and confidence intervals are 95%. Analyses were performed with STATA version 6.0 (College Station, Texas). From January 1, 1984, to December 31, 2000, 555 patients with HLHS underwent stage I reconstruction and survived to hospital discharge. Follow-up catheterization and/or autopsy data were available for 510 (92%). Restrictive IAC was identified in 21 of 510 patients (4.1%). In 20 subjects, restrictive IAC was identified or confirmed at catheterization at a median age of 6.1 months (range 2.1 to 11.9). The median transatrial gradient was 11 mm Hg (range 5 to 31). The median left atrial pressure was 18 mm (range 10 to 32). The mean room air saturation at catheterization was 73.9 6.7%. One subject developed profound hypoxemia 10 weeks after stage I discharge. A limited echocardiogram suggested a restrictive IAC. Before an intervention could be undertaken, the patient developed cardiovascular collapse and could not be resuscitated. At postmortem examination, the IAC measured only 2 mm in diameter. The restrictive IAC was thought to be the cause of death. Review of echocardiographic studies among the 21 patients who developed restrictive IAC demonstrated that 7 subjects (33%) had a restrictive or intact atrial septum before stage I surgery (Table 1). In 1 subject, the atrial septum was thought to be intact. This patient also had total anomalous pulmonary venous drainage with a vertical vein to the right superior vena cava, which was repaired at the time of the stage I surgery. According to the classification proposed by Rychik et al, this patient had a type A intact atrial septum. In the 6 other patients the IAC was restrictive measuring 3 mm on 2-dimensional subcostal imaging. Deviation of the septum primum was identified in 8 of 21 patients (38%) at presentation. A dilated coronary sinus in the setting of a left superior vena cava to coronary sinus connection was identified in 2 patients. The mitral valve was hypoplastic in 12 patients and atretic in 9. Only the presence of a restrictive atrial septum at presentation was significantly associated with the risk of developing a restrictive IAC after stage I surgery (p 0.03). Echocardiographic studies obtained in the immediate postoperative period demonstrated that 18 of 21 subjects were thought to have an adequate IAC 5 mm in diameter. There were 3 subjects whose IAC measured 4 mm in diameter, but who were found to have low-velocity phasic flow on pulse wave interrogation. The diameter of the IAC can decrease signifFrom the Divisions of Cardiology and Cardiothoracic Surgery at The Children’s Hospital of Philadelphia, and the Department of Pediatrics and Surgery at the University of Pennsylvania, Philadelphia, Pennsylvania; and Children’s Healthcare of Atlanta, Emory University School of Medicine, Atlanta, Georgia. Dr. Mahle’s address is: Children’s Healthcare of Atlanta, Emory University School of Medicine, 1405 Clifton Road, NE Atlanta, Georgia 30322-1062. E-mail: mahlew@kidsheart.com. Manuscript received March 29, 2001; revised manuscript received and accepted August 24, 2001.