Histomorphometric analysis of pulmonary vessels in single ventricle for better selection of patients for the Fontan operation

OBJECTIVE: In cases of single-ventricle physiology, the Fontan procedure often fails even when the usual selection criteria are strictly respected. We analyzed specimens from intraoperative open lung biopsies performed on 40 patients with single-ventricle physiology who were considered to be good candidates for the Fontan procedure. Histomorphometric study was performed to determine histologic factors predictive of failure of the Fontan procedure. METHODS: Histomorphometric studies were performed on samples from 40 patients aged 6 months to 23 years with single-ventricle physiology, either tricuspid atresia (n = 14) or univentricular heart (n = 26). The preoperative pulmonary arterial pressure was 18 mm Hg or less in 35 cases and greater than 18 mm Hg in 5 cases. Eighteen patients underwent total cavopulmonary connection, 16 patients underwent partial cavopulmonary connection, and 6 underwent a palliative procedure, as determined according to clinical and hemodynamic findings. RESULTS: Lung biopsy specimens from all 5 patients with pulmonary arterial pressure greater than 18 mm Hg appeared abnormal, whereas they appeared abnormal only 51% of the time in the low pulmonary arterial pressure group. The most frequent histologic abnormality observed was extension of smooth muscle cells in the wall of distal intra-acinar pulmonary arteries. Of the 18 patients who underwent the Fontan procedure, 9 had normal distal pulmonary arteries and good surgical results (except 1 with the Fontan circulation taken down for an anatomic reason). The remaining 9 had thick-walled distal intra-acinar pulmonary arteries with poor results of the Fontan procedure, and 6 died. The mean percentage wall thickness of small intra-acinar pulmonary arteries was significantly greater among the patients with bad results than among those with good results of the procedure (P <.01). CONCLUSIONS: Lung biopsy specimens were abnormal in 51% of patients with low pulmonary arterial pressure, there was no relationship between preoperative pulmonary arterial pressure and outcome, and extension of muscle in peripheral arteries was always present in cases of failure of the Fontan procedure. Histomorphometric study is therefore a useful adjunct to the usual selection criteria for surgical decision making in cases of single-ventricle physiology.