Background: The various types of cavopulmonary connection are occasionally unsuccessful even when the indications have been strictly fulfilled based on preoperative hemodynamic studies. We performed a detailed study of lung specimens from 60 patients who were judged to be candidates for the modified Fontan procedures based on a catheterizaton study in order to reevaluate the role of histologic studies of the pulmonary vasculature and to determine histologic criteria for the Fontan-type operation.
Methods: We performed a histomorphometric analysis of specimens from 53 biopsy and 7 autopsy cases (0.5 to 23 years of age), with single ventricle physiology. Twenty-eight cases were treated with a bidirectional Glenn shunt (BDGS) and 32 cases were treated by means of total cavopulmonary connections (TCPC) with or without fenestration, on the basis of the clinical and hemodynamic findings. To evaluate the medial thickness of small pulmonary arteries (SPAs), we used a measurement, D(R = 100 microm), that is unaffected by various degrees of vasoconstriction of the media or the age of the patients and that is representative of all SPAs in a section. Other variables, such as intimal lesions, SPA density, and the percentage of vessels containing a thrombus, were also measured.
Results: There was a significant difference in D(R = 100 microm) values between the BDGS cases with good and bad outcomes at p = 0.0007 (8.9 +/- 2.4 versus 13.4 +/- 1.9 microm), and the cutoff point for the success of BDGS was 13.7 microm. The same was true of the TCPC cases at p less than 0.0001 (8.4 +/- 1.7 versus 14.7 +/- 1.5 microm), and the cutoff point was 11.6 microm. There were no significant differences in other histomorphometric variables. Investigation of the relationship to hemodynamic data revealed a correlation between D(R = 100 microm) and mean pulmonary artery pressure at p = 0.028. There were no statistically significant correlations between other variables.
Conclusions: The study revealed marked differences in D(R = 100 microm) values between patients with good and bad outcomes and provided D(R = 100 microm) cutoff points for BDGS and TCPC. In some cases, there were discrepancies between the results of the preoperative hemodynamic data and of the histomorphometric analysis; and because some patients were wrongly assessed based on clinical and hemodynamic criteria, histomorphometric study might be a useful method of supplementing the variety of clinical data used to determine the indications for this operation.