Histologic alterations in tetralogy of Fallot.

Background: This study was performed to investigate the pre-existing histologic alterations at the time of complete repair in patients with tetralogy of Fallot (TOF) and evaluate their effects on the early postoperative outcomes.

Methods: Fourteen patients, seven with acyanotic TOF (SO  > 90, group I) and seven with cyanotic TOF (SO  < 90, group II), undergoing complete repair, were enrolled. Right ventricular biopsies were examined for cardiomyocyte injury and fibrosis by light microscopy and mitochondrial injury by electron microscopy. The association of the severity of histologic alterations and postoperative inotrope use, intensive care unit, and in-hospital stays were evaluated.

Results: Compared with group I, patients in group II had a higher inotrope score (p = 0.03) and longer intensive care unit (p = 0.01) and in-hospital stays (p = 0.04). Cardiomyocyte injury and mitochondrial damage scores were higher in group II (p = 0.01 and p = 0.02, respectively). Fibrosis was detected in all specimens but was more severe in group II (p < 0.001). However, we could not demonstrate any correlation between histologic alterations and early surgical outcomes. The history of spell was significantly associated with worse early surgical outcomes (p < 0.05).

Conclusions: Pre-existing cardiomyocyte injury accompanied by mitochondrial damage and fibrosis were more pronounced in cyanotic TOF patients. Early repair may prevent the development of histopathologic alterations in these patients.