HISTOPATHOLOGIC CHANGES IN THE INFUNDIBULAR SEPTUM AFTER BALLOON PULMONARY VALVULOPLASTY IN TETRALOGY OF FALLOT

Balloon pulmonary valvuloplasty (BPV) has been applied to tetralogy of Fallot (TOF) as a palliative procedure. To investigate the histopatho logic changes by BPV in the infundibular sept-um of TOF, we performed histopathologic examinations of the infundibular septum resected at co rrective surgery. The subjects were 5 patients with TOF, who underwent BPV at the median age of 2.2 months and the corrective surgery at the median age of 15.0 months (BPV group), and 4 patients with TOF who ha d no prior BPV and who underwent the corrective surgery at the median age of 14.5 months (control group). There was no significant differenc e between the two groups in the endocardial thickness, myocardial vacu ole degeneration, or fraction of fibrous and interstitial space. Howev er, the specimens from 3 patients in the BPV group had localized dense fibrous lesions in the myocardium. The findings in this limited sampl e suggest that BPV for TOF does not produce overall histopathologic al terations such as fibrosis, thick endocardium, and myocardial vacuole degeneration, but may sometimes damage the myocardium of the infundibu lar septum resulting in the formation of localized dense fibrous lesio ns. The clinical significance of this damage is still unknown, and fur ther cases should be investigated.