Structural Abnormalities of the Pulmonary Trunk in Tetralogy of Fallot and Potential Clinical Implications : A Morphological Study

ObjectivesThe purpose of this study was to determine whether intrinsic histological abnormalities of the pulmonary trunk (PT) are present from birth and interact with palliative surgery and/or repair.BackgroundLittle is known about PT histology in patients with tetralogy of Fallot (TOF), especially in the era of surgical intervention in childhood.MethodsWe studied 39 formalin-fixed necropsy heart specimens with TOF and compared them with 17 normal control heart specimens. Sections of the PT and aorta were studied by light microscopy using various stains; histological findings were graded according to severity.ResultsAmong the TOF group (1 fetus, 11 infants, 14 children, and 13 adults), 11 patients had undergone palliative and 10 patients had undergone reparative surgery at a median age of 8 years (range 2.5 to 18 years). Histological changes of grade 2 or higher were present in 59% (medionecrosis), 36% (fibrosis), 56% (cystlike formation), and 56% (abnormal elastic tissue configuration) of TOF patients. Total histology grading scores were higher in TOF hearts (median 6, range 1 to 9) compared with controls (median 1, range 0 to 6; p < 0.0001). Histological abnormalities were present among infants (median score 3.5, range 1 to 9) and after palliative surgery (median score 5, range 2 to 9) or repair (median score 7.5, range 4 to 9).ConclusionsMarked histological abnormalities in the PT of hearts with TOF exist compared with controls. These changes were present from infancy and among patients who had undergone palliative or reparative surgery, although operations in this cohort were performed late. Our data suggest that structural abnormalities of the PT, similar to these recently shown in the aorta, are intrinsic.