Objective: Little is known about pulmonary trunk (PT) histology in patients with tetralogy of Fallot (TOF), especially in the era of palliative surgery and total repair during childhood. We hypothesized that intrinsic histological abnormalities of the PT are present from birth and may be affected by palliative surgery and/or total repair.
Methods and Results: We studied 39 formalin-fixed necropsy heart specimens with TOF and compared them with 17 normal control hearts. Sections of the PT were studied by light microscopy using various stains; histologic findings were graded according to severity. Amongst the TOF group (1 foetus, 11 infants, 14 children, 13 adults), 11 patients had undergone palliative and 10 reparative surgery at median age of 8 (range 2.5-18) years. Grade ≥2 PT histological changes were present in 59% (medionecrosis), 36% (fibrosis), 56% (cyst-like formation) and 56% (abnormal elastic tissue configuration, Figure 1) of TOF patients. Total histology grading scores were higher in TOF hearts (median 6; range 1-9) compared with controls (median 1; range 0-6). Histological abnormalities were present amongst infants (median score 3.5, range 1-9), after palliative surgery (median score 5, range 2-9) or repair (median score 7.5, range 4-9).
Conclusions: Marked intrinsic histological abnormalities in the PT of hearts with TOF exist compared to controls. These changes were present from infancy and amongst patients who had undergone palliative or reparative surgery, albeit the latter was performed late. Our data suggest structural abnormalities of the PT, which may affect overload i.e. pulmonary regurgitation, and thus outcome.