Myocardial histopathology in late-repaired and unrepaired adults with tetralogy of Fallot

Survival of patients after repair of tetralogy of Fallot (TOF) is worse than for the general population. We aimed to assess the time-related effects of surgical repair on right (RV) and left ventricle (LV) myocardium by quantifying hypertrophy and fibrosis. Cardiomyocyte transverse diameter and percent of fibrosis were measured in 8 adult heart specimens with late-repaired TOF, 6 with unrepaired TOF, and 11 normal hearts (controls). The RV and LV mean and median cardiomyocyte diameter and percent of fibrosis were significantly greater than controls in both repaired and unrepaired hearts. The mean RV inferior wall myocyte diameter in unrepaired hearts was significantly greater at average age at death than in repaired hearts (24.9 ± 2.5 vs. 16.4 ± 1.3 μm, P = .015), but not the mean RV anterior wall myocyte diameter (21.5 ± 2.2 vs. 17 ± 1.2 μm, P = .09) or the mean LV myocyte diameter (19.7 ± 1.5 vs. 16.7 ± 0.8 μm, P = .10). Of the RV myocyte diameter measurements, only the RV anterior wall myocyte diameter for repaired hearts correlated with age at death, while LV myocyte diameter for both repaired and unrepaired hearts correlated with age at death. None of the measures of myocyte diameter correlated with age at repair. The mean RV anterior wall, inferior wall, and LV percent fibrosis were all significantly greater in unrepaired hearts at average age at death compared with repaired hearts (16.3 ± 1.3 vs. 13.0 ± 0.7%, P = .04; 18.1 ± 1.9 vs. 12.7 ± 1.0%, P = .03; 15.7 ± 0.8 vs. 11.6 ± 0.4%, P = .004, respectively). There was a significant correlation between RV percent fibrosis (both locations) and age at death for repaired hearts but not for unrepaired hearts, while LV wall percent fibrosis correlated significantly with age at death for both groups. RV percent fibrosis was not significantly correlated with age at repair, while LV percent fibrosis was negatively correlated with age at repair. Hypertrophy and fibrosis in RV and LV of late-repaired TOF hearts progress during follow-up despite a good repair. These could be the substrate of ventricular dysfunction and arrhythmia seen clinically late after correction.