Implication of Aortic Root Dilation and Stiffening in Patients with Tetralogy of Fallot

Progressive aortic root dilation and stiffening have been reported in patients with tetralogy of Fallot (TOF), even after repair. However, the implications of such aortic dilation and stiffening have not been fully assessed. A stiff aorta has a negative effect on the coronary circulation. 15 patients with TOF after repair were enrolled in this study. Using a left ventriculogram and pressure waveform recorded by a pressure sensor-mounted catheter, we analyzed the diameter and distensibility of the ascending and descending aorta. We also calculated the subendocardial viability ratio (SEVR), which measures the cardiac blood supply-workload balance. These values were compared with those in one-to-one age-matched controls. Moreover, the correlation between the diameter ratio (aortic diameter of the patient/aortic diameter of the matched control subject) and the distensibility ratio (distensibility of the patient/distensibility of the matched control subject) was analyzed. The mean age of patients was 3.9 ± 1.6 years. In patients with TOF, the indexed diameter was larger (0.20 ± 0.02 vs. 0.15 ± 0.02 mm/cm, p < 0.0001) and the distensibility was lower (5.1 ± 2.2 vs. 7.7 ± 2.0 cm² dynes^-1 10^-6, p = 0.0009) in the ascending aorta than in control subjects. There was no difference in the SEVR between patients and control subjects. The distensibility ratio was significantly negatively correlated with the indexed diameter ratio in the ascending aorta (r² = 0.35, p = 0.019). Regardless of the aortic stiffening, the cardiac blood supply-workload balance was maintained. We speculate that the aortic root dilation might be a mechanism to functionally complement aortic stiffness in patients with TOF.