Right ventricular hypertrophy in tetralogy of Fallot.

Histopathological studies were carried out on right ventricular myocardium in 104 patients with tetralogy of Fallot (T/F). Detailed analysis of the correlation between morphological and clinical data was performed. Right ventricular hypertrophy in T/F was found to initiate immediately after birth, and the diameter of right ventricular muscle fiber (D) increased with age (r = 0.74). There was a correlation between D and the hemoglobin level. There was, however, no correlation between D arterial oxygen saturation (SaO2), and pulmonary trunk/aorta diameter (PA/Ao) ratio. Histopathological alterations were related directly to D and to the age of the patient, and were unrelated to hemoglobin, SaO2, and PA/Ao ratio. Irreversible histopathological alterations were first observed when the D exceeded 15 micron, when most patients were four years old or more. From these findings, it is considered that the optimal age for corrective surgery to prevent irreversible alteration of the right ventricular muscle fibers in patients with T/F is less than three years.