Restrictive right ventricular physiology after Tetralogy of Fallot repair is associated with fibrosis of the right ventricular outflow tract visualized on cardiac magnetic resonance imaging

AIMS: To determine whether the restrictive physiology seen in Tetralogy of Fallot (TOF) patients can be explained by fibrosis of the right ventricular (RV) outflow tract. The aetiology for restrictive RV physiology after TOF repair is not known. METHODS AND RESULTS: TOF patients (n = 31, 13 girls, 10.2 years ± 2.8) were included 9.2 ± 2.9 years after total correction and examined with cardiac magnetic resonance (CMR) and Doppler echocardiography. Cine, flow, and late gadolinium contrast enhanced (LGE) CMR imaging were performed to quantify RV volumes, pulmonary flow and regurgitation (PR), and fibrosis. Healthy children (n = 12) were investigated with CMR of the pulmonary flow. Forward flow during atrial contraction above mean + 2 SD of healthy subjects was set as a marker of restrictive physiology. Four patients were excluded due to suboptimal LGE-CMR. Fisher's exact test was used to determine the association between restrictive physiology and fibrosis. Sixteen patients showed fibrosis in the right ventricular outflow tract (RVOT) on LGE-CMR and 14 of them showed restrictive physiology on CMR. Of the 11 patients without fibrosis in the RVOT, 1 showed restrictive physiology. The odds ratio for RVOT fibrosis in patients with restrictive RV physiology was 70.0 (CI: 5.6-882.7, P < 0.001). The transannular patch repair did not differ between the groups (P = 0.37). The degree of RVOT fibrosis correlated positively with PR (r(2) = 0.38, P < 0.001) and RV volumes (r(2) = 0.51 for end-diastolic volume and r(2) = 0.47 for end-systolic volume, P < 0.001). CONCLUSION: There is a strong association between the restrictive RV physiology detected on CMR and fibrosis of the RVOT in children after TOF repair.