Background: Pulmonary valve replacement (PVR) is required to address residual lesions after tetralogy of Fallot repair (rTOF). We wished to determine the progression of ventricular dilation after rTOF, using cardiac magnetic resonance (CMR) data in children, to determine age related RV and LV volume differences in patients who did or did not require PVR.

Methods: Single center, retrospective longitudinal study, including 214 patients with rTOF who had primary repair before 24 months and at least one CMR performed from 2000-2020. During follow-up, 142 patients (66.3%) had PVR at median age 12 years (IQR 9-15.5). Linear mixed effect modeling was used to evaluate time-related changes in ventricular volumes by log-transformed age at CMR adjusted for sex and regurgitant lesion status. Patients were grouped as per need for PVR during follow-up.

Results: A total of 323 CMR from 201 patients performed before PVR were analyzed. The median age at first CMR was 9.4 years (IQR 5.9-12.3): 126 (62.7%) patients had one CMR, 34 (16.9%) had 2 and 41 (20.4%) had 3 or more. Prior to PVR there was steeper time-related RV dilation compared to non-PVR requiring patients: RVEDVi = 19.4 (CI 15.1 - 23.7) vs 2.8 (CI -2.5 - 8.2) ml/m2/log2year, p<0.001; RVESVi = 11.9 (8.9 - 14.8) vs 0.8 (CI -2.9 - 4.4) ml/m2/log2year, p<0.001. A time-related increase in LV volume also occurred in the PVR group compared to non-PVR: LVEDVi = 7.2 (CI 4.7 - 9.7) vs 1.5 (CI -1.6 - 4.6) ml/m2/log2year, p=0.005; LVESVi = 3.2 (CI 1.9 - 4.6) vs -0.4 (CI -2.1 - 1.3) ml/m2/log2year, p=0.001) (Figure 1). The factors associated with PVR were presence of regurgitant residual lesion, more prolonged QRS duration and transannular patch as surgical technique for TOF repair.

Conclusion: Early and significantly increased progression of RV dilation and LV dilation are identifiable by CMR in patients destined to require PVR following rTOF. Early MRI surveillance may be indicated to permit early identification of progressive remodeling.