Impact of residual right ventricular outflow tract obstruction on biventricular strain and synchrony in patients after repair of tetralogy of Fallot: a cardiac magnetic resonance feature tracking study

Background: Residual right ventricular outflow tract obstruction (RVOTO) is considered beneficial in patients after repair of tetralogy of Fallot (TOF). We sought to elucidate differences in myocardial strain and dyssynchrony parameters in patients after TOF repair with and without residual RVOTO using cardiovascular magnetic resonance feature tracking (CMR-FT) analysis.

Methods: Fifty-four patients (mean age 16.4 ± 8.4 years) were assessed by CMR. Residual RVOTO on echocardiography was defined as a peak systolic RVOT gradient >25 mmHg. Right (RV) and left ventricular (LV) strain measurements were performed using CMR-FT software (TomTec, Germany).

Results: The groups (n=27, respectively) were well matched for age at CMR-scan, time and type of surgical repair. Patients with RVOTO showed significant higher RV circumferential (CS) (p=0.02) and RV radial strain (RS) (p=0.02) values, whereas RV longitudinal strain (LS) did not differ between the two groups (p=0.39). The degree of RVOTO showed a significant correlation with RV-CS and RV-RS while RV-LS was unrelated to RVOTO. Significant relationships between RV and LV strain parameters were only found in the RVOTO group. Interventricular dyssynchrony was significantly higher in the group without RVOTO (p=0.03) while LV-LS (p=0.03) and LV intraventricular synchrony (p=0.05) were impaired in the RVOTO group.

Conclusions: In patients after TOF-repair, residual RVOTO seems to preserve RV strain and results in stronger RV-LV interactions and less interventricular dyssynchrony and may therefore possess an early protective effect on RV remodelling. However, the potential negative impact of residual pulmonary stenosis on LV strain and intraventricular synchrony needs further investigation.