Right Ventricle Myocardial Work in ToF-repair survivors: no longer behind the scenes
Authors: Sabatino J , Gozzi A , Ruggeri S , Avesani M , Reffo E , Di Salvo G 
Published: June 2023

Abstract

Funding Acknowledgements
Type of funding sources: None.

Background
Tetralogy of Fallot is the most common cyanotic CHD and survivors after ToF repair are growing rapidly. Children and, more frequently, young adults spToF develop late complications: life-threatening ventricular arrhythmias and SCD remain a great concern in these patients. This study has the aim to analyse advanced Right Ventricle echocardiographic and CMR features sp-ToF in the long-term follow-up, finding non-invasive predictors of adverse prognosis.

Methods
This is a retrospective cohort study. 240 patients sp-ToF were included (mean age 13 ± 11 years). The electrocardiographic, echocardiographic, CMR and CPET data were reviewed retrospectively. Non-invasive RV Global myocardial Work Index (RVGWI) was calculated as the area of the RV pressure-strain loops. RV Global Constructive Work (RVGCW), RV Global Wasted Work (RVGWW) and RV Global Work Efficiency (RVGWE) were estimated. Patients were screened according to age at surgery, time since the radical repair at the follow-up, increased estimated RV systolic pressure, differences in instrumental findings after PVrep. A composite end-point of MACEs (syncope, sustained and non-sustained ventricular tachycardia, sudden cardiac death) was used.

Results
Older patients at surgery (≥12 months) have significantly reduced VO2 max at CPET, larger RA and LA areas and larger RV basal diameter. CPET values are not significantly different in patients with more than 25 years since the corrective surgery but echo and CMR-LVEF measured are slightly but significantly reduced and RVGWE is significantly lower. Patients with RVSP ≥ 60 mmHg have significantly higher RVGWW, worst RV FWLS, lower RVGCW and RVGWE. Patients who have undergone PVrep show improvement in RV GLS, RV FWLS and RVGWE and a RVGWW reduction. As reguards the CMR RV volume evaluation sp-ToF, patients with RVESVi ≥80ml/m2 have lower RVGWE and show an inverse correlation between RVEDVi and RVGWE. Sp-ToF patients with borderline/impaired predicted VO2 max at CPET have a reduced RV FWLS, higher RVGWW and an inverse correlation between METs and RVGWW. Patients who have suffered MACEs (2 NS-TV, 3 S-TV, 7 syncopes, 8 sudden deaths) hadsignificant impairment of RV systolic function (FAC, RV FWLS, CMR-RVFE), significantly higher RVGWW, lower RVGWE and RVGWI.

Conclusion
Long-term survival and clinical condition sp-ToF in infancy are generally good and late functional status in survivors could be excellent up to 25 years after radical correction. However, older patients at surgery have relative reduced functional status compared with those undergoing early repair. The advanced echocardiographic and CMR evaluation of RV function sp-ToF are usually related to worse prognosis, VT and reduced functional status. RV myocardial work evaluation is feasible in patients with repaired ToF, it may be a more sensitive indicator of RV fuctional impairment compared with standard echocardiographic parameters and is able to predict exercise capacity.