Defining and refining indications for transcatheter pulmonary valve replacement in patients with repaired tetralogy of Fallot: Contributions from anatomical and functional imaging.

Transcatheter pulmonary valve replacement (TPVR) is an important treatment option in repaired tetralogy of Fallot (TOF) and right ventricular outflow tract (RVOT) dysfunction. Indications for timing of TPVR are extrapolated from surgical pulmonary valve replacement guidelines, which are themselves controversial as published evidence is scarce and expert opinion therefore prevails. We review current indications for PVR following TOF repair, focusing on those for TPVR specifically, and discuss anatomical and functional considerations as these pertain to determination of candidacy for TPVR. Hemodynamic assessment surrounding PVR has focused on assessment of the right ventricle (RV) size and systolic function, with the goal of intervening in the asymptomatic patient prior to the development of irreversible RV deterioration and right heart failure. The impact of abnormal RV mechanics on the LV has been appreciated, with the assessment of LV function assuming higher priority in decision-making regarding possible PVR. In addition to the standard volumetric assessment, evaluation with indices of myocardial wall strain, tissue velocities, diastology, and ventricular response to exercise is emerging as tools with potential to further refine timing of PVR. We conclude that, at present, current evidence, although limited, supports a more aggressive approach in those who meet inclusion for TPVR in patients with repaired TOF and RVOT dysfunction guided by the discussed hemodynamic assessment, however, more importantly this review should lay the framework for future investigations regarding hemodynamic assessment of this population.