Right ventriculo-arterial coupling in repaired Fallot patients with pulmonary valve regurgitation before and after pulmonary valve implantation: a CMR study

Abstract

Background Right ventricular-pulmonary arterial coupling plays an important role in the occurrence of right ventricular failure. Ventricular-arterial coupling is defined as Ea/ Emax. Ea is the effective arterial elastance and an index of the post-load, and includes vascular resistances, vessel compliance, vascular impedance, systolic and diastolic time intervals. Ea = (arterial end-systolic pressure/stroke volume), where arterial end-systolic pressure = (mean pulmonary arterial pressure wedge capillary pressure). The role of wedge capillary pressure can be considered negligible in subjects with normal pulmonary artery pressure and normal left ventricular (LV) function. Therefore, the formula can be simplified to Ea = (mean pulmonary arterial pressure/stroke volume). Emax is the maximal systolic ventricular elastance. This is a loadindependent index. It occurs at the end of the systole and is given by the formula Emax = [end-systolic pressure/(end-systolic volume volume (theorical) at zero load)]. Volume at zero load can be considered negligible, and end-systolic pressure can be approximated by mean pulmonary arterial pressure. Therefore Emax = (mean pulmonary artery pressure/end-systolic volume). Consequently, Ea/Emax = [(mean pulmonary artery pressure/ stroke volume)/(end-systolic volume/mean pulmonary artery pressure)] and results in Ea/Emax = (end-systolic volume/stroke volume). Optimal ventricular-arterial coupling is when Ea/Emax=1. Objective of this study is to evaluate by CMR the right ventricular-arterial coupling before and after surgical or transcatheter pulmonary valve implantation (PVI) in subjects who underwent surgery for tetralogy of Fallot (ToF) and have pulmonary valve (PV) regurgitation and/ or stenosis.