End-Diastolic Forward Flow (EDFF) After Tetralogy of Fallot Repair: Evolution of Its Role in Management and Prognosis

In the era of personalized medicine and multimodality imaging, renewed attention is directed toward the restrictive right ventricular (RV) physiology, including its historic hallmark, the end-diastolic forward flow (EDFF), in Tetralogy of Fallot (ToF) repair. Initially perceived as a marker of favorable restriction, EDFF has been repositioned as a multifactorial hemodynamic phenomenon rather than a specific indicator of myocardial stiffness, based on recent imaging and mechanistic studies. Methods: This review synthesizes the evolution of perception, the diagnostic assessment, and the prognostic relevance of EDFF in repaired ToF. A comprehensive PubMed search spanning from 1987 to 2024 identified relevant studies, including clinical trials, observational analyses, and meta-analyses on EDFF and RV restrictive physiology. Results: EDFF was initially associated with smaller “protective” RVs and improved exercise tolerance in early echocardiographic studies. Later, a dual-restrictive model distinguishing beneficial (primary) from maladaptive (secondary) patterns was proposed, with the addition of cardiac magnetic resonance (CMR). EDFF has recently been demonstrated to also occur in non-restrictive RV due to altered RV-pulmonary arterial coupling, regurgitant flow dynamics, or atrioventricular dyssynchrony. Novel 4D-flow imaging has enriched the general understanding of RV restrictive physiology but has not added significant prognostic value to EDFF. Conclusions: Advances in imaging and physiology have shifted EDFF from a unidimensional marker of restriction to a complex manifestation of right atrio-ventriculo-arterial interaction. While mechanistically informative, EDFF appears to lack prognostic specificity in isolation. Future research aimed at establishing standardized definitions that integrate volumetric, kinetic, and coupling parameters could enhance the diagnostic and clinical relevance.