The grey zone before pulmonary valve replacement in repaired tetralogy of Fallot: a paediatric perspective on the 2024 American Heart Association scientific statement

Abstract

The 2024 American Heart Association scientific statement broadened risk assessment in repaired tetralogy of Fallot beyond right ventricular volume, bringing together ejection fraction, exercise capacity, pressure load, and a validated risk score. One group of patients remains difficult: those whose right ventricular volumes are borderline and who meet no threshold for intervention. We describe this borderline range as a grey zone, with an indexed end-diastolic volume of approximately 140 to 160 mL/m ² and an indexed end-systolic volume of approximately 70 to 80 mL/m ² . Within this range, no single value decides the timing of pulmonary valve replacement, and the direction of change across serial studies carries more information than any single borderline result. We outline a structured approach that places volume alongside markers of ventricular function, exercise capacity, the rhythm substrate, tissue characterisation, and loading conditions, in order to estimate the risk of continued surveillance and to set the interval to the next review. We also note that the imaging methods underlying this framework are unevenly available and unevenly taught across centres, drawing on a recent survey from the Association for European Paediatric and Congenital Cardiology, and that a framework intended for diverse centres is most useful when it separates assessments available to every unit from those available only to some. We present this framework as a way to structure reasoning at the bedside and to seed prospective multicentre study of borderline patients, rather than as a new set of cut-offs.