Beyond the Resting State: Why Exercise Pulmonary Vascular Resistance is the New Gold Standard for Fontan Prognosis

Introduction: The Challenge of the Aging Fontan Population

The Fontan procedure has revolutionized the management of children born with single-ventricle physiology, allowing survival into adulthood for a population once faced with a terminal prognosis. However, the Fontan circulation is inherently non-physiological. By bypassing the subpulmonary ventricle, the system relies on passive venous return to drive pulmonary blood flow. Over time, this results in a state of chronic venous hypertension and low cardiac output, commonly referred to as the Fontan paradox.

As this population ages, clinicians are increasingly encountering ‘Fontan failure,’ characterized by exercise intolerance, protein-losing enteropathy, liver cirrhosis, and premature death. Traditional hemodynamic markers measured at rest have often failed to accurately predict which patients are at the highest risk of clinical decline. Two recent landmark studies, published in the European Heart Journal and the Journal of the American Heart Association, provide a paradigm shift in how we assess and risk-stratify these complex patients, emphasizing the critical role of exercise hemodynamics and novel non-invasive surrogates.