Articles
Science Matters
About the Author: Michael Katsnelson MD, PhD, FACC is currently a research fellow at Washington University in St. Louis School of Medicine. He specializes in advanced heart failure/transplant cardiology and his main research interest lies in studying the role of the innate immune system in the progression of ischemic cardiomyopathy. In this article he provides a summary of a recent JACC publication.
Background: A recent publication in the December 17/24 issue of JACC by Wolfe et al. investigated the risk factors associated with arrhythmia-related sudden cardiac death in patients with single ventricle physiology treated with a palliative Fontan shunt. The Fontan procedure involves a series of surgeries to divert the large central veins (SVC and IVC) directly to the pulmonary artery, thus bypassing the heart. Following the development of this procedure in 1971, single ventricle physiology was transformed from a condition that was almost universally fatal in early childhood to one where >80% of patient are able to survive to the age of 30. However, patients with a Fontan shunt are at increased risk of sudden cardiac death and one of the outstanding questions in the field is to identify risk factors for mortality in this population.
Study Design: Many of the previous studies in this field have been limited by small sample size due to the low prevalence of single ventricle physiology in the general population. The study by Wolfe et al. utilized the FORCE (Fontan Outcomes Registry Using CMR Examinations), an international multicenter registry of patients with single ventricle physiology that includes cardiac MRI (CMR) data. The authors defined a sudden cardiac event (SCE) to be either cardiac arrest from a shockable arrhythmia, need for emergent cardioversion or defibrillation, documented sustained ventricular tachycardia lasting >30 seconds or documented ventricular fibrillation.
Results: The study included >3,000 patients with single ventricle physiology, which is a larger sample size than most other studies in the field. The overall incidence of SCE was 3.5% in this patient population. The authors utilized a multivariable Cox proportional hazard regression model to determine that NYHA functional class>2, single-ventricle end diastolic volume index >104 ml/m2, single ventricular ejection fraction <50% and the presence of protein losing enteropathy and/or plastic bronchitis were associated with increased risk of SCE. Furthermore, the risks were cumulative with patients having three of these factors at greater risk compared to those with one or two risk factors. The surgical technique of the Fontan procedure also influenced the risk of arrhythmic events. Specifically, the lateral tunnel Fontan was associated with a greater risk of SCE compared to extracardiac or atriopulmonary Fontan. Patients with hypoplastic left ventricle were at greater risk for SCE compared to those with hypoplastic right ventricle.
Significance of Findings: This study highlights the potential use of CMR in identifying patients with Fontan physiology who are at increased risk of arrhythmia-related death. Those individuals with even a mild amount of dilation of the single ventricle and mild reduction in ventricular ejection fraction had a significantly increased risk of SCE. Patients who exhibit moderate or greater symptoms of heart failure are also at elevated risk for arrhythmic events. The results of this study suggest that patients with single ventricle physiology who exhibit evidence of ventricular dilation/ dysfunction on CMR or who have a history of heart failure symptoms limiting their daily activities should be closely monitored with imaging or invasive studies and targeted for more intensive therapy.
Wolfe NK, Schiff MD, Olivieri LJ, Christopher AB, Fogel M, Slesnick TC, Krishnamurthy R, Muthurangu V, Dorfman AL, Lam CZ, Weigand J, Robinson JD, Rathod RH, Alsaied T; FORCE Investigators. Cardiac MRI Predictors of Arrhythmic Sudden Cardiac Events in Patients With Fontan Circulation. J Am Coll Cardiol. 2024 Dec 17;84(25):2417-2426.
