Use of Cardiovascular Magnetic Resonance for Risk Stratification in Repaired Tetralogy of Fallot

The risk of premature death in adult patients with repaired tetralogy of Fallot is real and not inconsiderable. From the third decade of life, the incidence of malignant ventricular arrhythmia (VA) is known to exponentially rise. Progressive adverse mechanoelectrical modelling because of years of volume and/or pressure overload from residual pulmonary valve dysfunction and ventricular scar creates the perfect catalyst for VA. Although potentially lifesaving, implantable cardiac defibrillators are associated with substantial psychological and physical morbidity. Better selection of patients most at risk of VA, so that implantable cardiac defibrillators are not inflicted on patients who will never need them, is therefore crucial and has inspired research on this topic for several decades. Cardiovascular magnetic resonance (CMR) enables noninvasive, radiation-free clinical assessment of anatomy and function, making it ideal for the lifelong surveillance of patients with congenital heart disease. Gold standard measurements of ventricular volumes and systolic function can be derived from CMR. Tissue characterization using CMR can identify a VA substrate and provides insight into myocardial disease. We detail risk factors for VA identified using currently available CMR techniques. We also discuss emerging and advanced CMR techniques that have not all yet translated into routine clinical practice. We review how CMR-defined predictors of VA in repaired tetralogy of Fallot can be incorporated into risk scores with other clinical factors to improve the accuracy of risk prediction and to allow for pragmatic clinical application. Finally, we discuss what the future may hold.