Tetralogy of Fallot — Does MR imaging have the answers?

The population of adult survivors with tetralogy of Fallot (TOF) is growing over the last decades due to improvements in perinatal management, intensive care and surgical techniques. Pulmonary regurgitation (PR) plays a crucial role in the long-term outcome of these patients. Although PR may be tolerated well for many years, eventually it may lead to right ventricular (RV) dilatation, RV dysfunction, exercise intolerance, arrhythmia and sudden cardiac death. Cardiovascular magnetic resonance (CMR) imaging is an important tool in the follow-up of patients after TOF repair, because biventricular volumes and function and PR volume and fraction can be measured with great accuracy and reproducibility.

CMR imaging studies have identified risk factors for late adverse outcomes in patients after TOF repair. These include increased RV end-diastolic volume (EDV), reduced left ventricular ejection fraction and abnormal RV outflow tract function. Other applications of CMR include stress imaging, assessment of diastolic function and late gadolinium enhancement, which have provided additional insight in the function of the RV.

Timing of pulmonary valve replacement (PVR) is controversial and should balance between the preservation of RV function and the need for subsequent PVR surgery, since the life-span of a homograft is limited. Based on CMR imaging studies, PVR will be considered if the RVEDV reaches a threshold of between 150 and 200ml/m2 in the presence of severe PR. However, timing of PVR should be based on multiple factors, other than RV size and PR fraction alone.