Emerging roles for cardiovascular magnetic resonance in adult congenital heart disease electrophysiology

The population of adults with congenital heart disease is growing. Most children with congenital heart disease now survive into adulthood thanks to innovations in cardiac surgery that allow repair or palliation of many anatomical defects. However, arrhythmia and sudden death remain important causes of late morbidity and mortality. As the population of adult congenital heart disease (ACHD) ages there is an increasing burden of arrhythmia requiring specialist care. Rhythm disturbances may be the first presenting symptom and herald a need for surgical or transcatheter intervention in which case treatment should be directed at the underlying cardiovascular haemodynamics. In this case, electrophysiological (EP) intervention is a secondary concern. Arrhythmia and sudden cardiac death (SCD) may, alternatively occur in the absence of a target haemodynamic lesion. Arrhythmia mechanisms vary according to the exact underlying anatomic congenital defect and method and timing of surgical repair. Whilst the arrhythmia can relate to underlying structural heart disease, such as Wolff-Parkinson-White syndrome associated with Ebstein's anomaly, it often relates to surgically acquired scars combined with chamber enlargement as a consequence of abnormal pressure and volume loads. In congenital heart disease, atrial arrhythmias frequently emanate from the right atrium or right ventricle (RV) and are not generally confined to the left atrium as with atrial fibrillation triggered by pulmonary vein muscle bundles. ACHD patients with atrial arrhythmia are at particular risk of tachy-myopathy and existing haemodynamic lesions such as valvular regurgitation may be exacerbated by arrhythmia. There is also overlap in clinical presentations, such that ACHD patients presenting with atrial arrhythmia are at higher risk of ventricular arrhythmia [1]. Atrial arrhythmia is well recognised as an important indicator of ventricular dysfunction in congenital heart disease [2]. Adults with congenital heart disease are at risk of SCD and may be referred for diagnostic EP ventricular stimulation study to aid risk stratification [1, 3, 4]. Both atrial and ventricular stimulation at EP study may therefore be indicated for the same patient.