Prediction of ventricular arrhythmias using cardiovascular magnetic resonance

Ventricular tachycardia (VT) is the commonest cause of sudden cardiac death (SCD) in developed countries. Coronary artery disease (CAD) is the most frequent cause of VT in individuals over the age of 30, while hypertrophic cardiomyopathy (HCM), myocarditis and congenital heart disease in those below 30 years of age. Cardiac magnetic resonance (CMR), a non-invasive, non-radiating technique, can reliably detect the changes in ventricular volumes and the ejection fraction that can be predictive of VT/SCD. Furthermore, the capability of CMR to perform tissue characterization and detect oedema, fat and fibrotic substrate, using late gadolinium enhanced images (LGE), can predict VT/SCD in both ischaemic and non-ischaemic cardiomyopathy. The extent of LGE in HCM is correlated with risk factors of SCD and the likelihood of inducible VT. In idiopathic-dilated cardiomyopathy, the presence of midwall fibrosis, assessed by CMR, also predicts SCD/VT. Additionally, in arrhythmogenic right ventricle (RV) dysplasia/cardiomyopathy, CMR has an excellent correlation with histopathology and predicted inducible VT on programmed electrical stimulation, suggesting a possible role in evaluation and diagnosis of these patients. A direct correlation between LGE and VT prediction has been identified only in chronic Chagas' heart disease, but not in viral myocarditis. In CAD, infarct size is the strongest predictor of VT inducibility. The peri-infarct zone may also play a role; however, further studies are needed for definite conclusions. Left ventricle, RV, right ventricular outflow tract (RVOT) function, pulmonary regurgitation and LGE around the infundibular patch and RV anterior wall play an important role in the VT prediction in repaired Tetralogy of Fallot. Finally, in treated transposition of great arteries, the extent of LGE in the systemic RV correlates with age, ventricular dysfunction, electrophysiological parameters and adverse clinical events, suggesting prognostic importance.