Usefulness of contrast-enhanced cardiac magnetic resonance in identifying the ventricular arrhythmia substrate and the approach needed for ablation

Abstract

The endocardial vs. epicardial origin of ventricular arrhythmia (VA) can be inferred from detailed electrocardiogram (ECG) analysis. However, despite its clinical usefulness, ECG has limitations. Alternatively, scarred tissue sustaining VAs can be identified by contrast-enhanced cardiac magnetic resonance (ce-CMR). The objective of this study was to determine the clinical value of analysing the presence and distribution pattern of scarred tissue in the ventricles to identify the VA site of origin and the ablation approach required. A ce-CMR study was carried out before the index ablation procedure in a cohort of 80 patients with non-idiopathic VA. Hyper-enhancement (HE) in each ventricular segment was coded as absent, subendocardial, transmural, mid-myocardial, or epicardial. The endocardial or epicardial VA site of origin was also assigned according to the approach needed for ablation. The clinical VA was successfully ablated in 77 (96.3%) patients, all of them showing HE on ce-CMR. In segments with successful ablation of the clinical ventricular tachycardia, HE was absent in 3 (3.9%) patients, subendocardial in 19 (24.7%), transmural in 36 (46.7%), mid-myocardial in 8 (10.4%), and subepicardial in 11 (14.3%) patients. Epicardial ablation of the index VA was necessary in 3 (6.1%) ischaemic and 12 (42.9%) non-ischaemic patients. The presence of subepicardial HE in the successful ablation segment had 84.6% sensitivity and 100% specificity in predicting an epicardial origin of the VA. Contrast-enhanced cardiac magnetic resonance is helpful to localize the target ablation substrate of non-idiopathic VA and also to plan the approach needed, especially in non-ischaemic patients.