Electrocardiographic Imaging for Cardiac Arrhythmias and Resynchronization Therapy

Helder Pereira; Steven Niederer; Christopher A. Rinaldi

Disclosures

Europace. 2020;22(10):1447-1462. 

In This Article

Ventricular Arrhythmias

The effectiveness of ECGi also extends to ventricular arrhythmias, specifically VT, which is heterogeneous in nature. The location of activation sites in VT is a particular challenge in practice.[21] As with atrial arrhythmias, several studies have investigated the role of ECGi in accurately providing mapping sequences of ventricular activation sites.

Among the studies described below, three included participants with Wolf–Parkinson–White (WPW) syndrome,[2,4,62] nine included patients with premature ventricular complexes (PVC),[4,6,21,37,45,48,50,56,61] and one compared the ability of QRS duration and left bundle branch block (LBBB) to ECGi for predicting CRT outcomes.[39] The studies that examined patients with WPW syndrome approached the disease mechanism in different ways. One study used ECGi to predict if the ventricular origin was localized to the right or left side of the ventricular septum,[4] while the others used ECGi to predict the localization of essential accessory pathways and sites of ventricular pre-excitation.[2,62] In both studies, ECGi accurately predicted the mechanisms. Thus, ECGi could provide unique critical details that would be unavailable by other tools.

Several studies have validated the use of ECGi mapping for catheter ablation in patients with PVC/VT.[21,50,59,63] The localization of the VT and PVC pacing sites by non-invasive electrophysiological mapping using 120[21,59,63] or up to 208 body surface electrodes[50] prior to the invasive procedure was shown to be correlated with the results from the invasive mapping system CARTO.

Electrocardiographic imaging can also be clinically useful in cases of VT, where, by providing high spatial resolution and images of the activation sequences over the entire ventricles, it helps us better understand the processes of VT initiation and continuation. This further might give insights regarding relationships to an abnormal electrophysiological substrate or anatomical scars.[21] Three case reports demonstrated the successful application of ECGi in guiding the diagnosis and therapy of VT by accurately localizing pathologic foci.[64,66,67]

Most of the studies that investigated PVCs sought to address the ability of ECGi to localize the origin of the PVC to the specific ventricular chamber (Figure 7). Jamil-Copley et al.[6] reported that ECGi could predict the chamber of origin in 96% of the participants (23 of 24) and was 100% accurate at predicting localization in specific anatomical regions within the specified chamber. Compared to the results with ECGi, which were near-perfect, the three algorithms together predicted the correct location (i.e. chamber) of PVC in only 50–80% of the instances. Moreover, when the proper chamber was located, the specific region within the chamber was predicted only 37–58% of the time. The ability to correctly distinguish between chambers suggests that ECGi may be useful as a guide during invasive procedures, such as catheter ablation.[6]

Figure 7.

ECGi potential maps of RVOT and LVOT ectopy. The images show the ECGi potential PVC map from LAO views. On the left, early activation sequence favours LV. (B) On the right, early activation sequence favours RV. ECGi, electrocardiographic imaging; LAD, left anterior descending; LV, left ventricle; RV, right ventricle; RVOT, right ventricular outflow tract. Adapted from Jamil-Copley et al.6 Author's permission granted and RightsLink License number 4851580447554.

To date, only one randomized controlled trial has evaluated a novel ECGi technology called ECVUE™ (Medtronic, Dublin, Ireland), which showed 95.2% accuracy in identifying both the chamber and origin of VA compared to conventional 12-lead ECG algorithms (76.2% and 38.1%, respectively). ECVUE™ also led to a shorter time to ablation and a lower number of radiofrequency-energy applications.[37] Similar results were observed in another clinical study by Wissner et al.[45] with 95% and 86% precision of chamber and ventricular segment detection, respectively. In both investigations, patients experienced 95% ablation success.[37,45]

In a study of four patients, Wang et al.[58] showed that ECGi can be clinically feasible for scar-related VT by identifying the sites of myocardial scar and signal fractionation. The authors demonstrated that, in programmed induced VT, simultaneous epi-endo ECGi might be used for mapping scar substrates and re-entry circuits. Another investigation by Tsyganov et al.[8] showed that ECGi was able to detect various patterns of induced VT. Electrocardiographic imaging visualized macro-re-entrant circuits in patients with ischaemic cardiomyopathy (n = 3) and cardiac sarcoidosis (n = 1), and relatively stable rotor activity and multiple wavelets in patients with hypertrophic cardiomyopathy (n = 1), Brugada syndrome (BrS) (n = 2), and idiopathic ventricular fibrillation (VF) (n = 1).

The number of body surface leads varies depending on the manufacturer. However, some investigators have reported the successful application of simplified ECGi that utilized standard 12-lead ECG. In this model, images obtained from MRI or CT specify the correct placement of ECG electrodes for electrophysiological mapping.

In three small studies, van Dam et al.[56,61,68] were able to precisely localize the site of the PVC origin in patients undergoing catheter ablation with the help of electrophysiological mapping that utilized the inputs from 12-lead ECGs and MRI. Interestingly, this approach wasn't limited to the epicardial surface, as in many cases, but was able to quantitatively localize PVCs on the ventricular walls, endocardium and intra-myocardium,[56,68] or even to papillary muscles.[61]

In another investigation, a similar system called View into Ventricular Onset (VIVO) was shown to accurately predict earliest activation and foci of VA in 19 of 22 analysed patients with PVC or VT undergoing catheter ablation.[48]

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