Electrocardiographic Imaging for Cardiac Arrhythmias and Resynchronization Therapy

Helder Pereira; Steven Niederer; Christopher A. Rinaldi


Europace. 2020;22(10):1447-1462. 

In This Article

Atrial Arrhythmias

Five studies have examined ECGi and its role in assisting the diagnosis of atrial arrhythmias compared to standard 12-lead ECG.[2,4,23,36,65] Two of the studies examined participants with atrial tachycardia (AT);[4,36] while the other three examined participants with atrial fibrillation (AF).[2,23,65] All five studies obtained 3D mapping sequences to assess the accuracy in comparison to invasive ablation procedures (Figure 6).

Figure 6.

Adapted from Cakulev et al.4 On the left, ECGi map demonstrated focal activation of the left atrium. On the right, CARTO map shows the site of successful ablation, which matched the site of earliest activation through ECGi. ECGi, electrocardiographic imaging; LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; RAA, right atrial appendage; RSPV, right superior pulmonary vein; RIPV, right inferior pulmonary vein; and SVC, superior vena cava. Author's permission granted.

In the two studies that examined participants with AT, one (N = 52) reported a nearly complete agreement between the results of ECGi and invasive procedures for detecting the site of arrhythmia in 48 participants,[36] while the other (N = 10) reported a 100% success rate in the localization of atrial arrhythmia.[4] Shah et al.[36] reported a diagnostic accuracy of 85% for re-entrant ATs (23 of 27 cases) and 100% for focal ATs (21 cases), which represented an average accuracy of 92% (44 of 48 cases). Additionally, the accuracy was inferior for previously ablated atria (83%; 19 of 23 cases) compared to un-ablated atria (100%; 25 of 25 cases). Electrocardiographic imaging accurately identified all focal ATs as originating in the right atrium or left atrium. Further evaluation compared the diagnostic accuracy of ECGi between participants who had undergone previous AF ablation and those who were undergoing AF ablation for the first time.

In a study from 2010, Cuculich et al.[23] further demonstrated that ECGi could be used as an alternative non-invasive mapping tool to analyse mechanisms of AF in humans. Electrocardiographic imaging was shown to image low-amplitude signals of AF in patients with various clinical characteristics (wavelets and focal sites) with an accuracy of 97%.[23] The non-invasive mapping of epicardial activation patterns was successfully utilized to correctly identify locations critical to the maintenance of AF, ablation of which restored sinus rhythms with no further complications.[23,57] Ablation guided by ECGi converted AF into AT in one patient, whose follow-up showed no symptoms or need for AF-associated medication.[65]

Electrocardiographic imaging gave an accurate diagnosis 92% of the time, with accuracies of 83% and 100% in the previous and first-time ablation groups, respectively. Cakulev et al.[4] reported similar findings. They found that the use of ECGi assisted in the accurate identification of and discrimination between left and right atrium focal sources and re-entrant mechanisms in all participants.

A report by Cochet et al.[2] in AF patients described the successful detection of rotor activity on the epicardium and accurate detection of the core location of trajectories. Moreover, ECGi made it possible to map epicardial activation patterns specific to the patient, which provides insight into AF mechanisms and demonstrates its importance as a non-invasive technique.[23,65] It is evident from the studies described above that ECGi has strong diagnostic capabilities, consistent with a reliable and valid assessment method. As a result of recent advances, ECGi can measure and accurately depict atrial activation sites, rendered by a mapping system and consisting of beat-by-beat tracking. In addition, ECGi has enhanced the ability to determine whether atrial arrhythmia is focal or re-entrant, and to localize its origin to the left or right atrium. These studies show that ECGi reduces the need for further invasive procedures and can analyse AF patterns in a real-world setting over longer periods from minutes to hours.[57]

Electrocardiographic imaging can also identify AF driver domains (either focal or re-entry) along with their cumulative density map. In a study of 103 patients with persistent AF, Haissaguerre et al.[34] targeted ablation to the driver domains detected by ECGi. Compared to the conventional approach (involving pulmonary vein isolation-electrogram-based ablation lines), the investigators found similar termination rates at 12months, but reduced mean radiofrequency delivery to AF termination with driver domain identification (P<0.0001). In a similar study, a group of 108 patients with persistent AF from eight European centres underwent ECGi before ablation to detect AF drivers. Several sites were ablated if required. After 1year of follow-up, 78% and 77% of patients were off antiarrhythmic medications and free from AF recurrence, respectively. Nonetheless, a significant percentage of patients experienced AT recurrence that warranted further treatment.[33]