The ECG as a Tool to Determine Atrial Fibrillation Complexity
The ECG as a Tool to Determine Atrial Fibrillation Complexity
Another potentially useful application of surface ECG is to guide AF ablation. The cornerstone of catheter ablation for patients with paroxysmal AF is isolating the pulmonary veins. In patients with persistent AF different ablation strategies and methods have been recommended with varying results. In these patients, non-invasive ECG analysis could be useful to determine whether advanced ablation strategies should be applied. In 2004 the first human applications of ECG imaging (ECGI) was reported. In ECGI, the spatial ECG information obtained from a BSPM is combined with anatomical information of the atria using CT. First, the epicardial propagation of the atrial activation during SR and a typical counterclockwise atrial flutter was demonstrated. In 2010 the same group reported the first data of patients with AF using ECGI. They showed more pronounced AF complexity in patients with long-standing persistent AF compared with persistent or paroxysmal AF. Furthermore, they suggested that ECGI can distinguish various pathophysiological arrhythmogenic mechanisms, mostly in patients with persistent AF. They found simultaneous wavelets in 92% of the patients, a single-wave macro re-entry in 8%, rotors in 15%, and focal activity from the pulmonary veins in 69% and non-pulmonary vein regions in 62% of cases. Identifying different AF mechanisms in different patients could lead to a patient-tailored ablation strategy. A feasibility study in two patients based on this principle showed that ablating active sources identified by ECGI terminated AF during catheter ablation. Further research in a larger patient cohort with follow-up is needed to explore the potential of this approach.
The clinical application of ECGI is limited by its need for image modalities such as CT or MRI. The first study to use BSPMs during AF did not use an image modality. Nevertheless, the authors were able to demonstrate large variability in the activation patterns between individual patients. A limitation of this study was that no correlation with invasive measurements was investigated. More recent studies investigated the ability of BSPM to identify invasively measured high-frequency sources non-invasively during AF without an image modality. High-frequency sources are reflected on the surface electrode closest to the atrium of interest: right atrial signals are projected on the right-anterior part of the body surface. Left atrial signals are projected mainly on the posterior and the left-anterior part. Earlier research showed that the use of BSPMs may help to identify the location of focal triggers for AF using premature atrial activations during SR. Whether identifying high-frequency sources or focal triggers before arrival at the electrophysiology laboratory can guide ablation and improve long-term success certainly warrants further investigation.
ECG-Imaging Guiding Ablation Strategy
Another potentially useful application of surface ECG is to guide AF ablation. The cornerstone of catheter ablation for patients with paroxysmal AF is isolating the pulmonary veins. In patients with persistent AF different ablation strategies and methods have been recommended with varying results. In these patients, non-invasive ECG analysis could be useful to determine whether advanced ablation strategies should be applied. In 2004 the first human applications of ECG imaging (ECGI) was reported. In ECGI, the spatial ECG information obtained from a BSPM is combined with anatomical information of the atria using CT. First, the epicardial propagation of the atrial activation during SR and a typical counterclockwise atrial flutter was demonstrated. In 2010 the same group reported the first data of patients with AF using ECGI. They showed more pronounced AF complexity in patients with long-standing persistent AF compared with persistent or paroxysmal AF. Furthermore, they suggested that ECGI can distinguish various pathophysiological arrhythmogenic mechanisms, mostly in patients with persistent AF. They found simultaneous wavelets in 92% of the patients, a single-wave macro re-entry in 8%, rotors in 15%, and focal activity from the pulmonary veins in 69% and non-pulmonary vein regions in 62% of cases. Identifying different AF mechanisms in different patients could lead to a patient-tailored ablation strategy. A feasibility study in two patients based on this principle showed that ablating active sources identified by ECGI terminated AF during catheter ablation. Further research in a larger patient cohort with follow-up is needed to explore the potential of this approach.
The clinical application of ECGI is limited by its need for image modalities such as CT or MRI. The first study to use BSPMs during AF did not use an image modality. Nevertheless, the authors were able to demonstrate large variability in the activation patterns between individual patients. A limitation of this study was that no correlation with invasive measurements was investigated. More recent studies investigated the ability of BSPM to identify invasively measured high-frequency sources non-invasively during AF without an image modality. High-frequency sources are reflected on the surface electrode closest to the atrium of interest: right atrial signals are projected on the right-anterior part of the body surface. Left atrial signals are projected mainly on the posterior and the left-anterior part. Earlier research showed that the use of BSPMs may help to identify the location of focal triggers for AF using premature atrial activations during SR. Whether identifying high-frequency sources or focal triggers before arrival at the electrophysiology laboratory can guide ablation and improve long-term success certainly warrants further investigation.
Source...