Letter from the Editor in Chief Featuring af Section Editor Insights

DOI: 10.19102/icrm.2012.030101

Editor-in-Chief

Dear Readers,

We would like to start off by wishing everyone a happy and healthy 2012. The New Year brings forth a continued excitement of Innovations in Cardiac Rhythm Management, as the platform has grown by leaps and bounds since its inception. Additions to the Editorial Board along with the appointment of Section Editors, each of which has proven invaluable, have helped to contribute to this success.

2012 will be no different, as we are excited to continue to expand on our multimedia offerings. Within the next few weeks we are preparing to launch selected sessions from the AF Ablation Innovations event that recently took place. These lectures include some truly remarkable presentations and case studies by physicians that continue to stay on the forefront of patient care. You will be able to access all content directly from the InnovationsInCRM.com homepage.

Within this letter we would like to provide commentary on an original manuscript found in the Innovative Techniques section of this issue by Avitall et al, entitled “Novel Ablation Catheter Technology that Improves Mapping Resolution and Monitoring of Lesion Maturation.” This contribution focuses on the author’s experiences with a novel ablation catheter that utilizes four additional sensing pin electrodes at the tip of the catheter, which allow for higher resolution mapping of local electrograms and assessment of lesion formation.

Catheters designed to more efficiently increase energy delivery into the tissue, such as an 8 mm tip technology, make it much more difficult for the operator to determine whether or not a transmural lesion is being delivered. This is critically important with regards to catheter ablation of atrial fibrillation, as balancing safety by avoiding extra cardiac ablation versus durable pulmonary vein isolation remains a significant limitation of this therapy. In this manuscript, the authors present their findings of this novel ablation catheter in 7 dogs.

This study concludes the addition of pin electrodes to the tip of the ablation catheter allowed for a better indicator of transmural lesion creation by functioning as a surrogate of tissue contact. In particular, the authors found that both the reduction of the local electrogram amplitude as well as the frequency shift on the pin electrodes are uniquely associated with transmural atrial lesion formation. They also postulated that this novel technology may offer increased safety by focusing ablations only to viable tissue rather than delivering unnecessary further ablation of tissue where a transmural lesion has already been created.

How does this manuscript fit into our current understanding of lesion formation? At the end of the day, lesion formation is really determined by the energy delivered, which is a function of power, time, and catheter contact. The purpose of this novel ablation catheter is to provide enhanced mapping as well as to serve as a surrogate of a transmural lesion. With regards to the latter, can improvement to the sensing of electrograms and their amplitude response to ablation guide energy delivery? More importantly, does amplitude reduction, to a certain level, mean a transmural lesion has developed?

Prior data has suggested that you can use electrograms to guide the ablation, but the accuracy of this approach (i.e. amplitude reduction) is dependent on the myocardial tissue characteristics, energy delivery scheme, and catheter type.^1–3 However, since we currently do not have a better means to assess for completeness of the lesion, we use electrograms to guide the ablation. To this extent, enhanced electrogram determination with this novel ablation catheter may improve the efficacy of our ablations.

With our current generation of ablation catheters the use of electrograms to guide ablation is critically dependent on the orientation of the catheter.⁴ For example, nonparallel versus parallel catheter tip orientations have different electrogram response patterns. One advantage of this novel ablation catheter is that the impact of catheter orientation on electrogram analysis can be minimized, or even eliminated, with the additional multiple sensing electrodes on the catheter tip. Given this advantage, it is not surprising that the authors found more accuracy with this novel ablation catheter as compared to traditional bipolar sensing paradigm (tip-ring).

We suspect there may be additional diagnostic information from this novel ablation catheter outside of amplitude reduction. For example, the pattern of electrogram reduction noted by bipolar and/or unipolar sensing also has diagnostic potential in assessing for transmurality.⁵ With additional experience of this catheter, we anticipate that there will also be unique electrogram patterns associated with a transmural lesion.

How does this novel ablation catheter fit into the current evolution of ablation catheter technology? The next generation ablation catheters will have force sensing capacity, which will guide us during the ablation process to more effectively achieve a transmural lesion. However, the additional tip electrodes could allow us to better assess for transmurality or for “gaps” in our ablation lesion set to help minimize the need for redo procedures. Also, consistent catheter force and contact with the myocardium will enhance energy delivery. Enhanced sensing may also increase safety by providing an understanding of when to stop energy delivery or move the catheter to avoid heating tissues beyond the atrial myocardium.

We hope the thoughts and comments shared in this letter will be of additional benefit as they accompany Avitall and colleagues manuscript.

Editor-in-Chief

John Day, MD, FHRS, FACC
Editor-in-Chief
The Journal of Innovations in Cardiac Rhythm Management
JDay@InnovationsCRM.com
Director of Heart Rhythm Services
Intermountain Medical Center
Salt Lake City, UT

Editor-in-Chief

T. Jared Bunch, MD
Atrial Fibrillation Section Editor
The Journal of Innovations in Cardiac Rhythm Management
Jared.Bunch@imail.org
Intermountain Heart Rhythm Specialists
Intermountain Medical Center
Salt Lake City, UT

References

Schwartzman D, Michele JJ, Trankiem CT, Ren JF. Electrogram-guided radiofrequency catheter ablation of atrial tissue comparison with thermometry-guide ablation: comparison with thermometry-guide ablation. J Interv Card Electrophysiol. 2001;5:253–266. [CrossRef] [PubMed]
Azegami K, Satake S, Okishige K, Sasano T, Ohira H, Yamashita K. Monitoring the local electrogram at the ablation site during radiofrequency application for common atrial flutter. Jpn Circ J 1998;62:559–564. [CrossRef] [PubMed]
Otomo K, Uno K, Fujiwara H, Isobe M, Iesaka Y. Local unipolar and bipolar electrogram criteria for evaluating the transmurality of atrial ablation lesions at different catheter orientations relative to the endocardial surface. Heart Rhythm 2010;7(9):1291-300. [CrossRef] [PubMed]
Otomo K, Uno K, Fujiwara H, Isobe M, Iesaka Y. Local unipolar and bipolar electrogram criteria for evaluating the transmurality of atrial ablation lesions at different catheter orientations relative to the endocardial surface. Heart Rhythm 2010;7(9):1291-300. [CrossRef] [PubMed]
Otomo K, Uno K, Fujiwara H, Isobe M, Iesaka Y. Local unipolar and bipolar electrogram criteria for evaluating the transmurality of atrial ablation lesions at different catheter orientations relative to the endocardial surface. Heart Rhythm 2010;7(9):1291-300. [CrossRef] [PubMed]