Letter from the Editor in Chief
DOI: 10.19102/icrm.2014.050201
John Day, MD, FHRS, FACC
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Dear Readers,
Many years ago when I first began my career as an electrophysiologist, I was referred a young woman with a highly symptomatic recurrent right atrial tachycardia refractory to antiarrhythmic drug therapy. After several clinic visits, we decided to move forward with an ablation procedure. During the ablation procedure she had an easily inducible and sustained atrial tachycardia and we were able to map out the source to a position high in the right atrium near the superior vena cava.
As the site of earliest activation was near the phrenic nerve, we performed a very detailed pace map of the phrenic nerve and carefully marked all of these locations on our 3D electroanatomic map. We felt confident that the site of earliest activation did not have any phrenic nerve stimulation when pacing at maximum output. We then proceeded with ablation at this site while continuously pacing the phrenic nerve to detect any potential phrenic nerve injury.
At about 20 seconds into the ablation, we suddenly had loss of phrenic nerve stimulation. We immediately stopped the ablation and I stared in horror at the lack of diaphragmatic movement with the right hemidiaphragm. With this dreadful complication, we immediately stopped the procedure.
I spent hours with the patient and her family trying to explain what happened during the procedure and that this complication would likely resolve over time. While she was fine at rest, she was horribly short of breath with any physical activity. Her life was now in shambles and I felt horrible.
For eight long months I saw her on a regular basis while we waited for her phrenic nerve palsy to resolve. On many occasions I thought to myself, what if this never resolves? What if she is going to be like this for the rest of her life?
Of course, it did not help at all that her atrial tachycardia managed to return several months after the ablation procedure. Thus, not only could she not breathe with any activity, she was now also on antiarrhythmics again.
Fortunately, by the ninth month her phrenic nerve palsy and elevated right hemidiaphragm finally resolved. Following this incredibly painful experience, I swore that I would never experience this complication again. For this reason, I have been slow to embrace the cryoballoon technology for treating atrial fibrillation.
Given this experience many long years ago in my career, it is no wonder that the article by Dr. Peter L. Friedman and colleagues entitled “A New “Hands-Free” Non-Fluoroscopic Method for Monitoring Phrenic Nerve Function During Catheter Ablation” caught my attention.
Dr. Friedman and colleagues should be commended for identifying a potentially simple solution to prevent such a dreadful complication. As is well know, phrenic nerve palsy is a potentially devastating complication associated with cryoballoon ablation in the right upper pulmonary vein for atrial fibrillation.
While techniques and strategies to avoid phrenic nerve palsy have definitely improved, this complication still occasionally occurs with balloon based technologies. In this article, Dr. Friedman and colleagues describe using a modified pediatric blood pressure cuff to record pressure signals from the body surface generated by diaphragmatic contraction.
This novel approach then allows for early monitoring of a potential phrenic nerve injury without hand palpation or fluoroscopy. In this study, they tested this approach on 10 consecutive patients undergoing cryoballoon pulmonary vein isolation and found that it worked well and was very accurate in assessing for a potential phrenic nerve injury.
Certainly, one could imagine how this technology may not be completely reliable in the morbidly obese patient undergoing an atrial fibrillation ablation procedure. Also, levels of sedation or general anesthesia could also impact the ability to detect a potential phrenic nerve injury with this approach. However, as with most new technologies, these limitations will be certainly be overcome and the approach will be much better refined.
As balloon based technologies continue to improve, in conjunction with novel monitoring technologies, such as the technology described in this issue of the Journal, balloon based approaches will garner a larger share of the atrial fibrillation market size. Many centers, including our center, have been very leery of the cryoballoon given the potential risk of a phrenic nerve palsy when we have done thousands upon thousands of ablation procedures using the irrigated tip approach.
I should mention here that just because you may not use a balloon-based approach for treating atrial fibrillation, you still have to worry about the potential risk of phrenic nerve injury. Even one case of phrenic nerve injury in a thousand, or for that matter, one palsy in 10,000 cases is way too high of a risk.
To make this complication hopefully “go away”, for many years now we have pace mapped the antrum of the right-sided pulmonary veins to map out the course of the phrenic nerve. This simple pace map only adds two to three minutes to the case. However, if these two to three minutes could prevent even one phrenic nerve injury in 10,000 cases it would be worth it.
When we have evaluated this in our experience, 13% of all patients undergoing an atrial fibrillation ablation procedure have phrenic nerve capture in the body of the left atrium. Thus, even if you never ablate inside of the right upper or right lower pulmonary vein you are still potentially putting the phrenic nerve at risk for injury.
Once we have pace-mapped the course of the phrenic nerve, we then mark it on our 3D electoanatomical map and avoid ablation in these areas. In figure 1 you can see the typical areas where we can elicit phrenic nerve capture with pacing. In some patients, you will find phrenic nerve capture where you traditionally perform wide area catheter ablation.
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By using this approach, I have yet to experience a phrenic nerve injury from the more than 3,000 atrial fibrillation ablations that I have personally performed. To this day, the pain of this complication many years ago in a very young and physically active woman still haunts me.
It is my sincere hope that we will finally be able to identify a solution that will make phrenic nerve palsy with atrial fibrillation procedures a thing of the past. What techniques do you use to prevent phrenic nerve palsy? Please drop me a line and share your thoughts with me on this subject. In closing, I hope that you will continue to find this Journal an incredibly valuable resource in your management of patients with cardiac rhythm issues. As always we open any suggestions or comments you may have about the contents of this Journal.
Very best regards,
John D. Day, MD, FHRS, FACC
Editor-in-Chief
The Journal of Innovations in Cardiac Rhythm Management
JDay@InnovationsInCRM.com
Director of Heart Rhythm Services
Intermountain Medical Center
Salt Lake City, UT
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