Letter from the Editor in Chief
DOI: 10.19102/icrm.2012.031001
John Day, MD, FHRS, FACC
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Dear Readers,
Every once in a while I read a study that really makes me question why I do what I do in my clinical practice. In this month's issue of the Journal, we have just that type of an article. The article is entitled, “Single Coil Versus Dual Coil ICD Lead Shock Efficacy in a Large ICD Registry,” by doctors Christopher Ellis, MD and Jon Hurt, MD.
In the US, more than 90% of implanted ICD leads have dual shocking coils. If right-sided ICD implantations are excluded, this number is much closer to 100%. Just why do we implant dual coil shocking leads? For me, I must confess that it is likely “dogma” from my fellowship training days where I was taught that dual coil ICD leads result in lower defibrillation thresholds. Of course, this was from an era when we did not have the high-energy ICD systems. Now, as I look at the data, it really is not that compelling with regards to defibrillation thresholds. Perhaps you can achieve a 1–2 J lower defibrillation threshold with a dual coil lead. However, these data are from ICD implant testing that may not even correlate with clinical shock efficacy. Do these data justify routinely implanting a dual coil ICD lead system?
In this study, Ellis and Hurt looked at the clinical shock efficacy from a large St. Jude Medical ICD registry. A total of 5424 patients (269 single coil, 5155 dual-coil) were enrolled and over the course of the two-year follow up, 618 patients (22 single vs. 606 dual) received an appropriate ICD shock. Interestingly, there was no difference seen in the clinical shock efficacy of a single coil versus a dual coil ICD lead system. The single shock conversion rate was 85% in the single coil system and 87% in the dual coil system (p = 0.90).
Of course, it is readily apparent that there were just not that many patients in the single coil group to draw any definitive conclusions from this study. Moreover, it is not clear how many of these patients had a right-sided versus left-sided ICD implantation as right sided implantations may have a slightly higher defibrillation energy requirement. Regardless, it raises an important question, namely does it matter clinically whether or not the ICD lead is a single coil or dual coil system?
Why does it even matter if one implants a dual coil ICD lead system? Probably the biggest challenge with a dual coil system has to do with lead extractions. In this era of “ICD lead recalls” lead extraction has certainly become a very important aspect of device management. When extracting ICD leads, tissue ingrowth into the shocking coils can be particularly problematic and could lead to the potentially fatal complication of a superior vena cava tear with lead extraction. Certainly, adding an additional shocking coil just makes the lead that much more complex which could potentially increase the long-term failure rate of the lead. I'm sure we all wish that ICD leads had the same long-term durability of a simple pacemaker lead.
How does this study impact my clinical practice? As we still perform ICD shock testing at the time of implantation in most of our patients, I must admit that I do like the option of having a dual coil system to change shock vectors in that rare patient with an elevation defibrillation threshold. However, it is also ironic that often in these patients that by simply unplugging the proximal coil we can often achieve an acceptable defibrillation threshold.
However, in this era of ICD lead failures, FDA warnings, etc. we are also very aware of the need for future lead extraction particularly in our younger ICD patients. Fortunately, our healthcare system has negotiated an “a la cart” pricing strategy with ICD vendors. In other words, we can select an ICD pulse generator from one company and then select an ICD lead from a second company. Thus, my personal bias has traditionally been to select a “gore coated” ICD lead thus allowing me the potentially lower defibrillation energy of a dual coil system but yet also allow a potentially easier extraction as the gore coating minimizes tissue ingrowth over time into the ICD shocking coil.
Now as I study this article from Ellis and Hurt I must confess that perhaps I should consider just implanting the simpler single coil ICD shocking lead as “real world” data does not show any difference. As always, we welcome your comments to the Journal and I would be interested in learning your thoughts on single versus dual coil ICD lead systems. We hope you will find this issue of the Journal particularly helpful in your practice!
Warm regards,
John 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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