Cardiac Rhythm Management
Articles Articles 2013 June

Letter from the Editor

DOI: 10.19102/icrm.2013.040601

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Dear Readers,

It seems hard to imagine that the Heart Rhythm Society (HRS) Annual Scientific Sessions have now passed and my kids are out of school for the summer. Wasn’t it an absolutely fabulous meeting in Denver this past year? For me, it truly was a memorable experience to meet with President Bill Clinton.

As I had the opportunity to serve as the abstract chair this year I would like to share with you my top five list of the best innovative and impactful abstracts that were presented at this meeting. My list is as follows:

1. NanoStim leadless pacemaker
2. Continuous warfarin is safe for AF ablation and device implantation
3. Watchman is superior to warfarin for AF stroke prevention
4. The Durata ICD lead appears safe thus far
5. MRI may predict AF ablation outcomes

1. NanoStim leadless pacemaker

As you know, leads and the generator pocket have been the Achilles heal of device therapy. We have struggled with lead management and pocket infections for many years. Now, finally, we may have a solution to these challenges!

Dr. Vivek Reddy, as always, did a masterful job at presenting the outcomes of the first 33 implants in humans. This NanoStim “wireless” pacemaker is a self-contained unit implanted in the right ventricle. It is a VVI pacemaker with rate response capacity and has a battery life of approximately 8 years.

There were five implanting physicians from three different medical centers involved with this study. Their initial data are very limited and just include the time frame from the time of implantation to 3 months’ follow-up.

Fortunately, the data at 3 months look very good. These devices appear to be very safe and reliable. I’m sure that we will see much more sophisticated devices with subsequent generations of these leadless pacemakers, as many of the major device manufacturers have made large investments in these wireless technologies. Stay tuned as this innovative technology may completely transform the way we implant devices.

2. Continuous warfarin is safe for AF ablation and device implantation

As you are well aware, we have been hearing for several years now that performing an atrial fibrillation (AF) ablation or implanting a pacemaker/implantable cardioverter-defibrillator (ICD) in a patient on therapeutic warfarin is safe. Now, we finally have data from two multicenter trials confirming these early studies.

The first study reported the results of uninterrupted warfarin in patients undergoing device implantation called the Bruise Trial. This study was published the same day in the New England Journal of Medicine. The primary end-point of this large multicenter Bruise Trial was the risk of hematoma following device implantation.

While it may seem counterintuitive, the risk of a hematoma was much lower with uninterrupted warfarin rather than a bridging strategy. If you look deeper at the methodology, this study finding was predictable. In the bridging arm of the trial, patients were treated with full-dose low molecular weight heparin or intravenous heparin 24 hours after implantation, and this bridging strategy was continued until the international normalized ratio (INR) was therapeutic again.

In my own experience, full-dose enoxaparin 24 hours after pacemaker/ICD implantation has an extremely high risk of developing a significant device hematoma. Thus, over the years when bridging was required, I had always used half-dose enoxaparin until the INR was therapeutic without any complications.

The second study, called the Compare Study, looked at uninterrupted warfarin versus a bridging strategy in a multicenter AF ablation trial. Once again the findings were similar in that the bleeding risk and stroke/transient ischemic attack risk was lower with the uninterrupted warfarin arm.

How do we incorporate these findings into our clinical practice? First, it is very reassuring that performing device implantation or ablation procedures in patients with a therapeutic INR appears to be safe. Of course, there is a very narrow window where this is safe. Other studies have shown that if the INR is even slightly high, the risk/benefit analysis significantly changes.

Taking this a step further, does this now also apply to gastrointestinal, dental, eye or any other simple medical procedure? What about other minor surgeries? Also, how relevant are these data in a modern day cardiology practice where most of our patients are now on one of the new novel anticoagulants? This is certainly a fascinating area of research and I’m sure that guidelines will certainly be changing soon.

3. Watchman is superior to warfarin for AF stroke prevention

Wow, this has been a long-drawn-out story that we have been watching for years. The data just seem to get better for Watchman year after year. While the Europeans approved this technology years ago, the FDA is still not convinced that it works. Perhaps with these latest data presented at the HRS meeting things will change.

At the meeting, Dr. Vivek Reddy presented the 4-year outcomes from the Protect AF Trial. Amazingly, at 4 years, Watchman is now superior to warfarin with regards to stroke prevention and reduction of death. In fact, Watchman showed a 40% reduction in stroke, embolism, and cardiovascular death as well as a 34% reduction in total mortality.

At 4 years, the safety profile was similar even with the 4.8% initial risk of tamponade that was seen in the Protect AF Study with the Watchman device. The increasing risk of complications over time with warfarin is not unexpected as sooner or later these patients may unfortunately experience a bleeding complication. It should be noted that subsequent Watchman studies have shown that the current tamponade risk has been dramatically reduced to approximately 2%.

The big question now is whether or not these data are now finally good enough for the FDA? As a patient advocate, I can only hope that the FDA will finally change their mind on this life-saving technology.

4. The Durata ICD lead appears safe thus far

If there was one reassuring piece of data to come out of the HRS meeting it was that the Durata ICD lead from St. Jude Medical appears safe thus far! Ever since the Riata lead issue we have all been holding our breath and praying that the same fate would not befall our patients with an implanted Durata lead. Fortunately, we can now breath a big sigh of relief!

In a late-breaking clinical trial, Dr. John Cairns from McMaster University presented an independent analysis of 11,000 Durata leads. It should be noted that the Durata leads have an extra layer of insulation, Optim, added to the lead. With this extra layer of insulation, the Durata leads performed amazingly well. At 5 years, 99.4% of leads were still functioning normally. The only caveat would be that there were only 551 leads that were available for analysis at 5 years.

Thus, as these data are very reassuring and are in line with two other reliable ICD leads, the Quattro Secure from Medtronic and the Endotak Reliance from Boston Scientific, I would plead with these companies to please not change or retire these reliable ICD leads. Perhaps it is a sign of my age or my gray hairs but I would much rather use a time-tested reliable lead for my patients than the “latest and greatest” lead to come out of the R&D department of one of the device companies.

5. MRI may predict AF ablation outcomes

For several years now we have been hearing that left atrial fibrosis, as determined by magnetic resonance imaging, can predict who will favorably respond to ablation treatment. Now we have pretty compelling data from a multicenter trial confirming this.

Interestingly, from the DEECAF Trial, the only predictor of left atrial fibrosis in this study was hypertension. Contrary to common belief, AF duration or other cardiac comorbidities did not predict the extent of left atrial fibrosis. Also, 57% of the left atrial fibrosis was located to the posterior wall of the left atrium.

Even more impressive, was the ability of left atrial scar imaging to predict ablation success. For example, in Utah stage I (less than 10% left atrial fibrosis), the 1-year success rate was an impressive 86%. In contrast, in Utah stage IV (more than 30% left atrial fibrosis), the 1-year success rate was just 31%.

Clearly Dr. Marrouche and colleagues are on to something here as these results have now been replicated in a multicenter study. We await the market release of this technology which may then be used as a powerful predictor of who will respond to ablation therapy.

We hope that you have enjoyed this HRS recap and that you will enjoy the many interesting articles we have for you in this issue of the Journal. As always, we hope that this Journal will remain a valuable source of information as you care for your patients. We look forward to hearing from you!

Warm regards,

John Day, MD, FHRS, FACC
The Journal of Innovations in Cardiac Rhythm Management
Director of Heart Rhythm Services
Intermountain Medical Center
Salt Lake City, UT