Letter from the Editor in Chief
DOI: 10.19102/icrm.2012.031201
John Day, MD, FHRS, FACC
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Dear Readers,
It is hard to believe that 2012 has nearly come to a close! It has certainly been an exciting year, with many new discoveries and developments. For example, in this issue of the Journal, we have a very novel manuscript from Dr. Steven Bailin and colleagues describing a new approach for mapping persistent atrial fibrillation. In this manuscript, they present their results of performing substrate-based atrial fibrillation ablation as guided by voltage gradient mapping.
The ability to precisely map the source or substrate of persistent atrial fibrillation, rather than just triggers, truly represents the “holy grail” of atrial fibrillation mapping. The online images and movies accompanying this article are definitely worth viewing. While many groups around the world are evaluating different methods of identifying atrial fibrillation rotors or atrial fibrillation drivers, Dr. Bailin and colleagues may perhaps have developed a technique of mapping atrial fibrillation wavelets by voltage gradient mapping. I look forward to your comments as you evaluate this innovative article!
As this is the last issue of 2012, I thought I would take a minute and give you my “top 10” list of published articles in 2012 that will definitely impact the field of cardiac rhythm management for many years to come.
10. Estradiol promotes sudden cardiac death in transgenic long QT type 2 rabbits while progesterone is protective. Heart Rhythm 2012; 9:823–832.
While β-blocker therapy is life saving for long QT type 1, the benefits of β-blockade in preventing ventricular arrhythmias are not as significant for long QT type 2. In this study, the authors sought to evaluate the role of sex hormones on ventricular arrhythmogenesis in a rabbit model with long QT type 2. In this study, they found that oral progestins may potentially represent a new class of antiarrhythmic treatment in long QT type 2. Certainly, studies will need to be done in humans to validate these findings, but hormonal therapy may some day play a role in long QT management.
9. Rhythm versus rate control therapy and subsequent stroke or transient ischemic attack in patients with atrial fibrillation. Circulation 2012 Nov 2. [Epub ahead of print]
In this article, Tsadok and colleagues evaluated 57,518 patients who were treated with either a rate control strategy or rhythm control strategy for managing their atrial fibrillation. After a mean follow-up of 2.8 years, they found that a rhythm control strategy was associated with a lower rate of stroke or transient ischemic attack. Interestingly, this benefit was particularly striking among those patients with a moderate or high risk of stroke. Hopefully, this article will gain some traction within the general medicine community. Since the “rate versus rhythm” control trials were published about a decade ago, I have observed that many medical residents coming out of training have shunned a rhythm control strategy for treating atrial fibrillation.
8. Long-term frequency gradients during persistent atrial fibrillation in sheep are associated with stable sources in the left atrium. Circ Arrhythm Electrophysiol 2012 Oct 10. [Epub ahead of print]
This was an interesting article in that as part of our search for the “holy grail” of atrial fibrillation mapping, the authors describe that atrial fibrillation rotors in a sheep model appear to migrate and are found most frequently on the posterior wall of the left atrial. Moreover, the dominant frequency in atrial fibrillation changes as part of the transition from paroxysmal to persistent atrial fibrillation. If this is indeed the case, it will make it potentially more difficult to map atrial fibrillation rotors at the time of ablation and then expect a long-term cure based on the ablation of the rotors identified during the ablation procedure. This article may also help to explain why extensive left atrial posterior wall ablation has been reported to improve long-term success rates.
7. Outcomes of Medicare beneficiaries undergoing catheter ablation for atrial fibrillation. Circulation 2012; 126:2200–2207.
This article caught my attention as it reported the real world results of 15,423 atrial fibrillation ablation patients from the Medicare population. Interestingly, they reported that the cardiac tamponade rate was 1.7%, 0.8% of the patients had a clinical stroke, and 0.8% of the patients died within 30 days of the procedure. Quite surprisingly, in this study only 11% of the patients had a repeat ablation procedure. The 1-year hospitalization rate following ablation was 43%, generally for non-arrhythmic indications, which is comparable to the reported 47% 1-year hospitalization rate of Medicare patients undergoing any surgical procedure. Probably the most striking finding of this study was that the 1-year mortality rate of Medicare atrial fibrillation ablation patients was 3.8%, which is much lower than the reported 1-year mortality rate of 25% for Medicare patients with atrial fibrillation. All in all, this study shows that Medicare patients selected for atrial fibrillation ablation procedures have a very favorable outcome.
6. Does the left atrial appendage morphology correlate with the risk of stroke in patients with atrial fibrillation? Results from a multicenter study. J Am Coll Cardiol 2012; 60:531–538.
This study was very important in that it contributes significantly to our understanding of the left atrial appendage. The left atrial appendage is an important structure within the heart about which little is known. For example, what is the contribution of the appendage to the left atrial ejection fraction? While we know that clots arising within the appendage are the cause of 90% of cardiac emboli, little is known regarding which appendage factors contribute to clot formation. In this study of 932 patients who had undergone computed tomography or magnetic resonance imaging, the authors described four different left atrial appendage morphologies, namely “Cactus”, “Chicken Wing”, “Windsock,” and “Cauliflower.” Of these morphologies, they found that the “Chicken Wing” morphology was present in 48% of these patients. Moreover, the “Chicken Wing” morphology was associated with a low risk of stroke despite controlling for comorbidities and CHADS2 score. If validated, this study could have a significant impact on atrial fibrillation anticoagulation management, as many patients who are currently prescribed anticoagulation therapy may not need such aggressive therapy if they have a “benign” left atrial appendage morphology.
5. Deaths caused by the failure of Riata and Riata ST implantable cardioverter-defibrillator leads. Heart Rhythm 2012; 9:1227–1235.
This manuscript added to our knowledge of Riata implantable cardioverter-defibrillator (ICD) lead failures and also generated significant media attention. It is widely known that Riata ICD leads are prone to externalized conductors. In this study, Dr. Hauser and colleagues searched the Food and Drug Administration’s Manufacturers and User Facility Device Experience database for deaths associated with Riata, Riata ST, and Quattro Secure leads. From this database search, they reported 22 deaths that had been caused by Riata or Riata ST lead failure and five deaths that had been caused by Quattro Secure lead failure. Quite unexpectedly, they found that Riata and Riata ST lead failure deaths were typically caused by short circuits between high-voltage components and that there were no deaths due to externalized conductors.
4. Percutaneous left atrial appendage suture ligation using the LARIAT device in patients with atrial fibrillation. J Am Coll Cardiol 2012; pii: S0735-1097(12)03035-5. doi: 10.1016/j.jacc.2012.06.046. [Epub ahead of print]
In this study, we finally have data regarding the safety and efficacy of the recently FDA approved LARIAT suture device for elimination of the left atrial appendage. Using an endocardial and epicardial percutaneous approach, the authors report the results of performing this procedure for 89 patients. While just an observational study in a small group of patients, the outcomes appear rather favorable. Certainly, a randomized controlled trial of the LARIAT in comparison to warfarin for atrial fibrillation stroke prevention would have been preferable; however, at least we now have some data regarding this device which was FDA approved as part of a 510K process. As this technology is now readily available, we hope that the long-term real-world clinical experience will also be favorable.
3. Treatment of atrial fibrillation by the ablation of localized sources CONFIRM (Conventional Ablation for Atrial Fibrillation With or Without Focal Impulse and Rotor Modulation) trial. J Am Coll Cardiol 2012; 60:628–636.
This is certainly another new technology which has created a significant “buzz” within the cardiac rhythm management community since it was presented as a late-breaking clinical trial at the Annual Scientific Sessions of the Heart Rhythm Society in 2011. The rotor mapping technology used in this study has also been FDA approved as part of a 510K process. The results of the published manuscript are similar to what was presented at the late-breaking clinical trial session last year, namely that ablation of atrial fibrillation, which also includes targeting focal rotors, in addition to pulmonary vein antral isolation, dramatically improves long-term success rates in patients with persistent atrial fibrillation. This study has also launched many other competing technologies designed to identify and map atrial fibrillation rotors and drivers.
2. Elimination of local abnormal ventricular activities: a new end point for substrate modification in patients with scar-related ventricular tachycardia. Circulation 2012; 125:2184–2196.
Once again, the Bordeaux group has published yet another manuscript which will have a huge impact within the ventricular tachycardia (VT) ablation community. In this study, they report a new ablation approach for VT. With this approach, the entire procedure is done in sinus rhythm and VT is never induced. From an ablation approach, they target high-frequency sharp signals within the ventricular myocardium which is considered indicative of local electric activity arising from pathological tissue. The endpoint of this ablation strategy is to electrically isolate these surviving myocardial fibers located within areas of ventricular scar. Their conclusion was that elimination of local abnormal ventricular activities is feasible and safe and is associated with superior survival free from recurrent VT. This approach to VT ablation will allow for a safe, efficient, and effective ablation procedure.
1. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med 2012 Nov 6. [Epub ahead of print]
Building on the legacy of over two decades of groundbreaking MADIT trials, MADIT-RIT once again will definitely impact cardiac rhythm management. In this study, Dr. Moss and colleagues randomized 1,500 primary prevention ICD patients to three different “delayed therapy” programming strategies for ventricular tachycardia in comparison to the standard 2.5-s delay of treating VT of 170–199 bpm and a 1.0-s delay of treating ventricular arrhythmias ≥200 bpm. Interestingly, they found that “delayed” VT therapy resulted in about a 75% reduction in the first appropriate therapy (antitachycardia pacing or shock) and an approximately 50% reduction in all cause mortality. The take home message of this study is that ICD programming that allows for slow VT and short runs of VT minimizes shocks and improves survival. This study also suggests that any shock may be hazardous and should be avoided unless death is imminent otherwise.
Yes, 2012 was certainly a very active year with many exciting discoveries and newly approved FDA technologies. We hope that you have enjoyed reading this Journal over the past year and that it has positively impacted your practice and the lives of your patients. As always, please feel free to share with us your thoughts and insights regarding the material in this Journal. We wish you all a safe and prosperous 2013!
Sincerely,
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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