Letter from the Editor in Chief

DOI: 10.19102/icrm.2013.040101

Editor-in-Chief

Dear Readers,

We are very excited to share with you our first issue of 2013! As you will clearly notice, this issue contains many clinically relevant articles that will directly benefit our practices. As January is the Boston Atrial Fibrillation Symposium month, I would like to focus my comments on three particularly strong atrial fibrillation articles.

The first article is from Dr. Mann and colleagues from the Massachusetts General Hospital and is titled “Role of Epicardial Fat in Atrial Fibrillation Pathophysiology and Clinical Implications.” This topic is particularly relevant as all of us are seeing more and more obese atrial fibrillation patients in our practice. Much of this comes as a direct result of our “culture of comfort” in the U.S. and other developed nations where we are bombarded by unhealthy food choices and increasingly more sedentary lifestyles.

Just how does the obesity epidemic translate into the atrial fibrillation epidemic? In this article, Mann and colleagues discuss the potential role of epicardial fat as an important source of inflammation in the development of atrial fibrillation. Epicardial fat has been shown to be an important source of many pro-inflammatory cytokines and hormones. This adipocyte-myocyte interaction may then lead to structural and electrical changes within the myocardium thus creating a milieu of atrial fibrillation. This mechanism is independent of the effects of obesity on hypertension, sleep apnea, and other conditions that also promote atrial fibrillation.

What does epicardial fat mean clinically? As we all know, epicardial or visceral fat has been shown to directly correlate with clinical obesity. Certainly, epicardial fat can be diagnosed very easily with a test as simple as a routine surface echocardiogram. If we see an echo-free space between the myocardium and pericardium then it is likely epicardial fat. Sadly, this clinically important echo finding is rarely discussed in most echo reports. Perhaps the simplest approach would be to sit down with our patients when we see significant epicardial fat in the setting of atrial fibrillation and share with them this “abnormal” echo finding. After reading this article, I have now resolved to have my echo techs include this finding in the report and I will now discuss this echo finding with patients in hopes that it may help them in their quest for real health.

Like most of you, it has been particularly challenging for me to empower my patients to fight against our “culture of comfort”. Oddly, many of my obese atrial fibrillation patients tell me that they “eat healthy” but yet they cannot figure out why they are not losing weight. One thing I have found very helpful in combating the atrial fibrillation and obesity epidemic is to simply have my patient's keep a food journal of what they eat, how much they eat, and when they eat. When they come back for their atrial fibrillation follow-up visit I have my nurse practitioner review this food journal with them. Certainly, if there are recurrent poor food choices counseling can quickly take place during a follow-up visit. Just this simple act alone can be the catalyst to profound and sustained weight loss by creating an awareness of what they are actually consuming. In my experience, if they can keep a real-time food diary they will lose weight and it will stay off as long as they are diligent in maintaining the real-time food journal. This really is a small price to pay for better health.

Outside of weight loss, epicardial fat may also be a potential target in the catheter or surgical ablation of atrial fibrillation. While it would be very exciting if we could just surgically excise this excess epicardial fat or ablate it with a catheter, I'm not sure it will have a huge clinical benefit as it likely has a limited effect on the underlying metabolic derangements associated with obesity. I certainly hope that future studies will show a real and sustained clinical benefit by targeting epicardial fat.

The next article I would like to discuss is “Atrioventricular Node Ablation in Atrial Fibrillation Patients with Cardiac Resynchronization Therapy: Benefits Beyond Rate Control,” by Dr. Nazmul and colleagues or former colleagues from the Mayo Clinic. In this article, Nazmul and coworkers reported on 137 cardiac resynchronization therapy (CRT) patients with atrial fibrillation. They found that while there was certainly more biventricular pacing in the group of patients who underwent AV node ablation that there was also a trend toward an improvement in left ventricular reverse remodeling among other findings.

As I discuss this article, I must admit that this is an area where my opinion has been gradually changing over the years as I see more and more articles extoling the virtues of AV node ablation in heart failure patients with cardiac resynchronization therapy (CRT) devices. A fascinating article I recently reviewed on this subject was published this year in PACE by Dr. Efimova and colleagues from Russia¹. By way of background to this study, Dr. Jared Bunch and I have been particularly interested in studying the long-term effects of atrial fibrillation on cognitive function. We have clearly shown in a large group of more than 36,000 patients that atrial fibrillation significantly increases the risk of all forms of dementia including Alzheimer's disease.²

While we have postulated that one of the mechanisms whereby atrial fibrillation may cause dementia is due to cerebral hypoperfusion, it was interesting in this article by Efimova and coworkers that AV node ablation and pacing may normalize cerebral blood flow in patients with atrial fibrillation.

Historically, I have always viewed AV nodal ablation as a “last resort” option for my patients. However, in heart failure our AF therapies may not always be durable. While the issue of pacemaker dependency is always in the back of my mind, after reading these articles, perhaps I should be more aggressive in recommending AV node ablation in CRT patients as mechanical device failure is much less common with two ventricular pacing leads.

The last AF article I would like to discuss from this issue of the Journal is a complex case study from Dr. Harding and colleagues in Doylestown, PA entitled “Reduction in Cryothermal Energy Delivery During Isolation of the Left Persistent Superior Vena Cava: Implications for Safety and Efficacy.” This was a particularly innovative article as they report the first use of the cryo balloon for coronary sinus isolation in patients with a persistent left superior vena cava.

Fortunately, encountering a persistent left subclavian vein in the catheter ablation of atrial fibrillation is a very rare occurrence. However, if you do enough of these procedures sooner or later you will encounter this complex clinical situation. Unfortunately, in these patients just performing pulmonary vein isolation is generally insufficient in controlling their clinical atrial fibrillation as nothing has been done to eliminate the atrial fibrillation originating from their “5^th heart chamber” or the massive coronary sinus (persistent left subclavian vein).

Certainly, it could be reasonable to just perform pulmonary vein isolation as part of the first AF procedure in these patients with a persistent left subclavian vein. If this does not control the AF, and a second procedure is indicated, then the coronary sinus will likely need to be targeted for ablation. The problem is that with a standard ablation catheter it is extremely difficult to completely electrically isolate a persistent left subclavian vein. Moreover, there are many potential complications such as AV block if isolation is attempted near the coronary sinus ostium, phrenic nerve injury, or potential esophageal injury. Some investigators have suggested that a surgical MAZE procedure may be indicated for these patients.

While this study only included two patients in what is definitely an off-label indication of the cryo balloon, the results are extremely encouraging. With minimal cryo ablation and the appropriate precautions, coronary sinus electrical isolation was easily obtained and these patients did very well clinically. While I have not been an enthusiastic supporter of early generation balloon based ablation strategies, this study may have opened up a potentially new application of these technologies for the patient with a persistent left subclavian vein.

We truly hope that you will find this issue of the Journal an important component to your continuing education and the care of your patients. As always, I look forward to any comments you may have with this Journal.

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

References

Efimova I, Efimova N, Chernov V, Popov S, Lishmanov Y. Ablation and Pacing: Improving Brain Perfusion and Cognitive Function in Patients with Atrial Fibrillation and Uncontrolled Ventricular Rates. PACE 2012 March; 35:320–326. [CrossRef] [PubMed]
Bunch TJ, Weis JP, Crandall BG, May HT, Blair TL, Osborn JS, et al. Atrial Fibrillation is Independently Associated with Senile, Vascular, and Alzheimer's Dementia. Heart Rhythm 2010 Apr ; 7:4433–7. doi: 10.1016/j.hrthm.2009.12.004. Epub 2009 Dec 11. [CrossRef] [PubMed]