AF ablation Atrial fibrillation

Do hundreds of left atrial burns reduce dementia risk?

Atrial fibrillation remains one of the most common cardiac diagnosis, and dementia is one of Neurology’s most frequent diagnosis.  Recently, a study from a Utah group of electrophysiologists showed that AF predisposes to all forms of dementia, especially Alzheimer’s disease.

The study involved 37.000 patients, and was published in the prominent and well respected Heart Rhythm Journal. Although the mechanism is speculative, it comes as little surprise to those of us who care for AF patients that it could be associated with an increased risk of dementia. Excluding the very young, “lone AF” patient, this arrhythmia is–like dementia–a disease of birthdays, a disease of wear and tear.  Associated conditions like high blood pressure, obesity, disordered sleep, sedentarism and diabetes all predispose to both dementia and AF.

However, the most recent headlines from this same group, suggesting that AF ablation may reduce the risk of dementia is troublesome. A prominent cardiac website had the AF ablation-dementia connection as its lead story most of the week.

Denver, CO - Treating atrial fibrillation (AF) with radiofrequency catheter ablation significantly reduces the risk of Alzheimer’s disease and reduces the risk of developing all forms of dementia, according to the results of a new study [1]. In addition to these findings, researchers showed that catheter ablation reduced the risk of mortality and stroke at three years [2].

Unlike the previous peer-reviewed report which showed a statistical, not causative, relationship between AF and dementia, the claim that AF ablation reduces dementia risk stems from a meeting abstract. The distinction between an abstract and a peer reviewed journal are critically important.  The over-publicizing of abstract (preliminary) data from medical journalists is chronicled here.

Abstracts are preliminary data presented at scientific meetings, before the usual peer-review. For instance, the general public should know that nearly a third of presented abstracts never get published in a peer-reviewed journal.  Also, due to space and time limitations, abstracts are often presented without important details of methodology. Nonetheless, these preliminary data often make headlines as if they were just published in major medical journals.

A few specific comments on this particular study highlight some of the important distinctions between peer-reviewed journal publications and abstract presentations at scientific meetings.  As background, it seems fair to accept as a given that if one is claiming an extremely complex and invasive procedure–AF ablation–will diminish a disease as widespread as dementia, a high bar of evidence should be required. Moreover, in this case the headlines do not say maybe, they say AF ablation does reduce dementia.

Some specific issues with this particular study (abstract presentation) on AF ablation and dementia are as follows:

First, this group reports an amazing 80% of their AF ablation patients are free of AF, and off drugs at three years of follow-up.  These results are much better than the 60-70 percent reports from many other respected centers. The remarkable success rates suggests that their ablation cohort might have been a healthy bunch of intermittent AF patients. They say that their patients were age and sex matched, and that AF ablation patients were more likely to have high blood pressure, CHF or valvular disease, but an abstract cannot give us details.  I would ask whether fewer of their AF ablation patients developed dementia is simply because they were less ill, and had fewer co-morbid medical problems than the more chronically ill long-standing AF patients who were not offered ablation. The cohort defined by their unsuitability for AF ablation would therefore be more likely to also develop dementia.

Maybe the patients who underwent AF ablation were less likely to develop dementia, but the ablation had nothing to do with it. Rather, the ablation was just a marker for a healthier cohort.

A more accurate storyline might have had been:

An observational, single-center, uncontrolled and un-blinded preliminary report–presented in abstract form only–suggested that a cohort of AF patients who were healthy enough to undergo AF ablation had a lower risk of dementia. The data are yet to be published in a peer reviewed journal, and the dementia-preventative effects of AF ablation, if any, are yet to be defined.