CardioExchange Archive

CardioExchange welcomes this guest post reprinted with permission from Dr. John M, a blog by private-practice electrophysiologist and CardioExchange member, Dr. John Mandrola.

“No data are better than bad data…If you can’t see it, don’t call it,” Dr Feigenbaum often admonished us young fellows during the old Thursday Echo conference at IU.

Calling more than is actually there seems to be increasingly prevalent in this era of sensational, but often misleading medical headlines. Take the case of AF, AF ablation, and Dementia as the most recent example.

Atrial fibrillation remains one of the most common cardiac diagnosis, and dementia is one of Neurology’s most frequent diagnosis.  Recently, as background, a study from a Utah group of electrophysiologists showed that AF predisposes to all forms of dementia, especially the specifically defined 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 chronicling a statistical, not causative, relationship between AF and dementia, this claim of AF ablation reducing dementia risk stems from an abstract presented at a meeting.  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 the NEJM.

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 pretty unbelievable; much better than the 60-70 percent reports from many other respected centers.  No, I am not accusing them of dishonesty, rather their remarkable success suggests that their ablation cohort must have been a healthy bunch of intermittent AF patients—rather than the more challenging cohort of persistent or permanent fibrillators.  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 the details.  I would suggest that a likely reason why 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.

Study any EP doctors AF patient population, and it will be obvious that those patients offered ablation are a much healthier cohort than those felt too ill for successful ablation.  So, of course, the cohort defined by their unsuitability for AF ablation would be more likely to also develop dementia.

Maybe the data are true: patients who underwent AF ablation are 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.

The senior author, Dr Day, is on the Heart Rhythm Meeting Organizing Committee. Did this have anything to do with the extensive media coverage?  Also, nearly all the readily available data on AF ablation and dementia arise from this one group of researchers.  Are these facts worthy of reporting?

I am not saying the study is dishonest or false, just preliminary.

The troubling aspect for a provider of AF care is the obvious and overt sensationalism. Taking an abstract and proclaiming that AF ablation reduces dementia risk is irresponsible and misleading.

Shouldn’t the storyline read something closer to this:

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.

AF therapy is complicated enough already.  Over-sensationalized misinformation in the lay press make it even harder to explain the issues at hand to patients.

JMM