Study is the first to show that stature influences atrial fibrillation risk

Analysis of data from a registry of patients with left ventricular dysfunction indicates that height is an independent risk factor for an arrhythmia of the upper chambers of the heart, according to a new study in the April 18, 2006, issue of the Journal of the American College of Cardiology.

"Tall stature is a potent risk for the development of atrial fibrillation and is independent of other clinical risk factors. Indeed, the male predominance of atrial fibrillation appears to be explained by the difference in height between men and women," said Jonathan J. Langberg, M.D. from Emory University in Atlanta, Georgia.

Atrial fibrillation is the most common sustained cardiac arrhythmia. During an episode, the upper chambers of the heart flutter instead of pumping blood effectively. The incidence increases as people age, with a prevalence of more than 5 percent in patients over the age of 65 years.

The size of the left atrium of the heart is known to be associated with atrial fibrillation, so the researchers wanted to see if bigger people have a higher risk of atrial fibrillation.

"It is well known that small animals do not develop atrial fibrillation, while those larger than humans, particularly horses, seem to be quite susceptible. I also encountered a string of very tall patients, most of whom were former basketball players, with lone atrial fibrillation," Dr. Langberg said.

The researchers, including first author Ibrahim R. Hanna, M.D., reviewed data on 25,268 enrolled in the ADVANCENT registry. ADVANCENT is a prospective, longitudinal, multicenter, observational registry designed to collect and report data on the histories, diagnostics, therapies, and interventions for patients with left ventricular dysfunction (ejection fraction < 40 percent). They separated the patients by height into four groups each for men and women and then compared atrial fibrillation rates.

The patients in the tallest quartile group had an atrial fibrillation prevalence that was 32 percent higher than those in the shortest quartile. Extrapolating from this result indicates that every 16 centimeters (about 6 inches) increase in height is associated with a 50 percent increase in the chance of developing atrial fibrillation.

"Tall patients may need more aggressive attempts to attenuate risk factors. Controlled trials should evaluate stature in treatment and control arms," Dr. Langberg said.

He noted that this study just used a snapshot of the health information of the patients at a single point in time, although the patients of course reached their adult height long before they were likely to develop atrial fibrillation. And while all the subjects in this study were patients with impaired left ventricular function, Dr. Langberg speculates that the same results would be found in other groups.

Professor Michael Feneley, M.D., F.R.A.C.P., F.A.C.C. from St Vincent's Hospital in Sydney, Australia, who was not connected with this study, pointed out that height is not a modifiable risk factor.

"Although the paper supports previous evidence of a relationship between atrial size and atrial fibrillation, there is no therapeutically applicable outcome from the study, because you can't alter your height as a risk factor for atrial fibrillation!" Prof. Feneley said.

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