Drinking Alcohol Linked to Atrial Enlargement and AF
“While alcohol as a risk factor for atrial fibrillation, at least among some people, is now fairly well established, we still really have no idea how this occurs,” said study author Gregory M. Marcus, MD, MAS, director of clinical research, Division of Cardiology, University of California at San Francisco. “To my knowledge, this is the first study to provide a potential mechanistic explanation underlying chronic consumption of alcohol and the development of atrial fibrillation. Our findings suggest that a substantial proportion of the relationship between chronic alcohol consumption and new onset atrial fibrillation is due to enlargement of the left atrium. Just as we know that very heavy alcohol use can weaken and dilate the ventricles of the heart, it may be that even moderate amounts of alcohol are sufficient to adversely affect the smaller and thinner atria.”
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Researchers evaluated the relationship between cumulative alcohol consumption and risk of incident AF in 5220 Offspring and Original Framingham Heart Study participants (mean age, 56.3 years; 54% women) with echocardiographic left atrial size measurements. The incidence of AF was 8.4 per 1000 person-years, with 1088 incident AF cases occurring over a median 6.0 years (25th-75th percentiles 4.0-8.7 years) of follow-up.
After multivariable adjustment for potential confounders, every additional 10 g of alcohol per day (just under 1 drink per day) was associated with a 0.16-mm larger left atrial dimension. Also, in multivariable adjusted analysis, every 10 g per day of alcohol consumed was associated with a 5% higher risk of developing new-onset AF. An estimated 24% of the association between alcohol and AF risk was explained by left atrial enlargement.
“We were somewhat surprised that the magnitude of the increased amount of alcohol associated with a larger left atrium fit into a range compatible with moderate alcohol intake on a regular basis,” Dr Marcus said.
He said that they will continue to pursue this research in several ways. “First, we have ongoing parallel animal experiments to try and understand the fundamental mechanisms responsible for these observations,” Dr Marcus said. “Second, there may yet be acute effects of alcohol that also promote atrial fibrillation related to the electrical rather than structural properties of the atria. We are randomizing atrial fibrillation patients undergoing catheter ablation procedures to intravenous alcohol carefully titrated to a blood alcohol level of 0.08% vs placebo and rigorously characterizing the electrical properties of the atria before vs during the presence of alcohol vs placebo.”
McManus DD, Yin X, Gladstone R, et al. Alcohol consumption, left atrial diameter, and atrial fibrillation [published online September 14, 2016]. J Am Heart Assoc. doi:10.1161/JAHA.116.004060.