Alcohol and the Heart: Boozing May Boost A-fib Risk by Enlarging the Left Atrium
Moderate consumption of alcohol is often touted as being heart healthy based on studies of coronary disease risk, but the message around drinking might be more complicated than that. Results of a new observational study show that middle-aged and older adults who imbibe even a little less than one drink per day on average have larger left atria and elevated risks of developing A-fib.
Each additional 10 grams of alcohol consumed per day (a standard US drink contains 14 grams) was associated with an estimated increase in left atrial dimension of 0.16 mm and in A-fib risk of 5% (HR 1.05; 95% CI 1.01-1.09), lead author David McManus, MD (University of Massachusetts Medical School, Worcester, MA), and colleagues report in a study published online September 14, 2016, ahead of print in the Journal of the American Heart Association.
The latter relationship was attenuated after accounting for left atrial size, suggesting that “left atrial enlargement may be an intermediate phenotype along the causal pathway linking long-term alcohol consumption to [A-fib],” they write.
Speaking with TCTMD, senior author Gregory Marcus, MD (University of California, San Francisco), said the fact that those relationships were seen even at consumption levels of only roughly one drink per day was “a little bit surprising” and suggests “the even the amounts of alcohol that are considered acceptable by the American Heart Association, for example, could be harmful to those prone to atrial fibrillation.”
The AHA recommends that for those who choose to drink alcohol, it should be done in moderation, defined as one to two drinks per day for men and one drink for women.
An important message for the public, however, is that alcohol should not necessarily be considered heart healthy, Marcus said, noting that any protective effect likely involves coronary disease, with unknown effects on other types of disease.
For patients with left atrial enlargement, A-fib, or risk factors for A-fib such as family history, the message might be different, he said. “Physicians should always recommend moderation in drinking, but they might recommend abstinence to those patients.”
A relationship between alcohol consumption and A-fib has been observed in multiple studies, but the main unknown has been the mechanism, Marcus said. Heavy alcohol use has been shown to impair ventricular function, and it’s possible that the atria—which seem to be more prone to damage than the ventricles—could be enlarged with even small-to-moderate amounts of alcohol, he explained.
To test whether that occurs and whether it could represent a possible mechanism to explain the link between drinking alcohol and A-fib, the investigators looked at data from 5,220 participants in the original or offspring cohorts of the Framingham Heart Study who had echocardiographic measurements of left atrial size. Most were free from cardiovascular disease at baseline.
At the beginning of the study, the mean left atrial dimension was 38.3. mm. Average alcohol consumption was 13.3 grams per day. Through a median follow-up of 6 years, the incidence of A-fib was 8.4 per 1,000 person-years.
Although incrementally greater amounts of alcohol consumption were associated with larger left atrial sizes, there was no relationship between intake and the change in left atrial dimension over time.
After adjustment for left atrial dimension, the link between alcohol intake and A-fib became nonsignificant. The authors estimated that 24% of the association could be explained by left atrial enlargement, although the confidence interval around that point estimated indicated that the figure could be as low as 8% and as high as 75%.
“These data, although observational, are consistent with the notion that chronic alcohol consumption, even at moderate levels, can be cardiotoxic and lead to pathological atrial structural change that can, in turn, enhance vulnerability to [A-fib] later in life,” the authors write.
An Individualized Approach Needed
It will be important to tease out what makes certain people more susceptible to left atrial enlargement and subsequent A-fib so advice about drinking alcohol can be tailored to specific patients, Marcus said, pointing out that it would be wrong to generalize these types of results to all people.
“Where we need to go is more of an individualized approach, because I suspect there are some patients who really would benefit from abstinence,” he said. “But there may be some who actually would still benefit from moderate drinking—those prone to coronary disease, for example.”
Further research is needed to identify genetic or environmental exposures that can identify at-risk patients, he said.
Speaking for the AHA, Mariell Jessup, MD (Hospital of the University of Pennsylvania, Philadelphia), agreed that the message surrounding alcohol needs to be personalized.
“I think there has always been some confusion in many people’s minds about alcohol and the effects on the heart versus the impact on cardiovascular disease,” she told TCTMD.
“If you’re completely healthy in every other way, have no hypertension, exercise, your cholesterol’s perfect, and you don’t smoke, is it alright to have moderate use of alcohol? Probably,” Jessup said, stressing that nobody should be drinking to excess. “But if you’re drinking more than moderately every day and you have other risk factors including hypertension or older age, I think alcohol may contribute to the development of atrial fibrillation. And the reason, of course, that that’s so important is that atrial fibrillation leads to stroke.”
- McManus DD, Yin X, Gladstone R, et al. Alcohol consumption, left atrial diameter, and atrial fibrillation. J Am Heart Assoc. 2016;5:e004060.
- The study was supported by the National Institute on Alcohol Abuse and Alcoholism and the National Heart, Lung, and Blood Institute.
- McManus reports receiving research funding from Biotronik and Philips Healthcare; serving as a consultant to and equity holder of ATRIA and MobileSense; and serving as a consultant to Pfizer and Bristol-Myers Squibb.
- Marcus reports receiving research funding from Medtronic, Pfizer, and Rhythm Diagnostic Systems and serving as a consultant to and equity holder of InCarda Therapeutics.
- Jessup reports no relevant conflicts of interest.