Caffeine and Atrial Fibrillation

You may not realize it, but your heart is an electrical system. Each beat of your heart is started by an electrical pulse of what is called the sinus node, which is in the upper part of the right atrium (the top section of your heart, towards your right side). In normal sinus rhythm, the sinus node sends electrical impulses to the two upper chambers of your heart, the atria, and they then contract, or beat, simultaneously. The electrical impulse then travels into the ventricles, or lower chambers of your heart, which also contract together, forcing blood out of the heart and into the lungs and the rest of the body.

While the sinus node sends, on average, about 300 electrical impulses per minute to the atria, each actual beat of the heart expends the heart's chemical and electrical ability to pass on that electrical impulse. In between each beat of the heart, the heart essentially recharges its abillity to pass on that electrical impulse, resulting in a regular heartbeat of about 75 beats per minute (on average).

Atrial fibrillation is an irregular heartbeat. Instead of the heart's electrical impulses traveling through the heart in an orderly way, the impulse becomes disorganized, resulting in an irregular heartbeat and often a faster heartbeat (two or more times the normal heart rate). This irregular heartbeat can cause blood to pool in the left atrium of the heart, which can lead to blood clots in the heart that can travel to or brain and cause stroke.

While those with atrial fibrillation may have no symptoms at all, the usual symptoms include heart palpitations (feeling like your heart is pounding or fluttering), dizziness, chest pain or shortness of breath. Many patients will point to drinking coffee or another caffeinated beverage as the cause of their a-fib, but it's never been truly clear whether caffeine has really had any real role in atrial fibrillation.

Fortunately, researchers from Harvard recently published a study in the American Journal of Clinical Nutrition that investigates the possible link between caffeine and atrial fibrillation (2010;92(3):509-14). They made use of data collected in the Women's Health Study, which was conducted between 1993 and 2009 and included over 33,000 women at least 45 years of age who had no history of heart disease, cancer or other major illnesses. At the start of the study participants submitted a food frequency questionnaire which included detailed questions about their intake of caffeine, including both beverages and chocolates.

After grouping the women's intake of caffeine into five increasing levels of intake, the researchers evaluated the incidence of atrial fibrillation against their level of caffeine intake. Even after controlling for such variables as age, physical activity level, Body Mass Index and the like, they found that those women who consumed the most caffeine were no more likely to have an incident of atrial fibrillation than those who consumed the least caffeine. Indeed, those in the third level of caffeine intake (an average of about 285 milligrams per day, or about two cups of drip coffee) actually had slightly fewer instances of atrial fibrillation than those who consumed the most or the least caffeine.

What this means for you

More good news for people who love their coffee (or tea, or chocolate). This large, long-term study seems to show quite clearly that caffeine intake has little to do with the likelihood of developing atrial fibrillation. Indeed, we know that coffee is the single largest source of antioxidants in the Western diet, and that it may even help protect you from developing type 2 diabetes. So if you have a-fib, there's no need to blame your morning cup of joe. Drink your coffee and enjoy it.

First posted: September 22, 2010