Extreme athleticism and the risk of atrial fibrillation

Consider the following sports icons: tennis legend Billie Jean King, basketball veteran Larry Bird, triathlete Karsten Madsen, baseball pitcher Kenley Jansen, and cyclist champion Haimar Zubeldia.

What do all of these well-known professional athlete heroes have in common? They are athletes with atrial fibrillation, also called AFib. AFib is the most common heart rhythm disorder worldwide, accounting for 750,000 hospitalizations per year in the US alone. It is estimated that 6 million Americans have AFib, and this number will increase exponentially over the next few decades. Traditionally AFib was considered a disease of aging. However, younger patients are now being seen. This includes athletes.

It’s a bitter irony that athleticism can be a risk factor for AFib, particularly for high-endurance athletes who have reached their forties and fifties. While athleticism isn’t considered among AFib causes, it is certainly being recognized by the cardiac electrophysiologist community as a contributor and trigger. We will come back to this point.

Regular exercise and movement are two major ingredients to an enjoyable and long-lasting life. They are also key in the recipe on how to improve your heart health. So many conditions and ailments can be traced back to a simple lack of physical movement, which is sadly far too prevalent among Americans in particular.

Among people living with AFib, the fact that athletes can develop this heart condition is particularly counterintuitive. Shouldn’t an avid triathlon be in tip-top shape? Shouldn’t a pro-football player or basketball star be protected from this electrical cancer? You would certainly think so. However, ongoing research has found a strong link between athleticism and risk of AFib. In fact, a 2019 study by Aagard and colleagues from the Journal of the American Heart Association found that former National Football League players are six times more likely than their non-NFL peers to develop AFib.

One hypothesis is that these individuals often have low resting heart rates, called bradycardia, and that the low heart rate may predispose them to arrhythmias. In relation to bradycardia, two mechanisms have been proposed.

The first is that the lower the heart rate, the greater the chance of premature atrial beats – the triggers for AFib – initiating a given episode. This is often why AFib occurs in a resting state when the heart rate is lower (in the evening, for example). In fact, if someone is experiencing premature beats, I recommend getting up and going for a walk or some form of aerobic exercise. The increase in heart rate can overdrive and suppress premature beats. The secondary benefit is the mental-emotional release due to endorphins, which helps calm the fight-or-flight response that can trigger AFib.

The second proposed mechanism is that athleticism is associated with a highly activated parasympathetic nervous system (PNS) represented by the vagus nerve. The PNS is one branch of the autonomic nervous system (ANS) that is responsible for all critical bodily functions. The ANS also includes the counterbalance to the PNS, the sympathetic nervous system. The SNS is a cornerstone of our flight-or-fight response and survival.

Steps athletes can consider

What additional steps can athletes consider to stay on the safe side?

My recommendations for athletes with AFib:

Taking a magnesium supplement
Reduce or entirely cut out alcohol, caffeine, and stimulants
Aerobic exercise on an ongoing basis
Avoid activities or extreme temperature liquids which trigger AFib
Reduce stress, including both work-related causes and physical stress, such as ignoring potential injuries and the body’s warning signs

I worked with one high-endurance athlete who has gone into atrial tachycardia – about 190 beats a minute – every time he hits a certain threshold heart rate during his long rides. I ultimately recommended that he lessen his cycling to remain below the triggered rate. It wasn’t news he wanted to hear, but it was necessary to ensure his ongoing health.

Another triathlete would go into AFib right after a race, especially after drinking a cold beverage such as Gatorade. This activates the vagus nerve via esophageal stimulation, which then can act as a trigger for AFib.

Staying active is an essential part of a long, balanced life. The heart and body like consistency and stability. Extreme athleticism can create a body out of balance.