Most atrial fibrillation patients are over 65 years old and have known risk factors, especially high blood pressure, obesity, and sleep apnea. Why do cyclists, runners, and other physically fit athletes sometimes face such risks? This is a topic that is not well understood. It may involve genetic factors and cardiac remodeling related to exercise and its impact on heart rhythm.
Elite rowers participating in the rowing project. Image Source: MARK NOLAN/GETTY IMAGES
According to Science magazine, Australian St. Vincent's Institute sports cardiologist Andre La Gerche is researching this paradox. His study, named Pro@Heart, shows the impact of endurance exercise on the heart.
Mina Chung, a cardiac electrophysiologist at the Cleveland Clinic in the United States, says these efforts are crucial because atrial fibrillation represents a "rapidly spreading epidemic," mainly driven by obesity and an aging population. She notes that over 5 million people are affected in the U.S. alone, with a projected doubling of global prevalence from 2010 to 2030.
In atrial fibrillation, the upper chambers of the heart, called the atria, beat irregularly and out of sync with the lower chambers. This condition can lead to fatigue, fainting, chest pain, and other symptoms, with long-term consequences posing even greater risks. For years, doctors have been urging sedentary atrial fibrillation patients and those at risk to get moving.
Adrian Elliott, a cardiac physiologist at the University of Adelaide in Australia, states that exercise is a beneficial force that can reduce heart stiffness, improve blood flow, promote electrical stability, all of which may help prevent and control atrial fibrillation.
However, research over the past 20 years suggests that engaging in years of high-intensity exercise may put the heart in an "unhappy" electrical state, increasing the risk of atrial fibrillation by five times compared to non-athletes of the same age. Elliott notes that most studies indicate endurance athletes may develop atrial fibrillation in later years, although in some cases, it may have already appeared during their athletic careers.
In 2016, La Gerche, along with partners from Australia and Belgium, launched Pro@Heart, with nearly 500 elite athletes aged 16 to 23 enrolled to date. The study aims to track elite athletes for at least 25 years and monitor changes in their hearts, including size and electrical conduction patterns. Another group of subjects includes 128 former elite rowers aged 45 to 80, as well as a group of non-competitive athletes.
In this study, cardiac MRI scans during exercise in young elite athletes revealed that some athletes' hearts were "so big that they were pushed against the chest wall and spine," La Gerche said. He is interested in whether the friction between the atria and the spine could trigger heart inflammation. Inflammation has long been considered a potential driver of atrial fibrillation, which can also be caused by conditions like diabetes and obesity.
The incidence of atrial fibrillation in retired rowers is staggering - 20%, compared to 3% in the control group. They may have a higher risk of atrial fibrillation than other endurance athletes. Perhaps this is because this sport attracts taller individuals, and height is a risk factor for atrial fibrillation. Another factor could be that rowers train 20 or 30 hours per week.
Jack Goodman, an exercise physiologist at the University of Toronto in Canada, says this work not only helps athletes affected by atrial fibrillation but also provides an opportunity to study atrial fibrillation without the confounding effects of other health issues.
