by Steve S. Ryan
A 2009 study stated, “Vigorous exercise increases the risk of atrial fibrillation.” But a close examination of the observational study used to support this statement showed that A-Fib is associated only with men under 50 years of age who jogged/ran over four miles a day 5-7 times a week. This is a level of running usually associated with elite athletes.
Other types of vigorous exercise such as cycling, swimming or racquet sports were not associated with an increased risk of A-Fib.
Why elite runners develop A-Fib
The authors of this study hypothesized that several factors might explain the increased risk of A-Fib in elite male runners under 50 years old.
▪ left atrial enlargement
▪ left ventricular hypertrophy
▪ left ventricular dilation
▪ inflammatory changes in the atrium
▪ an increase in parasympathetic tone (the most commonly cited factor)
“Jogging in particular results in greater enhancement of the parasympathetic nervous system compared to other exercise types.” “Heightened parasympathetic tone has been associated with A-Fib onset in patients with structurally normal hearts; and in animal and human studies, parasympathetic stimulation frequently induces and maintains A-Fib.”
Vigorous Exercise good for most people
The authors of this study recognized the benefits of vigorous exercise for most people. “Exercise has multiple beneficial effects on cardiovascular health that may lower A-Fib risk.” In particular, exercise lowers blood pressure, improves lipid profile and glucose control, decreases risk of cardiovascular disease, has positive effects on traditional risk factors such as hypertension, diabetes, cholesterol and obesity, improves arterial elasticity which tends to deteriorate with age, and extends life expectancy.
(Physical inactivity and a sedentary life style is a far bigger health problem for most people than excessive physical activity.)
New Swedish study—intense exercise linked to A-Fib
A new study from Sweden is more critical of vigorous exercise and the risk of developing A-Fib. Men who exercised more than 5 hours/week when they were in their 30s had a 19% higher risk of developing A-Fib later in life than those who exercised less than one hour/week. “Vigorous long-time physical activity seems to increase the risk for atrial fibrillation…Leisure-time exercise at younger age is associated with an increased risk of A-Fib.” But this study was primarily concerned with older men aged 45-79 years (mean age=60).
It also found that high levels of leisure-time exercise at an older age did not increase the risk of developing A-Fib. The authors hypothesized that leisure-time exercise may be of lower intensity at an older age.
They also found that more leisurely activities such as brisk walking or cycling at age 60, even if over 60 minutes a day, were associated with a 13% decrease in A-Fib over those who got no exercise at all. An accompanying editorial suggested when it comes to exercising “maximum cardiovascular benefits are obtained if performed at moderate doses, while these positive aspects are lost with (very high) intensity and prolonged efforts.”
(This study didn’t address the interval exercise technique often used in sports training and in gym workouts of varying intensity exercising—pushing oneself to the max, resting, then alternating with less vigorous workouts.)
What about those of who love to compete at a very high fitness level?
Dr. T. Jared Bunch of the Intermountain Heart Institute in Utah sees a number of very highly skilled endurance athletes. They go from marathons to triathlons to 100-mike bike races. Even though they are amazingly fit, they tend to develop A-Fib. The A-Fib develops despite these athletes having normal blood pressure levels and heart function.
Studies have confirmed an increased incidence of A-Fib in healthy older world-class endurance athletes. But, other than A-Fib, they usually had no other medical or heart problems.
There are many potential reasons why. These extreme athletes often develop what is called an ‘athletic heart’. The heart chambers are slightly enlarged. These adaptive changes allow for a higher cardiac output during exercise. However, some of these changes may also promote abnormal heart rhythms by changing the underlying architecture of the atrial chambers.
It is possible that repetitive wear and tear from the intense daily workouts is a factor and results in small areas of fibrosis in the upper and lower heart chambers which promote A-Fib and other arrhythmias. With improved MRI cardiac imaging, these small areas of fibrosis can now be visualized. Also, changes in the autonomic nervous system may irritate tissues responsible for generating A-Fib.
Finally, the personalities that often allow excellence in endurance athletes may also promote heart disease by the way the body and mind responds to stress. In total, endurance athletes put significant stress on their heart.
Should Intense athletes stop running and training?
Should intense athletes stop running and training? No. The intense athlete lifestyle reduces other heart risk factors and improves quality of life, not to mention the personal satisfaction and sense of fulfillment that comes from competing at a high level or winning a race. In the above Swedish study, low activity level people (couch potatoes) had more disease-related deaths.
Dr. T. Jared Bunch gives the following recommendations, which intense athletes can use to help their heart health:
▪ In periods in which they are not training, interval training that allows the heart to recover during exercise, can be used to maintain aerobic function and muscle strength.
▪ Intense athletes who train early in the morning should make a conscious effort to get restorative sleep. For most of us this means about 8 hours of sleep.
▪ Intense athletes who have prolonged training schedules need to pay close attention to maintaining their electrolytes. Loss of sodium, potassium, magnesium, and calcium are sources of heart electrical irritability.
▪ All athletes need to get routine screening of their blood pressure, cholesterol, and fasting sugar. Most of the time these are normal. But in those with genetic risks, they can be abnormal. If treatment is started early, lower doses of therapy can be used that do not impact athletic performance as much as treating the disease later in life.
Intense athletes have to face the fact that they’re more at risk of developing A-Fib and conditions like small heart injuries and fibrosis and need to monitor their heart health more carefully.
‘Knowing your heart’ is the best tool in prevention. Understand your heart rate: your normal rate at rest, early in exercise, during peak exercise, and in recovery.
If you develop changes in this normal heart rate spectrum or start to feel palpitations, you may need to see an Electrophysiologist (EP) before A-Fib develops. Testing may include an MRI to look for heart function and fibrosis as well as an ultrasound of the heart (echocardiogram) and a heart monitor. Your EP should measure the diameter of your left atrium and monitor for enlargement over time.
That doesn’t mean you have to stop running, but you have to be smart about it. Did you give yourself enough time to recover after the last race? What did the EP tell you about your overall heart health? Are you taking time to rest, sleep, and decrease other stressors in life? Is your diet a healthy one, centered on whole foods?
The intense athlete might think: “But if I develop A-Fib, I can just have a catheter ablation (PVI), can’t I? I’ll be A-Fib free and can resume my training and racing.” Not necessarily. Even though your pulmonary veins have been isolated, it’s possible to develop A-Fib in other parts of your heart. The conditions (intense running and training) that pushed you into A-Fib are still there. We can’t say for sure that you will develop A-Fib again, but we also can’t say that you won’t.
As an intense athlete you may not want to hear this. But if you develop A-Fib, you may have to think seriously about changing your life style or training schedule. You will find that alternative exercises and programs yield positive benefits. Of these, Yoga and walking seem to have the strongest beneficial effect on A-Fib. For intense athletes, walking is part of life, but Yoga may not be. Yoga is a great way to shape up both mind and body and help with the body’s stress response.
After a successful ablation, the intense athlete, may decide to just live with the risk of developing A-Fib again. (There’s always a possible second ablation.)
If you reach a time in your life when you transition to lower daily intensity programs, your risk of developing A-Fib may start to come down.
Last updated: Monday, March 13, 2017