Atrial Fibrillation in Endurance Athletes


Medical researchers agree that exercising into old age helps to prevent heart attacks, strokes and cancers and prolongs lives, but one report shows that sometimes competing in endurance sports may cause atrial fibrillation (Am J Case Rep, May 26, 2020;21:e924580). One 80-year-old non-smoking, non-drinking life-long competitive marathon runner, with a resting heart rate of 40 beats per minute, fell while running and died from a blood clot thrown from his heart to his brain, caused by an irregular heartbeat called atrial fibrillation.

How Endurance Sports May Increase Risk for Atrial Fibrillation in Older Athletes
Competing in endurance sports often requires exercising through pain and discomfort. Contracting skeletal muscles send large amounts of blood back to the heart, which stretches the heart muscle to cause it to beat faster and with greater force (Starling’s Law). When you are just exercising and feel some discomfort, you usually reduce the intensity of your workout to get back into your comfort zone. On the other hand, when you are competing in an endurance event, you try to push yourself through pain and discomfort, which can stretch the heart muscle fibers to near their limits.
• This stretching of the heart muscle can cause damage to the muscle filaments that increases stimulation of the vagus nerve that regulates heart rate, which can cause a slow heart rate (bradycardia) that can sometimes cause atrial fibrillation.
• Atrial fibrillation means that the atrium, the upper part of the heart, starts to flutter instead of contracting before the bottom part of the heart contracts. This allows blood to collect and stop moving in the upper part of the heart, which increases risk of forming clots in the upper part of the heart.
• Then a clot can travel from the upper heart to other parts of the body, particularly the brain to cause a stroke (Brit J of Sports Med, Oct 24, 2012;46(Suppl 1)). Atrial fibrillation effects 3-6 million North American adults, with increasing incidence with aging.

More than 20 years ago, doctors noted that a group of men over 80 who competed in cross country ski races longer than 100 kilometers (60 miles) were at increased risk for atrial fibrillation (BMJ, 1998 Jun 13; 316(7147): 1784–1785). Extensive studies have since confirmed this increased incidence of atrial fibrillation in older world-class endurance athletes (Scan J Med & Sci in Sports, Nov 21, 2013;24(4); 2014;24(4):e238–e244). The incidence of atrial fibrillation in younger athletes is very much lower than in the general population (JAMA Cardiol, 2018;3(12):1200-1205). Most of the older competitive endurance athletes with atrial fibrillation were healthy athletes and had no obvious problems with their hearts. The majority of abnormal heart rhythms reported after all-out endurance competitions return to normal afterwards (Eur Heart J, Apr 2012;33(8):998-1006). However, because of the risk for clots, doctors put virtually all patients with atrial fibrillation on medicines or treatments to prevent clots and strokes:
• drugs to slow heart rate
• drugs to thin blood and prevent clots
• electric pacemakers to control the maximum heart rate
Sometimes, they even use electrical waves to destroy heart nerves in an effort to change the irregular heartbeat.
We do not know if the healthy older athletes need these treatments, but rightfully so, doctors are afraid not to treat the athletes because of the possibility of strokes. Even though there is an increased frequency of atrial fibrillation in older endurance athletes (Scand J Med Sci Sports, 2014;24(4):e238–e244), moderate exercise is associated with reduced likelihood to suffer atrial fibrillation (Circulation, 2008;118(8):800–807). We do know that regular exercisers with atrial fibrillation are significantly less likely to suffer strokes than non-exercisers with atrial fibrillation (European Heart Journal, Apr 14, 2020;41(15):1467–1475.

Older Athletes Have Less Heart Damage Than Non-Exercisers
• Studies found little or no evidence of irregular heartbeats from damage to the right ventricular heart chamber in elite lifetime-endurance athletes (Circulation, May 17, 2016;133(20):1927-35).
• Thirty-three world-class endurance athletes, 30-60 years old, training for more than 15 hours per week, received extensive heart function tests that were compared to the same number of healthy men who did not have a regular exercise program. Of course, the athletes had larger and stronger heart right ventricles, but they had no evidence of damage or potentially harmful effects. Their hearts pumped more blood, beat at a much slower resting rate, and most importantly, had no evidence of atrial fibrillation.
• Olympic endurance athletes followed for up to 17 years had no evidence of any damage to the size, shape and function of their main pumping chambers (left ventricles) and suffered no evidence of heart damage or disease (J Am Coll Cardiol, 2010;55(15):1619-1625).
• A review of fourteen articles on the life spans and death rates of elite endurance athletes shows that they live longer than the general population, and suffer far less from heart disease (J of Sci and Med in Sport, July 2010;13(4):410–416).
• A review of 174 studies shows that gardening, household chores and more strenuous activities are associated with a lower risk of stroke, heart disease, breast cancer, colon cancer, or diabetes, that the largest risk reductions come with increasing intensity and duration of exercise (British Med J, August 9, 2016).

Reports of Heart Damage
Some studies suggest that lifelong intense exercise may damage the heart to cause irregular heartbeats (Mayo Clinic Proc, June, 2012;87(6):587–595). Male participants in a 54 mile (90 km) cross-country skiing program were followed for several years. The faster skiers and those who competed in multiple events were at increased risk for atrial fibrillation and they also had slower resting heart rates (European Heart Journal, June 11, 2013;34(47):3624 – 3631). However, they were not at increased risk for the types of irregular heartbeats in the lower heart chambers that are more likely to kill them: ventricular tachycardia and ventricular fibrillation. Many other studies show that regular exercise is associated with a reduced risk of atrial fibrillation (Heart, July 27, 2015).

Risk Factors for Atrial Fibrillation
Heart disease in master athletes is associated with the same risk factors for heart disease in the general population, such as high cholesterol, high blood pressure or high blood sugar (Sports Med Open, Aug 9, 2016;2:29). Damaged hearts and irregular heartbeats are associated with obesity; lack of exercise; eating red meat, sugared drinks, sugar-added foods and fried foods; not eating lots of fruits and vegetables; and smoking, drinking alcohol or taking recreational drugs. Obesity is a major risk factor for atrial fibrillation (J Am Coll Cardiol, Jul 7, 2015; JAMA, 2004 Nov 24;292(20):2471-7), but elite endurance athletes are virtually never obese. Athletes are also less likely to have high blood pressure (J Am Soc Hypertens, Mar 2015;9(3):191-6). Walking, bicycling or other regular exercise in older peoples associated with decreased risk for heart disease (Heart, May 14, 2014;100(13):1043-1049), and not exercising is a major risk factor for atrial fibrillation (Am J Cardiol, 2012 Aug 1;110(3):425-32).

Symptoms of Atrial Fibrillation
Common symptoms of atrial fibrillation can include fatigue, chest pain, shortness of breath, lightheadedness, dizziness, chest pain or discomfort and fainting, or there may be no symptoms at all. Athletes often have low resting heart rates that have not been associated specifically with heart damage, but apparently healthy non-exercising men with slow resting heart rates are at increased risk for atrial fibrillation (Circ Arrhythm Electrophysiol, Aug 2013;6(4):726-31).

My Recommendations
I believe that almost everyone should try to exercise every day. Older athletes can and should continue to compete into their later years, but they need to remember that preventing heart problems involves more than just exercising. Atrial fibrillation is associated with everything that causes inflammation, such as lack of exercise or obesity. You can help to prevent atrial fibrillation with an anti-inflammatory lifestyle:
• Eat lots of fruits, vegetables, nuts and beans
• Avoid red & processed meats, sugared drinks, sugar-added foods, and fried foods
• Lose excess weight if overweight
• Keep hydroxy Vitamin D levels above 30 ng/ml (Current Atherosclerosis Reports, Jan 23, 2017)
• Avoid overtraining

Caution: The existing evidence is that intense exercise is good for you, provided that you do not have any underlying disease. Many different factors can damage your heart. While vigorous exercise helps to prevent heart disease and heart damage, it does not guarantee protection against irregular heartbeats. If you have chest pain or any questions about your health, check with your doctor.

Checked 8/22/23