A study from Norway shows that 13 of 78 (16 percent) older competitive cross country skiers have atrial fibrillation, a condition in which the upper chambers of the heart flutter and collect blood (European Journal of Cardiovascular Prevention & Rehabilitation, February 2010). Blood that is not moving collects in the upper chambers of the heart where it can form clots that travel to the brain to block the flow of blood to cause a stroke. Almost all people who suffer from atrial fibrillation at any age are treated with drugs to prevent clotting, since they are at increased risk for strokes and heart attacks. However, the older endurance athletes are different from other people with atrial fibrillation.
• The incidence of atrial fibrillation in these great older endurance athletes is the same as for non-athletic Norwegian men over 75. However, the skiers developed their atrial fibrillation at the average age of 58, which is much younger than its occurrence in the general population.
• People who suffer from atrial fibrillation usually have a history of something damaging their hearts, such as high blood pressure, high cholesterol, heart disease, heavy drinking or chronic inflammation, but ten of the 13 skiers with atrial fibrillation had none of these risk factors. The older endurance athletes have the highest rate of fibrillation without any known cause in the entire world's literature.
• The vast majority of endurance athletes live significantly longer than average citizens.
Nobody has adequate data to show why athletes are at increased risk for atrial fibrillation or whether they are at increased risk for forming clots. My explanation is that life-long endurance athletes have large healthy hearts that contain much more heart muscle than nerves. This can interfere with the normal sequence of an electrical impulse starting each heart beat from a spot in the upper heart that causes the upper heart to contract. This electrical messages then travels along nerves down to the lower heart to cause it to beat. The large athletic healthy heart has such large muscles that they outgrow the nerves that carry each heart beat so that not all upper heart electrical impulses pass to the lower heart. Future studies will show whether this is harmful or a harmless condition in athletes.
Since doctors have no data to show that older endurance athletes with atrial fibrillation are not at increased risk for strokes, they usually put them on drugs to prevent clotting. The symptoms of atrial fibrillation include• a sensation of a rapid or irregular heartbeat • a fluttering feeling in the chest • sudden anxiety that the heart is beating irregularly • sudden dizziness or faintness • sudden shortness of breath • sudden chest pain • sudden loss of strength going up stairs or getting up from a chair • sudden fatigue anytime