Potential for atrial arrhythmias from long-term endurance training
Fanselow was rushed to the local ER, hooked up to an electrocardiogram and soon diagnosed with AFL ...
Illustration by Kevin Howdeshell
Last March, accomplished trail runner Bill Fanselow, 43, of Golden, Colorado, stepped off a treadmill after a routine, two-hour tempo run in preparation for his first 50-mile trail race, slated for May. Minutes later he began to feel unusually fatigued, even after sitting downresting for a few minutes. Twenty minutes later, he felt his heart still racing. Checking his pulse, he counted a rate of approximately 140 beats per minute (bpm) and thought the listless rhythm felt strange.
"I thought I had major dehydration and/or electrolyte imbalance so I skipped the shower and drove home, chugging energy drink the whole way," says Fanselow. "At home I checked my pulse several times again, and it still hadn't dropped at all!"
With his wife driving and young son in tow, Fanselow was rushed to the local ER, hooked up to an electrocardiogram and soon diagnosed with atrial flutter (AFL), an atrial arrhythmia characterized by very fast, anomalous pacing of the atria, upwards of 350 atrial beats per minute. In other words, Fanselow's heart was under unnecessary stress because his normal pacemaker was being silenced by an irregular pacer. Luckily his ventricular rate of 140 bpm was much slower, a heart safety mechanism, than the quivering atria.
Three hours after his workout, Fanselow's atrial arrhythmia returned to normal without intervention, a common occurrence in younger, fit individuals. The main consequence of his ER visit was being prescribed a daily dose of baby aspirin to decrease the likelihood of throwing a clot and causing a stroke, should the AFL occur again.
What is atrial flutter?
The following week, Fanselow walked into the office of Dr. Sameer Oza, a cardiologist with a specialty in electrophysiology at Rocky Mountain Cardiology P.C. in Boulder, Colorado.
"Over the past five years in Boulder, I've seen atrial flutter about one time per month in athletes, who have engaged in hard endurance training for decades and now are 40-plus years old," says Dr. Oza. "Usually atrial flutter is seen in much older adults who have risk factors such as high blood pressure and preexisting heart abnormalities." Also, according to Dr. Oza, very rarely saw atrial flutter in fit 40-plus year olds when he practiced in Buffalo, New York, a less physically active region.
Dr. Oza is seeing more endurance athletes (mostly males) over 40 with athlete's heart or larger-than-normal chambers (e.g. atria), and it could be that this condition is predisposing some individuals, such as Fanselow, to early onset AFL.