Saturday, August 3, 2013

Endurance Exercise Leads to Arrhythmia

Endurance Exercise and Arrhythmia: It's Time to Believe

John M. Mandrola, MD
DisclosuresJun 24, 2013

The idea that long-term endurance exercise increases the risk for arrhythmia should no longer be considered counterintuitive. The list of published studies confirming this association is long, and this week, it got a little longer.
In a study published in the European Heart Journal,[1] researchers from Sweden report a cohort study of more than 52,000 cross-country skiers followed for decades. These were no ordinary weekend athletes; the analyzed group included finishers of the Vasaloppet,[2] a grueling 90-km (55-mile) cross-country ski race. Reliable sources tell me that cross-country skiing over that distance is the Nordic equivalent of an Ironman or double marathon. Yikes.
The null hypothesis of the study held that both the number of races completed (exercise dosage) and finishing time (exercise intensity) would be associated with arrhythmia. (I would have bet my new mountain bike on that one.)

The Results

The average age of athletes at study entry was 38 years, while the average age at first arrhythmia was 57 years. Of the 52,000 athletes studied, there were 919 inpatient visits for any arrhythmia during a mean follow-up of 9.7 years.
The most common diagnosis was atrial fibrillation (n = 681), followed by bradyarrhythmia (n = 119), including 34 athletes with complete atrioventricular (AV) block. Typical supraventricular tachycardia (SVT) occurred in 105 athletes, and premature ventricular contractions (PVCs)/ventricular tachycardia (VT) in 90. Only patients with symptoms were counted.
Athletes who completed the highest number of races had the highest risk for arrhythmia. Arrhythmia risk increased on a continuum by races completed, up to 30% higher for 5-time finishers. Exercise intensity mattered too: Those who had the fastest finishing times had the higher risk for arrhythmia.

Three Features of This Report Stand Out

The study group included mostly high-level endurance athletes. The aerobic capacity required to finish such an event selects a narrow group. For instance, nearly 80% of Vasaloppet finishers participate in intense training all year round. These are not moderate exercisers dabbling in weekend 5Ks or spin classes.
The second finding was the strong correlation with dosage of exercise. The more races completed, the higher the risk for arrhythmia. The increase in risk was linear, with a 10% increase per race completed. And do not be fooled by the seemingly low overall incidence of arrhythmia (1.97%). That's more than double the rate one would expect in an age-matched group.
The third, and perhaps most striking, finding was the association with finishing time. The fastest finishers had the highest risk for arrhythmia. The "strollers," or those who finished in more than double the fastest finishing time, had the lowest risk for arrhythmia.

Summary and Parting Shots

It's pretty simple: Extreme endurance exercise, done over the long term and with great intensity, increases the risk for arrhythmia. There's no refuting this strong association. These observations are both plausible and consistent with prior studies.
There should be no surprise when an endurance athlete shows up with atrial fibrillation (AF) or some other arrhythmia. We are not surprised when masters-aged athletes suffer from other inflammation-induced maladies, such as overuse injuries, heart attacks, infections, and even divorce; why are we surprised they get AF?
But context is important. Previous studies have shown Vasaloppet finishers enjoy lower overall mortality. They smoke less, carry less body fat, and report better eating habits. This bolsters the idea that the lifestyle of endurance racing confers good overall health to most participants. Exercise is good. That observation remains unchanged and unchallenged. In the United States, we would do better with an epidemic of over- rather than underexercise.

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It's also important to emphasize that association is not causation. We don't know whether excessive exercise alone caused the arrhythmia episodes. There are too many possible confounding variables to make a causation link.
And...just because intense and long-term endurance exercise increases the risk for arrhythmia does not mean athletes should avoid a sport they love. These studies don't tell us to recommend against endurance exercise. They simply inform both doctor and athlete of possible consequences. There are always trade-offs.
As physicians and teachers, knowledge of the association between chronic inflammation and disease might help us give better advice to our athletic patients. My guess -- and it is just a guess, I am no coach -- is that the same things that help an athlete avoid AF might also make them faster. Do you think getting adequate rest and recovery improves VO2max? Do you think being content with something less extreme than an Ironman or cross-country ski marathon might be antiarrhythmic? What's wrong with a fast 10K?
On a personal note, I admit to being drawn to these findings. It's normal to like science that validates one's beliefs; in this case, the dose/response relationship of exercise with arrhythmia only strengthens my theory that excess inflammation is the connector.

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michael young

michael young|  Other Healthcare Provider 15 prof 15
This is an interesting article. I too have observed this while acting as medical standby during endurance events. My question would be concerning whether these abnormal cardiac findings are temporary, permanent, or easily converted. I have seen few studies which followed the patients after the event.

Bernice Keutzer

Bernice Keutzer|  Nurse - Ob/Gyn & Women's Health 49 spec 12
I'm with cj on looking at dehydration as a factor.  I know that will set mine off.

Dr. sirpa autio

Dr. sirpa autio|  Family Medicine 38 spec 10
As a former ironman finisher I have had palpitations too in middle of my training sessions. Glad I am not training on that level anymore. What about High Intensity exercises plan that is now claimed by Anti Aging medicine to be the best form of fitness. This includes short burst of pretty high heart rates mixed with resting periods, and also includes strength training in forms of calisthetics/body weight etc. For example burbees, half burbees, push ups followed by fast runs and more push ups. Has anyone hear of studies on this type of exercise? I personally feel more fatigue in the end of these, and hence do not do them. 30 min jog is enough for me at the moment.

Paul Jacobs

Paul Jacobs|  Other Healthcare Provider 15 prof 15
Good report that may be relevant to not only extreme endurance training but to the average exerciser who does it excessively & frequently.

Dr. gene whitman

Dr. gene whitman|  Family Medicine 38 spec 10
Whwt hasn t been looked at is actual heart size. People s hearts are not the same size....smaller heart exposed to the same work load as a larger heart over time may often simply not hold up as well, ie slowly progressive tissue changes could easily cause conduction abnormalities.

c j

c j|  Psychologist 23 prof 23
What about dehydration during endurance exercise and/or the repeated excessively high heart rates that occur during such exertion as hypotheses regarding the etiology of afib in athletes?

Maryann Castro

Maryann Castro|  Nurse - Dermatology, General 35 spec 12
This topic has been perplexing to many and this article was most helpful in answering several questions .

Dr. Blake Prescott

Dr. Blake Prescott|  Geriatrics 80 spec 10
Certainly should not come as a surprise since provocative stress testing (quickly jumping to more demanding levels) as opposed to cautionary and training stress tests (gradual and less stressful protocols) are more successful in elucidating dysrrhythmias, especially when emphasizing and taking advantage of the "85 - 100%" of max range (a mother lode easily neglected especially when counting upon a contrast injected toward the end). The surprise is that so many superb athletes have this. I wonder how many have an impressive resting bradycardia. Bradycardia is the mother of tachycardia.

Dr. Eduardo Quinteros

Dr. Eduardo Quinteros|  Internal Medicine 43 spec 10
The big problem with this information , is that when it spread to the mass media, the patients will say us things Likes the participant  Me Hew write here . Also the recently study Published in the New England J wit diabetic patiens is discouraging . May be we have to send people only to walk? .This is important to myself .I have an strong family history of early CHD , I Have  Hypertension, Hipercholesterolemia , I take my pills, but also I'm a regular (3 times/w) 10 Km runner plus an hour a day walk .No to fast.  10 km in an hour , far from records , but ¿that`s put me at arrhytmia  risk ?  I question it myself and I have the obligation to give a right answer to my patients. I Invite again To Medscape to organize a worwilde database of  5-10 km runners  

Dr. Eduardo Quinteros

Dr. Eduardo Quinteros|  Internal Medicine 43 spec 10
Which is important first is understand that this people are atletes , but I think is imperative to know what happen with the few good patients (and doctors ) engaged in 5-10 KM  /hour runnings , 3 times a weeck , an  objetive that I ussually teach to reach to young or midle age patients. May be we have to colaborate around the world to aport data to a big database to know in 5-10 years what happen withmore common people.   

Dr. Y M Chan

Dr. Y M Chan|  Family Medicine 38 spec 10
Like everything else on earth, there is always a breaking point in everything that we do.   It is important to let  patients know that there is a definite threshold for everyone and it is wise not to exceed that threshold, whether in sports, work or wealth (just joking)

Dr. David Bolivar

Dr. David Bolivar|  Cardiology, General 32 spec 10
Realmente no debe sorprender estos hallazgos.Los caballos no se ejercitan tan fuerte ni sostenido en el tiempo.
Incluso los caballos de carrera  tienen descansos,y el entrenamiento para una competencia en mas suave y ocasional .
Cuando compiten con mucha frecuencia se deterioran y rinden menos. El hombre no es un caballo.
Ademas los excesos son dañinos en todo. Error muy frecuente en medicina donde parece gustar mucho aquello
de que si una cantidad es buena ,mas es mejor. Error injusficado pues son excepcionalmente raras las enfermedades
con una solo o unica etiologia(por ejemplo,las infecciones) y se  nos olvida el huesped (con su sistema inmunologico,
estado de animo, deficiencias nutritivas, etc).

David Triplett

David Triplett|  Health Business/Administration 13 prof 13
What would be interesting to study would be the correlation between resting heart rate in these athletes and the risk for arrythmia. I also would hypothesize that the athletes that developed arrythmia exercised more frequently at higher intensity levels in between competition with little or no recovery time. Do we know what HR exertion % of Maximum HR these folks maintained in training and in racing?

Yuri Blok

Yuri Blok|  Other Healthcare Provider 15 prof 15
This is not quite new but very useful information: also in non-athlete men and women not infrequently arises arrythmia against a
background of exessive loadings

Dr. Bonnie-Jo Grieve

Dr. Bonnie-Jo Grieve|  Pediatrics, General 60 spec 10
What about hypoxic damage to the cardiac conduction system during prolonged intense competition? That could be the underlying connecting factor.

Dr. B M

Dr. B M|  Cardiology, General 32 spec 10
Agreed, I have looked after several endurance hobby cyclists, doing stages of Tour de France etc, all with SVT, AFib etc, good to know my sneaking suspicion of association is possibly fact based!

Me Hew

Me Hew|  Other Healthcare Provider 15 prof 15
I was an endurance athlete and exercised intensely from a young age and well into my 20's. I was diagnosed with Paroxysmal Atrial Fibrillation at 26 after having "chest flutters" from the age of around 21.  I continued to exercise as my episodes were limited to about 1 or 2 a month. My Arrhythmia became so bad (episodes every day) that I had to discontinue exercising (or even living life properly) at around the age of 33. If I had been told that the cause of my AFib was due to my exercising, I would have laughed in my Cardiologists face. In retrospect, it is very apparent, to me, that the exercise was a major contributing factor to my Arrhythmia. It is also easy to say now that I wish that I had undertook a more sedentary lifestyle during those years of exercising. I had a PVI ablation 3 months ago and am still recovering but at this time, I am of the opinion that I am actually feeling worse now than before.  I look at a lot of my friends who drink, smoke,work hard and they are not only fitter than me but look ten years younger too. Exercise - ??? who needs it?

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