Enlarged Heart A Consequence of Sports (But Thats Ok)

Yahoo News reports on a recent study by Dr. Francois Carre of the Centre Hospitalier Universitaire de Rennes, France, which found that almost all cyclists competing in the Tour de France had enlarged hearts. The size increase was on the order of 20-40% larger than normal! He thought it would interesting to see whether the cyclists' hearts are large to begin with or expand to accomodate the rigors of training (probably both). A bigger heart translates to more blood-pumping ability which in turn translated to increased oxygenation of blood and tissues.

In his study, Carre tracked seven former professional cyclists through their final year of competition and three years of retirement. Once a year, the cyclists took tests to check the size and function of the heart. They were also tested on their fitness levels. Carre found that the athletes' hearts shrank nearly a quarter in size after they finished riding professionally. Still, the cyclists remained in excellent physical condition.

"Some athletes have a genetic predisposition to perform better," Carre said. "But we found that in these cyclists, their hearts adapted to the hard training conditions by just getting bigger."

While this study is not yet published (it was presented at a meeting), a quick PubMed search on the author yielded another interesting paper he'd published on the topic, "Sports-Specific Features of Athlete's Heart and their Relation to Echocardiographic Parameters" published last year. Carre noted that the extent to which the heart's left venticle changed depended upon the sport the individual was involved in (graph below, by sport).

i-3a3e0abe7ac2f50f35b4340c6c8efa5c-heart thickness.bmp

In Carre's rating system, the lower ranks corresponded to larger cardiac dimension, so in this case swimmers showed both the largest ventricular diameter and septal thickness. In general, athletes participating in endurance sports were found to have increased diameter and thickness, and the levels of these changes were benefical and not at all harmful.

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To whom it may concern:

I am looking for nominal deminisions of the the heart chambers for a paper in a Cardiovascular Program. Can you help?


Jeff Renfro

By Jeff Renfro (not verified) on 12 Mar 2009 #permalink

I remember being fascinated when they said Lance Armstrong had a larger heart than "normal" people. Of course, now it seems as though he's not that unique among the cycling community.

Also, keep in mind that if you're left-handed then the right ventricle is enlarged, right? It's like the brain isn't it?



New reader linked by VodkaPundit.

Tiny quibble. Your illustration is a classic picture of dilated cardiomyopathy, evidenced by the thinning of the left ventricular wall as the ventricle became larger. So that ventricle is actually less effective than a normal or athletic heart.

An athlete's ventricular wall retains it's thickness or gets slightly thicker. I tried to find a better illustration, and like you, came up empty.

Yeah, it was really the best image I could get for gross, overall enlargement but you are essentially correct that the image on the right shows thinning.

Ignore it! :)

I had a teacher who went in for a check up, just a regular physical. After running some tests the doctors wanted to do a full blown check on his heart since they found something weird. The next thing really shocked the doctors. He had something like over 85% blockage in a major artery to his heart, but yet he had not had a heart attack or any major problems. What the doctors found was that my teacher's body built multiple veins to bypass the blockage and allow for regular blood flow to the heart.

My teacher told my class the only reason he is alive today is because he used to exercise a lot up until his fifties. And frankly, I believe him!

More reasons to ignore the illustration on the right:

The septal thickness is less in the "athletic heart", when it should retain the same thickness, or should be even slightly thicker in the case of sports that produce a high degree of vascular resistance.

The dimensions of the right ventricle have not changed in the "athletic heart" to accomidate the increased stroke volume produced in the dilated left ventricle. [stroke vol RV = SV LV]. The heart on the right should, indeed, be considered an example of compensated left ventricular myopathy [heart failure] with reduced ejection fraction subsequent to infarcts or other problems.

An addendum: I don't believe what the '76ers doctor says about EPO doping in the article. The red blood cells don't become thicker, they just become more numerous, which increases the viscosity of the blood. And it is probably NOT more dangerous for athletes to use EPO than non-athletes because high intensity training increases blood volume greater than it increases erythrocyte volume - making a trained athlete's blood actually thinner. But, it still can become thick enough to cause problems during the stresses of training, as several cyclists have died from cardiovascular problems and were known to be blood dopers.

By natural cynic (not verified) on 04 Sep 2007 #permalink

Just a question, though... How do you know that "that's ok"? Is there any research on whether this is a good or bad thing for the athletes in question?

That's a buildup of collateral circulation, which is typical of slowly-developing heart disease. I'm sure there's a family history there.

My buildup of placque was quicker, and even though I was exercising fairly regularly, diet and family history did me in. Fortunately the heart attack was recognized early (paramedic, heal thyself) and I got away with a stent and really minimal damage.

And now I don't need to eat breakfast - I eat a healthy handful of pills instead!

Hi Maria,
There has been quite a bit of research on the topic. Most studies concluded that the changes were a normal adaptation to rigorous exercise, but with all anatomical changes, they may rarely have a bad consequence. The paper below describes it along those lines.

Br J Sports Med. 1999 Aug;33(4):239-43. Links
Cardiac assessment of veteran endurance athletes: a 12 year follow up study.Hood S, Northcote RJ.
Department of Cardiology, Victoria Infirmary, Glasgow, Scotland.

OBJECTIVES: Sustained aerobic dynamic exercise is beneficial in preventing cardiovascular disease. The effect of lifelong endurance exercise on cardiac structure and function is less well documented, however. A 12 year follow up of 20 veteran athletes was performed, as longitudinal studies in such cohorts are rare. METHODS: Routine echocardiography was repeated as was resting, exercise, and 24 hour electrocardiography. RESULTS: Nineteen returned for screening. Mean (SD) age was 67 (6.2) years (range 56-83). Two individuals had had permanent pacemakers implanted (one for symptomatic atrial fibrillation with complete heart block, the other for asystole lasting up to 15 seconds). Only two athletes had asystolic pauses in excess of two seconds compared with seven athletes in 1985. Of these seven, five had no asystole on follow up. Two of these five had reduced their average running distance by about 15-20 miles a week. One athlete sustained an acute myocardial infarction during a competitive race in 1988. Three athletes had undergone coronary arteriography during the 12 years of follow up but none had obstructive coronary artery disease. Ten of 19 (53%) had echo evidence of left ventricular hypertrophy in 1997 but only two (11%) had left ventricular dilatation. Ten athletes had ventricular couplets on follow up compared with only two in 1985. CONCLUSIONS: Although the benefits of moderate regular exercise are undisputed, high intensity lifelong endurance exercise may be associated with altered cardiac structure and function. These adaptations to more extreme forms of exercise merit caution in the interpretation of standard cardiac investigations in the older athletic population. On rare occasions, these changes may be deleterious.

PMID: 10450477 [PubMed - indexed for MEDLINE]

The chart is incomplete. Where is "Endurance Loafing"?

By Tegumai Bopsul… (not verified) on 05 Sep 2007 #permalink

Marathon runners, triathletes and other fans of extreme sport need to take lessons in ancient history. Do they realize that Pheidippides, the Greek soldier who ran from Marathon to Athens in 490 B.C.E., died after delivering his message???

The cardiac hypertrophy that results from extreme endurance training can result in arrhythmias that are anything but benign. Eighteen of 46 endurance athletes followed in the linked study developed major arrhythmic events, including 9 cyclists with sudden death.

Usually cardiac problems occur in those with underlying heart defects who unmask their defects during aerobic exercise, but the jury is still out on those who take things to the extremes. They may be actually creating problems by taking things too far. More and more isn't always better and better.