Exercise & the heart

In the News: Atrial Fibrillation in Cross Country Skiers

February 17, 2010 By Larry Creswell, MD 2 Comments

We have talked previously here at the blog about arrhythmias….and specifically about atrial arrhthmias–those that arise in the upper chambers of the heart.

In an interesting study summarized in an article last week at ScienceDaily.com, Norwegian investigators reported on a longitudinal study of cross country skiers, focusing on the development of atrial fibrillation. Starting in 1976, a group of 122 athletes have been followed, with monitoring for the development of arrhythmias. The study is remarkable because of the length (30+ years) of follow-up.

It turns out that, among participants who were alive for the entire period, the prevalence of “lone atrial fibrillation” (that is, without other heart disease) was 12.8%. And this compares to a prevalence of ~0.5% in the general population. Among the athletes with atrial fibrillation, there was also a higher frequency of enlargement of the left atrium and bradycardia (a heart rate
Other studies have also shown an increased prevalence of atrial fibrillation among endurance athletes. It’s not entirely clear yet what the long-term implications might be. And it may well be the case that no specific treatment is needed for athletes who have “lone atrial fibrillation.”

I imagine that more information from this study (and commentary, as well) will become available, and I will share anything else I learn.

In the News: Hidden Benefits of Exercise

January 8, 2010 By Larry Creswell, MD Leave a Comment

A while back, I wrote about the athlete’s cardiac paradox. I pointed out that there were many benefits of regular exercise, but that the exercise itself puts some athletes at increased risk for sudden death.

I came across an article in the Wall Street Journal earlier this week entitled “The Hidden Benefits of Exercise.” I enjoyed reading the article because it pointed out some health benefits of exercise that I hadn’t thought much about.

I thought you’d enjoy reading the article, too.

In the News: Why Do Athletes Live Longer?

December 8, 2009 By Larry Creswell, MD 2 Comments

I came across an interesting article in the November 30th edition of U.S. News & World report online and thought I’d share it with you here. It’s interesting reading.

There is an abundance of data that indicate beneficial effects of exercise….and one of those benefits may be a longer life-expectancy. But why?

Last week, in the online version of Circulation, an American Heart Association medical journal, a group of investigators in Hamburg, Germany report some novel findings in young and middle-aged track and field athletes in an article, entitled “Physical exercise prevents cellular senescence in circulating leukocytes and in the vessel wall.”

It turns out that endurance athletes have longer telomeres–the DNA at the tips of the chromosomes that protect cells–in their white blood cells compared to non-athletes. The authors speculate that this feature provides, over a lifetime, an anti-aging effect.

It’s also interesting to note that three American scientists shared the Nobel Prize in Medicine this year for their work, over many years, to understand the telomeres and the process of cell death and aging. You can read about this in a report at cnn.com from earlier this week.

Scientists are only beginning to understand the process of aging in humans, but it is nice to know that endurance athlete’s may have a leg up!

Do You Have "Athlete’s Heart"?

December 6, 2009 By Larry Creswell, MD 298 Comments

Do you have “athlete’s heart”?

If you’re a well-trained endurance athlete, you probably do. And don’t even know it. But that’s okay, because “athlete’s heart” is generally a good thing. Here’s why….

We’ve known for more than a century that there are a variety of cardiac changes that are associated with exercise. As long ago as 1899, S. E. Henshen at the University of Uppsala Sweden published a report entitled, “A Study in Sports Medicine; Skiing and Competitive Skiing,” recognizing that skiers developed enlarged hearts that were a response to exercise. And we’ve learned a lot more during the past 100 years about the heart’s adaptation to exercise.

Today, we use the terms, “athlete’s heart” or “athlete’s heart syndrome” to refer to the entire collection of the heart’s physiological adaptations to exercise. Those adaptations come in 2 main forms: structural changes and electrical changes.

Structural changes

Over time, the well-trained athlete’s heart adapts in order to provide a high cardiac output (volume of blood pumped per unit of time) in the most efficient manner. Because of mechanical advantage (after all, the heart is only a pump), the heart adapts by increasing the volume of its chambers, decreasing its heart rate, and increasing the thickness of the heart’s muscular walls–particularly the ventricles (the pumping chambers).

Changes in the structure of the heart will not be the same for every athlete. These changes will be most pronounced for athletes who engage in the aerobic sports (running, swimming, cycling, rowing, etc.).

The thickness of the left ventricular wall is usually less than 1.3 cm in thickness, with many individuals having a thickness of 1.0 cm or so. Well-trained athletes may have a left ventricular wall thickness of up to 1.5 cm, again an adaptation that helps with the generation of additional cardiac output during exercise.

Electrical changes

Athletes can have a variety of electrical changes that show up on an ECG. The most common finding is a slow heart rate (that we call “bradycardia” when the heart rate is less than 60 beats per minute). You’ll know that you and your athletic friends may have a resting heart rate that is much less than even 60 beats per minute. Yet the medical profession arbitrarily calls 60 to 100 beats per minute “normal”….for most individuals. For the well-trained athlete, though, a heart rate less than 60 beats per minute is typical and simply reflects the efficiency that the heart has developed over time due to exercise.

There are many other findings that can be present on the athlete’s ECG, including sinus arrhythmia, wandering atrial pacemaker, first- and second-degree heart block, junctional rhythm, and various types of repolarization abnormalities. These terms will only be meaningful to a medical professional, but suffice it to say that, when we add up the frequencies of all of these findings, an athlete’s ECG is very often “abnormal.”

Physical examination

In addition to the structural and electrical changes, there can be changes in the physical examination, as well. Athletes are more likely than non-athletes to have murmurs or other heart sounds (heard by stethoscope) that are simply a manifestation of the structural and electrical changes mentioned above.

Why is this important?

I’ve said that all of these changes, or adpations, are a good thing. And they are! But here’s the problem….

Imagine this scenario. And it’s pretty typical. A 42-year-old man, an avid triathlete, crashes while cycling, fractures his clavicle, and requires operation for repair of the clavicle fracture. He gets an ECG before the operation to screen for any unrecognized heart problems….and behold, he has an abnormal ECG. His physicians overlook the fact that the “abnormal” ECG may be very “normal” for an endurance athlete….and they order a variety of (possibly unneeded) additional heart tests to look for any specific heart disease. And, in the end, they don’t find anything wrong.

It’s important for you and your physicians to remember that you’re an athlete and that you may have features of the “athlete’s heart syndrome.” The next time you’re at the doctor’s office and he or she is listening to your heart with a stethoscope, you might ask the doctor if there was a murmur. Mention that you’ve learned something about athlete’s heart syndrome and ask if any murmur might be due to that. You’ll impress your doctor….and you’ll be helping your doctor remember that athlete’s are special.

This another area where you can be as knowledgable (or perhaps more knowledgable) than your doctor. Take charge.

In the News: Acute Effects of Marathoning on the Heart

December 2, 2009 By Larry Creswell, MD 2 Comments

At last month’s annual scientific meeting of the American Heart Association, investigators from the William Beaumont Hospital in Royal Oak, Michigan, reported on a small study of runners who participated in the 2008 Detroit Marathon.

The abstract for their presentation was published in the Abstract Book for the meeting and their findings are also summarized in this article from ScienceNews online.

There has long been the concern that there is acute (and possible long-lasting) heart damage in amateur runners who participate in marathon events. The study participants underwent blood tests, a cardiac MRI scan, and 24-hour Holter monitoring (tape recording of the ECG) 4 weeks before and then immediately after the marathon. The authors reported that, although there is release of a small amount cardiac enzymes into the bloodstream (indicating potential heart stress) during and immediately after a marathon, there is no evidence of damage per se to the heart. They also confirm the findings of many previous investigators that there is mild to moderate enlargement of the right atrium and right ventricle when they are measured immediately after the marathon. These changes are thought to resolve within 3 to 6 months after the event.

The detailed findings from this study probably won’t appear in medical journal for a year or more, but long-distance runners should take some comfort from this report.