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.
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.
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.”
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.