Who Is an Athlete?
Joerg Herrmann, MD: I'm Dr Herrmann, associate professor of medicine and cardiologist at the Mayo Clinic. During today's Mayo Clinic Talks we will be discussing arrhythmias in high-performance athletes. I am joined by Dr Robert Rea, professor of medicine and an expert in arrhythmia disorders.
This topic has received attention over the past years and quite a bit of press this year. In October 2014, the proceedings of a special meeting on this subject were published in the Journal of the American College of Cardiology, titled "Protecting the Heart of the American Athlete." What is the scope of the problem? What defines an athlete, and what are athletes at risk for? Are there differences between competitive and noncompetitive athletes?
Robert F Rea, MD: What is an athlete? We all have our own ideas. We would all like to think that at some point we were athletes. For the purposes of the document that you have referenced, we define the American athlete as any individual who engages in routine, vigorous, physical exercise in the settings of competition, recreation, or occupation. That is quite broad. It has to be broad. Most of the focus on arrhythmias in athletes has been on the competitive athlete, but this is the definition that this think tank chose. It is casting a very wide net in terms of capturing who might be an athlete.
Their estimate is in adolescents. That is where a lot of the focus has been, because there are 35 million young people in the United States who participate in sports. Within that group, about 7.5 million participate in competitive sports at a high school level. These numbers may underestimate the total number, because there are people who are so-called "off the grid." They participate, but they are not organized. There is no way to tabulate their participation. It is a huge number of people. If we are talking about screening athletes for potential cardiac conditions, we are talking about a huge amount of resources being expended, and that has been one of the focuses of the research. Is the cost/benefit analysis in favor or not in favor of various types of screening?
Arrhythmias and Athletes
Dr Herrmann: The greatest concern is related to sudden cardiac death in this population. What is the contribution of arrhythmias to this risk? Which arrhythmias are most commonly seen in these athletes? Which ones should worry us, and when do they occur—during exercise or anytime?
Dr Rea: Sudden death in an athlete is a tragic event. I have participated in resuscitation of a runner during a marathon, and this person defied the common wisdom. The common wisdom is that in an athlete under age 35 who has sudden death, it is most likely hypertrophic cardiomyopathy; and over age 35, it's coronary artery disease. That is a crude division. This person was ahead of me in the race. He was 32 years old, had a cardiac arrest, and, unfortunately, was not resuscitated; he had advanced coronary artery disease on autopsy.
This is a blunt instrument. The common conditions that we are concerned about are hypertrophic cardiomyopathy, the first manifestation of which can be sudden death; and heritable channelopathies in the young. In older athletes, we are concerned about coronary artery disease or other acquired conditions.
The most common arrhythmia seen in athletes is not one that gives rise to sudden death; it's atrial fibrillation. A very large study came out of Sweden, involving tens of thousands of people who participated in a grueling cross-country ski race called the Vasaloppet, and because of the healthcare system in Sweden, they had longitudinal follow-up over many years. They divided the participants into tertiles according to their finishing place in the race. If you were in the top tertile, it means that you were within a certain percentage of the winning time; the middle would be slower, and third tertile would be for normal human beings like you and me.
They found that over time atrial fibrillation was substantially more common in the first tertile. Why is that? There are many theories, but at least part of it is because the heavily aerobically trained athlete—and cross-country skiers are among the most aerobically fit athletes in the world—have cardiac dilation, hypervagotonia, which is a consequence of training, and we know that vagal predominance can predispose to atrial fibrillation. But atrial fibrillation rarely gives rise to sudden death. The only situation in which it does is if the patient has Wolff-Parkinson-White syndrome, which is evident on an ECG.
Atrial fibrillation is the most common arrhythmia that we see. The second most common is supraventricular tachycardia, which is not life-threatening. The reason we see it is that the adrenergic discharge associated with exercise can provoke or stimulate the arrhythmia because you have to have the circuitry built in, but the adrenergic discharge can facilitate it.
We see patients who have sudden death with exertion. We see those who are resuscitated, and we search for the common causes. The common causes are hypertrophic cardiomyopathy and coronary artery disease.
The interesting thing about hypertrophic cardiomyopathy—although we are very concerned about arrhythmias during exercise, most cardiac arrests in patients with hypertrophic cardiomyopathy do not occur with exertion. Exercise is voluntary. It's avoidable as a risk factor if it is deemed necessary to avoid it. We can't avoid daily living, so if you have a condition that predisposes you to sudden death, you have to go about your life, but you may be able to avoid certain conditions that put you at risk. That is one of the focuses on prevention in this situation.
Dr Herrmann: The time period of risk seems to be a very important aspect in multiple dimensions. It relates to what you just mentioned, also the question of screening. Should we screen during exercise conditions to tease this out, or at rest, or even over longer periods of times? Which tools should we use?
Dr Rea: The period of risk seems to be mostly in adolescence and young adulthood, at least in terms of competitive athletes. Most college athletes and most professional athletes undergo some screening. Young sports participants often don't.
As we get to the higher levels of competition, the group of subjects at risk narrows, because only a few will go on to become college or professional athletes, so it's more justifiable to screen a smaller group. If you are a professional athlete, you are a commodity, and the team wants to protect its commodity and be darned sure that the person it is investing in is well.
The All-Important Screening Question
Dr Rea: Screening has focused on the younger athlete and is done almost exclusively at rest. The question is, what screening is appropriate? There is a great deal of controversy about this and I would refer the interested reader to an article in the New England Journal of Medicine titled "Cardiac Screening Before Sports," with four well-known experts who don't agree, reflecting the controversy in this area.
The recommended screening is different from professional society to professional society. For instance, the American Heart Association, American College of Cardiology, and Heart Rhythm Society in the United States have one set of recommendations. The European Society of Cardiology has another set of recommendations. Those are all referenced in this article. At a minimum, if there is going to be screening, it should be a history and physical examination. That is not going to pick up everybody, but it will pick up some.
The controversy is when you move on to such diagnostic tests as electrocardiography and, in some situations, echocardiography. In Italy, there is a physician, Dr Corrado, who is quite well published in this realm.[6,7] They do routine electrocardiographic screening. In fact, that is the recommendation in Europe.
The problem, as expressed by the other participants in the to-and-fro in the New England Journal of Medicine article, is that there are false positives and false negatives. The false positives are more problematic in the heavily trained athletes. Very aerobically trained athletes can have what would otherwise be deemed very abnormal electrocardiograms that are simply a result of training. The person who is doing the screening needs to be familiar with the vagaries of electrocardiography in this group.
The second group is the resistance-trained athletes—football players, weightlifters—who essentially develop hypertrophy as a result of exercising against a very high afterload. You see some electrocardiographic changes suggestive of hypertrophy. These can be expected in this group of patients and may not place them at risk for arrhythmias.
The other problem with using diagnostic tests for screening is that it may lead to a recommendation to not participate in sports, which can have tremendous psychosocial implications for the young person who is committed to athletics, sports, and fitness.
The final thing to realize is that in the more advanced athletes (college and above), their emphasis is performance. They want to perform well. In the more casual athlete (the younger athlete) it may be more about fitness. Heavily committed athletes are willing to subject themselves to risk for the sake of performance. That is their choice. Sometimes they will do crazy things for performance. Witness Lance Armstrong and the rest of the people in the Tour de France and the sport of professional cycling.
When the nonprofessional athlete or the least committed athlete encounters symptoms or evidence that he or she should not participate, the reasonable person will back off. There is a difference in the psychic makeup of the professional and highly committed athlete vs the casual athlete. We have all pushed ourselves too far and injured ourselves, and I'm a victim of that, but at least all I have had are muscle strains and joint pulls. I have not collapsed on the road.
When the Athlete Becomes a Patient
Dr Herrmann: For the practitioner who is seeing these individuals in daily practice and considering the 12-lead ECG, there are published criteria to follow, but do you think the 12-lead ECG is enough? When should they take it to the next level and do an exercise stress ECG, or possibly a Holter-event monitor? There is always the question about premature ventricular contractions [PVCs], too, should they be encountered. When should even an electrophysiology study considered?
Dr Rea: The controversy is whether you should even go as far as a 12- lead ECG. If the patient's history suggests an arrhythmia, with sustained or paroxysmal palpitations, the most common cause would be a supraventricular tachycardia. In that case, you should treat this person not so much as an athlete at risk but as a patient who has symptoms.
After you do a screening, if you pick something up in the history or exam, then in my mind, you stop looking at this person as somebody who should or shouldn't participate in sports but as a patient who needs care. From that point forward, it's a patient who needs care. The patient is going to ask, "Can I continue to participate?" When you have cemented a diagnosis or excluded a diagnosis, you can make the recommendation.
Whatever test you do down the pike depends on the patient's symptoms. If the patient transitions from a person who didn't want to see you for a screening test to someone who needs some care, then we are in a different arena.
Dr Herrmann: The same applies for imaging techniques, as well. In the Italian studies, they thought that the prevalence of arrhythmogenic right ventricular dysplasia being a little bit higher in that part of the world was a reason that they have higher event rates and screening success.
I take it you would advise the same thing to the practitioner; about pursuing echocardiography in these individuals?
Dr Rea: The problem with echocardiography, which is even fuzzier than electrocardiography, is that it depends on the quality of the echocardiogram, the interpretation, and the implications of a false-positive or a false-negative test. It's a diagnostic test. This is a great example of Bayesian analysis. The pretest probability of a problem is small. If you have a test with a high false-positive rate, you are going to run into problems.
Saving the Spectators
Dr Herrmann: Finally, there is the very tricky aspect of counseling on sports activities and what can be done from a prevention standpoint. One aspect that we haven't talked about is greater availability of automated external defibrillators (AEDs) at sporting venues, for the spectators, too. Sometimes they experience events. And what about implantable cardioverter-defibrillators (ICDs) and antiarrhythmic therapy for athletes?
Dr Rea: AEDs should be available, no question about it. They are cheap and effective. If you have 100 athletes on the field and 50,000 spectators, it is more likely that a spectator is going to have a problem. Athletes are trained. They are fed well. The people in the stands are often sedentary. They are out there eating burgers and hot dogs and are more at risk. Be that as it may, it is a reasonable, cheap public-health intervention.
Which athlete requires an ICD? Someone who is clearly at high risk, someone who has had an event, someone with a very adverse family history, or someone with a high-risk channelopathy.
Can athletes with ICDs participate? Yes, they can. Mike Ackerman has been an advocate for this. Telling a person who is committed to athletics not to participate has huge psychosocial consequences, and we should do whatever we can to allow these people to participate safely and not arbitrarily restrict them.
Dr Herrmann: Thank you for these very important insights. And thanks to your listeners for tuning in to Mayo Clinic Talks at theheart.org on Medscape.
Cite this: The Athletic Heart: Who to Screen, Who to Bench - Medscape - Feb 17, 2015.