Clinical Context
Regular exercise can increase life expectancy by an average of 7 years compared with a sedentary lifestyle, according to an editorial by Sharma and Zaidi, which accompanies the current study. Even modest doses of exercise can reduce the risk for mortality.
Endurance athletes may perform physical activity at levels 5 to 10 times greater than the exercise recommendations for preventing coronary atherosclerosis. Previous research suggests that athletes maintain indices of systolic and diastolic function associated with healthy cardiac function, although up to half of marathon runners can demonstrate elevated levels of serum cardiac troponin (cTnI).
This finding, along with a higher risk for atrial fibrillation among endurance athletes, has led to questions regarding whether endurance training among athletes is truly heart healthy. The current study by La Gerche and colleagues examines cardiac function among endurance athletes to address this issue.
Study Synopsis and Perspective
Endurance athletes may perform physical activity at levels 5 to 10 times greater than the exercise recommendations for preventing coronary atherosclerosis. Previous research suggests that athletes maintain indices of systolic and diastolic function associated with healthy cardiac function, although up to half of marathon runners can demonstrate elevated levels of serum cardiac troponin (cTnI).
This finding, along with a higher risk for atrial fibrillation among endurance athletes, has led to questions regarding whether endurance training among athletes is truly heart healthy. The current study by La Gerche and colleagues examines cardiac function among endurance athletes to address this issue.
Study Synopsis and Perspective
Intense physical exercise appears to cause transient dysfunction of the right ventricle, and while the short-term recovery is complete, researchers say the ventricle, often neglected in cardiac research in favor of the more-often-studied left ventricle, could be a weak point in endurance athletes [1].
"For athletes, they want their heart functioning as well as possible for as long as possible," lead investigator Dr André LaGerche (University Hospitals Leuven, Belgium) told heartwire . "The athletes we work with are very keen to know what the long-term implications of sport are on their heart. To put this in context, I don't think this study provides any answers yet, but it does raise some very important questions and focuses our attention on the right ventricle. We really do believe it's sort of the Achilles' heel in the athlete's heart."
The study, published online December 7, 2011 in the European Heart Journal, included 40 athletes who recently completed an endurance event that lasted anywhere between three and 11 hours, such as a marathon, triathlon, or alpine-skiing event. To heartwire , La Gerche said that biochemical abnormalities, such as troponin elevations, have long been documented in endurance athletes, but echocardiography often showed the heart was normal. In addition, most of the current research has been directed toward the effects of exercise on left ventricular function, with studies showing that there is some chronic left ventricular remodeling resulting from long-term endurance training, but it is not associated with adverse outcomes.
"In 2004, we were basically doing a similar thing," said La Gerche. "We wanted to see what the heart function was like, and we were looking at the left ventricle, and it all looked fairly normal. But then we noticed that in some people the right ventricle looked quite terrible. It was almost an incidental finding at the beginning, and then over the years we've built evidence showing that we think the right ventricle is the problem."
Measures of Right Ventricular Function in 40 Athletes
In this study, the researchers measured cTnI and B-type natriuretic peptide levels and assessed 3-D volume, ejection fraction, and systolic strain rate with echocardiography, as well as quantified myocardial fibrosis on cardiac magnetic resonance (CMR) imaging using delayed gadolinium enhancement, in the 40 athletes immediately and one week after their endurance event.
Relative to their baseline measurements, right ventricular volumes increased and all other measures of right ventricular function decreased following the endurance event. In contrast, left ventricular volumes were reduced and function was preserved from baseline.
B-type natriuretic peptide and cTnI both increased following the endurance event and were correlated with the reduction in the right ventricular ejection fraction, but not with the left ventricular ejection fraction. Right ventricular ejection fractions were reduced in athletes who were involved in longer endurance events and in individuals with highest measurements of VO2 max. All right ventricular function measurements returned to normal after one week.
On CMR imaging, five athletes had evidence of delayed gadolinium enhancement, and this was confined to the intraventricular septum, "in the vicinity of the right ventricular attachment," according to the researchers.
To heartwire , La Gerche said that in strenuous physical exercise, such as in marathons or Ironman triathlons, pulmonary arterial pressure increases, more so than in systemic circulation, and with this increased strain the right ventricle is "bearing the brunt" of the workload. "If the right ventricle is having to work hard, and it has to do this for three, five, eight, or 10 hours, we would expect that this would create greater fatigue and have the potential for damage."
In an editorial accompanying the study [2], Drs Sanjay Sharma and Abbas Zaidi (St George's University, London, UK) note that there are more than 500 marathon races in the US and Europe each year, and this figure is only increasing. The past 30 years have been somewhat paradoxical in the sense that obesity and morbidity caused by lack of exercise is on the rise, yet the number of individuals participating in ultra–long-distance events has increased. Regarding the current study, Sharma and Zaidi say that more detailed studies are needed, including longitudinal studies, to determine the long-term effects of endurance activities in some athletes.
Unsure of the Implications Right Now
Right now, La Gerche and colleagues are unsure of the implications of the right ventricle enlargement, although there are some causes of concern. Animal studies have shown that strenuous physical exercise caused right ventricular changes, and these were associated with serious arrhythmias. In humans, there are no prospective studies evaluating the effects of right ventricular changes, but one study, led by Dr Hein Heidbüchel (University Hospitals Leuven, Belgium), also an author of this paper, found complex right ventricular arrhythmias in cyclists, said La Gerche.
"There is a bunch of circumstantial evidence all pointing to the right ventricle," he said.
"For athletes, they want their heart functioning as well as possible for as long as possible," lead investigator Dr André LaGerche (University Hospitals Leuven, Belgium) told heartwire . "The athletes we work with are very keen to know what the long-term implications of sport are on their heart. To put this in context, I don't think this study provides any answers yet, but it does raise some very important questions and focuses our attention on the right ventricle. We really do believe it's sort of the Achilles' heel in the athlete's heart."
The study, published online December 7, 2011 in the European Heart Journal, included 40 athletes who recently completed an endurance event that lasted anywhere between three and 11 hours, such as a marathon, triathlon, or alpine-skiing event. To heartwire , La Gerche said that biochemical abnormalities, such as troponin elevations, have long been documented in endurance athletes, but echocardiography often showed the heart was normal. In addition, most of the current research has been directed toward the effects of exercise on left ventricular function, with studies showing that there is some chronic left ventricular remodeling resulting from long-term endurance training, but it is not associated with adverse outcomes.
"In 2004, we were basically doing a similar thing," said La Gerche. "We wanted to see what the heart function was like, and we were looking at the left ventricle, and it all looked fairly normal. But then we noticed that in some people the right ventricle looked quite terrible. It was almost an incidental finding at the beginning, and then over the years we've built evidence showing that we think the right ventricle is the problem."
Measures of Right Ventricular Function in 40 Athletes
In this study, the researchers measured cTnI and B-type natriuretic peptide levels and assessed 3-D volume, ejection fraction, and systolic strain rate with echocardiography, as well as quantified myocardial fibrosis on cardiac magnetic resonance (CMR) imaging using delayed gadolinium enhancement, in the 40 athletes immediately and one week after their endurance event.
Relative to their baseline measurements, right ventricular volumes increased and all other measures of right ventricular function decreased following the endurance event. In contrast, left ventricular volumes were reduced and function was preserved from baseline.
B-type natriuretic peptide and cTnI both increased following the endurance event and were correlated with the reduction in the right ventricular ejection fraction, but not with the left ventricular ejection fraction. Right ventricular ejection fractions were reduced in athletes who were involved in longer endurance events and in individuals with highest measurements of VO2 max. All right ventricular function measurements returned to normal after one week.
On CMR imaging, five athletes had evidence of delayed gadolinium enhancement, and this was confined to the intraventricular septum, "in the vicinity of the right ventricular attachment," according to the researchers.
To heartwire , La Gerche said that in strenuous physical exercise, such as in marathons or Ironman triathlons, pulmonary arterial pressure increases, more so than in systemic circulation, and with this increased strain the right ventricle is "bearing the brunt" of the workload. "If the right ventricle is having to work hard, and it has to do this for three, five, eight, or 10 hours, we would expect that this would create greater fatigue and have the potential for damage."
In an editorial accompanying the study [2], Drs Sanjay Sharma and Abbas Zaidi (St George's University, London, UK) note that there are more than 500 marathon races in the US and Europe each year, and this figure is only increasing. The past 30 years have been somewhat paradoxical in the sense that obesity and morbidity caused by lack of exercise is on the rise, yet the number of individuals participating in ultra–long-distance events has increased. Regarding the current study, Sharma and Zaidi say that more detailed studies are needed, including longitudinal studies, to determine the long-term effects of endurance activities in some athletes.
Unsure of the Implications Right Now
Right now, La Gerche and colleagues are unsure of the implications of the right ventricle enlargement, although there are some causes of concern. Animal studies have shown that strenuous physical exercise caused right ventricular changes, and these were associated with serious arrhythmias. In humans, there are no prospective studies evaluating the effects of right ventricular changes, but one study, led by Dr Hein Heidbüchel (University Hospitals Leuven, Belgium), also an author of this paper, found complex right ventricular arrhythmias in cyclists, said La Gerche.
"There is a bunch of circumstantial evidence all pointing to the right ventricle," he said.
References
- La Gerche A, Burns AT, Mooney DJ, et al. Exercise-induced right ventricular dysfunction and structural remodelling in endurance athletes. Eur Heart J 2011; DOI:10.1093/eurheartj/ehr397. Available at:http://eurheartj.oxfordjournals.org.
- Sharma S, Zaidi A. Exercise-induced arrhythmogenic right ventricular cardiomyopathy: Fact or fallacy? Eur Heart J2011; DOI:10.1093/eurheartj/ehr436. Available at: http://eurheartj.oxfordjournals.org.
Study Highlights
- 40 well-trained endurance athletes participated in the trial. All were free of cardiac symptoms and had no structural or electrophysiologic abnormalities during stress echocardiography.
- Researchers examined athletes 2 to 3 weeks before an endurance race, immediately after the race, and 6 to 11 days after the race. Participants received CMR, biochemistry studies, and echocardiography.
- The main study outcomes were changes in cardiac performance and testing profiles before and after the endurance race.
- The mean age of participants was 37 years, and 90% were men. The average amount of training was more than 16 hours per week.
- Systolic right ventricular function was reduced after the race compared with baseline, with a 9% average reduction in ejection fraction.
- However, measurements of left ventricular function were generally unchanged, although left ventricular eccentricity increased after the race. Post-race left ventricular diastolic filling was impaired.
- Whereas serum cTnI levels were detectable in 9 athletes at baseline, all participants had detectable troponin levels after racing. There remained a slight increase in troponin levels from baseline at 6 to 11 days after the race.
- Greater reductions in right ventricular function correlated with higher post-race increases in troponin and brain natriuretic peptide levels.
- Longer events and higher exercise capacity, but not age or weekly training volume, were associated with greater reductions in right ventricular ejection fraction.
- There was evidence of increased cardiac fibrosis in 12.8% of participants. This fibrosis was limited to the interventricular septum. Participants with cardiac fibrosis had been competing longer in endurance sports compared with other participants.
- Regular exercise, even at modest doses, can improve life expectancy, but research among endurance athletes had demonstrated a higher risk for atrial fibrillation as well as an increase in serum cTnI concentrations after exercise.
- In the current study of endurance athletes by La Gerche and colleagues, the right ventricle ejection fraction declined after a race, whereas the left ventricular ejection fraction did not.
Obtained from Medscape...
http://www.medscape.org/viewarticle/756248 
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