A study involving 281 elite athletes from Australia and Belgium has found that one in six has cardiac measures that would normally suggest reduced heart function. Genetic analysis further revealed that those athletes also had an enrichment of genes associated with heart muscle disease.

The results, reported by a research team in Australia and Belgium, indicate that a genetic predisposition may be “stressed” by exercise to cause significant heart changes. The international collaboration will continue to monitor the athletes over the long term to determine the consequences on their heart health.

The findings highlight the need for far closer monitoring of the heart health of elite athletes, suggests associate professor Andre la Gerche, PhD, who heads the HEART Laboratory that is jointly supported by St. Vincent’s Institute in Melbourne and the Victor Chang Cardiac Research Institute in Sydney. “We discovered that one in six athletes had reduced heart pumping action, as well as showing for the first time the role genetics plays in heart function in these athletes,” la Gerche further noted. “We want to keep our athletes healthy and prevent them from suffering a sudden cardiac arrest. The better we understand the athletes’ heart, the more we will be able to identify risks in advance of tragedy.”

La Gerche and colleagues reported on their findings in Circulation, in a paper titled, “Reduced Ejection Fraction in Elite Endurance Athletes—Clinical and Genetic Overlap with Dilated Cardiomyopathy.”

Athletes generally enjoy excellent health, the authors wrote, “… but a minority present with extreme changes in cardiac structure and function that invoke consideration of underlying cardiac pathology.” Cardiac adaptations resulting from habitual intense endurance exercise —often termed “the athlete’s heart”—include dilation of all the heart chambers, and a tendency to lower measures of systolic function.

Endurance athletes who exhibit abnormal ejection fraction (EF) present what the authors term “a clinically challenging overlap” between athlete’s heart and dilated cardiomyopathy (DCM). “Also, intense endurance exercise has been linked to an increased prevalence of fibrosis and both atrial and ventricular arrhythmias, some of which might predispose to sudden cardiac death,” the team continued.

“We have long known that elite athletes have very different hearts to the general population. Exercise promotes profound heart changes,” noted la Gerche. “The heart is large in all elite athletes but there is still considerable variation ranging from large to enormous. The long-term significance of the most extreme changes is not yet certain.”

For their newly reported study the team wanted to evaluate the prevalence, genetic associations, and consequences of reduced left and/or right ventricular EF in healthy young elite endurance athletes. The 281 athletes recruited from elite training programs underwent cardiac phenotyping and genetic analyses, and were followed over a mean of 4.4 years. Athletes with either reduced left ventricular EF (LVEF), or reduced right ventricular EF (RVEF), which was determined by MRI imaging, were compared with athletes that had a normal EF. Genetic testing was carried out to assess a validated polygenic risk score for left ventricular end-systolic volume (LVESVi-PRS), that has previously been associated with DCM.

The results found that one in six athletes (15.7%) had heart measures that fall in a range normally associated with heart disease—including an enlarged heart, irregular rapid heartbeat, and changes in the heart’s left ventricular chamber that is responsible for pumping blood full of oxygen out to the body. However, reduced heart function was only observed when the individuals were at rest. When exercising, the heart functioned at levels known as super normal, in effect their hearts were able to substantially increase the pumping action when needed to boost cardiac output. The results from genetic screening to assess genes associated with developing DCM found that those elite athletes with the highest genetic load were 11 times more likely to have a reduction in heart function measures.

Outlining the clinical significance of their findings, the authors stated, “The finding of reduced ejection fraction in the clinical evaluation of an elite athlete may be considered part of the athletic phenotypic spectrum rather than a marker of cardiac disease … Asymptomatic athletes with reduced ejection fraction should be allowed to continue competitive sport but continued follow-up. The risk of future DCM development in athletes with high LVESVi-PRS is currently unknown and prospective follow-up is warranted.”

First author professor Guido Claessen, MD, PhD, who is affiliated with the Jessa Hospital, University of Hasselt and KU Leuven in Belgium, said the findings primarily argue for close cardiological follow-up of elite athletes and that genetic screening in the future could become part of the preventive examinations that top athletes receive. “The significance of the most extreme changes on long term needs to be further investigated,” Claessen said. “It is crucial we continue to monitor these athletes over the long-term to determine the future health effects—which could prove positive or negative.” The researchers have now recruited over 400 elite endurance athletes, including winners of the world’s biggest cycling races, to take part in the Pro@Heart study.

Professor Diane Fatkin, MD, of the Victor Chang Cardiac Research Institute, who undertook the genetic analysis of the athletes alongside associate professor Eleni Giannoulatou, PhD, said the study was the first in the world to look at the role of genetics in susceptibility to DCM in athletes. “The phenomenon of the athletes’ heart has long been known, but we were the first team to investigate the role an athlete’s genetic makeup plays in their heart function and structure,” Fatkin said. “What we have found is that there are far more profound changes than thought and that a high number of these athletes do have altered heart function. It’s very important we don’t think of these athletes as having sick hearts because they can still function at a very high level. But we don’t know what the long-term effect will be and if this means these athletes will go on to develop cardiomyopathy.”

Co-author professor Hein Heidbuchel, MD, PhD, at the Antwerp University Hospital (UZA) suggests it’s now vital to continue to follow the same group of athletes over the next 25 years to see if they do indeed develop heart problems. “Regular exercise is associated with clear health benefits. But there may be a small group with a genetic predisposition that is good for developing an elite sports heart at a young age, but could be dangerous in the long term if they continued exercising at this very high level. The main objective of our research is to make sports practice safe for all participants. A better understanding of the interplay between genetic characteristics and intensive exercise is an important step towards this goal.”

In their paper, the team noted, “The finding of reduced ejection fraction in the clinical evaluation of an elite athlete may be considered part of the athletic phenotypic spectrum rather than a marker of cardiac disease,” and concluded, “Genetic and imaging markers may help identify endurance athletes in whom scrutiny about long-term clinical outcomes may be appropriate.”

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