Some high-level athletes who take part in endurance sports can develop a rare but life-threatening condition called ventricular arrhythmia (VA) in which the heart beats at an abnormal rate and rhythm. Now, a new study has shown that most of the athletes with VA have dysfunctional right ventricles.
The finding adds weight to the hypothesis that endurance sports might contribute to changes in the heart that lead to dysfunction and heart rhythm disturbances, according to the authors of the report published in the European Heart Journal  today (Monday 22 January).
VA is a heart rhythm disturbance that occurs in the ventricles (lower chambers) of the heart. It can be the cause of sudden death in athletes. There are many underlying causes of VA and often it is due to inherited diseases. Previous studies have found that VA in endurance athletes, such as cyclists, runners and kayakers, often originates from the right ventricle (RV), even when there are no previous symptoms that would enable a diagnosis of a condition called arrhythmogenic right ventricular cardiomyopathy (ARVC) to be made, and no family history of ARVC. A family history is usually present in 30-50% of reported cases of ARVC.
Researchers at the University Hospital Gasthuisberg at the University of Leuven in Belgium, set out to study whether abnormalities in the functioning of the RV might be present in endurance athletes with VA.
They studied 22 endurance athletes  who had been referred to them with VA between July 1997 and April 2005. None had abnormal wall thickening of the left ventricle (hypertrophic cardiomyopathy) or coronary abnormalities. They compared them with 15 endurance athletes without VA and a control group of non-athletes without VA. The athletes were Belgian and Dutch men aged between 18 and 55.
Using four methods for quantitative angiography (X-ray of the heart chambers) to study the RV, they measured the volume of blood in the relaxed RV (end-diastolic volume, EDV), the volume of blood left in the RV after the heart had contracted (end-systolic volume, ESV) and the fraction of blood pumped out of the RV in each heart beat (ejection fraction, EF). In addition, they measured the change in the diameter of the part of the RV where the blood flows out to the arteries (RV outflow tract shortening fraction, SF), and the thickness of the ventricular walls.
Hein Heidbüchel, professor of cardiology/electrophysiology and director of the clinical EP laboratory who led the team, explained: “Although arrhythmogenic right ventricular cardiomyopathy is a known cause of arrhythmias in athletes, we found that we could diagnose it unequivocally in only six of the 22 athletes (27%). However, we could assign arrhythmias as definitely or probably originating from the right ventricle in 82% of the patients – an RV origin of the arrhythmia was manifest in 12 (55%) of the 22 and probable in six (27%) of them.
“All athletes had a higher end-diastolic RV volume compared to controls, as expected in an athlete’s heart. Importantly, we found that athletes with VA had an RV end-systolic volume that was significantly higher than athletes without VA, and, accordingly, athletes with VA had a significantly lower RV ejection fraction. This significance remained after we had excluded two athletes with presumed ARVC because of a family history of arrhythmias or sudden death.”
The decrease in EF was not profound (down by approximately a fifth) but consistent among all athletes with VA and consistent across all measurement methods. The difference between the two groups of athletes indicated that the RV was not fulfilling its function of pumping blood out from the heart effectively in those with VA.
Prof Heidbüchel said: “Our study clearly demonstrates RV functional abnormalities in high-level endurance athletes with VA. The observed RV dysfunction is more subtle than in familial or overt ARVC. ARVC was only present in a minority of the athletes, based on conventional, internationally accepted criteria. One explanation could be that these athletes presented with arrhythmias in the early stage of underlying ARVC, triggered by intense exercising. However, we know that athletes with ARVC are at increased risk of dying suddenly, in which case, diagnostic criteria for ARVC should be adapted to better detect this early manifestation of the disease.
“An alternative explanation for our findings is that exercise also acted as a promoter of the RV changes, maybe in synergy with other environmental or genetic factors, and hence led to arrhythmias. Our study does not provide definitive proof for either of these explanations, but our data contribute to the accumulating, indirect evidence that endurance exercise may have detrimental effects on the RV in some athletes.
“Determination of the underlying genetic profile of these athletes may provide further data and that work is under way. We also do not know whether substance abuse may have contributed to the observed changes, although all study subjects denied such use and there was no other evidence for it in any of them.”
Although they are still awaiting results of the genetic tests, Prof Heidbüchel and his colleagues questioned whether the findings were due to the expression of early ARVC, especially as there was other evidence to support the second explanation. “The hypothesis that high-level endurance exercise is an underlying cause of the VA is supported by other studies that suggest that endurance exercise and volume overload subject the thin-walled RV to a greater increase in workload than the thick-walled left ventricle, with subsequent changes to the structure of the RV.”
Prof Heidbüchel said that athletes who undertake endurance sports should not worry too much. Ventricular arrhythmias are very uncommon. “But they need to be vigilant and honest with themselves: if they have a family history of ARVC, arrhythmias, sudden death or other heart complaints, or if they have experienced exercise-induced light-headedness, palpitations or fainting, then they should see their doctor for an evaluation.”
Reduced right ventricular ejection fraction in endurance athletes presenting with ventricular arrhythmias: a quantitative angiographic assessment. European Heart Journal. doi:10.1093/eurheartj/ehl468.
“Endurance athletes” were men who had participated regularly in sessions of intense endurance sports lasting for at least two hours, three times a week for at least five years.
Emma Mason | alfa
A sudden drop in outdoor temperature increases the risk of respiratory infections
11.01.2017 | University of Gothenburg
Urbanization to convert 300,000 km2 of prime croplands
27.12.2016 | Mercator Research Institute on Global Commons and Climate Change (MCC) gGmbH
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration
"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Machine Engineering
17.01.2017 | Physics and Astronomy