Researchers identify cause of heart block in athletes

Researchers have worked out why some athletes experience heart block, after studying the effects of long-term exercise in mice and retired racehorses.

Scientists from Manchester, Montpellier and Copenhagen discovered that regular, intense exercise caused molecular changes in the animals’ atrioventricular (AV) node.

They spotted a reduction in key proteins called ion channels, which control conduction in this part of the heart.

According to the researchers, this could explain why sportspeople sometimes develop abnormal heart rhythms, including heart block.

Although heart block is normally benign, it could be “‘a canary in a coalmine’” indication of more serious problems, the study’s lead author Dr Alicia D’Souza said.

Dr D’Souza, an academic at the University of Manchester, said the team’s research was groundbreaking, as it was the first study to notice “fundamental adaptations” occurring in the heart due to exercise.

She added: “Because we found similar effects on both mice and racehorses, it’s fair to assume this mechanism is present in humans too.

“It must be stressed that exercise is good for you - and its benefits far outweigh the risks.”

The publication of the University of Manchester-led research comes less than two weeks after Danish footballer Christian Eriksen had a heart attack at the European Championship and needed to be resuscitated.

Eriken was later released from hospital after being fitted with a defibrillator implant. As the cause of his cardiac arrest has not been announced, it remains unclear if there is a connection between the research and his heart condition.

Dr Pietro Mesirca, a researcher from the Institute of Functional Genomics in Montpellier who worked on the study, said: “Understanding the physiology of the athlete’s heart is incredibly helpful.

“It could help us develop new interventions for heart block as well as help doctors more effectively monitor heart rhythm disturbances in top-flight professional athletes.”

Dr Mesirca and his colleagues also noted that heart block caused by training was reversible if the animals stopped exercise or if a compound called anti-microRNA was given to the mice.

The study, which was funded by the British Heart Foundation (BHF), is published in the journal Circulation Research.

Additional reporting from PA