University of Manchester researchers, funded by the British Heart Foundation, have revealed how a faulty gene can cause fatal abnormal heart rhythms that are brought on by exercise.
Dangerous heart rhythms called arrhythmias, often caused by
undiagnosed heart conditions, can cause sudden cardiac arrests that take
the lives of seemingly healthy young men and women including sports
people.
A healthy, functioning heart has a regular electrical
impulse that causes the heart to beat and pump blood around the body. If
this impulse is interrupted or becomes irregular, it causes an abnormal
heartbeat, called an arrhythmia. Arrhythmias can be a long-term
condition, treated with medication or surgery or they can occur
unexpectedly, suddenly stopping the heart from beating. For some people,
sudden arrhythmias can be brought on by exercise and are often fatal.
A
faulty gene was identified in 2001, pointing to a calcium channel in
heart cells not functioning as it should. The channel should open and
shut to regularly let calcium into the heart cells, kicking off the
required electrical impulse for the heart to beat. A research team from
The University of Manchester, funded by the British Heart Foundation
(BHF), has found that when someone has the faulty gene, this channel
can stay open for too long, making it leaky. This causes a rare but
potentially fatal heart condition called CPVT (catecholaminergic
polymorphic ventricular tachycardia)
When someone exercises,
adrenaline is released which increases the amount of calcium stored in
the cells. If someone has CPVT and has these leaky channels, calcium can
flood into the heart cells, causing a fatal arrhythmia. The leaky
calcium channels might go completely unnoticed until this happens.
Professor Clifford Garratt and Dr Luigi Venetucci,
clinicians in the team, are working with the families of those who have
died from sudden arrhythmic death syndrome (SADS) to determine if they
are also at risk. As the gene is inherited, the team want to know if
everyone with the faulty gene develops an arrhythmia or if there are
other genes involved.
BHF Professor David Eisner from The University of Manchester’s Institute of Cardiovascular Sciences,
who led the research, said: “People who are prone to sudden arrhythmias
often die young. Survivors may have an internal defibrillator fitted
at a young age, to shock their heart back into a regular heartbeat if
needed but the device does not last forever and needs replacing as the
child or young person grows.
“A better understanding of what goes
wrong inside the heart during an arrhythmia is crucial to finding the
genes that can cause abnormal heart rhythms, and developing better
treatments for people at risk of the tragedy of sudden cardiac death.”
Professor
Jeremy Pearson, Associate Medical Director at the BHF, which funds the
Manchester research team, said: “Exercise is a vital part of maintaining
a healthy heart and for the vast majority of people, it should be part
of their daily routine but, for some people, exercise can trigger an
underlying condition that they didn’t know they had. We know that
screening doesn’t find everyone with the genes that can make them prone
to sudden cardiac death and we urgently need more research to understand
the causes of these rare, but potentially fatal, arrhythmias.”