At least 620,000 people have the inherited condition but may be wandering around without realising it
More than 600,000 Brits could die at any moment because they have a faulty gene, experts have warned.
At least 620,000 people in the UK have an inherited heart condition that puts them at risk of sudden death, the British Heart Foundation said.
But the vast majority of those affected do not know it.
As many as 12 people aged 35 or under die suddenly without explanation every week – and most of the deaths are due to these inherited genetic faults, the charity added.
Most were unaware they carried a faulty gene putting them at higher risk of heart disease, heart attack or cardiac arrest.
The BHF said the true figure could be even higher due to under-diagnosis and the presence of other, as yet unknown, faulty genes.
The charity is not calling for nationwide screening for genetic conditions but says close family members of anyone found to have a fault should be tested.
A spokesman said: “If someone in your family has been diagnosed with or has died from what is suspected to be an inherited heart condition, you should speak to your GP or call our genetic information service for more information and support.”
Last April, ex-England cricketer James Taylor was forced to retire early due to a rare but serious genetic heart condition.
Scans revealed he had arrhythmogenic right ventricular arrhythmia (ARVC), an inherited condition caused by a change or mutation in one or more genes.
It meant the right side of his heart fails to pump blood around the body properly and can cause abnormal heart rhythms.
The condition is progressive, which means it will get worse over time, and there is a risk of sudden death.
In a fresh warning issued today, the BHF said inherited heart conditions can affect people of any age.
Children have a 50% chance of inheriting the faulty gene from a parent who has it.
Around 12 people aged 35 or under die every week with no apparent explanation, mostly due to these inherited genetic faults.
Prof Sir Nilesh Samani, medical director at the British Heart Foundation, said: “The reality is that there are hundreds of thousands of people across the UK who are unaware that they could be at risk of sudden death.
“If undetected and untreated, inherited heart conditions, can be deadly and they continue to devastate families, often by taking away loved ones without warning.
“Thanks to the public’s kind support, BHF-funded researchers have discovered some of the genes responsible for these frightening conditions but there is still much to do.
“We urgently need to fund more research to better understand these heart conditions, make more discoveries, develop new treatments and save more lives.”
Taylor said: “It is safe to say that being diagnosed with ARVC was the toughest and scariest week of my life. I never would have thought it would happen to me.
“I was 26 years old and playing cricket for England but my condition meant that I was at risk of sudden death from a cardiac arrest.
“I was lucky as my condition was detected early and, despite having to give up my career, with medication I can lead a relatively normal life. But it could have been an incredibly different story.”