Jon Cotterill-Bolsover had everything to look forward to.  His fiancé was expecting his baby and his life was falling into place after a stressful divorce.

But Jon, just 28, was about to get the shock of his life. 

Sitting in front of a consultant, he was hoping for a simple explanation for the blackouts he'd been having. 

Instead, he was told he had a rare genetic condition that could kill him at any time. 

Any sudden noise - like the beep of an alarm clock or the piercing tone of a mobile phone - could be enough to give him a fatal heart attack. 

"What frightened me most was that he said I could die at any second without any warning," says Jon.

"I'd gone to the appointment by myself and all of a sudden I was being told I could just drop dead.

"I left the hospital in tears not knowing if I would survive the journey home." 

Jon's nightmare began during his divorce two years earlier. 

"I kept blacking out, which at the time doctors assumed was a form of epilepsy," he says. 

But last August Jon developed a serious kidney infection which caused hallucinations and hear palpitations. 

He was admitted to hospital but doctors were baffled by his irregular heartbeat.

Jon was showing all the signs of a heart attack without actually having one. 

"The doctors were so confused they thought their machine was broken," says Jon, from Barnsley, South Yorkshire. 

In a desperate attempt to find out what was wrong the doctors sent a fax to other heart specialists - and one came up with the answer. 

Having just returned from a conference on sudden unexpected death syndrome he knew that Jon had Brugada Syndrome.  this is a hereditary condition which disrupts the heart's normal rhythm and was only identified in the 1980s. 

Jon was referred to an expert who broke the bad news.  He explained the syndrome was caused by too much electrical activity in the body and the slightest shock could lead to blackouts, palpitations and even death. 

His best chance of survival was to be implanted with a cardiac defibrillator - a small device to regulate his heart - and to send it an electrical shock if it stopped beating.  the defibrillator has improved Jon's chances of survival by ore than 90 per cent. 

He said: "the condition usually affects men and most only live until their early 30s without the defibrillator."

But there was one snag - he had eight weeks to wait before the operation. 

Jon had to break the news to his pregnant fiancé Katrina, 30. 

Katrina, who is a teacher, says: "I was worried but I had to be strong for Jon.  The way I looked at it, he had survived until that point, so I was sure he could get through another eight weeks." 

Jon says: "All I wanted to do was stay in bed to prevent anything from causing me to go into shock. 

"I was always active - I loved karate - but I had always been very jittery.  If someone turned the TV on loud, or the car radio blasted music out when I turned on the engine, it would make me very jumpy.  Strangely, I was OK in busy or crowded places as the noise levels were constant." 

Jon and Katrina, who each have children from previous relationships - Natalia, five and Anastasia, four - had to make changes to their lifestyle. 

Katrina says: "I made sure everything we did was at a far more relaxed pace.  Instead of running around trying to cram in children's parties, visiting friends and going out, we took a huge step back. 

"We had early nights, gave up dashing around to see relatives and asked the children not to get so excited as it could make daddy ill." 

They switched their mobiles to vibrate, swapped their morning alarm to gentle music and warned the children not to jump on Jon suddenly or surprise him. 

Ironically Jon works for a mobile phone company as a recruitment manager, but luckily he's in an office away from any constant ringing. 

"I still felt like I was a ticking time bomb," Jon says. 

"Katrina was more positive and did her best to reassure me it would be OK. 

But I was absolutely petrified.  Katrina was pregnant with our first baby together and I had a beautiful little girl.  the thought that I might not see Natalia grow up or see my unborn baby was horrifying." 

But the switch to a mellower lifestyle did the trick and Jon was wheeled in for his op last November. 

"I was extremely anxious," he recalls. 

"After all, it is a heart operation and I was worried something would go wrong." 

Once the defibrillator had been fitted, the surgeons had to stop Jon's heart to check it was working.  fortunately it kicked in and restarted Jon's heart without any hiccups. 

"It was such a relief to wake up and know the defibrillator had been fitted," says Jon. 

"It's like my personal safety net.  Chances are I will now live a normal life." 

Jon still can't pass through airport security gates and isn't allowed to use the doors at work, as the magnets can damage his £30,000 defibrillator. 

Although his chances of survival have improved massively, Jon knows his life is still at risk every day. 

"It is petrifying to think the slightest shock could cause me to drop dead," he says. 

"But it's out of my control and I have to keep myself calm." 

John and Katrina will marry on Saturday and are due to have their baby in May. 

"Natalia will have to be tested, as will our new baby when it's old enough," says Jon. 

"But we will deal with that as and when we need to.  We don't want to dwell on something that might not even be a problem." 

He is setting up a support group for people with Brugada Syndrome. 

Jon says: "If I had been able to talk to other sufferers when I was diagnosed, I don't think I'd have felt so frightened.  Also, if it spreads awareness about the condition, it might save someone's life." 

Many sufferers die before they realise they have it. 

"I feel very lucky to still be alive," says Jon. 

"I just want others to be given that opportunity." 

BRUGADA SYNDROME:  THE FACTS     

Brugada Syndrome is a hereditary condition which affects the electrical conduction system of the heart, causing an abnormal heart rhythm. 

It can be life-threatening in some cases and may take effect with little warning.  It appears to be most common in active and apparently healthy young men. 

As well as abnormal heart rhythms, someone who has Brugada syndrome , may suffer from spells of fainting and at times feel quite short of breath.  There is usually no other underlying physical abnormality of the heart. 

Electrocardiograms (ECGs) and 24-hour Holter monitor tapes are used to diagnose Brugada syndrome.  this procedure can show any changes in the electrical activity of the heart. 

Treatment depends on each person's tests but may involve inserting an implantable cardioverter defibrillator. 

FOR FURTHER INFORMATION:

CRY, Cardiac Risk in the Young - call 01737 363 222 or visit www.c-r-y.org.uk or SADS UK (Sudden Adult Death Trust) - call 01277 230642, email info@sadsuk.org or visit www.sadsuk.org