She had climbed the Great Wall of China, canoed down one of France's longest rivers and danced for more than a decade. And all this time, Karen MacLachlan had no idea she had a lethal, undiagnosed heart condition that could have killed her at any time. The self-confessed fitness fanatic was born with a heart defect that kills 90 per cent of babies before their first birthday if left undetected. The 25-year-old, from Glasgow, had no idea she had the deadly disease - which is usually diagnosed at birth - until her heart suddenly stopped beating. Ticking timebomb: Self-confessed fitness fanatic Karen MacLachlan had no idea she had a lethal, undiagnosed heart condition that could have killed her at any time . 'When I collapsed, my mum thought I'd tripped over,' she said. 'It wasn't until she heard a deathly rattling sound coming from my chest that she called an ambulance. 'She thought I was dead because my skin had turned a deathly black colour as I lay lifeless on the floor.' Ms MacLachlan was rushed to hospital and put into a medically induced coma. And remarkably, after surgery to rewire her heart, she has made a full recovery. Ms MacLachlan was diagnosed with Anomalous Left Coronary Artery from the Pulmonary Artery (ALCAPA). This is a rare heart condition where the main ventricle of the heart, which supplies oxygen to the body, is wired incorrectly. Usually, the condition is diagnosed at birth, but there is 90 per cent chance a patient will die from heart failure by the age of one if undetected. Ms MacLachlan said: 'At first, doctors believed my heart stopped as a result of Sudden Adult Death Syndrome not ALCAPA - it's very rare for someone to survive past infancy with it.' 'Doctors were amazed that I'd lived with this condition for so long and never had any problems before.' Indeed, she had always prided herself on being fit and healthy. 'Doctors asked if I'd struggled walking up hills, but I've walked the Great Wall of China - I'm really fit and active,' she said. 'I'd danced for 10 years, canoed one of the longest rivers in France and never had any symptoms, so it was a shock to everyone.' 'Even was taken aback because doctors told me I should have been so unwell, it was really scary. Danger: The self-confessed fitness fanatic was born with a heart defect that kills 90 per cent of babies before their first birthday if left undetected . 'It's terrifying as I now know I could have died at any moment.' Months after her collapse, Ms MacLachlan underwent corective open heart surgery. She then had a year of rehabilitation to get her heart used to even the most gentle exercise. She said: 'After doctors fixed my heart I was really poorly, I didn't realise how much the surgery would affect me. 'I couldn't walk four steps without sweating buckets like I normally do during strenuous exercise. 'I had to learn to build up my energy and became physically fit again. 'Every hour I'd have to walk one length of my parents' hallway to try and build my strength up. 'It hurt to sit down on sofas and I'd struggle to lift myself up because I didn't have enough energy to push myself up. 'Mentally it was pretty draining as well - at first I was scared to leave the house in case my heart stopped again. The 25-year-old said: 'When I collapsed, my mum thought I'd tripped over. It wasn't until she heard a deathly rattling sound coming from my chest that she called an ambulance' 'It took me a year to battle through everything but I've came out the other end independent and stronger again.' She now goes to the gym every day and takes the stairs everywhere she can. And she says she's glad she wasn't diagnosed any earlier. 'In some ways I'm glad I didn't know I had ALCAPA because I know I would have been wrapped up in cotton wool. If I knew about my condition I had this I don't think I would have gone off to climb mountains or go on adventure holidays. 'It took me a year to battle through everything but I've came out the other end independent and stronger again.' Since recovering, Ms MacLachlan has returned to a normal life but was keen to raise awareness of ALCAPA and other Congenital Heart problems. She has also bared her six-inch scar in a photography exhibition 'Scarred for Life' exhibition to raise awareness for the face behind heart problems. Unaware: Doctors were amazed she had lived with this condition for so long and never had any problems before. 'Doctors asked if I'd struggled walking up hills, but I've walked the Great Wall of China - I'm really fit and active,'  said Ms MacLachlan . Proud: After major surgery to re-wire her heart, Ms MacLachlan has been left with a six-inch. She has now bared this in the photography exhibition 'Scarred for Life' to raise awareness . Her picture joined those of seven other people who had pacemakers fitted and underwent heart surgery, at the Kelvingrove Art Gallery and Museum, in Glasgow. She said: 'Before I would always hide my scar, it wasn't very nice to look at and it's taken me a while to reveal it. 'I never wanted people to ask about my scar or to notice it so I'd hide behind clothing that would cover me from my chest up to my neck. 'Since having my scar on show at the exhibition I feel like I can talk about it and I'm no longer ashamed of my mark. 'Having survived everything I've been through has made my love my scar. 'One little boy at the exhibit pointed at the picture of my scar and said to his mum that it was like his, which really warmed my heart. 'We really want to get people talking about heart conditions as we've nothing to be afraid of. 'Having revealed my scar I now feel so much more confident and for the first time wore a lower cut top last week. 'Now I feel strong enough to show it, the mark is a reminder of everything I've overcame.' ALCAPA is a rare heart condition you can be born with. Left undiagnosed, it kills in 90% of cases . June Davison, Senior Cardiac Nurse at the British Heart Foundation, said: 'ALCAPA is a rare heart condition that you can be born with. 'Blood that is lacking in oxygen is carried to the left side of the heart, depriving the heart of oxygen, which can cause damage to the heart muscle. 'Surgery is needed to correct the condition and nowadays people with ALCAPA have a much better prognosis.' An 'ALCAPA (anomalous left coronary artery from the pulmonary artery) is a problem that occurs when the baby's heart is developing early in the pregnancy. The developing blood vessels in the heart do not connect correctly. In the normal heart, the left coronary artery starts in the aorta. The aorta is the major blood vessel that takes oxygen-rich blood from the heart to the rest of the body. In children with ALCAPA, the left coronary artery starts at the pulmonary artery. The pulmonary artery is the major blood vessel that takes oxygen-poor blood from the heart to the lungs. When this defect occurs, blood that is lacking in oxygen is carried to the left side of the heart. Therefore, the heart does not get enough oxygen. When the heart muscle is deprived of oxygen, the tissue begins to die. This condition leads to a heart attack in the baby. A condition known as 'coronary steal' further damages the heart in babies with ALCAPA. The low blood pressure in the pulmonary artery causes blood from the abnormal left coronary artery to flow toward the pulmonary artery instead of toward the heart. This results in less blood and oxygen to the heart. This problem will also lead to a heart attack in a baby. Coronary steal develops over time in babies with ALCAPA if the condition is not treated early. Source: Medline Plus .
Karen MacLachlan had no idea she had lethal, undiagnosed heart condition . Born with a heart defect that kills 90% of babies before 1 if left undetected . Only realised something was wrong when she suddenly collapsed . Tests revealed she had rare condition where heart was wired incorrectly . Has now undergone corrective surgery and is on road to recovery .