Boy, three, with FIVE heart conditions needs £400,000 for life-saving surgery in US, says his desperate mother

A toddler born with five rare heart conditions is in a race against time to receive specialist surgery in the US - but the operation to save his life will cost £400,000.Sebastian Silver, three, was born with several complex conditions, including congenital corrected transposition of the great arteries (ccTGA), criss-cross heart, an underdeveloped right ventricle, ventricular and atrial septal defects, and Wolff-Parkinson-White syndrome.Each condition on its own is rare, but together they present 'an exceptionally rare and perilous clinical picture'.The youngster has spent most of his life in and out of Great Ormond Street Hospital (GOSH), while a procedure when he was just 18 months old resulted in him suffering a life-threatening cardiac arrest.Sebastian's mother Hannah has now been told 'there are no next steps' for her son in the UK - but specialists at Boston Children's Hospital believe he is a candidate for surgery that will keep him alive. A GoFundMe fundraiser launched in September has so far raised £350,000 - with another £50,000 still needed to cover the cost of the operation, as well as a further £30,000 for medical transport, travel expenses and accommodation. Hannah, a single mother-of-two from north London, hopes to fly to the US with Sebastian's older sister, Sidney, five, as soon as they have reached their target.Once the family are in Boston, doctors are planning on carrying out a specialised double switch biventricular repair, which will help balance the blood flow between the two chambers of Sebastian's heart. Sebastian Silver, three, pictured with his mother, Hannah and sister Sidney, five, was born with several complex heart conditions The youngster is a in a desperate race against time for life-saving surgery in the US. Pictured: Sebastian following an operation aged 18 months Sebastian's mother Hannah has launched a fundraiser for the operation in the USHannah, 42, who works for Google as an executive assistant, told Daily Mail: 'Sebastian is the happiest child. He is always smiling, he loves people, he loves life. 'The chance we have now means absolutely everything to us. I have been fighting to keep this boy alive for three years - and this fight is not over yet.'Sebastian's complex conditions were first noticed at Hannah's 20-week pregnancy scan, when doctors noticed the right-side of his heart looked small.After he was born, Sebastian was transferred to GOSH, where he was diagnosed with multiple and rare heart defects.'I had no idea, no understanding that our lives had just completely changed,' said Hannah. 'The doctors kept telling me his conditions were rare, but the combination was even less common. The first two years for us were horrific.'She recalled how Sebastian had to be fed through a tube and could only take a limited amount of liquids each day. He was often unwell and had to be rushed to hospital on several occasions. At two weeks old he faced his first surgery, a pulmonary band to stop over-circulation of blood to his young lungs, with doctors expecting to undertake further surgery as he grew older.But at 18 months, when doctors attempted to close the ventricular septal defect - also known as a hole in the heart - Sebastian experienced a massive cardiac arrest. Hannah was later told that he only survived because the nurses physically pumped his heart until he could be transferred onto a life support machine. 'We were given three choices,' said Hannah. 'One was to take him off life support - but he would die. The second was to give him a heart transplant, but doctors said he was not viable. 'So the only choice we had was for the doctors to reverse the surgery, but they said it was extremely risky.'I genuinely believe they thought he was not going to survive the reversal surgery, but he made it through. I think it's a miracle that he is alive.'Sebastian spent months recovering from the physical trauma of his surgery and cardiac arrest, and had to learn how to sit up and walk again. Now aged three, the youngster faces the same situation he was in before he underwent his operation at GOSH - but doctors have said that other options have now been exhausted. Hannah said it would mean 'absolutely everything' if they can fly to the US for the operationHis mother said: 'Everything is becoming more difficult for him, because he is more active. So, walking, eating, everything, he just gets a lot more tired, and sometimes if he exerts himself too much, his nails and lips turn blue. 'When the pulmonary band gets too tight he will need more surgery, but the doctors have told us there are no next steps for him. 'The surgery in the US offers us a chance. He'll still be fragile, but he will be alive - and he can have a really good quality of life.'She added: 'It gives me hope that I can start talking about Sebastian going to school in two years' time or that he will actually get to grow up. I've never been able to think that far ahead with him. 'The chance to do this means absolutely everything.'Donations can be made to Sebastian's GoFundMe appeal here