Sylvia's is a compelling tale, and not just because of its hi-tech medical drama (at one point she lies anaesthetised on the operating table with her chest cavity completely empty, as her new heart and lungs arrive by Learjet). What really sets her story apart is that she claims to have "inherited" the personality traits of her donor.
Sylvia, a former professional dancer suffering from primary pulmonary hypertension, had a heart-lung transplant when she was 47. Five months afterwards she had a vivid dream about a tall, thin young man whose name was Tim, and whose surname began with L.
In the dream, writes Sylvia, "we kiss, and as we do I inhale him into me. It feels like the deepest breath I have ever taken. And I know at that moment the two of us, Tim and I, will be together for ever. I woke up knowing - really knowing - that Tim L was my donor and that some parts of his spirit and personality were now in me."
Sylvia had heard from a nurse that her donor was an 18-year-old boy from Maine who died in a motorcycle accident, but the hospital refused to tell her more, arguing (as most hospitals do) that this is an emotional can of worms for all concerned.
At first, Sylvia accepted the advice to leave well alone, but she continued to experience disturbing, unfamiliar feelings and appetites - from her strange new desire to drink beer and eat chicken nuggets, to the profound sense that "the very centre of my being was not mine".
Like Humpty Dumpty, as she puts it, she had experienced a traumatic breaking- apart. Her surgeon had put her body back together again - but not her emotions. "That new, reconstructed person just wasn't me," she writes.
The mysterious new entity within her body reminded her of pregnancy, when she felt she embodied something "foreign and beyond my control, yet terribly precious and vulnerable [as if] a second soul were sharing my body". And that soul was stereotypically masculine, making her more aggressive and confident. Friends remarked that after the transplant she was walking more like a man, and she found herself attracted by rounded, blonde women - "as if some male energy in me was responding to them". Other changes included her increased libido, stronger body odour, a restless energy and a craving for junk food.
Sylvia accepts that some of the changes - such as an increase in facial hair - were the result of medication, but she doesn't believe that these accounted for all the differences. Her mind "spinning with confusion", she kept a record of her dreams, sought help from a Jungian analyst and started a support group that echoed many of her perceptions about feeling a "hybrid", as though two people were sharing the same body.
It was not until 1990, she says, that she traced the identity of her donor through his obituary in a local paper. His name was Tim, his surname did begin with L, and when Sylvia eventually visited his family she learnt that he had been restlessly energetic, with a love of chicken nuggets, junk food and beer.
Sylvia consulted a range of what she calls "open-minded scientists"; several came up with the notion of "cellular memory" - meaning that the cells of our bodies are instilled with our memories (rather as homoeopathic treatments are based on the concept of "memory in water").
Eastern concepts of energy or "chi" also chimed with Sylvia's experiences: she has come to believe that after the sudden trauma of a fatal accident the spirit of the victim gets "stuck".
"I did the work needed to release Tim's spirit," she says. "I feel integrated now. I don't dream about Tim any more; his spirit let go of me after a ritual motorbike ride." She is now following the work of healers who claim they can "free" the donor's organs at the time of transplant, rather like an exorcism.
So what are sceptical Brits to make of Claire Sylvia? In her book, she is disarmingly open about her unhappy childhood, her sense of longing to belong, and her series of relationships. She is the sort of person who needs to look for meaning in everything, describing herself as "sensitive, intuitive and open to psychic phenomena".
She believes in God and destiny, and that there is no such thing as coincidence. She admits her daughter takes the mickey by calling her "Oh Spiritual One!"; so her story comes across as an honest, even naive, account of her personal experiences. "I am not trying to prove anything," she says, and she doesn't.
But how will she be received on this side of the Atlantic? Britain's Transplant Support Network, which includes some 40 heart-lung recipients, is likely to give her short shrift, for a start. "This is a ghastly idea coming from America which is not good for our transplant programme," says Jo Hatton, founder of the network, who was one of Papworth Hospital's first heart-lung recipients in 1986.
Jo Hatton says she knows of only one individual in the 320-strong organisation who claims to have had comparable experiences. "This is a lady who likes eating sweets and going on swings, and thinks this is because her donor was a little girl. But once you have an idea of who your donor is, you can read all sorts of things into yourself," she says. "I like swings, too, but that's because I never had the chance to play on them as a child when I was ill."
As for the phenomenon of changed food preferences, Hatton explains that steroid drugs can give transplant patients the munchies. "At Papworth we call it the `cheese sandwich syndrome', because you want to eat anything in sight."
John Wallwork, director of transplantation at Papworth, says that stories like Sylvia's do crop up from time to time among his patients, and he doesn't believe Sylvia is making anything up. Instead, he points to auto- suggestion and powerful psychological factors. "I can understand why people feel like this, but the attribution of her feelings is wrong," he says. "Our culture sees the heart as the seat of life, love, the soul. There is no basis in science for this - but it will make a great movie"n
`A Change of Heart', by Claire Sylvia, is published by Little, Brown, price pounds 15.99.