The 'Back to Black' singer's family and managers, who say she has lung condition emphysema, actually fear that the troubled star would die from coronary failure, the sources have said.
According to insiders, the 24-year-old singer, who has had two serious attacks, is suffering terrifying heart attack-like symptoms, including chest pains, breathlessness, numbness and confusion.
Last month the Rehab singer had a fit and had been hospitalised, with her dad Mitch saying that she had emphysema, but a source revealed otherwise.
"We were terrified she'd had a heart attack," News of the World quoted the source as saying.
"Her pulse was barely there and she was struggling to breathe and complaining of chest pains. It was awful.
"She got Mitch to take her to hospital because she didn't want a fuss but it was really serious. Far more serious than she's made out since then.
"Amy is far more at risk from drug-induced heart failure than emphysema," the source stated.
News of the World GP Dr Hilary Jones said on July 12 that it was "very likely" drug-addict Amy had damaged her heart.
"Crack cocaine is a stimulant. It can send the heart haywire, leading to irregular beats, palpitations, breathlessness, chest pains-all the symptoms of a heart attack," Jones explained.
"It could be very dramatic and frightening for Amy. She would also be very breathless and have water on the lungs as a result, which might suggest a lung complaint like emphysema.
"But emphysema is more common in people over 50. She's way too young to have damaged her lungs to that extent, and the fact she can still sing amazingly suggests they aren't badly damaged.
"It's more likely her breathing problems are a side-affect of having damaged her heart by taking drugs," Jones added.