Her owners Paul and Pauline Daley of Malpas, Cheshire, were warned by veterinary doctors that the one-year-old only had a few months left to live.
But thanks to a team of surgeons from the Royal Veterinary College in London, black Labrador Lottie underwent a double bypass surgery never performed on dogs before.
The puppy is expected to make a full recovery.
The complex heart procedure, which cost a whopping £12,000, repaired a valve in Lottie’s heart and divided the heart’s atrium back into two chambers.
It had never been performed in combination on a dog before with surgeons seeking advice from paediatricians before going ahead.
Explaining why they went on with the surgery, Pauline, 58, said:
‘When it came to making the decision about whether to go ahead with the surgery it was so difficult.
‘Lottie is such a special little dog and we thought there would be so much to gain by giving her a chance.
‘She’s the most adorable dog, the sweetest thing, she’s so angelic and has the most beautiful little face.
‘She just looks at you with these big brown eyes and my heart melts. She’s one in a million.’