Catherine Lee, of Cottingham, near Hull, is making medical history after being chosen as one of only four women in the world to take Cialis, which is commonly used to treat erection problems in men.
Doctors are so encouraged by the results, they have effectively torn up their previous prognosis, which warned she could be dead inside three years from the rare condition primary pulmonary hypertension, or PPH.
Now Mrs Lee, 32, is looking forward to many happy years with her two-year-old daughter Poppy.
She takes enough of the impotence drug to fuel 10 men on a daily basis.
She said: "Before I started taking the Cialis I was mainly sedentary.
"Even simple tasks such as loading the washing machine were impossible, and contemplating going for any sort of walk – even across the room – was out of the question.
"Rather than being scared when I was diagnosed, I was actually relieved.
"I was pleased to know what was wrong with me, and I just thought 'It's the 21st century, there must be something that can be done', but I didn't think Viagra would be the drug to help me."
Mrs Lee, who used to be a switchboard operator before the one-in-a-million disease struck her down, was first diagnosed with the progressive heart and lung condition about a year ago.
Symptoms began five years ago when she started getting heart palpitations and would often feel dizzy.
Doctors initially diagnosed anxiety and she was put on Prozac for three years.
It was not until she gave birth to her daughter prematurely, at 27 weeks, that her condition worsened.
Simple day-to-day tasks began causing her to lose breath and everything become a struggle. Looking after her daughter was exhausting and she would often black out from the intensity of the palpitations.
Mrs Lee, who is married to 33-year-old joiner Matthew, was eventually sent to a neurologist. He referred her to a cardiologist and her condition, which results in the progressive narrowing of the blood vessels of the lungs, was finally diagnosed.
She was then referred to Professor Alyn Morice, from Castle Hill Hospital in Cottingham who is a world expert and is conducting research to see if the drug can prolong the lives of people with PPH.
Cialis works for Mrs Lee because it is a vasodilator drug, which means that it helps to dilate the blood vessels in the lungs.
Prof Morice, who is a professor of respiratory medicine, said: "I am the only person in the world prescribing this drug for PPH and so far, over the last 18 months or so, we have had tremendous results. PPH was a condition that was almost 100 per cent fatal 20 years ago and now I have lost only one patient in the last five years.
"The drug works in the same way as Viagra. The only difference is that Cialis has a much longer-lasting effect. It works by relaxing the blood vessels, which enables blood to flow through the penis and create an erection. But in Catherine's case, it helps relax arteries in her lungs, allowing blood to be pumped through."
The only set-back is that Mrs Lee is developing a tolerance to the medication and she has to keep increasing her doses.
Dave.Mark@ypn.co.uk