A vegetarian teenager from Scotland, who was suffering from a rare cardiac condition, is now being kept alive by a pig’s heart valve.

Robyn Cairney, 18, of Ruckazie, Glasgow was diagnosed with aortic stenosis and regurgitation after she collapsed at the gym.

Over time, the condition caused her aorta to narrow, which allowed blood to dangerously flow back to her heart. The most common symptom is shortness of breath with exertion, resulting in some patients feeling “out of shape,” according to the American Heart Association.

"It came totally out of the blue,” Cairney told The Sun. “I was at the gym and became unwell during a mile run. I couldn't breathe and wouldn't stop coughing. Then my lips started turning blue and I knew that something was seriously wrong.”

When the aortic valve becomes excessively obstructed or leaky, the valve must be repaired or replaced.

"The doctors told me that I would need to have a valve taken out and replaced by one from a pig,” Cairney said. "It was a bit of a shock being a vegetarian, but I realized it was a life or death choice. Obviously everyone is going to pick life, so now I'm a vegetarian being kept alive by a pig."

Cairney was fitted with the pig's valve during open heart surgery at the Golden Jubilee Hospital near Glasgow.

The pig's valve should last for 20 years. Cairney will then have to undergo surgery to have a mechanical valve fitted.

"I'm just glad I can get on with my life now and am determined to make the most of everything I do,” she added.

Click here to read more and see photos from The Sun.