Knitting is usually seen as a homely pastime. But in Bolivia, it is part of the latest developments in high-tech heart medicine.

Due to the high altitude and lower levels of oxygen, babies born in La Paz are an estimated 10 times more likely to develop a condition known as patent ductus arteriosis - or a hole in the heart.

The hole means that blood and oxygen flow less efficiently around the body.

Although some people are unaware of their condition, others can struggle to gain weight or be easily fatigued as their hearts have to work three times harder.

A simple operation can cure a person for life.

But for many children, the mass produced plugs used to block the hole are too big.

Now much smaller, more intricate plugs are being hand-made by an army of Bolivian knitters.

Ignacio de los Reyes reports from La Paz.