French company Carmat confirmed on Monday that it had fitted a second patient with one of its artificial hearts.

Shares in Carmat rose as much as 19 percent on Friday after French media reported that doctors had implanted an artificial heart made by the company for a second time, Reuters reported.

The clinical trial will be considered a success if Carmat's first patients survive with the implant for at least a month. The patients selected suffer from terminal heart failure - when the sick heart can no longer pump enough blood to sustain the body - and have only a few weeks, or even days, to live.

Carmat's device, developed by a team of engineers from Airbus parent company EADS, weighs about 900g (around 2 lb)- nearly three times more than an average healthy human heart. It mimics heart muscle contractions and contains sensors that adapt the blood flow to the patient's moves.

It is powered by external, wearable lithium-ion batteries. Inside the heart, surfaces that come into contact with human blood are made partly from bovine tissue instead of synthetic materials such as plastic that can cause blood clots.