Shares in artificial heart maker Carmat slumped on Thursday after France's national drugs agency ordered it to suspend further implants following the death of a patient in October.

Carmat shares were down by 18.5 percent at 27.50 euros in morning trading, with around 40 million euros ($42.5 million) wiped off its stock market value.

Carmat Chief Executive Stephane Piat said in a statement on Wednesday that the artificial heart was not involved in the patient's death, and that the company's last three implantations had functioned normally.

A spokeswoman for the French drugs agency said it had requested further information from Carmat following the patient's death. The patient, who died in October, had the artificial heart implanted at the end of August and is the fifth patient to die with one fitted.

Carmat's products could represent a major medical breakthrough if proven reliable.

They are designed for people with end-stage heart failure, a deadly condition where the heart is unable to pump blood adequately around the body - an alternative to heart transplants given the shortage of donor organs.

Carmat has not generated any significant revenue but is closely followed by investors as heart diseases represent a leading cause of death worldwide.

Carmat shares are down by around 30 percent since the start of 2016, underperforming a 14 percent decline in the broader STOXX Europe 600 Healthcare index.