THE Medical Council is waiting for the family of a man who died after being given an artificial heart valve made of ox tissue to come forward before investigating the case. Council secretary, Rupert Cheung Ming-por, said the family had not lodged a complaint so far. Wong Tse Lai-kuen, widow of Wong Wai-wah who died a year ago, pledged on Monday to find out if there had been any negligence during the surgery. Mr Cheung said according to legislation governing the professional body, they could only act when a formal complaint was made. But he said the situation might change if the Government adopted their proposal to empower the body to look into professional ethics. As it would be a long process to amend the legislation, Mr Cheung said there were plans to introduce the proposal through a private member's bill in the Legislative Council to cut short the time needed. Meanwhile, the Prince of Wales Hospital is to conduct more experiments on the use of artificial heart valve made of ox tissue in animals before using them on patients again. The innovative treatment caused controversy after half of the 12 patients given the transplant died. It was claimed that only one of the patients had died as a result of the failure of the valve.