Hi. My Wife's Father Recently Suffered Severe Damage To His

Hi. My wife's father recently suffered severe damage to his leg, and ended up having his ankle restructured and hospitalized for more than 2 weeks. As well, he ended up with a blood clot that formed in his leg, but ended up on his lung resulting in an almost fatal PE. He was covered by Worker's Compensation, but they now have pulled their support and told him that they did not believe it was work related. He is an industrial electrician and stands or crouches stationary for long periods of time. He has done this type of work for more than 40 years. He is 70 this year, and now cannot work. The surgeon he had says that this type of clot can be caused by the work he does, but Compensation's doctors say "No"? Can you confirm either way, or point me to some literature or documentation that may help us to help him appeal?