The Provincial Archives of Alberta does not hold any hospital or medical records. These records would remain in the custody of the hospital where the death occurred, though I do not know if they would be retained for 40 years after the patient has died.

You may wish to request a death certificate from Vital Statistics:

Service Alberta Alberta
Registries, Vital Statistics
Box 2023
Edmonton, Alberta
T5J 4W7

E-mail: vs@gov.ab.ca
Phone: (780) 427-7013