Mr Cook, 59, collapsed while walking in the Highlands on Saturday and was pronounced dead after being airlifted to hospital.
A Crown Office statement said: "The procurator fiscal for Tain and Dornoch can confirm that a post-mortem examination following the death of Robin Cook MP has established the cause of death as hypertensive heart disease. Next of kin has been informed of the cause of death, and a death certificate has now been issued."
Hypertensive heart disease is a late complication of high blood pressure (hypertension). According to the US-based Medline Plus website, it is the leading cause of illness and death from hypertension.
Tony Blair came under fierce attack yesterday from a close friend of Mr Cook for not planning to attend the funeral, which will be at at 11am on Friday at St Giles Cathedral in Edinburgh.
Channel 4 racing pundit John McCririck accused the Prime Minister of snubbing the family and the memory of Mr Cook. Mr McCririck said: "It is contemptible that the Prime Minister cannot be bothered ... It is a deliberate, selfish snub to the family, millions of New Labour supporters, and the memory of a man who did so much to bring about his premiership."
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