New Zealand Prime Minister David Lange was hospitalized on Saturday night suffering from a flu virus and chest pains, his office said Sunday.
The statement said Lange spent a comfortable night and is in good spirits.
A spokesman for the hospital said an X-ray revealed a partial blockage of a coronary artery.
Influenza has swept New Zealand and has been linked to about a dozen deaths, according to the Health Department.
Lange, 45, who became the country's youngest prime minister when the Labor Party won power in July 1984, has had his stomach stapled to reduce his eating. At one time he weighed 370 pounds.
Because of Lange's illness, deputy prime minister Geoffrey Palmer has cut short an overseas trip and is expected back later on Sunday. Lange is expected to remain in hospital several days and return to work in one or two weeks.