Japanese officials say Emperor Akihito will undergo heart bypass surgery this week after an examination found a heart problem had worsened.

The Imperial Household Agency said Sunday that the 78-year-old emperor had a catheter angiogram at the University of Tokyo Hospital on Saturday. The test showed that blood vessels had narrowed, and he was scheduled for surgery next Saturday.

Emperor Akihito has had various health problems in recent years, including pneumonia and prostate cancer.