Hyosuke Niwa, a former Japanese labor minister, died Friday of heart failure caused by excessive bleeding at age 72, nearly two weeks after he was stabbed by a mental patient at a military ceremony. Niwa, a 12-term member of the governing Liberal Democratic Party in Parliament, was labor minister from December 1988 to June 1989 in the Cabinet of former Prime Minister Noboru Takeshita. Niwa was attacked Oct. 21 while walking to a military ceremony at the Moriyama military base in Nagoya, 170 miles west of Tokyo. He was stabbed with a knife by a 47-year-old mental patient.