(CNN) -- Former U.S. Secretary of State Henry Kissinger underwent heart surgery to replace an aortic valve at a New York hospital Tuesday, according to a hospital statement.
Kissinger, 91, served as national security adviser and secretary of state during the Nixon administration. He remained secretary of state through the short Ford presidency and held the adviser position for part of that administration.
"He is resting comfortably," a New York-Presbyterian Hospital statement said.
Kissinger has a history of heart trouble, including undergoing a triple coronary bypass in 1982 and an angioplasty procedure in 2005.
Born in Germany, he came to the United States with his family to escape Hitler's Nazi regime in 1938. Kissinger became a U.S. citizen and joined the U.S. Army in 1943.
He joined the Harvard University faculty in 1954, but he soon began consulting with the U.S. State Department and Pentagon on national security matters.
Nixon took Kissinger with him to the White House in 1969 to serve as his national security adviser, a job that included the initiation of Strategic Arms Limitation Talks (SALT) with the Soviet Union.
Time magazine named Nixon and Kissinger as the magazine's Men of the Year for 1972.
Kissinger shared the 1973 Nobel Peace Prize with Vietnamese revolutionary Le Duc Tho for helping establish a cease-fire in Vietnam. Le Duc Tho declined the honor.