HOUSTON (AP) — Dr. Michael DeBakey, the world-famous cardiovascular surgeon who pioneered such now-common procedures as bypass surgery and invented a host of devices to help heart patients, has died. He was 99.

DeBakey died Friday night at the Methodist Hospital in Houston from "natural causes," according to a statement issued early Saturday by Baylor College of Medicine and the Methodist Hospital.

DeBakey counted world leaders among his patients and helped turn Baylor from a provincial school into one of the nation's great medical institutions.

"Dr. DeBakey's reputation brought many people into this institution, and he treated them all: heads of state, entertainers, businessmen and presidents, as well as people with no titles and no means," said Ron Girotto, president of the Methodist Hospital System.

While still in medical school in 1932, he invented the roller pump, which became the major component of the heart-lung machine, beginning the era of open-heart surgery. The machine takes over the function of the heart and lungs during surgery.