Denton A. Cooley is shown in 1999 next to a display at the Texas Heart Institute in Houston. (David J. Phillip/AP)

Denton A. Cooley, a heart surgeon who performed the first successful heart transplant in the United States and helped make many other advances in cardiac surgery, including valve replacement, bypass operations, removing aortic aneurysms and the development of heart-lung machines, died Nov. 15 at his home in Houston. He was 96.

His death was announced by Texas Heart Institute, which he founded in 1962, and where he continued to work until earlier this week. The cause was not disclosed.

As early as the 1940s, when he was a medical student at Johns Hopkins University, Dr. Cooley built a reputation as one of the most innovative and productive surgeons of his time. He assisted on the first “blue baby” operation in 1944, correcting once-fatal congenital heart defects in infants, and over the course of his career performed or supervised more than 100,000 surgeries.

In the 1950s, he collaborated with another Houston heart surgeon, Michael DeBakey, developing techniques in heart-bypass surgery and working on a heart-lung bypass machine, which could keep patients alive during open-heart surgery. Working under the older DeBakey at the Baylor College of Medicine in Houston, Dr. Cooley helped develop surgical methods to repair aortic aneurysms.

But the two strong-willed surgeons had an acrimonious split in 1969, after Dr. Cooley performed the world’s first transplant using an artificial heart. DeBakey said the device had been developed by his own team and was, in essence, stolen by Dr. Cooley to promote his glory and in violation of medical ethics.

Denton A. Cooley holds up a Jarvick 7 heart pump model at a news conference in 1989, while discussing the 20-year anniversary of the first implant of an artificial heart in a man. (Pam MacDonald/AP)

The resulting quarrel became so public and rancorous that it was featured on the cover of Life magazine under the headline “A Bitter Feud.”

What no one could dispute, however, was Dr. Cooley’s sure-handed proficiency in the operating room. The 6-foot-3 onetime college basketball star improved his dexterity and precision by tying surgical knots in a small matchbox. His skill led to an early specialty in cardiovascular surgery on children.

“In many people’s opinions, including mine, he is the finest heart surgeon to ever live,” James Willerson, Dr. Cooley’s successor as president of the Texas Heart Institute, told the Houston Chronicle. “He was the most rapid. Had the finest hands.”

As the rivalry between DeBakey and Dr. Cooley continued to fester, DeBakey remained affiliated with Baylor and Houston Methodist Hospital, while Dr. Cooley ran the Texas Heart Institute at St. Luke’s Episcopal Hospital. The two facilities were within a few hundred feet of each other and provided an unexpected benefit to heart patients.

“The two [doctors] transformed what had been a medical backwater into the cardiovascular surgery center of the world,” Thomas Thompson wrote in the 1971 book “Hearts: Of Surgeons and Transplants, Miracles and Disasters Along the Cardiac Frontier.”

During the 20th century, heart disease emerged as the leading cause of death throughout the developing world. Advances in treatment and surgical methods were at the forefront of medicine across the globe during the 1960s, culminating in the world’s first successful heart transplant, by South African doctor Christiaan Barnard, in December 1967.

When Dr. Cooley sent him a congratulatory telegram, he couldn’t resist adding a boastful twist: “Congratulations on your first transplant, Chris. I will be reporting my first hundred soon.”

After studying Barnard’s surgical technique, Dr. Cooley completed the first successful U.S. heart transplant on May 3, 1968, giving a 47-year-old man a heart from a 15-year-old girl who had committed suicide. The patient survived for 204 days. Over the next year, Dr. Cooley performed 22 heart transplants.

Even as Dr. Cooley and other surgeons opened new medical possibilities, religious leaders and medical ethicists pondered the morality of the transplant procedure. The debate revolved around whether death occurred when the brain stopped functioning or when the heart stopped beating.

“I look upon the heart only as a pump, a servant of the brain,” Dr. Cooley told Life magazine in 1968. “Once the brain is gone, the heart becomes unemployed. Then we must find it other employment.”

The DeBakey imbroglio was in part rooted in this ethical dilemma. In 1969, Dr. Cooley sought to use an artificial heart as a temporary measure while the patient awaited a human heart from a donor. It was never clear how Dr. Cooley obtained the artificial heart developed by DeBakey, but a member of Dr. Cooley’s medical team had once worked for DeBakey.

At any rate, the episode put federal grants at risk and resulted in Dr. Cooley’s censure by the American College of Physicians. DeBakey said his onetime colleague “disappointed me with his ethics” and that his actions were “a little childish.”

They didn’t speak for almost 40 years before they reconciled in 2007, one year before DeBakey’s death at 99.

Denton Arthur Cooley was born Aug. 22, 1920, in Houston, where his father was a dentist and real estate investor.

Dr. Cooley studied zoology at the University of Texas at Austin, where he starred on the basketball team and graduated in 1941. He received a medical degree from Johns Hopkins University three years later.

He assisted his mentor, Alfred Blalock, in the first “blue baby” operation in 1944, correcting a heart defect that prevented an infant from obtaining a sufficient amount of oxygen. The experience led Dr. Cooley to his specialty as a heart surgeon. He later performed a successful “blue baby” procedure on the child of a Houston war hero, earning plaudits in his home town.

Dr. Cooley served as an Army surgeon in Austria from 1946 to 1948 before continuing his medical training at Johns Hopkins and in London. He returned to Houston in 1951.

Working with DeBakey, he helped develop a heart-lung machine — using parts from a coffee pot — to maintain the circulatory functions of the heart during surgery. Dr. Cooley became known for his work on infants and for his skill at replacing damaged heart valves and correcting aneurysms in arterial walls.

As the use of artificial hearts declined in the 1970s, Dr. Cooley focused more on coronary bypass procedures. He supervised as many as 30 operations a day and, for a time, his Texas Heart Institute reportedly performed one-tenth of all open-heart surgeries in the United States. He performed his final operation when he was 87.

Among those who observed Dr. Cooley in the operating theater was Barnard, who in his book “One Life” (1970) described one operation as “the most beautiful surgery I had ever seen. . . . Every movement had a purpose and achieved its aim. Where most surgeons would take three hours, he could do the same operation in one hour.”

Dr. Cooley’s wife of 67 years, the former Louise Thomas, died in October. A daughter, Florence Cooley, committed suicide in 1985. Survivors include four daughters, Mary Craddock, Susan Cooley, Louise Cooley Davis and Helen Fraser; 16 grandchildren; and 17 great-grandchildren.

Dr. Cooley, who made as much as $10 million a year in his medical practice, filed for bankruptcy protection in 1988 after failed real estate investments. He paid back $85 million to his creditors.

He received the Presidential Medal of Freedom, the nation’s highest civilian honor, in 1984. He was the author of eight medical textbooks and more than 1,000 articles and published a memoir, “100,000 Hearts,” in 2012. Among his avocations, he played the upright bass in the Heartbeats, a swing band made up of physicians.

Like many surgeons, Dr. Cooley was brimming with self-confidence and was not known for false modesty. When he was a defendant in a medical liability trial, a lawyer asked Dr. Cooley if he thought of himself as the world’s best heart surgeon.

“Yes,” he said.

“Don’t you think that’s being rather immodest?” the lawyer asked.

“Perhaps,” Dr. Cooley replied. “But remember, I’m under oath.”