Dr. Naip Tuna had a love affair with hearts. For decades, his patients at the University of Minnesota Medical Center entrusted him with theirs. In return, Tuna dedicated his life to studying the body's central organ and diagnosing tricky cases.

The University of Minnesota cardiologist, professor and general doctor kept working until he was 90. He died June 23 at 95 in a later stage of heart disease of his own.

Tuna, of Edina, lived and breathed his career. He'd thumb through medical magazines in bed. He'd pop into hallways to ask whether colleagues had read a recent medical journal study. As his illness progressed, he diligently monitored his own health.

"He was his own last patient," said his daughter, Nilgün Tuna of St. Paul.

Tuna was born in Romania and spent his childhood there, Nilgün said. He sidestepped conscription on the Nazi and Communist sides of World War II by fleeing to Istanbul. There, he scored a seat in the city's top high school and graduated from Istanbul Medical School.

A college friend introduced Tuna to his future wife, Türkân, on a summer trip. The two wed in 1949.

A medical fellowship took him westward to the United States. Tuna moved to Kentucky in the early 1950s before landing a spot at the University of Minnesota's medical school for his Ph.D.

That era was a heyday for cardiology, especially in the Twin Cities. The University of Minnesota pioneered the first open-heart surgery and created the first successful heart-lung machine, which keeps blood circulating during surgery. Tuna was thrust in the middle of it all.

He became an expert in a then-emerging field of electrocardiography, what doctors use to track the heart's electrical impulses and examine irregularities. He also did early research on cholesterol and its link to heart disease.

"His work was his hobby," said Dr. Robert Bache, a retired cardiologist who also worked in the U's cardiovascular division. Tuna's duties were threefold: teach, research and treat patients.

The cardiologist had an agreeable demeanor, "kind of like a teddy bear," said Rosie Robinson, a senior office supervisor at the University of Minnesota cardiology division.

Tuna was a kind teacher, said Bache, who had interned at the U hospital in the 1960s. "He had great respect for individuals, he had great respect for knowledge and for truth," he said. "That really is what drove his teaching."

Complicated cases were often referred to the university, Nilgün said, and Tuna would throw himself into ones that would stump other doctors. Once, a woman had complained of fatigue, and Tuna discovered an underlying cell problem. Another time, an open-heart surgery patient had chest pain. Doctors were ready to open him up, but Tuna discovered the problem was a wire poking him, and not a heart issue.

Bache took over some of Tuna's clients when he retired and said they'd always ask about their former doctor. His honors included a Lifetime Education Award from the university's cardiovascular division. He also was published in the New England Journal of Medicine.

When his wife died in 2002, Tuna immersed himself even more into his work at the U. His daughter said that he knew his condition wouldn't improve and he was ready to die. He was then back in a hospital bed in the U's cardiology division — the same hallways he'd walked while caring for patients himself.

In addition to his daughter, Tuna is survived by his son, Ishik Tuna of Portland, Ore., two sisters and four grandchildren. Services have been held.

Beena Raghavendran • 612-673-4569