MIAMI – Inside the corridors of Mount Sinai Medical Center, he was known as “Wild Bill,” courtesy of the custom-made cowboy boots he always wore.

Dr. William Zachary Yahr was also known for his contribution to developing the intra-aortic balloon used to help patients after cardiac surgery.

Yahr, 74, died at his Miami Shores home Thursday from brain cancer, just one day after his 99-year-old mother was buried in New York.

“No matter how critical the patient was when he was at the bedside, I just felt so secure and confident with him around because he made decisions on a dime, they were just spot-on,” said Carol Lang, a retired nurse who worked with Yahr for many years.

Born in Brooklyn, N.Y., on March 16, 1937, Yahr attended Dartmouth College and then graduated from Harvard Medical School in 1961. He was a major in the Air Force and worked at Andrews Air Force base during the Vietnam War.

In need of a job, Yahr moved to South Florida in 1970 at the urging of fellow Harvard alumnus Dr. Jack Greenberg. The two had hit it off — both shared a love of cowboy boots — and they continued research on the intra-aortic device and instituted it at Mount Sinai.

In the mid-’60s, Yahr had been part of the team at Maimonides Hospital in New York that developed the pump used on post-operative cardiac patients who were struggling.

“That pump is still one of the main devices we now use,” said Dr. Manuel Sivina, Mount Sinai’s chief of vascular surgery.

Equally comfortable using both his left and right hands, Yahr patented an ambidextrous clamp in 1965, and his research in the use of lasers to aid surgery was highlighted in Life Magazine that same year, said his daughter, Harriette Yahr.

Yahr worked at Mount Sinai from about 1970 to 1995, according to Harriette Yahr. He also worked at Miami Heart Institute and St. Francis Hospital.

“He was very supportive of the nurses, especially his ICU staff,” Lang said.

“There was a commemorative stamp made for nurses years ago and a pin for that stamp. He always wore that pin on the lapel of his lab coat — the nursing pin.”

Former colleagues described Yahr as a bright, meticulous surgeon who worked hard — regularly making hospital rounds at 5:30 a.m.

“He never lost his train of thinking during the operation, he never lost his cool,” Sivina said.

Yahr was also known for his sense of humor and enjoying life. He threw great parties at the family’s home, and he’d invite everyone from the hospital.

When he went to see “Phantom of the Opera” one Halloween with friends, he rented black capes for them to wear to the performance.

Charles Byrd, Yahr’s former surgical partner and also a cowboy-boots wearing doctor, recalls when Yahr — a lover of cars — drove a hearse to work.

“I don’t know where he got it,” Byrd said. “The next day it just appeared in the doctors’ parking lot and we were all like ‘What is that?’ It was almost like a practical joke.”

Yahr, a father of two girls and one boy, was a dedicated father.

Harriette Yahr recalled how her father supported her desire to play football — as an 8-year-old, she was the first girl on a tackle football team at Flamingo Park in Miami Beach. He would leave the hospital to pick her up after football and bring her a Gatorade.

“Dad always supported our highest calling, which for me at the time was playing football with the boys,” she said.

In addition to his daughter Harriette, Yahr is survived by daughter Elizabeth Southard; son Alexander Yahr; brother Peter Yahr; and grandchildren Ashley and Ryan Southard.