Dr. Gerard A. Kaiser, a Jackson Memorial Hospital surgeon who pioneered heart surgeries for young children, died Friday morning at the hospital he’d helped lead for almost 40 years. He was 80 years old.

Kaiser became chief of Jackson Memorial’s cardiac and thoracic surgery program in 1971 and led the hospital’s creation of a heart transplant department in the mid-1980s.

“Gerry was really a legend at Jackson,” said Pascal Goldschmidt, dean of the Miller School of Medicine at the University of Miami. “He probably was the most influential physician in Miami over the past 40 years. He has helped tens of thousands of patients, and saved so many lives.”

Kaiser became executive vice president and chief medical officer of the Jackson Health System and senior associate dean of the Miller School. He was the one people called when things went wrong, said Goldschmidt.

“They’d call Gerry in the middle of the night to solve a problem,” Goldschmidt said. “And he would.”

Kaiser’s son Jordan Kaiser, 54, remembers those night calls well.

“The middle-of-the-night calls, patients coming in from other countries — you name it, dad was giving directions,” he said. “It was as if when people called 911, dad was the one who answered.”

Kaiser’s passion for medicine began when he was a boy. His father was also a doctor, and Kaiser followed him on house calls and watched him treat patients in his office in the family’s Brooklyn basement.

He decided to become a doctor, and went to Princeton, and later Columbia University, to prepare.

In his third year of school he met his future wife, Joyce, and they married two years later.

But as Kaiser was preparing to follow in his father’s footsteps and enter medicine, his father died of a heart attack at the age of 52.

That loss, said Jordan Kaiser, determined his father’s career path. “At that time, dad decided to go into heart surgery,” he said. “The inspiration was to not have it kill other people.”

By the time he came to Miami in 1971, Kaiser was performing heart surgeries on children.

It was exacting work, Jordan Kaiser said. Some of the hearts his father operated on were the size of a walnut, and he said he had to “think small” to do it, Jordan Kaiser said.

Kaiser returned to the University of Miami and Jackson Memorial Hospital and founded the Lubb Dubb Club, an organization for children who’d undergone heart surgery.

He focused on his work, and didn’t tell his family about his own health problems because he didn’t want to worry them.

But throughout his life, said Kaiser’s daughter Beth Kaiser, 55, he was there for everybody.

“We shared him with a lot of people,” she said. “And it was our pleasure, because he was needed.”

Gerard A. Kaiser is survived by his wife Joyce Ellen Kaiser, his sister Teri Goldstone and his three children: Beth Kaiser, Jordan Kaiser and Charles Kaiser.

A service will be held for Kaiser at 1 p.m. Sunday at Temple Israel, 137 NE 19th St. in Miami. He will be buried at Mount Nebo Cemetery in Miami immediately after the service.