A man who killed a respected Otago-trained heart surgeon with a single punch has been jailed for manslaughter.

Joseph Esmaili, 24, punched Patrick Pritzwald-Stegmann in the head in May 2017 inside Box Hill Hospital.

The heart surgeon was on his way home after a shift when he saw Esmaili and his friends smoking cigarettes near the hospital entrance.

He was told by Esmaili "you need to suck my d***" and punched once in the head before he fell to the ground and landed hard on a tiled floor.

The 41-year-old was hospitalised for a month before he died.

This morning in the Victorian Supreme Court Judge Elizabeth Hollingworth sentenced Esmaili to 10 years and six months in jail.

Esmaili is the first Victorian to be sentenced under new fatal one-punch laws which carry a minimum jail term of 10 years.

He will not be eligible for parole for 10 years.

Judge Hollingworth said the attack on the surgeon was captured on CCTV cameras and witnessed by hospital staff and visitors.

"Shortly after the exchange outside, you walked back into the hospital and turned left, heading in the direction of public toilets," she said today.

"Mr Pritzwald-Stegmann re-entered the hospital, only a few steps behind you. As he walked towards the reception staff at the front counter, he told them to call security to move the smokers away from the entrance.

"As you walked through the foyer area, you overheard what (he) was saying. You stopped, turned in his direction and called out: "Why don't you go f*** yourself."

The court heard the pair were seen gesturing with their arms in the direction of the exit. They came face-to-face and Pritzwald-Stegmann said Esmaili deliberately spat in his face.

Esmaili walked away towards the toilets but the heart surgeon followed, demanding Esmaili leave the hospital.

Pritzwald-Stegmann dropped his bag.

"Suddenly, without warning, you pulled your right hand out from behind your back and punched him with a clenched fist to the head," Judge Hollingworth said.

"You hit him with sufficient force to knock him unconscious. He fell straight to the floor, without any attempt to break his fall.

"When his head hit the floor, Mr Pritzwald-Stegmann sustained catastrophic brain injuries which led to his eventual death."

The court heard Esmaili left the scene immediately without checking on Pritzwald-Stegmann's welfare.

A jury last year rejected Esmaili's claim he punched the 41-year-old in self-defence.

Judge Hollingworth said Esmaili made the trial process more painful for Mr Pritzwald-Stegmann's family "because you accepted no responsibility".

The court heard Esmaili started abusing drugs from a young age and left school in year 10. He was been unable to hold down steady employment.

On the day of the fatal assault, Esmaili had no used drugs but had been drinking alcohol the night before.

He told investigators he punched the heart surgeon because he was being pressured and "couldn't handle things like that very well".