An initial post-mortem examination held in Thailand found Kitchen had died from congestive heart failure.
The inquest earlier was told he had undergone an operation to fit stents to his right coronary artery in April 2019.
However, a review in October that year found he had returned to “normal exercise capacity”, a statement from his GP said.
Dr Edward Sheffield, who performed an additional post-mortem examination on Kitchen’s body in Bristol, said his cause of death had been cardiac failure due to coronary artery atheroma and the physiological effects of turbulence.
A report into the incident, which Harrowing partially read to the inquest, said 56 people had been seriously injured, 23 suffered minor injuries and one man – Kitchen – had died.
“The aircraft was cruising at 37,000ft (11277.6m) when it was approaching the west coast of south-western Myanmar.
“At 07:49 GMT, the aircraft flew past a waypoint when the aircraft experienced severe turbulence.
“By 07:53, the aircraft had stabilised,” the report said.
The crew reported the severe turbulence and made a Mayday call at 08:01 with a request to divert to Bangkok.
The plane landed there at 08:45 and was met by medical personnel.