Mirko Civic, 70, was found unresponsive in bed by another prisoner at Palen Creek Correctional Centre west of Brisbane on September 16, 2018.
A jury had found the Croatia-born electrician guilty of manslaughter in May 2013 after an associate who owed him money died at his residence in an altercation.
The father of four received a recommendation for parole on strict conditions and submitted an application on September 3, 2018 which the board was considering.
Thirteen days later Civic was found in his cell.
Paramedics arrived about 30 minutes later but could not revive Civic.
A police investigation found Civic had died of natural causes and there were no suspicious circumstances.
An autopsy determined Civic's cause of death was a severe coronary artery disease, counsel assisting the coroner Sarah Lane said on Tuesday.
Civic had a history of heart disease and suffered cardiac arrest 10 years before he was imprisoned, the inquest was told.
Ms Lane said an independent medical review of Civic's death noted a failure to provide aspirin or drugs to treat his high blood pressure while in custody for years.
The independent review stated the medical care provided to Civic was of a lesser standard than provided to members of the community, she said.
Queensland Health's Metro South responded, saying Civic had mild blood pressure and it appeared "readily controlled" at Palen Creek while also pointing out that the prisoner had refused to take medication for years, the inquest was told.
Metro South Health said Civic's blood pressure remained "only modestly elevated" until he started taking medication again 15 months before his death.
Cardiology expert Greg Starmer also examined Civic's treatment in prison and described their secondary preventative care as imperfect but acceptable, Ms Lane said.
Dr Starmer said data suggested Civic was "highly likely" to have a heart attack at his age if not sooner despite medical therapy.
Queensland Health's Metro North held its own review and found there was little monitoring of Civic's condition and no long-term management plan in place until he was transferred from Woodford Correctional Centre to Palen Creek.
Woodford Correctional Centre has since adopted a recommendation to implement a primary clinical care manual including blood pressure management guidelines, the inquest heard.
"In my submission the evidence shows Mr Civic's death was due to natural causes and there are no issues to be examined at this inquest," Ms Lane said.
State Coroner Terry Ryan, who presided over the mandatory inquest into the prison death, said he would publish his findings this week but indicated he would be consistent with Ms Lane's submission.
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