Although the provocation defence was abolished by the Government in 2009, it could potentially have been available to Hieatt because the offence took place before the law change.
However, Justice John Priestly said the circumstances of the killing were not consistent with provocation and so he did not allow the jury to consider it.
He sentenced Hieatt to life imprisonment with a minimum non-parole period of 11 years.
Hieatt lodged an appeal, with his lawyer Peter Kaye arguing that Justice Priestley had erred his decision not to make the provocation defence available.
Mr Kaye argued that Ms Viakaew's verbal attacks on Hieatt and him not being able to stand her shouting anymore could be seen as provocation.
Also, her repeating the words "you want to kill me" before he strangled her to death was provocative, Mr Kaye submitted.
However, in its decision released today, the Court of Appeal agreed with Justice Priestley that the words and actions of Ms Viakaew before her death would not have caused the ordinary New Zealander to lose the power of self-control.
"The accused's narrative, which he gave to the jury in a quiet, deliberate, and chilling fashion, shows that the accused was very much in control," Justice Priestley said in sentencing.
"He wanted to shut the deceased up. First, he retreated into his room to find some masking tape. Then he assaulted the deceased by placing the masking tape over her mouth. When she retaliated by ripping the tape off and scratching him, he punched her on a number of occasions causing her to bleed. From then on, his calculated strategy was to try to shut the deceased up and to ensure that she would not seek help from the neighbours or call the police.
"It would, in my judgement, be idle, and totally contrary to the situations in which the partial defence of provocation was designed to operate and indeed has operated in past homicides, to say that in this situation, where the accused was the assaulter and the aggressor, that any subsequent acts or words of the deceased be provocative."
Mr Kaye further submitted that Hieatt should have been given a 10 year minimum non-parole period, given this would have been more in-line with similar cases.
However, the Court of Appeal said these cases were not comparable and dismissed the appeal.