Tennessee is set to execute death row inmate Byron Black on Tuesday despite raised concerns about his implanted heart device which could cause a "prolonged and torturous execution."

The state executed Black after Tennessee Gov. Bill Lee declined requests from attorneys, advocacy groups and even some Republicans to intervene.

Byron Black, 69, was executed for the 1988 South Nashville murders of his ex-girlfriend Angela Clay and her two daughters Latoya, 9, and Lakeisha, 6.