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

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.

Tennessee is scheduled to execute death row inmate Byron Black on Tuesday morning despite concerns his heart implant will shock him repeatedly during the lethal injection. Black, 69, is one of the longest residents on the state's death row.