Tennessee executed an inmate Tuesday without deactivating his implanted defibrillator, despite uncertainty about whether the device would shock his heart when the lethal chemicals took effect.

Byron Black's execution marked the first time a man has been put to death with a working defibrillator in his chest, experts say.

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."