Single wire? I think that means it’s strictly a defibrillator without pace making ability. I could be wrong. Hopefully he doesn’t get shocked - it hurts like hell (but it’s worth it if it saves you). Expect the battery to last about 7-10 years.
My understanding is the single wire is only needed for a chamber that has issues. My dad has some hardening of the the heart muscle and takes Vyndamax. It took the doctors several years to diagnose the problem