_FOR 10 POINTS—_ name
The first ones, powered by mercury-zinc batteries, often failed within two weeks. By 1960, models powered by lithium batteries lasted over a year; in 1972, the first plutonium-powered devices were made available. _FOR 10 POINTS—_ name these devices which take over the normal function of the SA and AV nodes of the heart to ensure regular contraction of cardiac muscles.
The first ones, powered by mercury-zinc batteries, often failed within two weeks.
{pacemaker}s