If a heart beats too slowly, the pacemaker will use electrical signals to help set a normal rate.

VOA: special.2010.06.02

Some devices include a defibrillator, which gives a shock if the heart beats too fast.

VOA: special.2010.06.02

Some pacemakers include a defibrillator, which gives a shock if the heart beats too fast.

VOA: special.2010.06.29

We leave you with Miley Cyrus performing "My Heart Beats for Love,"

VOA: special.2010.08.06