A pacemaker is not classified as a specific ventricular assist device instead it is a device that is implanted into the chest and used to treat arrhythmias (abnormal heart rhythms) such as atrial fibrillation and heart block. The pacemaker is implanted under the skin and a wire is threaded through to the heart. Leads connect to the pulse generator part of the pacemaker and to the chamber or chambers of the heart where it is needed. A pacemaker is designed to correct problems with the electrical impulses of the heart and is able to be used as a backup generator.