For many years after pacemakers were introduced in the 1960s, the only form of the internal device was the single-chamber pacemaker (also referred to as a single-lead or simple pacemaker). A single-chamber pacemaker can be placed in either an atrium or ventricle and stimulates one chamber of the heart.

In the early 1990s, the use of the dual-chamber (or dual-lead) pacemaker became more common. The dual-chamber model sends electrical leads to both an atrium and a ventricle, stimulating both chambers. The dual-chamber model has the ability to synchronize the contraction of the atrium and ventricle to more closely resemble the natural action of the heart, which is why it is often preferred by physicians. However, single-chamber pacemakers have been found to last about six months longer than the more complex models. They are also less expensive and easier to implant and maintain.

Although there is some controversy over whether the newer dual-chamber pacemakers are better than the single-chamber versions, most physicians believe that dual chamber pacemakers are preferred for most patients (except for those in chronic atrial fibrillation).