How do pacemakers work?

Pacemakers consist of two major parts: the generator and the leads.

The generator is essentially a tiny, hermetically sealed computer – along with a battery to run it – housed in a titanium container. Most modern pacemaker generators are roughly the size of a 50-cent piece, and approximately three times as thick. The battery life of most pacemaker generators today is 5 – 8 years.

The lead is a flexible insulated electrical wire. One end is attached to the generator and the other end is passed through a vein into the heart. Most pacemakers today use two leads – one placed in the right atrium and the other in the right ventricle

How it works: The pacemaker leads detect the heart’s own electrical activity (in the right atrium and right ventricle,) and transmit that information to the pacemaker generator. The generator – which, again, is a computer – analyzes the heart’s electrical signals, and uses that information to decide whether, when, and where to pace. If the heart rate becomes too slow, the generator transmits a tiny electrical signal to the heart, thus stimulating the heart muscle to contract. (This is called pacing.)

Pacemakers that have two leads not only keep the heart rate from dropping too low, they can also maintain the optimal coordination between the atria and the ventricles (by pacing the atrium and the ventricle in sequence.)

Thus, pacemakers do not take over the work of the heart – the heart still does its own beating – but instead, pacemakers merely help to regulate the electrical timing of the heart beat.