Learning Center

What's Inside of Me?

Pacemakers. Defibrillators. Leads. ICDs. It can be hard to understand the difference. To help, LifeBeat Online has written some simple explanations for devices and procedures. We'll let you know exactly what they are. We'll also tell you what makes them different from one another.

What is the difference between a pacemaker and an ICD?
Both a pacemaker and an ICD ("implantable cardioverter defibrillator") are devices put into the chest to deliver electrical impulses to the heart. A pacemaker is used when the heart beats too slowly. An ICD is used when the heart beats too quickly.

Impulses in a pacemaker speed up the heart rate. These impulses are mild and patients generally cannot feel them. Pacemakers work or "fire" often and regularly. They are about the size of a matchbook.

Electrical impulses from an ICD slow down the heart. The impulses from an ICD can be intense and may feel like being hit in the chest. But it is good to know that the ICD is treating the problem. ICDs activate as needed and most are about the size of a small pager.

All ICDs these days are dual-function ICDs. That means they are a combination of an ICD and a pacemaker.

What is a pulse generator?
A pulse generator is part of a pacemaker or defibrillator system. The pulse generator is the power source for the system. It is also the "brain" of the device. The doctor programs the pulse generator to monitor a specific heart problem.

The pulse generator monitors the heart. It determines if the heart is beating too fast or too slow. Then, when needed, it sends an electric impulse to the heart through the leads to speed up or slow down the heart.

What is a lead?
A lead is a wire that connects a pulse generator to either the surface or the inside of the heart. Leads carry electrical signals between the heart and the pulse generator.

What's the difference between an angioplasty and a stent?
An angioplasty is a way to widen an artery that is narrowed or blocked by plaque. This procedure can be done without major surgery. A tiny balloon is passed into a blocked area of the artery. When the balloon is inflated, it presses the plaque against the blood vessel wall. This allows the blood to flow freely again.

A stent is a metal mesh tube that can be put into the artery during angioplasty. The stent remains in the artery. It helps keep the artery open. This allows the blood to flow freely.

You can also read findings from a recent breakthrough study about angioplasty and stents in Help for Heart Attack Survivors.

We hope that these explanations have been helpful. If you want to know more about any of the topics we've covered, take a look at the links below. And don't be afraid to ask your doctor to help you understand.

< Back to previous articles