Pacemakers and Defibrillators: What’s the Difference?

Pacemakers and defibrillators both help correct abnormal heart rhythms — but they do it in different ways. Pacemakers keep your heart beating at a steady pace, while implantable cardioverter defibrillators (ICDs) deliver a life-saving shock when your heart needs it.

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If you or a loved one has been told you may need one of the devices, it’s completely normal to feel unsure or even overwhelmed. You probably have questions, too, like why they might be used and how exactly they work.

We asked cardiac electrophysiologist Niraj Varma, MD, to explain.

What do pacemakers and defibrillators do?

Pacemaker vs. defibrillator, what they both do for heart rhythm problems

Your heart relies on precisely timed electrical signals to beat steadily. When those signals get disrupted, it can cause your heart to beat too slowly, too quickly or erratically. This can lead to symptoms like dizziness and fainting. Or in extreme cases, sudden cardiac arrest.

Pacemakers and ICDs both address those types of issues, just in different ways.

“People often confuse pacemakers and defibrillators,” notes Dr. Varma. “A pacemaker keeps your heart from going too slow. A defibrillator is there to step in when your heart’s rhythm becomes dangerously fast or chaotic.”

Let’s break that down.

Explaining how pacemakers work

A pacemaker is a small device that sends gentle electrical pulses to keep your heart beating steadily. It connects to your heart with thin wires (called leads) and sits just under the skin near your collarbone.

When your heartbeat slows down or becomes irregular, the pacemaker sends a mild electrical pulse to help it beat at a steady pace — like a metronome guiding your heart. You won’t feel this electrical pulse.

Pacemakers are often used for:

Bradycardia (a slow heart rate)
Heart block (when electrical signals are delayed or blocked between chambers)

Left untreated, these conditions can cause fatigue, lightheadedness or fainting. A pacemaker can correct those symptoms and help restore energy and improve quality of life, says Dr. Varma. A pacemaker may also extend lifespan.

Pacemaker surgery is typically done under local anesthesia with sedation. Your healthcare provider makes a small incision near your collarbone, then threads the leads through a vein into your heart. Most people go home the same day or the next day.

Explaining how defibrillators work

An implantable cardioverter defibrillator (ICD) is also a small device placed under your skin and connected to your heart with thin wires. In that regard, it’s very similar to a pacemaker. Some types of ICD have wires under the skin that don’t need to travel through the veins to your heart.

But an ICD monitors your heart for dangerously fast rhythms. If your heart starts racing or beating erratically, the defibrillator may deliver a quick shock to reset your rhythm. Think of it as an emergency responder, always on standby inside your chest.

ICDs address issues like:

Some people don’t feel an ICD shock at all. Others describe it as surprising but brief. Either way, the goal is the same: Saving your life.

Surgery to implant an ICD is the same as what’s done with a pacemaker, with a similar recovery.

Is one device for more serious heart issues?

A defibrillator is typically used for more serious or potentially life-threatening rhythm problems. A pacemaker is used for rhythms that are slow or irregular, but that aren’t immediately dangerous — though that doesn’t mean it’s not vital.

“Both devices are critical tools,” states Dr. Varma. “One isn’t better than the other. It’s about using the right tool for the specific rhythm problem we’re treating.”

To decide which device is right for you, your cardiologist will consider:

The type of rhythm abnormality you have
Your symptoms and health history
Your risk of serious arrhythmias

Can someone have both a pacemaker and a defibrillator?

Yes, and many people do. “Some people need help with both slow and fast heart rhythms,” Dr. Varma explains. “That’s where combination devices come in.”

Combination devices are essentially defibrillators with built-in pacemaker functions. They can serve double duty by pacing your heart when it’s too slow or delivering a shock if the rhythm becomes dangerously fast.