Defibrillators and pacemakers are two types of implantable medical devices. Both devices can be used to help with arrhythmia — a condition where the heart beats too fast, too slowly, or irregularly.

A pacemaker uses steady, low-energy electric shocks to help the heart maintain a normal beat or rhythm. Meanwhile, a defibrillator uses a low- or high-energy electric shock to help prevent or stop a potentially dangerous arrhythmia.

Continue reading to get further information about these devices, how they’re placed, and more.

A defibrillator is a medical device that uses a shock of electricity to help restore a normal heart rate. They can also be used to restore heart rate if an individual suddenly goes into cardiac arrest.

There are several types of defibrillators:

  • Implantable cardioverter defibrillators (ICD). An ICD is surgically implanted inside your body. We’ll be focusing on ICDs throughout this article.
  • Wearable cardioverter defibrillators (WCD). A WCD is worn on the body as a vest under the clothes. It has sensors that attach to your skin to monitor heart rhythm.
  • Automated external defibrillators (AED). You can find AEDs throughout various public spaces. They can be used in emergencies where someone has experienced a cardiac arrest.

Defibrillators detect your heart’s rhythm. In an ICD, a generator containing a battery and circuitry is attached to wired sensors. These sensors rest on or inside your heart and help the ICD to determine the intensity of the shock to deliver.

A low-energy shock will speed up or slow down your heart rate. In some situations, a high-energy shock is needed, such as when:

  • a low-energy shock isn’t effective
  • the heart is beating very quickly or irregularly
  • the ventricles begin to fibrillate (quiver)

Defibrillators like ICDs and WCDs can also record your heart rhythms. This can help your doctor understand how well your defibrillator is working to help prevent potentially dangerous arrhythmias.

An ICD is often used to prevent or correct life threatening arrhythmias. An arrhythmia is where your heart can beat too fast, too slowly, or at an irregular rhythm. There are several types of arrhythmias.

Severe arrhythmias can cause serious, potentially fatal, complications, such as sudden cardiac arrest. This is where the heart stops suddenly due to the effects of arrhythmia.

Most of the time, your doctor will recommend an ICD if you’re at risk for experiencing sudden cardiac arrest due to a life threatening arrhythmia. Some examples of when an ICD may be used are if you have:

  • previously experienced sudden cardiac arrest
  • developed arrhythmia after having a heart attack
  • arrhythmia that happens due to a genetic condition or a structural problem with the heart
  • issues with your heart’s electrical signaling pathways

ICDs are implanted through a minor surgical procedure. This is typically performed in a hospital using local anesthesia and takes a few hours to complete.

An incision is made in order to place the ICD generator. In most people, this is placed under the sternum (breastbone) or along your ribs. In infants, it may be placed in the abdomen.

Your doctor will use imaging to help them properly place the ICD sensors. These can either be placed along the breastbone or threaded through your blood vessels and into your heart. Some newer types may be threaded under the skin.

Once the ICD is in place, your doctor will test it to make sure that it’s working properly before closing the incision. You may be able to leave the hospital after the medications from your surgery wear off.

While an ICD can help to prevent or correct dangerous heart rhythms, there are also some associated risks. Many of these are related to the implantation procedure itself and can include:

  • swelling or bruising in the area where the ICD was placed
  • increased bleeding around the implantation site or the heart
  • blood clots
  • infection around the surgical site
  • damage to the heart, surrounding blood vessels, or nerves
  • collapsed lung (pneumothorax)
  • an allergic reaction to the medications used during the surgery

Additionally, an ICD may deliver shocks at the wrong time or at too strong an intensity. Make an appointment with your doctor if you notice symptoms like:

In many cases, your doctor can help fix problems with an ICD by adjusting the device’s programming. However, when this isn’t successful, the ICD may need to be replaced.

Having an ICD can significantly improve survival over a period of years. Let’s take a look at a snapshot of some research into this topic.

A 2017 study evaluated 12,420 people on Medicare who had received an ICD to prevent sudden cardiac arrest. Participants were followed for a period of 2 years.

Overall, about 4 out of 5 participants survived at least 2 years. However, researchers did note that significant medical care was required after implantation for many participants, particularly those who were older.

A 2020 study followed its participants for even longer. It assessed the long-term outcomes of 1,855 people with heart failure who received a placebo, the arrhythmia drug amiodarone, or an ICD.

A previous follow-up at a median of about 4 years (45.5 months) had found that the ICD reduced death from any cause by 23 percent. The median follow-up time for this new analysis was extended to 11 years. Researchers found that:

  • People who received an ICD had continued improved long-term survival at 11 years compared to those who received a placebo.
  • The most significant benefit of an ICD was observed over a period of 6 years after implantation. After this period, no additional survival benefit was found.
  • The benefit of an ICD varied by heart failure cause, with individuals with mild heart failure (class II) symptoms or ischemic heart failure receiving the most benefit from an ICD at 11 years.

A pacemaker works to help keep your heart beating at a normal rate and rhythm. It does this by sending steady, low-energy electric shocks to your heart. The speed at which these shocks are sent out is calling the pacing rate.

Like an ICD, a pacemaker has sensors that track your heart rhythm and respond accordingly. For example, if a pacemaker senses that the heart is beating too slowly, it will send electric shocks at a steady rate to help return it back to normal.

A traditional pacemaker uses wires to deliver shocks and consists of three parts:

  • a generator that contains the device’s battery and circuitry
  • one or more wires, called leads, that typically run through your veins and carry the electric shock to your heart
  • electrodes that work to sense your heart’s rate and rhythm and deliver the electric shocks when necessary

There are a few different types of pacemakers. The type you’re recommended depends on your specific condition:

  • Single-lead. Single-lead pacemakers have one lead that can be placed into either the right atrium or right ventricle of the heart. You may also see these called single-chamber pacemakers.
  • Double-lead. Double-lead pacemakers have two leads that are placed in the right atrium and the right ventricle. They’re also called double-chamber pacemakers.
  • Biventricular. A biventricular pacemaker has three leads connected to the right atrium, right ventricle, and left ventricle. This helps coordinate signaling between both ventricles. A biventricular pacemaker is also called a cardiac resynchronization therapy (CRT) device.

Wireless pacemakers are available as well. These are much smaller, about the size of a large pill, and don’t have leads. They’re placed into a chamber of your heart and send electric shocks to the right ventricle.

Pacemakers can also record and send data to your doctor. Your doctor can use this to monitor how your pacemaker is working for you. It can also inform them if they need to adjust your pacemaker’s programming.

Similar to ICDs, pacemakers may be used to treat arrhythmia. They’re often recommended when your heart rate is too slow (bradycardia) or if it frequently pauses. They can be used for other types of arrhythmias as well.

A pacemaker can help the chambers of your heart to better beat in sync. This in turn helps your heart to pump blood more effectively.

Some common causes of arrhythmia that may necessitate a pacemaker include:

  • certain structural problems in your heart
  • issues with your heart’s electrical signaling pathways
  • heart attack
  • having specific types of muscular dystrophy

Those with heart failure, cardiomyopathy, or awaiting heart transplant will likely receive an ICD. Newer models of ICDs may include a pacemaker function.

To place a pacemaker, your doctor uses echocardiography or X-rays to help them thread the leads through your veins so they can reach the chambers of the heart. Veins in the neck, chest, or thigh may be used for this purpose.

When the leads are placed, the doctor will make an incision in your chest or abdomen. The pacemaker generator will be slipped into this incision so it’s located just underneath your skin.

After the leads are connected to the generator, your doctor will test the pacemaker to ensure that it’s working properly. Then, they’ll close up the incision.

The entire placement procedure takes a few hours and can typically be done under local anesthesia. You may need to stay at the hospital for a few hours or overnight before returning home.

Similar to ICD placement, there is some potential for complications during or after pacemaker placement. Many of these occur only rarely and can include:

  • shoulder pain or discomfort
  • blood clots
  • hematoma
  • infection around the pacemaker site
  • formation of scar tissue around the device
  • displaced leads that may poke heart muscle
  • stimulation of muscles other than the heart
  • stimulation of only one ventricle (pacemaker syndrome), which causes symptoms like:
  • fluid or air that becomes trapped around the lungs (pleural disorder)
  • collapsed lung (pneumothorax)
  • fluid collecting around the heart (pericarditis)
  • an allergic reaction to the medications used during the placement procedure

It’s also possible for your pacemaker to malfunction or for one of the leads to move out of place. While some malfunctions can be fixed by reprogramming the pacemaker, sometimes part or all of the device may need to be replaced.

Be sure to see your doctor if you begin to have symptoms that indicate your pacemaker may not be working as it should, such as:

  • fatigue
  • shortness of breath
  • dizziness or lightheadedness
  • fainting

Similar to an ICD, pacemaker implantation can improve the outlook. Let’s take a look at some research on this topic.

A 2016 study followed 1,035 individuals with either a single-lead or a double-lead pacemaker over an average of about 4 years (46.5 months). The researchers observed:

  • The annual mortality rate was 4.7 percent and 3.7 percent for single- and double-lead pacemakers, respectively. This wasn’t statistically significant.
  • The annual risk of death due to cardiovascular causes was 1.9 percent and 1.5 percent for single- and double-lead pacemakers, respectively. This also wasn’t statistically significant.
  • While the type of pacing used didn’t impact mortality, some factors that were found to be associated with an increased risk of death included:
    • heart failure

A 2020 study evaluated outcomes in 6,362 people with pacemakers. It found that certain underlying health conditions can influence outlook:

A 2018 study asked individuals with a pacemaker to report their perceived outcome. In total, 342 responses were analyzed. The researchers found:

  • Overall, respondents reported a favorable outcome of pacemaker implantation, with males reporting more satisfaction than females.
  • Most respondents weren’t significantly impacted by pain, sleep troubles, or concerns about their pacemaker malfunctioning.
  • A total of 65 complications requiring surgery were reported over a follow-up period of 5.6 years.

Defibrillators and pacemakers can be used to help with conditions like arrhythmia and heart failure. They’re implanted into your body using a minor surgical procedure.

Defibrillators help to prevent or stop a potentially dangerous arrhythmia that could lead to sudden cardiac arrest. They can use both low- and high-energy electric shocks to achieve this.

Pacemakers work to help your heart maintain a normal beat and rhythm. To accomplish this, they send steady, low-energy electric shocks to your heart.

Having a defibrillator or pacemaker implanted can improve the overall outlook for people with arrhythmia or heart failure. If you have either of these conditions, your doctor will let you know if one of these devices is recommended for you.