What Is an ICD? A Complete Guide to Implantable Cardioverter-Defibrillators

An ICD (Implantable Cardioverter-Defibrillator) is a life-saving heart device used to treat dangerous heart rhythm disturbances.Many people have heard the term ICD, but find it difficult to understand what it actually does, how it works, and what it’s like to live with an ICD.

This article explains what an ICD is and is not, how it works in everyday life, and why some patients need one.

ICD

What Does ICD Mean?

ICD stands for Implantable Cardioverter-Defibrillator.

In simple terms: an internal defibrillator that is surgically implanted in the body.

An ICD continuously monitors the heart rhythm and can intervene automatically if the heart develops a dangerously fast or chaotic rhythm.

ICD vs Pacemaker – What’s the Difference?

This is one of the most common questions patients ask.

Pacemaker

• Helps the heart if the heart rate is too slow

ICD

• Can do everything a pacemaker does

• Plus it can stop life-threatening fast heart rhythms

In other words, an ICD includes pacemaker functionality, but also provides life-saving protection against sudden cardiac arrest.

ICD vs External Defibrillator (AED)

It is also important to distinguish between an ICD and an external defibrillator.

AED (Automated External Defibrillator)

• Located on walls in public places

• Used by healthcare professionals or bystanders

• Only works when someone actively uses it during cardiac arrest

  
  

ICD

• Implanted inside the body

• Works automatically

• Protects the patient 24/7

  
  

An ICD is not an emergency button. It is always on duty, even when you are asleep.

How Does an ICD Work?

An ICD continuously monitors your heart rhythm.If it detects a dangerous rhythm, it can treat it in two main ways:

1. Painless Anti-Tachycardia Pacing (ATP)

The ICD may deliver rapid, small electrical impulses to stop the abnormal rhythm.Most patients do not feel this at all.

2. Electrical Shock (Defibrillation)

If the rhythm is very dangerous or does not stop after ATP, the ICD delivers a strong, brief shock to restore a normal rhythm.

The shock can be uncomfortable, but it lasts only a moment - and it saves lives.

What Does an ICD Shock Feel Like?

Patients often describe an ICD shock as:

• a strong thump in the chest

• a sudden kick from inside

It can be frightening, but it means the ICD did exactly what it was designed to do.

In some cases, patients may lose consciousness just before the shock, and then do not feel it at all.

If you receive an ICD shock, you should contact your doctor for evaluation.

Why Do Some Patients Need an ICD?

You may be recommended an ICD if you:

• have had life-threatening heart rhythm disturbances

• have a high risk of sudden cardiac arrest

• have heart failure or an inherited heart condition

The primary goal of ICD therapy is to prevent sudden cardiac death.

What Is It Like to Live With an ICD?

Most people live a normal, active life with an ICD.

In general, you can:

• work

• exercise (with some individual adjustments)

• travel

• use mobile phones and everyday electronics

  
  

The ICD works silently in the background.Most patients do not notice it in daily life.

Follow-Up and Monitoring With an ICD

Regular follow-up is an important part of living with an ICD.

Monitoring usually includes:

• in-hospital checkups

• remote monitoring from home

  
  

Your doctor will check:

• battery status

• leads (wires)

• recorded or treated heart rhythm disturbances

This follow-up provides safety and reassurance.

Are There Different Types of ICDs?

Yes, there are several types of implantable defibrillators.

Transvenous ICD

• Traditional ICD with leads placed inside the heart through blood vessels

  
  

Subcutaneous ICD (S-ICD)

• Placed under the skin

• No leads inside the heart

  
  

New Extravascular ICD Systems

• Combine features from both systems

• Designed to reduce long-term complications

  
  

The most suitable type is chosen individually, based on medical needs.

Possible Risks and Concerns With an ICD

Most patients experience few problems, but it is important to be aware of potential issues:

• risk of infection after implantation

• shocks that may be physically or emotionally distressing

• lead damage over time

• anxiety related to fear of shocks

• rare inappropriate treatment of non-life-threatening rhythms

  
  

How Long Does an ICD Battery Last?

An ICD battery typically lasts around 10 years, depending on how often it is used.

When the battery becomes low:

• the ICD generator is replaced

• existing leads are usually reused

Always discuss concerns with your doctor.

Summary - Key Points About ICDs

• An ICD is an implantable defibrillator

• It can save your life during dangerous heart rhythms

• It also functions as a pacemaker

• Most people live a normal life with an ICD

• Regular follow-up ensures safety and peace of mind

  
  

ICDs are among the most effective treatments we have to protect against sudden cardiac arrest.

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FAQ: ICD (Implantable Cardioverter-Defibrillator)

What is an ICD?

An ICD (Implantable Cardioverter-Defibrillator) is a device implanted under the skin that continuously monitors heart rhythm and can treat life-threatening fast rhythms by pacing or delivering a shock. It helps prevent sudden cardiac death in selected patients.

What does ICD stand for?

ICD stands for Implantable Cardioverter-Defibrillator.

Is an ICD the same as a pacemaker?

No. A pacemaker mainly treats slow heart rates. An ICD can often provide pacemaker functions as well, but it also detects and treats dangerous fast rhythms that can lead to cardiac arrest.

What is the difference between an ICD and an AED?

An AED (automated external defibrillator) is an external device used during an emergency by a bystander or healthcare professional. An ICD is implanted inside the body and works automatically 24/7 without someone needing to activate it.

How does an ICD work?

An ICD monitors the heart rhythm continuously. If it detects a dangerous rhythm, it may treat it with painless rapid pacing (anti-tachycardia pacing) or, if needed, deliver a brief shock to restore a normal rhythm.

What does an ICD shock feel like?

People often describe an ICD shock as a strong thump or a sudden kick in the chest. It can feel scary, but the shock is brief and is intended to stop a dangerous rhythm. Some people may pass out just before a shock and not feel it.

What should I do if I receive an ICD shock?

If you receive an ICD shock, you should contact your doctor or device clinic for evaluation and guidance. If you feel unwell, have repeated shocks, chest pain, or severe symptoms, seek urgent medical care.

Why do patients get an ICD?

An ICD may be recommended for people who have had life-threatening ventricular arrhythmias, who are at high risk of sudden cardiac arrest, or who have certain conditions such as heart failure or inherited heart diseases where risk is increased.

Can you live a normal life with an ICD?

Many people live a normal, active life with an ICD. Most can work, travel, and exercise with individual guidance. The device typically works in the background and is not noticeable day to day.

Are phones and electronics safe with an ICD?

In general, everyday electronics and mobile phones are safe to use with an ICD. Follow your device clinic’s practical advice about keeping strong magnets or certain devices at an appropriate distance.

How often do ICDs need follow-up?

ICDs are followed regularly through in-clinic visits and often remote monitoring from home. Your care team checks battery status, leads, and whether the ICD has detected or treated abnormal rhythms.

What types of ICDs are available?

Common types include transvenous ICDs (leads placed through veins into the heart) and subcutaneous ICDs (S-ICD) placed under the skin without leads inside the heart. Newer extravascular systems aim to combine benefits of both approaches. The best choice depends on individual factors.

What are possible risks or downsides of an ICD?

Potential issues can include infection after implantation, distress from shocks, lead problems over time, anxiety related to fear of shocks, and rare inappropriate treatment of rhythms that are not life-threatening. Your doctor can explain your individual risk profile.

How long does an ICD battery last?

ICD batteries often last around 10 years, depending on how frequently the device delivers pacing or therapies. When the battery is low, the generator is replaced; existing leads can often be reused if they are functioning well.