Learn Indications of Implantable Cardioverter-Defibrillators (ICD)

Medically Reviewed by Dr. Aman Priya Khanna
Written by Sangeeta Sharma, last updated on 14 November 2023
Learn Indications of Implantable Cardioverter-Defibrillators (ICD)

According to the European Society of Cardiology Congress, the success rate of Implantable Cardioverter-Defibrillators (ICDs) is 98.7%. ICDs prevent life-threatening arrhythmias. 

In this blog, we will look into major ICD indications, exploring when and why these devices are recommended. This helps ensure the well-being of people at risk of sudden cardiac events.

Understanding Implantable Cardioverter-Defibrillators (ICDs)

A defibrillator is a heart-saving device that uses an electric charge to bring your heart back to its regular beat. In sudden cardiac arrest (SCA), where the heart rhythm abruptly ceases, prompt use of a defibrillator reestablishes a functional heartbeat. 

SCA is a severe condition, and the timely application of CPR alongside a defibrillator significantly increases the chances of a positive outcome.

It is surgically inserted beneath the skin, usually just below the collarbone. The technique is usually performed in a hospital under local anaesthesia. Leads (thin wires) are put through veins into the heart. The ICD continuously monitors the rhythm of the heart.

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Indications of ICD Insertion

Several implantable cardioverter defibrillator indications are primarily used to prevent sudden cardiac death. This is done by detecting and treating life-threatening arrhythmias. Here are common ICD insertion indications as per the classes:

Class I (Strong Indication):

Class I indications for ICDs include:

  1. Survived Cardiac Arrest: If someone has survived a cardiac arrest caused by unstable sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) after ruling out reversible causes.
  2. Structural Heart Disease: For those with structural heart disease experiencing spontaneous sustained VT, regardless of haemodynamic stability.
  3. Unexplained Fainting: If a person experiences unexplained fainting with significant sustained VT or VF found during an electrophysiology study (EPS).
  4. Ischaemic Cardiomyopathy: For individuals with ischaemic cardiomyopathy, a history of heart attack and a left-ventricular ejection fraction (LVEF) of less than 35% is indicated for an ICD.
  5. Non-Ischaemic Dilated Cardiomyopathy: In cases of non-ischaemic dilated cardiomyopathy with LVEF 35% or less and in patients with moderate and high risk of heart failure.
  6. LV Dysfunction Post Heart Attack: If someone with LV dysfunction due to a prior heart attack, at least 40 days post-heart attack, has an LVEF of less than 30% is recommended for an ICD.
  7. Non-Sustained VT Post Heart Attack: If a person has non-sustained VT due to a previous heart attack, LVEF less than 40%, and sustained VT or inducible VF found during EPS.

Class IIa (Moderate Indication):

Class IIa indications for Implantable Cardioverter-Defibrillators include:

  1. Unexplained Fainting with Heart Issues: If someone faints without a clear reason and has heart problems like non-ischemic dilated cardiomyopathy (DCM) with significant left ventricular (LV) dysfunction.
  2. Sustained VT with Normal Heart Function: Patients with ongoing rapid heartbeats (ventricular tachycardia) but with a normal or nearly normal heart function.
  3. Hypertrophic Cardiomyopathy with Extra Risks: Individuals with hypertrophic cardiomyopathy, a condition where the heart muscle is thickened, have one or more major risk factors for sudden heart problems.
  4. Long QT Syndrome: For people with Long QT syndrome, a condition affecting the electrical activity of the heart. It happens if they experience fainting or ventricular tachycardia to reduce the risk of sudden heart death.
  5. Waiting for Transplantation: If someone is not in the hospital and is waiting for a heart transplant, they might be considered for an ICD to manage potential heart issues.
  6. Specific Heart Conditions: ICDs might be considered for patients with cardiac sarcoidosis, Chagas disease, and giant cell myocarditis to prevent sudden heart problems.

Class IIb (Weak Indication):

Class IIb indications include:

  1. Heart Trouble with Mild Weakness: If someone has a heart problem unrelated to blocked arteries, a slightly weak heart (LVEF 35%), and is in good overall health.
  2. Long-QT Syndrome with Extra Risk: For those with long-QT syndrome, especially if there are more reasons to worry about sudden heart issues.
  3. Sudden Heart Troubles with Complex Heart Issues: ICDs might be considered for patients facing sudden heart problems and have advanced structural heart disease when doctors can't pinpoint the exact cause through tests.
  4. Family Heart Issues: If there's a family history of heart problems that lead to sudden death, ICDs might be an option.
  5. Unique Heart Structure: This is for individuals with a heart condition whose muscle doesn't form properly. This could increase the risk of sudden heart events.

Risks of Implantable cardioverter-defibrillators (ICD)

While implantable cardioverter-defibrillators (ICDs) are effective in preventing sudden cardiac death, they have a few risks. Carefully weigh the benefits against the risks. Here are the common risks associated with ICD implantation:

  1. Infection at the Implant Site: There is a risk of infection at the location where the ICD is placed in the body. It can occur after the surgery, leading to redness, swelling, and pain at the implant site. In severe cases, it may require medical attention and treatment with antibiotics.
  2. Swelling, Bleeding, or Bruising: This can occur due to the surgical procedure to implant the ICD. These are common side effects of the surgery and usually resolve over time.
  3. Blood Vessel Damage: The wires (leads) of the ICD may cause damage to blood vessels during the implantation procedure. This risk is generally minimised through careful surgical techniques.
  4. Bleeding: There is a risk of significant bleeding occurring around the heart, which can be a serious and life-threatening complication. Excessive bleeding around the heart can pressure the organ, affecting its ability to pump blood effectively.
  5. Blood Leakage through Heart Valve: The positioning of the ICD lead may lead to blood leakage through the heart valve. While uncommon, it underscores the importance of precise placement during the surgical procedure.
  6. Device or Lead Movement (Cardiac Perforation): The ICD device or its leads may shift, potentially causing a tear or cut in the heart muscle.


The defibrillator indications include a spectrum of cardiac conditions. This ranges from ventricular arrhythmias to congenital heart diseases. The criteria for ICD implantation continue to evolve, allowing for more precise and personalised interventions.

It's important for individuals considering or living with an ICD to discuss the potential risks and benefits with their doctors. Have some queries regarding ICD indications or any other medical issues? Contact HexaHealth!

Suggested Reads

Contraindications of ICD (Implantable Cardioverter Defibrillator)
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Heart Valve Disease - Symptoms, Causes, Signs and Treatment
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How to Prevent Ischaemic Heart Disease

Frequently Asked Questions

What is a defibrillator?

A defibrillator is a medical device that restores the normal rhythm of the heart in cases of life-threatening cardiac arrhythmias. This helps to improve the heart's pumping function and prevent sudden cardiac death.

What is the purpose of the ICD defibrillator?

An Implantable Cardioverter-Defibrillator (ICD) is a tiny device surgically inserted in the chest. It works similarly to a pacemaker but can detect and treat abnormal heart rhythms instantly.

What are the benefits of ICD devices?

The benefits of ICD devices are:

  1. Sudden cardiac death prevention

  2. Treatment of life-threatening arrhythmias

  3. Improved survival rates

  4. Enhanced quality of life

  5. Reduction in the risk of recurrent cardiac events

What are the common defibrillator indications?

The common defibrillator indications are:

  1. Ventricular fibrillation (VF)

  2. Ventricular tachycardia (VT)

  3. Previous cardiac arrest due to ventricular arrhythmias

  4. High-risk individuals with a history of sustained VT or VF

What are some of the rare indications of ICD insertion?

The rare indications of ICD insertion are:

When is the implantation of an ICD typically recommended?

The ICD implantation is typically recommended in individuals at high risk of sudden cardiac death. This can be due to a history of life-threatening ventricular arrhythmias, certain structural heart diseases, or specific genetic conditions.

What are the contraindications for an implantable cardioverter defibrillator?

The contraindications for an implantable cardioverter defibrillator are:

  1. Irreversible brain damage

  2. Terminal illness with less life expectancy

  3. Unstable psychological status

  4. Active systemic infection

Are there specific risk factors that lead to the consideration of an ICD implant?

The risk factors that lead to the consideration of an ICD implant are:

  • History of ventricular arrhythmias

  • Survived sudden cardiac arrest

  • Severe left ventricular dysfunction

  • Coronary artery disease

  • Heart failure

  • Prior heart attack

How do indications for ICDs relate to heart health and potential cardiac events?

ICD indications are typically related to a history of or high risk for life-threatening ventricular arrhythmias and sudden cardiac death. They are often associated with underlying heart conditions such as heart failure, prior heart attack, or certain genetic heart disorders.

Does ICD improve heart failure?

While an Implantable Cardioverter-Defibrillator (ICD) helps prevent sudden cardiac death in individuals at risk, it does not directly improve heart failure. However, some ICDs also function as cardiac resynchronisation therapy (CRT) devices. This can improve the coordination of heart contractions in certain heart failure patients.

What is the importance of identifying appropriate candidates for ICD implantation?

Identifying appropriate candidates for ICD implantation ensures the device is selectively used. This maximises the benefits, minimises complications, and optimises patient outcomes.

What role do medical professionals play in determining the indications for ICDs?

Medical professionals play a necessary role in determining ICD indications. This includes:

  1. Assessing patients' risk factors

  2. Conducting thorough evaluations

  3. Applying established guidelines to identify individuals benefitting from these devices

What is the evaluation process for determining ICD indications?

The evaluation process for determining ICD indications is as follows:

  1. Doctors evaluate the symptoms and medical history and then conduct physical exams to identify health issues in the patient.

  2. Specialized tests, like echocardiograms, measure the function and identify potential abnormalities in the heart.

  3. Doctors use risk stratification to assess the likelihood of life-threatening heart rhythms, helping determine if an ICD is necessary.

  4. Specific symptoms, such as fainting or heart palpitations, are considered in the decision-making process.

  5. If deemed necessary, the ICD is implanted through a minor surgical procedure.

How successful is ICD?

ICD is highly successful in preventing sudden cardiac death. The success rate is 98.7%, according to the European Society of Cardiology Congress. However, the results may vary depending on the patient and underlying cardiac conditions.


All the articles on HexaHealth are supported by verified medically-recognized sources such as; peer-reviewed academic research papers, research institutions, and medical journals. Our medical reviewers also check references of the articles to prioritize accuracy and relevance. Refer to our detailed editorial policy for more information.

  1. Iqbal AM, Butt N, Jamal SF. Automatic Internal Cardiac Defibrillator [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2021. link
  2. Ghzally Y, Mahajan K. Implantable Defibrillator [Internet]. PubMed. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Nov 14]. link
  3. Defibrillators - What are Defibrillators? | NHLBI, NIH [Internet]. www.nhlbi.nih.gov. 2022. link
  4. Freemantle M, Murtagh F. Implantable cardioverter defibrillator devices: when, how and who should discuss deactivation with patients: a systematic literature review. BMJ Supportive & Palliative Care. 2021 May 7;bmjspcare-2021-002894.link
  5. Devices that May Interfere with ICDs and Pacemakers [Internet]. www.heart.org. 2016.link
  6. Living With Your Implantable Cardioverter Defibrillator (ICD) [Internet]. www.heart.org. 2016.link
  7. Al-Khatib SM, Stevenson WG, Ackerman MJ, Bryant WJ, Callans DJ, Curtis AB, et al. 2017 AHA/ACC/HRS Guideline for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death: Executive Summary. Circulation. 2018 Sep 25;138(13).link

Updated on : 14 November 2023


Dr. Aman Priya Khanna

Dr. Aman Priya Khanna

MBBS, DNB General Surgery, Fellowship in Minimal Access Surgery, FIAGES

12 Years Experience

Dr Aman Priya Khanna is a well-known General Surgeon, Proctologist and Bariatric Surgeon currently associated with HealthFort Clinic, Health First Multispecialty Clinic in Delhi. He has 12 years of experience in General Surgery and worke...View More


Sangeeta Sharma

Sangeeta Sharma

BSc. Biochemistry I MSc. Biochemistry (Oxford College Bangalore)

6 Years Experience

She has extensive experience in content and regulatory writing with reputed organisations like Sun Pharmaceuticals and Innodata. Skilled in SEO and passionate about creating informative and engaging medical conten...View More

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