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Implantable Cardioverter Defibrillators (ICD)

Implantable Cardioverter Defibrillators (ICD)

An implantable cardioverter defibrillator (ICD) is a small device that is implanted in heart patients who are at a higher risk of getting a heart attack. Here's more...
Mayuri Kulkarni
Last Updated: Jan 21, 2018
The ventricles of heart pump blood containing oxygen to other organs. In patients of heart diseases like ventricular tachycardia and ventricular fibrillation, the heartbeats are irregular and the heart is unable to pump blood to the other organs of the body. Vital organs like the brain may stop working due to the inadequate supply of blood. It is necessary to bring back the normal heart rhythm within a few minutes, else the situation leads to a heart attack, and may even be a cause of death.
What are Defibrillators?
Defibrillation is a technique in which electric signals are given in order to restart the normal heartbeats. Every minute that goes untreated after a heart attack, decreases the chances of survival by 10%. Thus, it is necessary that defibrillation be done soon after a heart attack. If a patient is already hospitalized, defibrillation can be given without delay. However, if a person gets a heart attack outside a hospital, timely defibrillation may not be possible. Automated External Defibrillators (AED) and Implantable Cardioverter Defibrillators (ICD) are solutions for such situations.
AEDs are defibrillators installed at maximum public places and training is provided for operating them. An ICD is an implanted device in the patient's body that constantly keeps an eye on the heart rhythm, and reduces risk of death due to heart attack. It is generally recommended for people suffering from severe heart arrhythmia. An ICD is implanted in the following cases:
  • Patients who have survived from a severe cardiac arrest in the past.
  • Patients suffering from ventricular fibrillation or ventricular tachycardia.
  • Patient of dilated cardiomyopathy or hypertrophic cardiomyopathy.
Parts of an ICD
An ICD is an electronic device made up of three parts―the leads, the electrodes, and the pulse generator.
Generator
This part generates the electric shock that is given to the heart. The size of this generator is generally two inches wide, smaller generators are also available. The generator has lithium battery that can long for four to seven years. A small computer is placed in this generator, which decides the intensity of the electric shock to be given obtaining different signals.
Leads
These are flexible wires, made up of platinum. They carry the electric shock from the generator to the heart. These wires are coated with an insulation layer of silicon or polyurethane.
Electrodes
Electrodes are present at the tip of leads and they deliver the electric shock. For every patient, the leads may be placed in different manner.
Types of ICDs
The heart is made up of four chambers, and each has a different functioning. All the chambers work together for the proper pumping of blood. The lower two chambers are called atria and the upper two are referred to as ventricles. Most of the pumping of blood is done by ventricles. The right ventricle pumps blood from other organs that has less oxygen, to the lungs; while the left ventricle pumps blood from heart to other organs. Even the atria pump blood, but in lesser quantity as compared to the ventricles. The synchronization of these chambers is necessary for proper functioning of the heart. Thus, the ICD leads can be placed in any of the chamber of patient's heart, depending on the need. There are three types of ICDs, each of which differs in the placement of the leads.
Type of the ICD Chamber where the lead is placed
Single chamber ICD Right Ventricle
Dual chamber ICD Right atrium and right ventricles
Biventricular ICD Right atrium, right ventricle and left ventricle

Working of an ICD
An ICD is implanted in the chest by a surgery. There are two functions of ICD, cardioversion and defibrillation. Cardioversion means to supply low electric signals when the heartbeats are rapid, and defibrillation is to supply high electric signals when the ventricles quiver due to very high heart rhythm. The ICD can be programmed to function according to the need of the patient's heartbeat problem. Given below are the different ways in which the ICD can be programmed,
Bradycardia pacing: When the ICD receives signals indicating slower heartbeats, it supplies low intensity electrical signals until it attains the normal heartbeat.
Tachycardia pacing: When the ICD finds an increase in heartbeat, but in a rhythmic fashion, it sends electric signals at specific intervals to interrupt the heartbeat, and continues to do so until the heartbeats reduce to normal.
ICD may be programmed to perform all the above functions or a combination of all of them. Other than the above two functions, the ICD also keeps a record of heart activities taking place. These records help the physician diagnose the problem more effectively.
Post Implantation Care
The implantation of ICD is a minor surgery that does not take much time. However, the patients need to take care after the surgery. The patient is admitted in the hospital for at least three days after the surgery. The incisions made during the surgery may create problems. In such cases, consult your doctor at the earliest. The symptoms that you may notice are fever, redness of the skin in the implanted area, swelling. Try to avoid lifting heavier objects. Stay away from magnetic equipment, as these equipment interfere with the working of ICD. These equipment include, cell phones, radios, welding equipment, generators. Do not undergo imaging tests like MRI or CT scanning. Whenever you receive a shock, do not panic, but stay calm. You may get a feeling of being kicked in the chest during the shock. Call your doctor immediately, if you do not feel better after the shock. Understand the guidelines properly once it has been implanted. Get a regular checkup of the ICD, especially the lithium battery level.
The use of ICD has increased, as it has helped reduce the death rates due to cardiac arrest. In more than 90% cases, ICDs have proved to be useful in saving lives from cardiac arrest.
Disclaimer: This HealthHearty article is for informative purposes only, and should not be replaced for the advice of a medical professional.