Implantable cardioverter-defibrillators (ICDs)

Overview

An ICD, implanted in the chest, is a battery-powered device designed to detect and halt irregular heartbeats, known as arrhythmias. It continuously monitors the heartbeat and restores a regular heart rhythm by delivering electric shocks when needed. 

ICD Benefits:

An ICD regularly monitors irregular heartbeats and instantly rectifies them. It is of utmost use when there is a sudden loss of cardiac activity, a condition called cardiac arrest. It is one of the main treatment options for anyone who has had a cardiac arrest. They are of immense help more than medication alone in people at high risk of sudden cardiac arrest as they lower the risk of sudden death from cardiac arrest. 

Conditions for ICD placement:

Cardiac physicians recommend an ICD if an individual has symptoms of an irregular heart rhythm called sustained ventricular tachycardia, with fainting as one of the symptoms. An ICD is also placed among individuals who survived cardiac arrest or have a history of coronary artery disease, a heart attack that has weakened the heart or an enlarged heart muscle, or any genetic heart condition that increases the risk of dangerously fast heart rhythms like long QT syndrome.

ICDs are also used to effectively pump the blood in heart failure and electrical heart abnormalities. This is called cardiac resynchronization therapy. 

ICD Types: 

There are two types of ICDs. One is a traditional ICD placed in the chest with wires attached to the heart. The other is a subcutaneous ICD (S-ICD) placed under the skin below the armpit on one side of the chest without touching the heart. It has a sensor, called an electrode, that is placed along the breastbone. Traditional ICD is smaller than S-ICD.  

The most common location of an ICD is below the skin or the skin and muscle in the chest near the left collarbone and occasionally in the abdomen in particular conditions. 

ICD Working Mechanism: 

Electrodes, which are wires, link the ICD in the abdomen or upper chest to the heart. Doctors insert these electrodes through a blood vessel near the collarbone to reach the heart. In the heart, two or three electrodes are attached to the upper chambers (atrium) and the lower chambers (ventricles). Then, these electrodes are, in turn, attached to the battery that powers the heart and delivers shock-like sensations whenever needed. This method of implantation of ICDs is called transvenous ICDs. 

In some situations, ICDs are implanted in the abdomen or upper chest with leads attached to the outermost layer of the heart called the epicardium. Such ICDs are called Epicardial ICDs and are used in children and adults with heart diseases like congenital heart disease, endocarditis, or conditions where transvenous ICDs cannot be placed. 

If an ICD has an in-built pacemaker, it sends electrical signals to the heart to hasten the heartbeat. If the heartbeat is too fast, it sends defibrillation shocks to control the abnormal rhythm. It functions 24 hours a day. 

Before ICD placement:

To get an ICD, a few tests must be done, which include an Electrocardiogram (ECG) to understand the heart beating, an Echocardiogram to understand the size and structure of the heart, Holter monitoring to identify the cause of symptoms, an event monitor to identify arrhythmia and an Electrophysiology study to confirm a diagnosis of a fast heartbeat. 

During ICD implantation:

Individuals should not eat or drink for a few hours before the procedure. Notify the health care professionals about all the medicines and confirm if they can be taken before the procedure. An intravenous line is placed, and a sedative is given to relax the body. Later, electrodes in the form of sticky patches are placed on the chest and legs to monitor the heartbeat continuously during the procedure. 

A small incision is made on the chest skin, allowing for the insertion of one or more leads into a blood vessel near the collarbone. These leads are then guided to the heart. One end of the lead attaches to the heart, while the other ends attach to a device called a shock generator, which is placed under the skin beneath the collarbone. The total procedure finishes in a few hours. After the ICD is placed, it is programmed to a specific heart rhythm, which includes a low-energy pace or a higher-energy shock. Generally, only one shock is needed to restore a regular heartbeat, but some may have two or more shocks for 24 hours.

After ICD Implantation:

After the procedure, an individual is taken care till their vitals stabilize, and later, medications are prescribed and sent. However, for about two months after getting an ICD, the left arm should not suddenly be raised above the shoulder. Instructions are given not to drive, lift heavy weights, do heavy workouts, and not move suddenly displacing the leads. 

ICD effectiveness: 

An ICD can work effectively for 5 to 7 years. Regular monitoring by a healthcare professional should be done. 

Care from other devices: 

ICD generally does not encounter any problems with electrical signals from other devices. However, care should be taken while using cellular phones and passing through security alarms or metal detectors and power generators. Magnetic resonance imaging (MRI) is not recommended when one has an ICD. 

Risks of ICD: 

Infections at the implanted site, Swelling, bleeding, or bruising, damage to a blood vessel, life-threatening bleeding around the heart or through the heart valve, collapsed lung, and movement of the device or leads causing damage or perforation to the heart muscle are some of the risk factors or complications after an ICD placement. 

Conclusion: 

ICDs are vital devices placed in the heart to monitor and correct irregular heartbeats for individuals experiencing sudden cardiac arrest and with specific heart conditions. Despite being effective in restoring heart rhythm, ICDs need regular monitoring by a healthcare professional. Regular follow-ups and adherence to precautions are essential for the safety and effective functioning of ICDs.