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The story behind pacers and defibrillators

Pacemaker are used to treat an abnormally slow heart rate

Pacemakers and defibrillators are devices that sit under the skin, in the chest area near a patient's heart. They help with controlling abnormal heart rhythms.

A pacemaker can treat an abnormally slow heart rate. A defibrillator is designed to treat an abnormal and fast heart rhythm, or fast “arrhythmia”.

There are millions of people around the world, and hundreds of patients in Bermuda with such heart devices.

Why are these cardiac rhythm devices needed?

A person's heart needs to beat at a normal rate in order to efficiently pump blood to the different body organs. This is achieved through a specialised “native” electrical system. Sometimes, this electrical system does not work properly, causing a person's heart to beat too slowly or too fast.

Different cardiac and extra-cardiac diseases can lead to arrhythmias. Not all arrhythmias require a pacemaker or a defibrillator.

So who might need a pacemaker?

A person might need a pacemaker if they have an abnormally slow heart rate and have symptoms, which include:

● Fainting (syncope)

● Feeling light-headed

● Feeling your heart pounding (palpitations)

● Trouble breathing

How does a pacemaker work?

Most pacemakers have two parts:

● A "pulse generator" is a small metal box with a battery and a computer chip in it. The pulse generator creates and sends electrical signals to supplement, on demand, the slow heart rate. The computer can be programmed differently between patients, by a healthcare professional.

● Wires or "leads". These run between the pulse generator and the heart. There could be one, two or three wires supplying different cardiac cavities or “chambers”. Information about how the heart is working can travel from the heart chamber(s) to the pulse generator. If/when needed, electrical signals or pulses initiated by the generator can travel through the wire(s) back to the heart.

A newer type of pacemaker can be inserted directly into the heart, with no wires. This type of pacemaker is only used in special cases.

And who might need a defibrillator?

Patients at risk for fast and dangerous heartbeats may need a defibrillator, also called an ICD, as this type of arrhythmias can lead to fainting and, in some patients, to sudden death. They are usually related to a weak heart muscle or a primary disease of the cardiac electrical system.

They are usually referred to as “ventricular tachycardia” and “ventricular fibrillation”. They develop in the lower chambers of a sick heart. They can happen without warning. ICD is one way of treating these arrhythmias; medications and procedures are also available in lieu of or in complement with the defibrillator.

An ICD works by slowing down these arrhythmias and/or by shocking the heart out of them via an electrical current to restore a normal rhythm.

How does an ICD work?

Like a pacemaker, an ICD has two parts: the generator, that has a much more complex computer system making the ICD box bulkier; and the wires which receive information from the heart and deliver an intervention or “therapy” when needed.

Some defibrillators do not go in the blood stream of the neck vessels, but could be implanted totally under the skin.

What should one do after they receive a defibrillator shock?

Most people feel the shock, although it is possible one might pass out before they notice any pain. If either of these things happen, the treating team should know. Via a wireless machine, they would look at the shock event record stored inside the ICD’s memory, and decide accordingly.

What are some of the complications of a pacer or an ICD?

They are rare but could include:

– Infection at the implant site

– Bleeding or hematoma at the implant site

– Lead(s) dislodgement or fracture

– Malfunction or failure of the device

– Electrical stimulation of the phrenic nerve leading to hiccups and chest discomfort

– Inaccurate shocks from the ICD.

Generally, every five to ten years, the battery of these devices need to be changed.

General housekeeping measures with a pacer or a defibrillator:

1. The device should be checked on a regular basis via a special wireless equipment at the doctor’s office and/or from home.

2. Avoid certain electric or magnetic sources or equipment. For example, one can be near televisions and radios, but should not walk through a metal detector at the airport. An X-ray or a manual scanning should be considered in that case.

3. Some mobile phones and smart watches might have a strong magnet that could affect the device. One needs to check with the company that makes them or ask the doctor. In general, it's a good idea to carry mobile phones in a pocket or handbag below the waist.

4. Many people with a cardiac rhythm device should not have an MRI scan, but some new types of pacemakers or ICDs are safe in the MRI machine.

Joseph Yammine is a consultant cardiologist at the Bermuda Hospitals Board. He is also the director of the outpatient multi-speciality clinics and director of the Cardiac Computed Tomography programme.

The information herein is not intended as medical advice nor as a substitute for professional medical opinion. Always seek the advice of your physician. You should never delay seeking medical advice, disregard medical advice or discontinue treatment because of any information in this article.

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Published February 14, 2023 at 7:47 am (Updated February 14, 2023 at 7:47 am)

The story behind pacers and defibrillators

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