So, your doctor has told you that you need a pacemaker. A little box controlling my heartbeat with wires...does this make me the terminator? Maybe not as cool as the great Arnie, but a pacemaker is a nifty piece of equipment all the same! 

Before reading on about pacemakers, we strongly recommend you read the 'Electricity' section of our general overview - then come back! 

A pacemaker is a small device surgically inserted into the chest which acts as a safety net for your heart's conduction system - giving it the boost it needs to prevent the rate dropping too low.

A pacemaker can have one or two leads. The type you receive depends on the particular problem with your heart's wires. A single-lead pacemaker has one lead passed into the right ventricle and presses up against the muscle wall near the apex (bottom of the heart). A double-lead pacemaker has two leads, one into the right atrium and one into the right ventricle. 

A very common reason for pacemaker insertion is tachy-brady syndrome - let's give an example to explain. Bob is a 75 year old man who was experiencing a fluttering sensation in his chest before he collapsed. In the hospital, he was told he had a fast, irregular rhythm called atrial fibrillation. To slow the heart rate down, the doctors started a medication called a beta blocker, and slowly increased the dose until the heart rate came down to a normal range (60 - 100 beats per minute). Unfortunately, the medication worked too well - and Bob's heart rate went below 50, making him feel dizzy when he stood up. When the doctors lowered the dose of Bob's medication, his heart rate went back above 100 - into the fast, irregular rhythm. 

We can't give less medication because Bob's heart goes too fast on its own, and we can't give the amount we need to because Bob's heart is sensitive to the chemical and it goes too slow...if only we had a device that could prevent Bob's heart rate from going below 60 - ah yes, a pacemaker. Bob had a pacemaker inserted, and now anytime his heart wants to drop below 60 beats per minute, the pacemaker interprets this and takes control of the heart rate. 

So, does this mean the pacemaker always controls my heart? Not necessarily. If the pacemaker is set for a floor of 60 beats per minute, and your heart's natural electrical circuit is running at 65bpm on a particular Tuesday, the pacemaker will do nothing. It will happily sit in the background, monitoring the heart and will only add an electrical pulse when it needs to.

For some people, their heart's natural electrical circuit doesn't work correctly anymore whatsoever - in this case, the pacemaker will seize permanent control. For instance, people with a severe heart block (a disease we shall discuss separately). 

How do I know my pacemaker is working correctly? Nowadays, companies manufacturing pacemakers are incorporating wireless technology so that the pacemaker's activity (including the monitoring of your natural heart rate) can be downloaded and reviewed. 
In hospital, when somebody with a pacemaker feels dizzy, or has collapsed - we will always perform a 'pacemaker interrogation' - a strange term, we know (sounds like we bring the pacemaker to Guantanamo Bay). A device is held to the chest, and will download all of the information from the last few months wirelessly. This information will be sent automatically to the company that manufactured the product and within hours, we will receive a comprehensive report regarding your pacemaker. 

How does my pacemaker run? A pacemaker runs on batteries which last approximately seven years. Replacing the batteries will require a minor surgical procedure - and then you're as good as new. This may sound like a hassle, but if you think about it, your phone's battery needs a top up every day - and this machine runs your heart!
Seven years is pretty good if you ask me. 

Implantable Cardioverter-Defibrillator 

An ICD is often confused with a pacemaker. It too is a small device inserted into the chest with a lead running into the heart - but it has a different function.

Think of an ICD as a portable defibrillator, ready to be called into action when required. People with a propensity for entering dangerous fast rhythms will receive an ICD.
For example - famous Danish footballer, Christian Eriksen, collapsed on the pitch at the Euros in 2021. His heart had entered a dangerous rhythm, leading to a cardiac arrest. 
CPR was commenced, and a shock was delivered - restoring his heart to a normal rhythm. 
He has received an ICD and is now back playing professional football - talk about a sporting comeback!

There are genetic anomalies that lead to such a dangerous predisposition - sometimes we catch them on a routine ECG, sometimes we are only made aware after an event as drastic as Christian's.

The ICD is inserted to act as a safety net for defibrillation to protect against fast rhythms, whereas a pacemaker is inserted to act as a safety net to protect against slow rhythms.