When is an implantable device (pacemaker, ICD) recommended for arrhythmia? 

For some heart rhythm disorders, medication and external procedures reach a limit where they can no longer ensure the heart’s safety. In these cases, modern cardiology offers ‘internal’ solutions: pacemakers and Implantable Cardioverter Defibrillators (ICDs). These devices act as a 24-hour guardian for your heart, sitting just beneath the skin and constantly monitoring every single beat. While a pacemaker is designed to ‘kick-start’ a heart that is beating too slowly, an ICD is a more complex safety net designed to deliver a life-saving shock if the heart enters a lethal, rapid rhythm. In the UK, the recommendation for an implantable device is a major clinical milestone that significantly improves quality of life and, in many cases, provides essential protection against sudden cardiac arrest. This article explains the specific scenarios where these devices are recommended and how they work to maintain a safe and stable heartbeat. 

What We’ll Discuss in This Article 

• The clinical distinction between a pacemaker and an ICD. 

• When a pacemaker is needed to correct a slow heart rate (bradycardia). 

• The role of an ICD in preventing sudden cardiac death from fast ventricular rhythms. 

• How doctors use ejection fraction and ‘fainting episodes’ to decide on a device. 

• The difference between ‘primary prevention’ and ‘secondary prevention.’ 

• The procedure and long-term management of living with an implantable device. 

• Emergency safety guidance for sudden or severe cardiac symptoms. 

When is a Pacemaker Recommended? 

A pacemaker is primarily recommended for people with a slow heart rate (bradycardia) that is causing symptoms or putting them at risk of collapse. According to NHS guidance, the device sends electrical pulses to the heart to ensure it never drops below a safe ‘floor’ rate. 

1. Heart Block 

This is when the electrical signals from the heart’s upper chambers don’t reach the lower chambers properly. 

• Complete Heart Block: The most serious form, where the chambers beat entirely independently. A pacemaker is almost always recommended immediately. 

• Second-Degree Heart Block: Often recommended if it causes dizziness or fainting. 

2. Sick Sinus Syndrome 

This occurs when the heart’s natural pacemaker (the SA node) becomes worn out with age or disease. It can cause the heart rate to fluctuate between being too slow and too fast, leading to extreme fatigue or blackouts. 

3. Chronic Atrial Fibrillation with a Slow Rate 

If you have AF but your heart rate is naturally very slow, or if the medications needed to control the AF slow your heart down too much, a pacemaker may be used to provide a steady baseline. 

When is an ICD (Defibrillator) Recommended? 

An ICD is a more advanced device recommended for people at risk of life-threatening ventricular arrhythmias (VT or VF). Unlike a pacemaker, which gently nudges the heart, an ICD can deliver a high-energy ‘kick’ to stop a cardiac arrest. 

1. Secondary Prevention (After an Event) 

If you have already survived a cardiac arrest or a dangerous episode of sustained ventricular tachycardia, an ICD is recommended to prevent it from happening again. 

2. Primary Prevention (High-Risk Patients) 

NICE guidance recommends an ICD for patients who have not yet had a cardiac arrest but are at high risk due to: 

• Heart Failure: A severely weakened heart muscle (an ejection fraction of 35% or less). 

• Inherited Conditions: Genetic issues like Long QT Syndrome or Brugada Syndrome that make the heart electrically unstable. 

• Hypertrophic Cardiomyopathy: A condition where the heart muscle is excessively thick, which can disrupt electrical signals. 

Differentiation: Pacemaker vs. ICD 

While the two devices look similar and are implanted in the same way, their functions are very different. 

Feature	Pacemaker	ICD (Defibrillator)
Primary Goal	Prevents slow heart rates.	Prevents sudden cardiac arrest.
How it Acts	Regular, tiny electrical pulses.	Large, ‘resetting’ electrical shocks.
Who Needs It	Patients with blackouts or ‘heart block.’	Patients with heart failure or past arrest.
Pacing Ability	Yes (always).	Yes (most ICDs can also pace).
Size	Small (size of a large coin).	Slightly larger (size of a small pager).

The Implantation Procedure 

Both devices are usually implanted under local anaesthetic with sedation. A small incision is made near the collarbone, and the leads are threaded through a vein into the heart.¹⁰ The procedure takes about 1 to 2 hours, and most patients go home the same day or after one night in the hospital. 

Impact on Life 

Living with a device in the UK requires some adjustments. You will be given a ‘Device ID Card’ to carry at all times. You will need regular check-ups (usually every 6–12 months) where a technician uses a remote programmer to check the battery and any ‘events’ the device has recorded. Most modern devices are compatible with MRI scans, but you must always inform medical staff beforehand. 

Conclusion 

Implantable devices are the gold standard for managing heart rhythms that cannot be safely controlled by medication alone. Whether it is a pacemaker providing a reliable ‘metronome’ for a slow heart or an ICD standing guard against a sudden cardiac arrest, these devices offer unparalleled protection and peace of mind. In the UK, the recommendation for a device is based on a careful assessment of your heart’s structure, your clinical history, and your risk of future events. While the idea of having a device ‘installed’ can be daunting, the reality for most patients is a return to a more active, confident, and safer life. By providing a constant, internal safety net, pacemakers and ICDs ensure that your heart rhythm remains a stable foundation for your overall health. 

If you experience severe, sudden, or worsening symptoms, call 999 immediately. 

Authority Snapshot (E-E-A-T Block) 

This article was written by Dr. Stefan Petrov, a UK-trained physician with an MBBS and certifications in Advanced Cardiac Life Support (ACLS). Dr. Petrov has extensive experience in both acute hospital wards and intensive care units, where he has managed patients requiring the urgent and elective implantation of cardiac devices. This guide follows NHS and NICE standards to provide a clear, evidence-based overview of when heart rhythm devices are clinically indicated in the UK.