Will I feel the ICD shock if it goes off?

Yes. Most people describe the shock as a sudden thump or punch to the chest. It is startling and can be frightening, but it passes in a fraction of a second. After a shock, you should sit or lie down and contact your device clinic or emergency services as instructed by your cardiologist. A single appropriate shock that resolves an episode quickly is a sign the device worked.

Can I go through airport security with a pacemaker or ICD?

Yes. Modern cardiac devices are designed to be safe in airport security. Inform security staff that you have an implanted device — you may be offered a hand search. Standard security scanners (millimetre-wave and X-ray) do not harm devices. Avoid lingering directly in the gate of an older walk-through metal detector. Always carry your device identification card when travelling.

Are there restrictions on driving after device implantation?

Driving restrictions vary by device type, indication, and jurisdiction. In Australia, the private vehicle driving restriction after ICD implantation is typically 6 months if the device was implanted following a cardiac arrest or symptomatic ventricular arrhythmia, or at least 1 month after an elective implant in the absence of symptoms. Commercial vehicle driving may be permanently restricted. Always follow the specific advice of your electrophysiologist and refer to the relevant authority guidelines.

Can I have an MRI scan with a pacemaker or ICD?

Most modern devices implanted since approximately 2014 are MRI-conditional — meaning MRI is possible under specific conditions (field strength, body part, programming). Older devices and some leads are not MRI-compatible. Carry your device card and notify the MRI team in advance. The cardiac device clinic will assess and may reprogram the device around the scan. Never assume MRI is safe without checking.

Pacemakers and ICDs: What They Do and What to Expect

Cardiac implantable electronic devices — pacemakers, implantable cardioverter-defibrillators (ICDs), and cardiac resynchronisation therapy (CRT) devices — are small electronic units implanted under the skin to treat abnormal heart rhythms, prevent sudden cardiac death, and improve symptoms in heart failure.

For many people, these devices are life-saving. For others, they offer symptom relief and improved quality of life. This guide explains the different types of device, why they are used, what implantation involves, and what to expect when living with one.

The Heart’s Electrical System

The heart is a pump, but it is controlled by electrical signals. Each heartbeat starts in the sinoatrial (SA) node in the right atrium — the heart’s natural pacemaker. The signal travels through specialised tissue to the atrioventricular (AV) node, then down to the ventricles, causing them to contract and eject blood.

When this electrical system malfunctions, the heart may beat:

Too slowly (bradycardia) — causing dizziness, fainting, or collapse
Too fast and chaotically (ventricular fibrillation) — a cardiac arrest in which no blood is pumped
In a disorganised pattern (bundle branch block) — causing the ventricles to contract out of sync, wasting pump function

Cardiac devices are designed to detect and correct these problems.

Pacemakers

What a Pacemaker Does

A pacemaker monitors the heart rate continuously. When it detects that the heart rate has dropped below a set threshold (typically 60 beats per minute), it delivers a small, painless electrical pulse through one or more leads (thin wires) to stimulate the heart muscle to contract.

A pacemaker does not prevent fast heart rhythms. It treats slow rhythms only.

Why a Pacemaker Is Needed

Common reasons include:

Sick sinus syndrome — the SA node fires too slowly or erratically, causing pauses or a slow rate
Heart block — the electrical signal is delayed or completely blocked between the atria and ventricles (second or third degree AV block), causing the ventricles to beat too slowly
Symptomatic bradycardia — any persistently slow rate causing dizziness, breathlessness, fainting, or fatigue
After certain ablation procedures — if the conduction system is inadvertently damaged during catheter ablation
Carotid sinus hypersensitivity — the carotid sinus in the neck is overly sensitive, triggering sudden falls in heart rate that cause fainting

Types of Pacemaker

Single-chamber pacemaker — one lead in the right ventricle (or right atrium for selected patients)
Dual-chamber pacemaker — leads in both the right atrium and right ventricle; provides more natural co-ordination between the upper and lower chambers
Rate-responsive pacemaker — detects physical activity via a motion or breathing sensor and adjusts heart rate accordingly, allowing normal exertional rate increases

Implantable Cardioverter-Defibrillators (ICDs)

What an ICD Does

An ICD continuously monitors heart rhythm. If it detects a life-threatening fast rhythm — ventricular tachycardia (VT) or ventricular fibrillation (VF) — it delivers a high-energy shock (defibrillation) through the lead to reset the heart to a normal rhythm.

ICDs also contain pacemaker function and can pace the heart if it slows excessively. Modern ICDs can also deliver anti-tachycardia pacing (ATP) — a rapid burst of pacing that can terminate many VT episodes painlessly, without a shock.

Why an ICD Is Used

ICDs are used in two ways:

Primary prevention — implanted in people who have not yet had a cardiac arrest but are at high risk because of:

Significantly reduced ejection fraction (typically ≤35%) from any cause — including dilated cardiomyopathy or heart failure after heart attack
Hypertrophic cardiomyopathy (HCM) with high-risk features
Inherited conditions including long QT syndrome, Brugada syndrome, and arrhythmogenic right ventricular cardiomyopathy (ARVC)
Certain other structural heart diseases assessed as high-risk by an electrophysiologist

Secondary prevention — implanted after a cardiac arrest or life-threatening ventricular arrhythmia to prevent recurrence. This is the strongest indication for an ICD.

Subcutaneous ICD (S-ICD)

The subcutaneous ICD (S-ICD) is a variant in which the device and sensing lead are placed entirely under the skin without any leads entering the heart or blood vessels. It can defibrillate but cannot pace continuously or deliver ATP. It is used in younger patients without a pacemaker need, where avoiding vascular access reduces long-term lead complications.

Cardiac Resynchronisation Therapy (CRT)

What CRT Does

In heart failure, particularly when the left bundle branch is blocked (left bundle branch block — LBBB), the two ventricles contract out of sync. The left ventricle, which is the main pumping chamber, starts contracting too late or unevenly. This reduces pump efficiency.

Cardiac resynchronisation therapy (CRT) uses a specialised pacemaker with an additional lead placed in a vein on the left side of the heart (via the coronary sinus). This allows the device to pace both the right and left ventricles simultaneously — or with a precisely timed delay — to restore co-ordinated contraction.

CRT can:

Improve ejection fraction
Reduce symptoms of breathlessness and fatigue
Reduce hospitalisations and death in selected patients
Sometimes allow reduction in heart failure medications

CRT-P and CRT-D

CRT-P (CRT pacemaker) — provides resynchronisation and pacing only
CRT-D (CRT defibrillator) — provides resynchronisation pacing plus ICD function; used when both resynchronisation and defibrillation are needed

CRT-D is the most common device in patients with heart failure and significantly reduced ejection fraction (≤35%) plus LBBB.

Who Benefits from CRT?

CRT is recommended in patients with:

Symptomatic heart failure despite optimal medical therapy
Reduced ejection fraction (typically ≤35%)
A wide QRS complex on ECG (typically ≥130 ms), especially left bundle branch block

Not all patients respond to CRT — approximately one-third show little improvement. Predictors of response include the presence of LBBB and wider QRS duration.

Implantation: What to Expect

Before the Procedure

You will typically have blood tests, a chest X-ray, and an ECG. Your anticoagulation (blood-thinning) medications will be reviewed — most patients continue anticoagulants through device implantation with careful management, as interrupting them risks clots in high-risk patients. You will be asked to fast for several hours beforehand.

The procedure is performed by a cardiac electrophysiologist (an arrhythmia specialist) or an interventional cardiologist in a cardiac catheterisation laboratory.

The Implantation Procedure

Most pacemakers and ICDs are implanted under local anaesthetic with sedation — you are awake but comfortable and drowsy. General anaesthesia is sometimes used for more complex procedures or in anxious patients.

The skin below the left (or occasionally right) collarbone is cleaned and numbed.
A small incision (approximately 4–5 cm) is made below the collarbone.
One or more leads are passed through the subclavian or cephalic vein and guided, under X-ray, into the correct position in the heart.
Lead positions are tested electrically to confirm good sensing and pacing thresholds.
The device generator is connected to the leads and placed in a pocket created under the skin (subcutaneous pocket), above the chest muscle.
The incision is closed with sutures or adhesive strips.

The procedure typically takes 1–2 hours for a single-chamber or dual-chamber device. CRT implantation takes longer (2–3 hours or more) because the left ventricular lead requires positioning through the coronary sinus — which can be technically challenging.

After the Procedure

You will usually stay in hospital for one to two nights. The arm on the side of implantation will be restricted for four to six weeks — avoid raising it above shoulder height or performing heavy lifting, as this risks dislodging the leads while they are still embedding.

Before discharge:

The device will be programmed and tested
You will receive a device identification card to carry at all times
Wound care and activity restrictions will be explained
A follow-up appointment will be arranged, usually within 6–8 weeks

Follow-up and Remote Monitoring

Cardiac devices are checked regularly:

Early follow-up — 6–8 weeks after implantation to assess wound healing, check lead stability and thresholds, and review programming
Ongoing follow-up — typically every 6–12 months in a device clinic; this includes reading the device memory, checking battery life, assessing lead function, and reviewing any stored arrhythmia episodes
Remote monitoring — most modern devices transmit data wirelessly to a home monitor, which sends readings to the device clinic. Remote monitoring allows early detection of lead problems, arrhythmia episodes, and battery depletion between clinic visits

Battery Replacement

No battery lasts indefinitely. When the battery approaches end of life (ERI — elective replacement indicator), the device clinic will schedule a generator replacement.

Only the generator (the box) is replaced — the existing leads usually remain in place if they are functioning well
The procedure is shorter than the original implantation (30–60 minutes)
Local anaesthetic and sedation are used
Hospital stay is typically one night

Battery life indicators are monitored at every device check, so depletion is detected well in advance — there is no sudden failure.

Activity and Daily Life

Exercise and Physical Activity

Most patients with pacemakers and ICDs can return to moderate exercise after healing. Rate-responsive pacemakers adjust to activity automatically. Patients with ICDs should discuss specific exercise limits with their cardiologist — vigorous exercise that risks reaching the detection zone for therapy may need to be avoided in some situations.

Cardiac rehabilitation is recommended after device implantation in patients with heart failure or cardiomyopathy.

Work

Return to work depends on the job. Sedentary or desk-based work is usually possible within 2–4 weeks. Jobs involving heavy manual labour or work in close proximity to strong electromagnetic fields require individual assessment.

Driving

Driving restrictions are set by the relevant transport authority and vary by device type and indication:

Pacemaker for bradycardia — in Australia, most patients can resume private vehicle driving after 1–2 weeks if symptoms have resolved
ICD — elective (no prior arrhythmia episode) — typically 4 weeks
ICD — after syncope or cardiac arrest — typically 6 months; individual assessment required
Commercial vehicle licence — may be permanently restricted; always check with the relevant authority

Carry your device card and notify your insurer.

Airport Security and Electromagnetic Environments

Airport security scanners do not damage modern cardiac devices — inform staff and carry your device ID card
Avoid prolonged contact with large industrial magnets, arc welding equipment, or MRI machines without prior device clinic assessment
Mobile phones, microwaves, and standard household appliances are safe
Anti-theft pedestals in shops are safe — walk through normally without lingering

MRI Scanning

Most devices implanted in Australia since approximately 2014 are labelled MRI-conditional, meaning MRI is possible under specified conditions. Always inform the MRI team about your device before any scan. The cardiac device clinic will assess compatibility and may need to adjust device programming for the scan. Never proceed with MRI without this assessment.

Warning Signs After Implantation

Contact your device clinic or seek medical review if you experience:

Redness, swelling, warmth, or discharge at the wound site — possible infection
The device appearing to move or bulge under the skin
Palpitations, dizziness, or near-fainting after implantation
An ICD shock — even if you feel well afterwards, always notify the clinic
Multiple shocks in a short period — seek emergency care immediately
Persistent hiccups or muscle twitching — may indicate lead displacement

Seek emergency services immediately for:

Cardiac arrest (no pulse, no breathing)
Sustained fast heart rhythm with collapse or near-collapse
Multiple shocks within a short period (electrical storm)
Severe pain at the implant site with fever

End-of-Life Considerations

ICD deactivation is an important and ethical conversation for patients with advanced heart failure or terminal illness. A device that continues to deliver shocks in the final stages of life may cause distress without meaningful benefit. Deactivating the shock function does not deactivate the pacemaker function and does not hasten death — it removes unwanted intervention.

If these conversations are relevant to your situation, discuss them early with your cardiologist and palliative care team. Clear documentation of wishes is important.

FAQ

Q: What is the difference between a pacemaker and an ICD? A pacemaker treats slow heart rhythms with small electrical pulses. An ICD delivers a high-energy shock to reset the heart if a life-threatening fast rhythm develops. Many ICDs also function as pacemakers. A pacemaker alone cannot treat dangerous fast rhythms.

Q: Will I feel an ICD shock? Yes. Most people describe it as a sudden thump to the chest. It is startling but passes in a fraction of a second. Contact your device clinic or emergency services as instructed after any shock.

Q: How long does the battery last? Pacemaker batteries last approximately 7–15 years; ICD batteries last approximately 5–7 years. Battery level is monitored at every device check so replacement is planned well in advance.

Q: Can I go through airport security? Yes. Modern devices are safe in airport security. Carry your device ID card, inform security staff, and you may request a hand search.

Q: Are there restrictions on driving? Yes, and they vary by device type and indication. Discuss your specific restrictions with your electrophysiologist, and refer to Australian transport authority guidelines for your licence category.

Q: Can I have an MRI? Most modern devices are MRI-conditional. Always check with your device clinic before any MRI scan — never assume it is safe without assessment.