Free prep checklist · By an anesthesiologist
Surgery with a pacemaker or ICD — what happens to your device
The surgical "electric knife" can confuse cardiac devices — so teams follow a well-worn playbook: check, magnet or reprogram, monitor, restore. Answer two questions and get your personal prep list.
Quick answer
Surgical diathermy (electrocautery) can be misread by your device — a pacemaker may pause, an ICD may try to shock — so the team plans ahead: a recent device check (within ~12 months for pacemakers, ~6 for ICDs), sometimes a magnet over the device or temporary reprogramming, external defibrillator pads while any shock function is off, and everything restored before you leave monitoring. Your job is simple: bring your device card, your last check date, and your device clinic's name to pre-op — and mention the device at every booking (including MRI).
Your device and surgery:
The playbook, step by step
- Before: the team confirms device type, settings, battery and whether you're pacing-dependent — from your card and last check report.
- During: diathermy is used in short bursts with the grounding pad placed away from the device; a magnet or pre-programming handles interference; ICD shocks off = external pads on, rhythm watched continuously.
- After: anything switched off is switched back on and often re-checked before you leave the monitored area. Ask before discharge: "Has my device been restored and checked?"
Devices usually come with the conditions that earned them — see AF before surgery and heart disease before surgery, and add the device to your disclosure card.
Frequently asked questions
Why does surgery affect my pacemaker or ICD?
The main issue is electrocautery (diathermy) — the 'electric knife' surgeons use to seal bleeding. Its electrical noise can be misread by your device: a pacemaker may mistake it for your own heartbeat and pause, and an ICD may mistake it for a dangerous rhythm and try to shock you mid-operation. Entirely preventable — with planning. That's why the team wants to know about your device before the day.
Will they turn my ICD off during surgery?
For surgery near the device or with significant diathermy use, the shock function is commonly switched off temporarily — either by a programmer before surgery or by taping a magnet over the device. While it's off you're connected to external defibrillator pads and continuously monitored, so you're never unprotected. It's switched back on before you leave the monitored area.
What does a magnet do to a pacemaker vs an ICD?
Different things — worth knowing: on most PACEMAKERS a magnet makes the device pace steadily at a fixed rate, ignoring interference. On most ICDs a magnet suspends the shock function but does NOT change the pacing. This is why the team needs to know exactly what device you have — hence the device card.
What should I bring to my pre-op appointment if I have a device?
Three things: your device identification card (manufacturer, model), the date and result of your last device check, and the name of your cardiology/device clinic. Common expectations: a check within the last 12 months for pacemakers and 6 months for ICDs — if yours is older, ask your device clinic for a check before surgery. Also tell the team whether you're pacemaker-dependent (your heart relies on it beat-to-beat), if you know.
Can I have an MRI, and does that relate to surgery?
Separate issue, same theme: many modern devices are 'MRI-conditional' (allowed under specific settings), older ones may not be. If your surgical work-up includes an MRI, mention the device at booking — the radiology and device teams coordinate settings. Never assume; always flag it.