Anaesthetic Considerations in a Patient with a Cardiac Pacemaker

A. Introduction

B. Preoperative Assessment

• Determine indication for implantation, type of device (pacemaker vs ICD vs CRT), manufacturer, and date of last interrogation
• Sources of information: patient's device ID card, cardiology/EP clinic notes, chest X-ray (lead configuration/generator shape helps distinguish pacemaker from ICD), or a call to the manufacturer if no records exist
• Establish pacemaker dependence (no perfusing rhythm without pacing) - history of syncope, AV-node ablation, or complete heart block strongly suggests dependence

• Recommended interrogation window: within 12 months for pacemakers, 6 months for ICD/CRT (or per HRS/ASA 2020 advisory) - if outside this window, arrange interrogation before elective surgery
• Interrogation gives underlying rhythm, battery life, pacing thresholds, and current programmed mode

• At least 3 months of battery life should remain; if depleted, elective surgery should be postponed and the electrophysiologist contacted for possible generator change

• Liaise with the cardiology/EP team regarding whether the device needs reprogramming to an asynchronous mode (VOO/DOO) or rate increase, and whether ICD tachytherapy needs to be suspended before surgery (not needed for all procedures - e.g., not required if EMI risk is low, as in cases distant from the chest, using only bipolar cautery)

C. Intraoperative Management

• Prefer bipolar electrocautery over monopolar; if monopolar is unavoidable, use short intermittent bursts at the lowest effective power
• Position the grounding/return pad so the current path does not cross the device or leads (pad on the same side, away from generator, current vector perpendicular to the pacemaker-lead axis)
• Keep the active electrode as far as possible from the device (>15 cm rule of thumb)
• Avoid harmonic scalpel near device if possible; ultrasonic devices are generally lower risk than monopolar diathermy

• Placing a magnet over a pacemaker typically converts it to a fixed, asynchronous mode (VOO/DOO) at a manufacturer-specific rate, protecting against inappropriate inhibition from EMI - this is NOT reliable for all devices (e.g., some leadless pacemakers like Medtronic Micra do not respond to magnets)
• A magnet over an ICD only suspends tachyarrhythmia detection/therapy - it does not convert pacing to asynchronous mode
• Confirm the magnet response is functioning before relying on it; have the magnet immediately available in theatre

• Continuous ECG (accepting it may be masked by cautery artifact), pulse oximetry and/or arterial line waveform to confirm a perfusing rhythm independent of ECG during diathermy use
• Capnography and continuous palpable/plethysmographic pulse monitoring are essential since ECG alone can be unreliable during EMI

• External defibrillator/transcutaneous pacing pads applied and ready (placed antero-posteriorly, away from the generator), atropine and isoprenaline immediately available
• Anticipate that defibrillation, if needed, should be delivered as far from the device as practical (anteroposterior pad placement preferred)

• No specific contraindication to general or regional anaesthesia; choice depends on surgery
• Avoid succinylcholine-induced fasciculations and shivering, which generate myopotentials that can be misread as intrinsic activity and inhibit pacing in unipolar-sensing devices
• Peripheral nerve stimulators (for neuromuscular monitoring or regional blocks) can theoretically interfere with sensing if current path is near the device - keep away from the chest/device
• MRI is contraindicated unless the device is explicitly labelled "MR-conditional" and the appropriate protocol is followed
• Maintain normothermia, normokalaemia and haemodynamic stability, since bradycardia thresholds, capture and pacing behaviour are affected by electrolyte and temperature shifts

D. Postoperative Management

• If the device was reprogrammed or magnet-converted, or tachyarrhythmia therapy suspended, it must be reprogrammed/re-enabled before the patient leaves a monitored area
• Reinterrogate the device if: defibrillation/cardioversion was used, significant EMI exposure occurred, major haemodynamic/volume shifts occurred, or radiotherapy was given
• Continue ECG and haemodynamic monitoring appropriate to surgical severity, not merely because a CIED is present
• Watch for signs of device malfunction: unexplained bradycardia, hypotension, or loss of capture

E. Emergency Surgery (device details unknown)

• Get rapid information from wallet card, chest X-ray, or manufacturer hotline
• If unknown, place a magnet and observe: an abrupt change to a fixed paced rate confirms a pacemaker (rate suggests manufacturer - e.g., Medtronic ~85, Boston Scientific ~100); a magnet tone (beeping) confirms an ICD
• Treat every unknown device as pacemaker-dependent and EMI-sensitive until proven otherwise; use bipolar cautery, have pacing/defibrillation pads ready, and monitor pulse waveform continuously

Summary Table (quick recall)