Cardiac Implantable Electronic Devices

KEY LEARNING POINTS

Part 1

• The traditional dual-chamber transvenous system - leads in the subclavian vein, generator in the prepectoral pocket - remains excellent but leads bring complications: infection, venous occlusion, tricuspid interference, and difficult extraction. Leadless pacemakers were developed to remove hardware from the vasculature, with the first true dual-chamber leadless system (AVEIR) introduced in 2023.

• Single-chamber leadless pacemakers initially lacked AV synchrony; a later algorithm allowing atrial mechanical sensing partially addressed this. The dual-chamber AVEIR system delivers genuine atrial sensing and pacing, though the atrial component has a shorter battery longevity (~12 years) than the ventricular component.

• Implantable loop recorders have become small enough to be injected subcutaneously. Consumer wearable ECGs (smartwatches, finger-contact single-lead devices) now provide genuinely high-quality arrhythmia recordings but generate large data volumes and require systematic filtering before reaching the clinician.

• Conduction system pacing (CSP/LBBP) overcomes left bundle branch block by fixing a lead deep in the right ventricular septum to capture the left bundle directly, producing a narrow QRS and restoring synchrony. Emerging data suggest equivalence with traditional CRT in selected patients, with fewer leads and fewer complications. This approach is expected to grow substantially.

• Subcutaneous ICD (SICD) keeps all hardware extravascular but cannot deliver bradycardia or antitachycardia pacing. The extravascular ICD (EV-ICD) places the lead in the substernal space (requiring lung deflation during implant, surgical support for the first five cases, and mandatory GA for defibrillation testing) and adds effective antitachycardia pacing, addressing a key SICD limitation.

• Pulsed field ablation (PFA) uses non-thermal electrical energy to isolate pulmonary veins in AF, achieving the same endpoint as radiofrequency and cryoballoon with a dramatically lower risk of collateral damage to the phrenic nerve and oesophagus. The trade-off is procedural intensity and a mandatory requirement for general anaesthesia, which substantially increases resource demand per case.

Part 2

• Device infection is a class I indication for complete lead extraction. Untreated CIED infection carries 30–70% one-year mortality depending on the causative organism. Despite this, misconceptions about extraction - that it is too dangerous, or that leads can simply be left in situ - remain widespread and contribute to avoidable deaths.

• The fundamental challenge of lead extraction is fibrous binding: over time, leads adhere to venous walls, the SVC-atrial junction, and intracardiac structures. Extraction is not about pulling leads out - it is about methodically dissecting that binding using rotational sheaths (e.g. the Evolution tool), counter-traction from below (femoral snares), and minimising the dangerous traction force transmitted to cardiac structures.

• The SVC-atrial junction (the 'angle of death') is the highest-risk site for catastrophic vascular injury. Laser sheaths are associated with a seven-fold increase in SVC entry at this site and are not used in the Auckland service. An SVC bridge balloon, advanced via femoral access, is positioned on standby at every high-risk extraction to temporise SVC tears until surgical repair is possible.

• The Auckland national lead extraction service uses a standardised tandem approach: simultaneous superior and femoral access; a 12Fr femoral sheath (sutured in place, with a sidearm high-volume IV line) providing emergency volume access; surgical and anaesthetic teams present throughout; a structured team briefing and speak-up culture as non-negotiable elements of safe practice.

• Conduction system pacing (CSP) leads (now implanted with increasing frequency) will present novel extraction challenges. Their deep septal screw fixation risks tricuspid leaflet damage during both implantation and extraction, may cause septal injury, and their long-term fibrotic binding characteristics are entirely unknown; the extraction community is already planning new tooling and approaches.

• Valve surgery and cardiac transplantation in patients with implanted leads require deliberate pre-operative MDT planning. Cutting a lead inside the pericardium leaves a fragment that cannot subsequently be snared and is a source of ongoing infection risk. This is particularly dangerous in transplant recipients on immunosuppression. Leads should always be managed in a way that preserves extractability.

• Leadless pacemakers cannot be interrogated or rate-controlled with a magnet: perioperative management requires a pacing physiologist to reprogram the device. Updated New Zealand guidance (effective May 2026) permits cremation of patients with leadless pacemakers without device removal; patients with standard transvenous, subcutaneous, or extravascular devices still require removal prior to cremation.