The extravascular ICD (EV-ICD) is the newest defibrillator modality. The Medtronic Aurora generator sits in a left mid-axillary pocket, and the Epsila lead is tunneled and positioned in the substernal space — between the sternum and the pericardium — through a subxiphoid puncture.
The design intent: capture the venous-system-sparing advantages of an S-ICD while restoring the ATP and post-shock pacing capabilities that S-ICD lacks.
How the system works
- The generator delivers shocks between the lead’s defibrillation coil and the can.
- The substernal position puts the coil closer to the RV and apex than an S-ICD coil — translating into lower delivered energy for the same defibrillation effect.
- Sensing uses bipolar electrodes on the substernal lead with morphology-based discrimination.
- ATP is delivered via pace-capable electrodes on the same lead — captures the ventricle from outside the heart when the capture threshold is favorable.
- Post-shock pacing provides bridging for transient asystolic pauses after shock therapy.
Types / Variants
Single platform currently on the US market: Medtronic Aurora EV-ICD paired with the Epsila EV lead. No dual-chamber variant — atrial activity is not directly sensed.
Indications & candidate selection
Currently positioned for patients who:
- Need ICD therapy but want to avoid transvenous leads.
- Have monomorphic VT history where ATP capability is desired (S-ICD limitation).
- Have venous access concerns but also need post-shock bradycardia bridging.
- Don’t have a chronic pacing or CRT indication.
Not yet ideal:
- Patients with extensive prior cardiac surgery — substernal access is harder and riskier.
- Patients with chronic pacing needs — EV-ICD does not replace a pacemaker.
- Patients with congenital heart disease and abnormal substernal anatomy.
Key programming considerations
- Detection zones programmed similarly to TV-ICD: VT zone (170-200 bpm) with ATP attempts before shock, VF zone (>=200 bpm) with shock-priority therapy.
- Sensing vector and gain settings reflect the substernal vantage — expect different EGM morphology than transvenous; calibrate templates accordingly.
- ATP burst pacing relies on capture from the substernal lead — check ATP capture threshold periodically.
- Post-shock pacing is transient (seconds to a minute) and is not a chronic pacing solution.
- Morphology-based SVT discrimination is the main tool — no atrial channel.
What to know in the lab
- Implant is a hybrid EP-thoracic procedure mentality: subxiphoid puncture, substernal tunneling along the posterior table of the sternum, lead positioning under fluoroscopy.
- A dedicated tunneling tool advances the lead between the sternum and the pericardium — gentle, deliberate, with constant feedback.
- Pleural breach and pericardial entry are the recognised intra-procedural risks; have an ultrasound and chest tube setup ready.
- Confirm coil position over the cardiac silhouette in both AP and lateral fluoro.
- Confirm sensing, pacing thresholds, and shock impedance before closing.
Common issues & troubleshooting
- Implant-related complications — pericardial or pleural entry; recognise early and manage per institutional protocol.
- Sensing oversensing from skeletal muscle or diaphragm — vector reselection and gain tuning; rarely needs lead revision.
- ATP non-capture — confirm pacing threshold from substernal position; if marginal, rely on shock therapy and counsel the patient.
- Chest discomfort post-implant — typically settles over weeks; persistent pain warrants imaging to rule out lead migration or effusion.
- Lack of long-term extraction data — plan generator changes and any revision conservatively; document carefully for future operators.