Pulseless Patient with a Pacemaker: How to Perform Resuscitation Correctly

The number of patients with implanted cardiac devices – permanent pacemakers (PM), implantable cardioverter-defibrillators (ICD), and cardiac resynchronization therapy systems (CRT) – continues to rise. In both in-hospital and prehospital resuscitation, you will therefore increasingly encounter individuals with a subcutaneous device in the chest area. This changes some practical aspects of resuscitation but does not alter the overarching principle: The ACLS algorithm applies without restriction. No delay, no hesitation – chest compressions and defibrillation save lives, even when a device is implanted. This article highlights the relevant considerations when resuscitating PM and ICD recipients: pad positioning, defibrillation energy, managing ICD shocks, compression quality over the device, and post-resuscitation management.

Basics: What Devices Are There?

Before you begin resuscitation, a brief overview of the different cardiac implants is worthwhile, as device behavior during cardiac arrest varies considerably.

Permanent Pacemakers (PM)

• Function: Bradycardia therapy through electrical stimulation of the myocardium.
• Behavior during cardiac arrest: The pacemaker continues to pace – you will see regular spikes on the monitor, possibly followed by narrow or wide complexes. This does not mean there is effective cardiac output. Pulseless electrical activity (PEA) with a paced rhythm is common and must not be confused with a perfusing rhythm.
• No defibrillation function: A standard PM does not deliver shocks.

Implantable Cardioverter-Defibrillators (ICD)

• Function: Detection and termination of ventricular tachyarrhythmias through antitachycardia pacing (ATP) and/or internal shocks (up to approximately 40 joules).
• Behavior during cardiac arrest: An ICD detects ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) and delivers – after a detection time of typically 6–15 seconds plus charging time – an internal shock. Up to 6–8 shocks in series may be programmed.
• Important: Internal ICD shocks are frequently not sufficiently effective during cardiac arrest, particularly with prolonged VF. You must never rely on the ICD to solve the problem.

CRT Systems (CRT-P and CRT-D)

• Combination of a biventricular pacemaker and – in the case of CRT-D – defibrillator function. The same principles apply as for PM or ICD, depending on the device type.

Subcutaneous ICDs (S-ICD)

• The generator is typically located on the left lateral chest wall (approximately mid-axillary line), with the electrode running subcutaneously along the parasternal area. There are no transvenous leads. The positioning differs from conventional ICDs and influences pad placement.

The ACLS Algorithm Applies Without Modification

The AHA guidelines are clear: The presence of an implanted cardiac device is not a reason to modify the standard resuscitation algorithm. The sequence remains:

1. Recognize cardiac arrest – Check for a pulse (≤ 10 seconds)
2. Begin CPR – 30:2 or continuous compressions with an advanced airway
3. Analyze the rhythm – shockable vs. non-shockable rhythm
4. Defibrillate for VF/pVT – as early as possible
5. Administer medications per algorithm (epinephrine, amiodarone)
6. Search for and treat reversible causes (Hs and Ts)

However, there are specific points you need to be aware of – particularly regarding defibrillation and interpretation of the monitor display.

Chest Compressions with an Implanted Device

Do Not Compromise Compression Quality

Most PM and ICD generators are implanted subcutaneously or subfascially in the left (less commonly right) infraclavicular region. The compression zone per AHA guidelines is on the lower half of the sternum – well caudal to the device.

• Compress at the correct point. The device is not in the way.
• Compression depth 5–6 cm, rate 100–120/min – without restriction.
• Ensure complete chest recoil.

In rare cases – such as in very cachectic patients or with atypical device placement (e.g., abdominally implanted generators in pediatric patients) – the device may be closer to the compression area. Even then: Effective CPR takes priority. A theoretical risk of device damage is secondary to the person's survival.

Can CPR Damage the Device?

Lead dislodgements from chest compressions have been described in the literature but are rare. Device housings are robustly constructed. Even if lead dislodgement occurs, it has no consequence for the acute resuscitation – the device is not functioning effectively anyway when there is no circulation. Device interrogation takes place after successful resuscitation.

Defibrillation: Pad Positioning with an Implanted Device

The Basic Rule

The AHA guidelines recommend placing defibrillation pads at least 8 cm away from the device generator. The rationale: If defibrillation energy is delivered directly over the device, the following problems may occur:

• Current shunting through the metallic device housing, resulting in less energy reaching the myocardium
• Damage to the circuitry within the generator
• Temporary or permanent pacing failure due to increased stimulation threshold at the electrode-myocardium interface
• Reset to backup mode (VOO/DOO) with loss of programmed parameters

Practical Pad Positioning

Standard position (anterior-lateral):

• Anterior pad: Right parasternal, below the clavicle
• Lateral pad: Left mid-axillary line, at the level of V6

This position is often unproblematic with left infraclavicular devices, as the anterior pad is on the right side and the lateral pad is sufficiently caudal.

If the 8 cm distance cannot be maintained:

• Anterior-posterior position: Anterior pad over the sternum, posterior pad left infrascapular. This position reliably avoids the device and is often the preferred option for device recipients.
• Alternatively: Simply shift the pad closest to the device further caudal or lateral.

With a subcutaneous ICD (S-ICD): The generator sits laterally, and the electrode runs parasternally on the left. The anterior-posterior position is particularly recommended here, as the standard anterior-lateral position may run directly over the device components.

Defibrillation Energy

The recommended energy does not change because of an implanted device:

• Biphasic: Manufacturer recommendation, typically 120–200 J for the first shock, maximum energy for subsequent shocks
• Monophasic: 360 J

There is no evidence that energy should be reduced. On the contrary: Due to potential current shunting through the device, even less energy may reach the myocardium – an argument for using maximum energy.

Special Considerations for ICD Recipients

The ICD Shocks During Resuscitation

If the ICD detects ventricular fibrillation, it will attempt to deliver an internal shock. This can happen during resuscitation and has several implications:

• Risk to rescuers: The internal shock (maximum approximately 40 J) is delivered via the transvenous leads. The amount of energy reaching the chest surface is minimal (< 2 J). Studies show that rescuers may feel at most a slight tingling sensation. An ICD shock poses no significant risk to those performing CPR. Nevertheless, wearing gloves – as with any resuscitation – is standard.

• Effectiveness of the internal shock: With prolonged VF, the defibrillation threshold increases. Internal shocks of a maximum of 40 J are then frequently no longer effective. Do not wait for ICD shocks – defibrillate externally per algorithm.

• Repetitive ICD shocks during a non-shockable rhythm: Occasionally, an ICD misinterprets artifacts from CPR or electrical interference as VF and delivers inappropriate shocks. In this case:

  • Do not interrupt CPR
  • Place a magnet over the device – this deactivates the ICD's tachycardia therapy (the pacing function is preserved)
  • Continue resuscitation per standard protocol

Magnet Application on the ICD

Magnet application on the ICD is an important tool during resuscitation:

Situation	Magnet Application
ICD delivers repetitive inappropriate shocks	Place magnet → ICD shocks are suppressed
Patient in VF, ICD shocks ineffectively	Do NOT leave magnet on permanently → Do not deactivate ICD therapy; defibrillate externally
After successful resuscitation with a stable rhythm	Remove magnet → ICD therapy reactivated

Important: The magnet deactivates the ICD's tachycardia detection and therapy. On a standard pacemaker, however, the magnet causes a switch to asynchronous pacing mode (VOO/DOO) – this is a relevant distinction.

Caution: Some ICD models can be programmed so that the magnet response is disabled. In that case, only device interrogation with the programmer is possible. In an acute resuscitation setting, however, this is a secondary concern.

Rhythm Interpretation in Pacemaker Recipients

Rhythm analysis can be challenging in PM recipients:

Pacemaker Spikes and Pseudo-PEA

• Pacemaker spikes in VF: The pacemaker may continue to pace even during VF. You will see spikes interspersed within the fibrillation. This does not change the diagnosis of VF – defibrillate.
• Paced rhythm without a pulse = PEA: A regular paced rhythm with visible spikes and QRS complexes does not automatically indicate circulation. Check for a pulse! If pulseless, this is PEA → CPR, epinephrine, search for reversible causes.

AED Issues

Automated external defibrillators (AEDs) can be confused by pacemaker spikes. Older AED algorithms may interpret regular spikes as "no shock advised," even though fine VF is present but masked by the spikes. This is less problematic with manual rhythm assessment in the ACLS setting but should be kept in mind.

Post-Resuscitation Management: Device Interrogation

After successful resuscitation (return of spontaneous circulation, ROSC), the implanted device must be interrogated promptly:

• Functional check: Stimulation threshold measurement, sensing, impedances
• Lead status: Dislodgement? Fracture?
• Therapy history for ICDs: How many shocks were delivered? Were they appropriate?
• Reprogramming: Possible adjustment of detection parameters, stimulation thresholds, or therapy algorithms
• Device status: Check battery status after multiple shock deliveries

Device interrogation is performed by cardiologists or specialized technical personnel using the manufacturer-specific programmer. In the post-ROSC setting, this should be done promptly but not at the expense of other critical interventions (hemodynamics, temperature management, coronary angiography).

Summary: Key Take-Home Messages

• Never delay CPR and defibrillation because of an implanted device.
• Place defibrillation pads at least 8 cm from the device generator – anterior-posterior is often the best option.
• Do not reduce defibrillation energy – apply the standard protocol.
• Perform chest compressions at the usual quality – the device is typically not located in the compression zone.
• Internal ICD shocks do not replace external defibrillation – they are frequently not sufficiently effective.
• For inappropriate ICD shocks: Place a magnet over the device to deactivate tachycardia therapy.
• Pacemaker spikes ≠ circulation – always check for a pulse, recognize PEA.
• After ROSC: Arrange prompt device interrogation by specialists.

Hands-On Training

Resuscitating patients with an implanted pacemaker or ICD requires not only theoretical knowledge but above all practical routine: pad positioning under time pressure, rhythm interpretation with pacemaker artifacts, magnet application on the ICD, and consistent implementation of the ACLS algorithm despite an unfamiliar situation. In the ACLS courses offered by Simulation Tirol, you train these scenarios in realistic simulations with structured debriefing – so that in a real emergency, you make the right decisions without hesitation. All information and course dates can be found at simulationtirol.com.