Chapter 10. Cardiac pacing

Cardiac pacing is a life-saving intervention in peri-arrest situations. ALS providers must be proficient in non-invasive pacing and recognise when transvenous or permanent pacing is required. Special considerations must be taken when managing patients with implanted devices, ensuring proper placement of defibrillation pads and awareness of potential device malfunctions.

1. Indications for Cardiac Pacing

• Cardiac pacing is necessary when bradyarrhythmias result in haemodynamic instability or cardiac arrest.
• Situations requiring pacing include:
  • Complete heart block (CHB), especially broad-complex CHB.
  • Symptomatic severe bradycardia not responding to pharmacological treatment.
  • Risk of asystole (e.g., high-grade AV block, ventricular standstill).

2. Formation and Transmission of Electrical Signals in the Heart

• The sinoatrial (SA) node generates electrical impulses, acting as the heart’s natural pacemaker.
• If the SA node fails, secondary pacemakers in the atrioventricular (AV) node or ventricular myocardium take over.
• The conduction system includes the His-Purkinje fibres, which transmit impulses to the ventricles.

3. Methods of Pacing

Cardiac pacing can be classified into non-invasive and invasive methods:

A. Non-Invasive Pacing

1. Percussion Pacing (Fist Pacing)
   • Involves delivering rhythmic thumps to the praecordium.
   • Temporary measure when transcutaneous pacing is unavailable.
2. Transcutaneous Pacing (TCP)
   • Electrodes deliver electrical impulses externally to stimulate heart contractions.
   • Advantages: Quick setup, minimal training required.
   • Used as a bridge to transvenous pacing or spontaneous recovery.

B. Invasive Pacing

1. Temporary Transvenous Pacing (TTVP)
   • Involves inserting a pacing lead via a vein into the right ventricle.
   • Indicated for prolonged pacing needs.
2. Permanent Pacing
   • Involves implanting a pacemaker for long-term rhythm management.
   • Used for chronic bradyarrhythmias or heart failure (e.g., cardiac resynchronisation therapy).

4. Recognising and Managing Pacing Failure

• Loss of Capture: No QRS complex follows pacing spikes.
• Lead Displacement: Can cause intermittent failure or arrhythmias.
• High Thresholds: Excessive energy required for capture, possibly due to myocardial disease or metabolic disturbances (e.g., hyperkalaemia).

Management:

• Adjust pacing thresholds.
• Check for mechanical and electrical capture.
• Consider repositioning leads if transvenous pacing fails.

5. Managing Patients with Implanted Devices

• Pacemakers: Ensure defibrillator pads are at least 10-15 cm away from the device.
• Implantable Cardioverter Defibrillators (ICDs): Can deliver life-saving shocks for ventricular arrhythmias.
• Deactivation of ICDs Post-Mortem: Prevents inappropriate shocks in a deceased patient.