Do defibrillators deliver shocks for atrial fibrillation (afib)?

Defibrillators and Atrial Fibrillation

Standard defibrillators are not designed to automatically deliver shocks for atrial fibrillation (AF), but specialized implantable atrial defibrillators can be programmed to treat AF with synchronized shocks. 1

Types of Defibrillators and Their Use in AF

Standard External Defibrillators

• Standard external defibrillators (manual and automated) are primarily designed to treat life-threatening ventricular arrhythmias such as ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT)
• While these devices can be used for cardioversion of AF in controlled clinical settings, they do not automatically detect and shock AF 1
• External cardioversion of AF requires:
  • Patient sedation
  • Synchronized shock delivery (to avoid R-on-T phenomenon)
  • Physician supervision
  • Controlled clinical environment

Automated External Defibrillators (AEDs)

• AEDs are specifically programmed to detect and treat VF and pVT
• They are NOT designed to detect or deliver shocks for AF
• AEDs will not recommend a shock for a patient in AF with a pulse 1

Implantable Cardioverter Defibrillators (ICDs)

• Standard ICDs are programmed to detect and treat ventricular arrhythmias
• They do not typically deliver therapy for AF unless specifically configured with atrial leads and programming
• Dual-chamber ICDs can detect AF but are not routinely programmed to treat it 1

Specialized Implantable Atrial Defibrillators

• Specialized devices have been developed specifically for AF treatment
• These devices can detect AF and deliver synchronized low-energy shocks (typically 3-5 J) 1
• In clinical studies, these devices have shown a 93% conversion rate to sinus rhythm 1
• Major limitation: shock energy >1 J is uncomfortable to awake patients, making routine use problematic without sedation 1, 2

Clinical Considerations for AF Management

Cardioversion for AF

• External cardioversion for AF requires synchronized shock delivery
• Biphasic waveforms are preferred over monophasic waveforms for AF cardioversion 1
• For biphasic defibrillators, there is no specific recommended energy level or strategy (fixed versus escalating) 1
• For monophasic defibrillators, a high initial energy (360 J) is preferable 1

Patient Comfort and Sedation

• Patients receiving atrial defibrillation typically require sedation for comfort
• Studies show that the need for sedation increases with the number of shocks required 2
• Multiple shocks are often needed due to immediate reinitiation of AF or initial failure to cardiovert 2

Emerging Technologies and Approaches

• Implantable atrial defibrillators with dual-chamber sensing and cardioversion capabilities have been developed 1
• These devices can provide accurate monitoring of AF episodes and deliver therapy
• Some devices are designed to attempt pacing termination of AF before delivering shocks 1
• Current candidates for atrial defibrillators are often also suitable for catheter ablation, which may be preferred 1

Important Caveats and Pitfalls

• Do not confuse AF with VF when using a defibrillator - they require different approaches
• Never attempt unsynchronized cardioversion for AF due to risk of inducing VF
• Standard AEDs should not be used for patients with AF who have a pulse
• Remember that AF with rapid ventricular response can deteriorate into pulseless rhythms that do require defibrillation
• Patients with implanted devices (pacemakers or ICDs) require special electrode placement during external cardioversion

In summary, while standard defibrillators can be used for synchronized cardioversion of AF in controlled settings, they do not automatically detect and shock AF during routine operation. Specialized implantable atrial defibrillators exist but have limitations related to patient comfort and competing treatment options.