What is the sensation when an Implantable Cardioverter-Defibrillator (ICD) discharges?

The Sensation of ICD Discharge

ICD discharges are typically experienced as a sudden, painful electric shock or kick to the chest that can be extremely distressing for patients, with many describing it as feeling like being kicked by a horse or hit in the chest with a baseball bat. 1

Physical Sensations During ICD Discharge

• Pain intensity: On average, patients rate the shock intensity as 5.44 on a scale of 0-10 1
• Common physical sensations:
  • Generalized nervousness
  • Dizziness
  • General weakness
  • Palpitations
  • Chest soreness
  • Nausea and vomiting 1

Psychological Impact

• Immediate psychological response:

  • Terror/fear is one of the most frequently reported sensations
  • Anxiety during and after the shock
  • Distress increases with multiple sequential shocks 1

• Factors that increase distress:

  • Lack of warning before the shock
  • Multiple shocks in succession
  • Progressive increase in sensation intensity with multiple shocks 1

Clinical Considerations

Loss of Consciousness

• Approximately 9% of patients experience loss of consciousness during ICD shocks 2
• Important to note that absence of syncope during one shock does not predict absence of syncope during subsequent shocks 2
• No reliable clinical variables (age, sex, history of syncope, left ventricular function, type of heart disease) can predict which patients will experience syncope during shocks 2

Impact on Quality of Life

• Frequent ICD shocks can significantly reduce quality of life 3
• Guidelines from the American College of Cardiology/American Heart Association note that "frequent shocks from an ICD can lead to a reduced quality of life, whether triggered appropriately by life-threatening rhythms or inappropriately by sinus or other supraventricular tachycardia" 3

Phantom Shocks

• Some patients experience "phantom shocks" - the sensation of receiving a shock when device interrogation confirms no actual discharge occurred 4
• These are more common:
  • In the first 6 months after implantation
  • During nighttime
  • In patients with clinical depression and higher anxiety levels 4

Management Considerations

Reducing Inappropriate Shocks

• For patients experiencing frequent shocks, consider:
  • Antiarrhythmic therapy (most commonly amiodarone) for recurrent discharges triggered by ventricular arrhythmias or atrial fibrillation 3
  • Catheter ablation for recurrent ICD discharges from ventricular tachycardia despite antiarrhythmic therapy 3
  • Optimizing ICD programming with longer detection delays and appropriate rate cutoffs 5

Patient Education and Support

• Patients and families should be prepared for the possibility and sensation of ICD shocks before implantation
• Anticipatory guidance about the physical and emotional impact of shocks can help reduce anxiety 1
• Discussing the possibility of phantom shocks may help patients distinguish between actual and perceived discharges 4

Important Caveats

• The experience of ICD shocks varies considerably between individuals
• Patients should be informed that the absence of syncope during one shock does not guarantee they won't lose consciousness during future shocks 2
• Driving and other activities requiring vigilance should be approached with caution after ICD implantation, particularly for devices that deliver only high-energy shocks 2