What are the shockable heart rhythms?

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Shockable Heart Rhythms

The shockable heart rhythms are ventricular fibrillation (VF) and pulseless ventricular tachycardia (pVT). 1, 2

Definition and Classification

  • Shockable rhythms consist exclusively of ventricular fibrillation and pulseless ventricular tachycardia, which are the only cardiac arrest rhythms amenable to defibrillation therapy. 3, 2

  • These rhythms are distinguished from non-shockable rhythms, which include asystole and pulseless electrical activity (PEA), and require fundamentally different management approaches. 1, 2

Clinical Significance and Outcomes

  • Patients presenting with shockable rhythms have dramatically better survival outcomes, with 4-9 times higher survival rates compared to non-shockable rhythms. 1, 2

  • Cardiac arrest due to an initial rhythm of VF/pVT has better rates of survival to hospital discharge with favorable neurological function than arrests due to non-shockable rhythms. 3

  • In epidemiologic studies, survival statistics are consistently better when rhythms recorded by first responders are shockable (VF, pulseless VT) compared with pulseless electrical activity or asystole. 3

  • Over 80% of successful defibrillations occur within the first three shocks, with survival decreasing as the number of defibrillation attempts required increases. 2

Important Clinical Distinctions

  • Not all ventricular tachycardias are shockable—the critical distinction depends on whether the patient has a pulse. 2

  • Symptomatic VT with a palpable pulse is treated with synchronized cardioversion (not defibrillation), while pulseless VT is treated as VF with immediate unsynchronized defibrillation shocks. 4

  • The risk of VF/pVT steadily increases throughout childhood and adolescence but remains less frequent than in adults. 3

Automated Detection Considerations

  • AEDs demonstrate high specificity (99-100%) for correctly identifying non-shockable rhythms and excellent sensitivity for VF (94-96%). 2, 5

  • However, AEDs show lower sensitivity for rapid VT (60-71%), and some devices may not consistently advise shocks for monomorphic VT or Torsades de Pointes at certain rates. 2, 6

  • This variability in automated detection underscores the importance of manual rhythm interpretation by trained providers when possible. 6

References

1
Guideline

Management of Cardiac Arrest Rhythms

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

2
Guideline

Shockable Cardiac Rhythms

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

3
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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