Do clinically relevant transthoracic defibrillation energies cause myocardial damage and dysfunction?

Area of Science:

• Cardiology
• Medical Devices
• Emergency Medicine

Background:

• External defibrillation is critical for treating cardiac arrhythmias.
• The balance between defibrillation efficacy and cardiac damage from shock energy is not fully understood.
• Variability in patient factors and defibrillator use complicates optimal energy selection.

Purpose of the Study:

• To review existing evidence on cardiac damage and dysfunction caused by defibrillation shocks.
• To evaluate the safety and efficacy of different defibrillation waveform energies (monophasic and biphasic).
• To inform optimal energy selection for external defibrillation, particularly in pre-hospital settings.

Main Methods:

• Review of scientific literature on defibrillation shock effects.
• Analysis of evidence regarding cardiac damage thresholds for monophasic and biphasic waveforms.
• Examination of studies on shock energy levels in both perfused and non-perfused hearts.

Main Results:

• For perfused hearts, damage thresholds appear to exceed clinically delivered shock energies.
• In non-perfused hearts (human and animal), monophasic shocks up to 5 J/kg did not cause significantly more damage than smaller shocks; ischemia is a major factor.
• Biphasic shocks up to 360 J (5 J/kg) may be required for some patients, though comparative studies with lower energies are needed.

Conclusions:

• Current maximum energy limits for external defibrillation appear safe, especially for non-perfused hearts.
• Further research is needed to compare the efficacy and safety of 360 J versus 150 J biphasic shocks.
• Maintaining the 5 J/kg energy limit for biphasic shocks, consistent with monophasic shocks, is a reasonable interim approach.