Damage in canine hearts following defibrillator shocks

Area of Science:

• Cardiology
• Biomedical Engineering
• Pathology

Background:

• Myocardial cell damage is a concern with defibrillator use.
• Damped sine wave (DSW) and truncated exponential waveform (TEW) are clinically available defibrillator waveforms.
• Understanding waveform-specific myocardial injury is crucial for patient safety.

Purpose of the Study:

• To compare the potential for myocardial cell damage between DSW and TEW defibrillators.
• To evaluate morphologic changes in myocardial tissue following transthoracic shocks.
• To assess the impact of different defibrillator waveforms on cardiac function and histology.

Main Methods:

• Experiments utilized 13 dogs shocked with DSW and 11 dogs shocked with TEW at 10 Joules/kg.
• Transthoracic shocks were delivered in three intervals with paddles.
• Cardiac function was monitored via ECG, technetium-99m pyrophosphate (Tc-PyP) uptake, and detailed morphologic analysis including electron microscopy.

Main Results:

• DSW defibrillation in 11 of 13 dogs resulted in ventricular tachycardia, heart block, Tc-PyP uptake, myocardial cell death, and necrosis.
• TEW defibrillation in only two dogs showed minimal microscopic foci of necrosis, without arrhythmias or Tc-PyP uptake.
• Myocardial lesions in the DSW group progressed from 24 to 72 hours post-shock.

Conclusions:

• TEW defibrillators cause significantly less myocardial damage than DSW defibrillators at equivalent energy levels in a canine model.
• The findings suggest TEW waveform is a safer alternative regarding myocardial injury.
• Further clinical studies are warranted to confirm these findings in human patients.