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Effect of pulse separation between two sequential biphasic shocks given over different lead configurations on
E E Johnson1, C A Alferness, P D Wolf
1Department of Medicine, Duke University Medical Center, Durham, N.C.
Circulation
|June 1, 1992
Summary
Optimizing the interval between sequential biphasic shocks is crucial for defibrillation. Intervals of ≤10 ms or 75–125 ms improve efficacy, while 50 ms increases defibrillation thresholds.
Area of Science:
- Cardiovascular Research
- Electrophysiology
- Medical Devices
Background:
- Sequential biphasic shocks enhance defibrillation efficacy over single shocks.
- The impact of intershock intervals on defibrillation requires investigation.
Purpose of the Study:
- To determine the optimal intershock interval for sequential biphasic shocks.
- To assess how varying shock delays affect defibrillation thresholds and success rates.
Main Methods:
- Defibrillation thresholds (DFTs) were measured in dogs with varying intershock intervals (0.2–125 ms).
- Lead configurations included right ventricular apex to left lateral thorax and left ventricular apex to right ventricular outflow tract.
- Defibrillation probability-of-success curves were generated to confirm DFT findings.
Main Results:
- Mean DFTs were lower than single-shock thresholds at intervals ≤10 ms or 75–125 ms (p = 0.002).
- A significant rise in DFT to 27 J occurred at a 50 ms interval.
- Optimal intervals for minimum energy requirements were 0.2 ms and 90% of the activation interval.
Conclusions:
- Optimal intershock intervals for sequential biphasic shocks are ≤10 ms or 75–125 ms.
- A 50 ms interval may reinduce fibrillation, necessitating a stronger second shock.
- Timing is critical for maximizing defibrillation success with sequential shocks.
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