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Decline in defibrillation thresholds
M W Kroll1, K M Anderson, C G Supino
1AngeMed, Plymouth, MN 55447.
Pacing and Clinical Electrophysiology : PACE
|January 1, 1993
Summary
Defibrillation thresholds (DFT) have steadily declined over 18 years due to advancements in waveforms and electrodes. This meta-analysis reveals key factors influencing DFT reduction, impacting device development.
Area of Science:
- Biomedical Engineering
- Cardiology
- Medical Device Technology
Background:
- Research has focused on reducing defibrillation thresholds (DFT) through improved waveforms and electrodes.
- It was hypothesized that DFTs are declining steadily, similar to pacing thresholds.
Purpose of the Study:
- To conduct a meta-analysis of defibrillation thresholds (DFTs) from published reports.
- To identify factors influencing the decline in DFTs over time.
Main Methods:
- A meta-analysis of 105 reports on DFTs from 58 articles (1973-1991) was performed.
- Included human, dog, and pig studies; excluded transthoracic and isolated heart studies.
- Analyzed variables included publication year, study type, electrode type, waveform, and system configuration.
Main Results:
- DFTs showed a significant correlation with publication year (P = 0.013), dropping 0.75 joules/year.
- Multivariate analysis (r2 = 0.51) identified six significant variables: epicardial electrodes, subcutaneous patch, biphasic wave, and coronary sinus electrode decreased DFTs; human subjects and catheter-based systems increased DFTs.
Conclusions:
- Defibrillation thresholds have declined over 18 years due to electrode and waveform improvements.
- The trend suggests a need to re-evaluate the practice of creating devices with ever-increasing energy ratings.
- Animal models serve as useful predictors for clinical DFTs.