Defibrillation thresholds declined significantly over 18 years, showing an average drop of 0.75 joules per year correlated with publication year (P=0.013).
Meta-Analysis
Have defibrillation thresholds declined over time due to improved waveforms and electrodes?
Defibrillation thresholds steadily declined over an 18-year period due to technological improvements in electrodes and waveforms, suggesting that ever-increasing energy ratings for devices may need reexamination.
Effect estimate: average drop of 0.75 joules/year
p-value: p=0.013
UNLABELLED: Much research has been done to lower defibrillation thresholds (DFT) through improved waveforms and electrodes. We hypothesized that DFTs are declining steadily, as did pacing thresholds. We performed a meta-analysis of 105 reports of DFTs from 58 articles and abstracts published from 1973 to 1991. Human, dog, and pig studies were included. Transthoracic and isolated heart studies were excluded. Variables analyzed were: publication year, human study, epicardial electrodes only, multiple pathways (simultaneous or sequential), biphasic wave, subcutaneous patch, coronary sinus electrode, spring-patch combination, and catheter-based. DFTs are highly correlated with publication year (P = 0.013) and show an average drop of 0.75 joules/year by a linear univariate analysis. A linear multivariate analysis (r2 = 0.51) gave six significant variables for the DFT: epicardial electrodes only, subcutaneous patch, biphasic wave, coronary sinus electrode (each decreased DFTs), and human subject and catheter-based system (increased DFTs). CONCLUSIONS: DFTs have shown a decline over 18 years through electrode and waveform improvements. The practice of making devices with ever increasing energy ratings may eventually merit reexamination. The animal model is a useful predictor for clinical DFTs.
Kroll et al. (1993) conducted a meta-analysis in Defibrillation thresholds. Publication year was evaluated on Defibrillation thresholds (DFT) (average drop of 0.75 joules/year, p=0.013). Defibrillation thresholds declined significantly over 18 years, showing an average drop of 0.75 joules per year correlated with publication year (P=0.013).