Key result
Body surface area predicts defibrillation threshold in biphasic ICDs, explaining ~9% of total variation.
Why the study?
What clinical variables predict defibrillation threshold (DFT) in patients receiving nonthoracotomy biphasic ICD systems?
Observational (n=284)
What clinical variables predict defibrillation threshold (DFT) in patients receiving nonthoracotomy biphasic ICD systems?
Effect estimate: r = 0.3
p-value: p=< 0.01
Body surface area modestly influences defibrillation threshold for biphasic ICDs, while other factors like LVEF do not.
BSA modestly predicts biphasic ICD DFT but explains little variance; leaves open whether it informs testing or selection in practice.
The clinical variables affecting DFT for ICD systems are not completely determined, especially with regard to biphasic shocking devices. To distinguish which factors correlate with DFT, we examined data from patients who were enrolled in the Ventak P2/Endotak protocol. A total of 284 patients were enrolled in the study. Two patients had a DFT > 25 J and did not receive the device; 154 did not undergo stepdown to failure DFT testing. The remaining 128 patients had formal DFT testing and were suitable for analysis. Variables available for analysis included age, body surface area (BSA), LVEF, gender, lead configuration, primary arrhythmia, primary cardiac disease, and use of cardioactive medication. Data were evaluated using regression analysis, fitting DFT (range, 1-25 J, mean 11 +/- 5 J) as a function of each variable. As a univariate predictor. BSA was found to be significant in predicting DFT, but accounted for only 9% of the total variation on the DFT (P < 0.01, r = 0.3). This study suggests that DFT using a biphasic shocking waveform is modestly in fluenced by the BSA of the patient. Other specific factors, including LVEF, do not predict DFT.
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Horton et al. (1997) conducted an observational in ICD implantation (n=284). Body surface area (BSA) was evaluated on Defibrillation threshold (DFT) (r = 0.3, p=< 0.01). Body surface area was a significant univariate predictor of defibrillation threshold for biphasic ICDs, accounting for 9% of the total variation (r=0.3, P<0.01).
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