Signal Analysis of the Human Electrocardiogram During Ventricular Fibrillation: Frequency and Amplitude Parameters as Predictors of Successful Countershock,☆☆,,★★,

Presented in part at the Eight Purdue Conference on Cardiac Defibrillation, West Lafayette, Indiana, September 1994; and at the Second Chicago Symposium on Advances in Cardiopulmnoary Resuscitation Research, October 1994.
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Abstract

Study objective: To determine whether there is information in the human ventricular fibrillation (VF) ECG signal that is predictive of successful countershock. Methods: We carried out a retrospective analysis of ECG signals recorded during out-of-hospital treatment of adult patients in VF. Four parameters—-centroid frequency (FC), peak power frequency (FP), average segment amplitude (SA), and average wave amplitude (WA)—were extracted from the recorded ECG signal immediately before each countershock and compared with countershock outcome. Results: The outcome of each countershock (total, 128 countershocks) administered to 55 patients in VF was determined from available emergency medical services data sheets and time-domain ECG signal and voice recordings. The original 4-second time-domain ECG segment immediately before the countershock was used to extract SA and WA. The 4-second ECG segment immediately before each countershock was transformed into the frequency domain by means of Fourier analysis, and the parameters FC and FP were extracted from the result. These parameters were compared with countershock outcome by means of Kolmogorov-Smirnov analysis. Sensitivity and specificity of these parameters, as well as receiver operating characteristic curves, were constructed. FC was statistically higher for successful countershocks (FC, 5.48±.67 Hz) than for unsuccessful countershocks (FC, 4.85±1.16 Hz; P= .012). We found no statistical difference for FP (P=.066), SA (P=.549), and WA (P=.337). FP and FC, when used in combination and in certain ranges (3.5 Hz≤FP≤7.75 Hz and 3.86 Hz≤FC≤6.12 Hz) had a sensitivity of 100% and a specificity of 47.1% in predicting successful countershock. The probabilities of predicting countershock outcome for FC, FP, SA, and WA were .72, .70, .52, and .53, respectively. Conclusion: FC and FP are predictive of countershock outcome for patients in VF and hold the potential to guide therapy during cardiac arrest. [Brown CG, Dzwonczyk R: Signal analysis of the human electrocardiogram during ventricular fibrillation: Frequency and amplitude parameters as predictors of successful countershock. Ann Emerg Med February 1996;27:184-188.]

Section snippets

INTRODUCTION

Laboratory studies have shown that the success of electrical countershock in converting ventricular fibrillation (VF) to a supraventricular perfusing rhythm decreases with increasing durations of ischemia.1 More recently, in a second laboratory investigation the effect of immediate countershock versus epinephrine administration after 7.5 minutes of VF in a canine model of cardiac arrest was studied.2 In this study, when immediate countershock was followed by advanced cardiac life support

MATERIALS AND METHODS

This study was a retrospective analysis of ECG cassette recordings made during cardiac arrest. The study population comprised a convenience sample of 55 patients with out-of-hospital cardiac arrest in whom the initial ECG rhythm was identified as VF.

Patients in this study were monitored with a semiautomatic defibrillator/ECG monitor equipped with an ECG and voice cassette recorder (HeartAid 1000, HeartStart 1000, and HeartStart 2000; Laerdal). The ECG signals were reviewed with a HeartStart

RESULTS

Our patient population comprised 55 patients, who received a total of 324 countershocks. Of these countershocks, only 128 were free of artifact or had sufficient clinical information with which we could determine the result of the countershock and could therefore be used for analysis. Nine of the 128 countershocks analyzed in this study were successful. These nine successful countershocks were performed in seven patients. One patient accounted for three successful countershocks.

The Table

DISCUSSION

The results of this study suggest that the FC and the combination of FC and FP of the VF ECG signal are predictive of successful countershock in human beings during cardiac arrest.

Although we found a statistical difference in the frequency parameter FC relative to countershock outcome, the successful and unsuccessful distributions of the parameter data overlapped to some extent. Even with a combination of FC and FP, the highest cut-off point frequencies for 100% sensitivity for predicting a

Acknowledgements

The authors thank Paul Pepe, MD; David Michael; Richard Kessler; David Cheng; Kevin Ackley; Eric Drobney; and Eric Knipple for their assistance in the technical preparation of this study.

References (14)

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From the Departments of Emergency Medicine* and Anesthesiology, Ohio State University, Columbus, Ohio.

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Supported in part by a grant from Michigan Instruments, Incorporated.

A patent for the technology discussed in this article has been sought by Ohio State University and has been licensed to Michigan Instruments, Incorporated

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Address for reprints: Charles G Brown, MD, Department of Emergency Medicine, Ohio State University, 005 Upham Hall, 473 West 12th Avenue, Columbus, Ohio 43210, 614-293-8305, Fax 614-487-9584

Reprint no. 47/1/71223

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