Article

Influence of the skeletal muscle activity on time and frequency domain properties of the body surface ECG during evolving ventricular fibrillation in the pig.

Nora Eccles Harrison Cardiovascular Research and Training Institute, University of Utah, Salt Lake City, UT, United States.
Resuscitation (impact factor: 3.6). 09/2008; 78(2):215-23. DOI:10.1016/j.resuscitation.2008.03.010 pp.215-23
Source: PubMed

ABSTRACT To evaluate influence of the skeletal muscle activity (SMA) on time and frequency domain properties of ECG during VF.
We studied the first 9min of electrically induced VF (N=7). We recorded Lead II ECG, 247 unipolar epicardial ventricular electrograms (UEGs) and 3 bipolar skeletal electromyograms (EMGs) near the positions of the ECG electrodes (sampling rate, 500Hz). We reconstructed ECG (RECG) from UEGs using forward-solution transformation matrix. Spectral properties of ECG, RECG, UEGs and MEGs were assessed in the range 2-250Hz by the median frequency (MF) and the upper limit of frequency range containing 99% of spectral energy (Flim(99)). Scaling exponent of ECG, RECG and EMGs was calculated in the ranges of 1-8 and 5-20 sampling intervals (ScE1-8 and ScE5-20, respectively).
We observed non-monotonic increases in MF and Flim(99) of the ECG, but not UEGs and RECG, at 1-5min of VF. Maximum values of MF and Flim(99) in ECG, UEGs and RECG were (in Hz): 32+/-29 and 166+/-67; 11+/-2 and 36+/-7; 10+/-2 and 32+/-6, respectively. The transient increases in the high-frequency content of the ECG were correlated with enhanced activity in EMGs, characterized by an almost uniform spectrum in the range 2-250Hz (MF=92+/-29; Flim(99)=245+/-4Hz). Peak values of ScE(1-8) were the highest in EMGs (1.95+/-0.04), intermediate in the ECG (1.59+/-0.26), and the lowest in RECG (1.088+/-0.007).
SMA significantly contributes to ECG during VF and can bias metrics used for assessment of VF organization.

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  • Article: Ventricular fibrillation scaling exponent can guide timing of defibrillation and other therapies.
    James J Menegazzi, Clifton W Callaway, Lawrence D Sherman, David P Hostler, Henry E Wang, Kristofer C Fertig, Eric S Logue
    [show abstract] [hide abstract]
    ABSTRACT: The scaling exponent (ScE) of the ventricular fibrillation (VF) waveform correlates with duration of VF and predicts defibrillation outcome. We compared 4 therapeutic approaches to the treatment of VF of various durations. Seventy-two swine (19.5 to 25.7 kg) were randomly assigned to 1 of 9 groups (n=8 each). VF was induced and left untreated until the ScE reached 1.10, 1.20, 1.30, or 1.40. Animals were treated with either immediate countershock (IC); 3 minutes of CPR before the first countershock (CPR); CPR for 2 minutes, then drugs given with 3 more minutes of CPR before the first shock (CPR-D); or drugs given at the start of CPR with 3 minutes of CPR before the first shock (Drugs+CPR). Return of spontaneous circulation (ROSC) and 1-hour survival were analyzed with chi2 and Kaplan-Meier survival curves. IC was effective when the ScE was low but had decreasing success as the ScE increased. No animals in the 1.30 or 1.40 groups had ROSC from IC (0 of 16). CPR did not improve first shock outcome in the 1.20 CPR group (3 of 8 ROSC). Kaplan-Meier survival analyses indicated that IC significantly delayed time to ROSC in both the 1.3 (P=0.0006) and the 1.4 (P=0.005) groups. VF of brief to moderate duration is effectively treated by IC. When VF is prolonged, as indicated by an ScE of 1.3 or greater, IC was not effective and delayed time to ROSC. The ScE can help in choosing the first intervention in the treatment of VF.
    Circulation 03/2004; 109(7):926-31. · 14.74 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.

Keywords

247 unipolar epicardial ventricular electrograms
 
3 bipolar skeletal electromyograms
 
5-20 sampling intervals
 
ECG electrodes
 
electrically induced VF
 
first 9min
 
forward-solution transformation matrix
 
frequency domain properties
 
frequency range
 
high-frequency content
 
highest
 
Lead II ECG
 
Maximum values
 
median frequency
 
non-monotonic increases
 
sampling rate
 
skeletal muscle activity
 
spectral energy
 
transient increases
 
uniform spectrum