Document Detail

The effect of ischemia on ventricular fibrillation as measured by fractal dimension and frequency measures.
MedLine Citation:
PMID:  17630089     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Most animal studies of ventricular fibrillation (VF) waveform characteristics involve healthy animals with VF initiated by electric shock. However, clinical VF is usually the result of ischemia. The waveform characteristics in these two types of VF may differ. The angular velocity (AV), frequency ratio (FR) and median frequency (MF) are three frequency-based measures of VF. The scaling exponent (ScE), the logarithm of the absolute correlations (LAC) and the Hurst exponent (HE) are three measures of the fractal dimension of VF. HYPOTHESIS: We hypothesized that these quantitative measures would differ between ischemic and electrically initiated VF. METHODS: VF was induced in 14 swine by electric shock and in 12 swine by ischemia. For ischemia induced VF animals, an angioplasty catheter was positioned in the mid-LAD and the balloon inflated. A mean of 891+/-608 (S.D.)s later, VF occurred. For electrically induced animals, an AC current was passed through a catheter in the RV. Following initiation by either method, VF was recorded for 7min. Sequential 5s epochs were analyzed for AV, FR, MF and fractal dimension measures. RESULTS: Ischemic VF demonstrated a significantly higher fractal dimension as estimated by the ScE for the first 0-90s (p=0.021) and for 90-180s (p=0.016). The Hurst exponent was significantly higher for ischemic VF for both 0-90s (p<0.0001) and 90-180s (p<0.0001). The fractal dimension as estimated by the LAC method was not significantly different for 0-90s (p=0.056) but was highly significant for 90-180s (p=0.001). During the initial 90s the groups did differ in all measures of frequency as follows: AV (p<0.001), FR (p<0.001), MF (p<0.001). These differences did not persist beyond 90s except for a mild elevation of the FR after 270s (p<0.02). CONCLUSION: Fractal based measures indicate an increase in the fractal dimension of ischemia induced VF for the first 180s when compared to electrically induced VF. Frequency-based measures uniformly demonstrate a pattern of higher frequencies for electrically induced VF for the first 90s. The increased fractal dimension and decreased frequencies associated with ischemia induced VF may reflect changes in the underlying myocardial physiology that can be used to guide therapies.
Lawrence D Sherman; James T Niemann; John P Rosborough; James J Menegazzi
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural     Date:  2007-07-13
Journal Detail:
Title:  Resuscitation     Volume:  75     ISSN:  0300-9572     ISO Abbreviation:  Resuscitation     Publication Date:  2007 Dec 
Date Detail:
Created Date:  2007-11-12     Completed Date:  2008-03-07     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0332173     Medline TA:  Resuscitation     Country:  Ireland    
Other Details:
Languages:  eng     Pagination:  499-505     Citation Subset:  IM    
St. Francis Hospital, Federal Way, WA, USA.
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MeSH Terms
Disease Models, Animal
Electric Stimulation
Electrocardiography / methods*
Myocardial Ischemia / complications*
Random Allocation
Signal Processing, Computer-Assisted*
Sus scrofa
Ventricular Fibrillation / etiology*,  physiopathology*
Grant Support
R01 1HL080483/HL/NHLBI NIH HHS; R01 HL076671/HL/NHLBI NIH HHS; R01 HL076671-01A1/HL/NHLBI NIH HHS; R01 HL076671-02/HL/NHLBI NIH HHS; R01 HL076671-03/HL/NHLBI NIH HHS; R01 HL080483-01/HL/NHLBI NIH HHS; R01 HL080483-02/HL/NHLBI NIH HHS; R01 HL080483-03/HL/NHLBI NIH HHS

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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