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Caldwell JC, Burton FL, Cobbe SM, et al. Slowing of Electrical Activity in Ventricular Fibrillation is Not Associated with Increased Defibrillation Energies in the Isolated Rabbit Heart. Front Physiol. 2011;2:11doi: 10.3389/fphys.2011.00011.
Caldwell, J. C., Burton, F. L., Cobbe, S. M., & Smith, G. L. (2011). Slowing of Electrical Activity in Ventricular Fibrillation is Not Associated with Increased Defibrillation Energies in the Isolated Rabbit Heart. Frontiers in physiology, 211. https://doi.org/10.3389/fphys.2011.00011
Caldwell, Jane C, et al. "Slowing of Electrical Activity in Ventricular Fibrillation is Not Associated with Increased Defibrillation Energies in the Isolated Rabbit Heart." Frontiers in physiology vol. 2 (2011): 11. doi: https://doi.org/10.3389/fphys.2011.00011
Caldwell JC, Burton FL, Cobbe SM, Smith GL. Slowing of Electrical Activity in Ventricular Fibrillation is Not Associated with Increased Defibrillation Energies in the Isolated Rabbit Heart. Front Physiol. 2011 Apr 06;2:11. doi: 10.3389/fphys.2011.00011. eCollection 2011. PMID: 21519386; PMCID: PMC3078558.
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Front Physiol. 2011 Apr 06;2:11. doi: 10.3389/fphys.2011.00011. eCollection 2011.

Slowing of Electrical Activity in Ventricular Fibrillation is Not Associated with Increased Defibrillation Energies in the Isolated Rabbit Heart.

Frontiers in physiology

Jane C Caldwell, Francis L Burton, Stuart M Cobbe, Godfrey L Smith

Affiliations

  1. Institute of Cardiovascular and Medical Sciences, University of Glasgow Glasgow, UK.

PMID: 21519386 PMCID: PMC3078558 DOI: 10.3389/fphys.2011.00011

Abstract

Prolonged out-of-hospital ventricular fibrillation (VF) arrests are associated with reduced ECG dominant frequency (DF) and diminished defibrillation success. Partial reversal of ischemia increases ECG DF and improves defibrillation outcome. We have investigated the metabolic components of ischemia responsible for the decline in ECG DF and defibrillation success. Isolated Langendorff-perfused rabbit hearts were loaded with the voltage-sensitive dye RH237. Using a photodiode array, epicardial membrane potentials were recorded at 252 sites (15 mm × 15 mm) on the anterior surface of the left and right ventricles. Simultaneously, a global ECG was recorded. VF was induced by burst pacing, and after 60s, perfusion was either reduced to 6 ml/min or the perfusate composition changed to impose hypoxia (95% N(2)/5% CO(2)), pH 6.7 (80% O(2)/20% CO(2)), or hyperkalemia (8 mM). Using fast Fourier transform, power spectra were created from the optical signals and the global ECG. The optical power spectra were summated to give a global power spectrum (pseudoECG). At 600 s the minimum defibrillation voltage (MDV) was determined by step-up protocol. During VF, the ECG and pseudoECG DF were reduced by low-flow ischemia (9.0 ± 1.0 Hz, p < 0.01, n = 5) and raised [K(+)](o) (12.2 ± 1.3 Hz, p < 0.05, n = 7) compared to control (19.2 ± 1.5 Hz, n = 20), but were unaffected by acidic pH(o) (16.7 ± 1.1 Hz, n = 11) and hypoxia (14.0 ± 1.2 Hz, n = 10). In contrast, the MDV was raised by acidic pH (156.1 ± 26.4 V, p < 0.001) and hypoxia (154.1 ± 22.1 V, p < 0.01) compared to control (65.6 ± 2.3 V), but comparable changes were not observed in low-flow ischemia (61.0 ± 0.5 V) or raised [K(+)](o) (56 ± 3 V). In summary, different metabolites are responsible for the reduction in DF and the increase in defibrillation energy during ischemic VF.

Keywords: defibrillation; ischemia; optical mapping; ventricular fibrillation

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