Despite recent advances in the understanding of the mechanisms of interaction between electric fields and cardiac cells, and in the development of implantable cardiac defibrillators (ICDs), the fundamental principles of defibrillation have yet to be formulated. Despite the existence of several competing theories of defibrillation, the search for new strategies and techniques to lower defibrillation threshold (DFT) continues to be purely empirical. Previous work by the applicant's laboratory has shown that defibrillatory shocks delivered to the heart through a transvenous catheter electrode produce spatially heterogeneous transmembrane potential responses on the ventricular epicardium so as to create """"""""virtual cathodes"""""""", which may lead to heterogeneous action potential prolongation. Thus it is hypothesized that success or failure of defibrillation depends on the ability of the shock to (1) extinguish preshock-fibrillatory activity; (2) prevent remaining wavelets from sustaining ventricular fibrillation; and (3) avoid creating phase singularities (critical points). The investigator propose to systematically map patterns of shock-induced polarization and post-shock action potential prolongation from the entire epicardium of the Langendorff-perfused rabbit heart, using a state-of-the-art imaging system in combination with a voltage sensitive dye. The system has high spatial resolution and signal-to-noise ratio and is immune to shock- induced recording artefacts, The modulation of spatio-temporal characteristics of the polarization will be studied, as well as the resulting action potential prolongation or shortening by (1) the shock waveform, (2) the phase of pre-shock electrical activity; (3) the geometry of the heart and defibrillation electrodes. Whole heart patterns of polarization and action potential prolongation will be correlated with success or failure to defibrillate and with the defibrillation threshold (DFT).

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL059464-02
Application #
6030872
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Project Start
1998-07-15
Project End
2000-06-30
Budget Start
1999-07-01
Budget End
2000-06-30
Support Year
2
Fiscal Year
1999
Total Cost
Indirect Cost
Name
Cleveland Clinic Lerner
Department
Type
DUNS #
017730458
City
Cleveland
State
OH
Country
United States
Zip Code
44195
Kurian, Thomas K; Efimov, Igor R (2010) Mechanisms of fibrillation: neurogenic or myogenic? Reentrant or focal? Multiple or single? Still puzzling after 160 years of inquiry. J Cardiovasc Electrophysiol 21:1274-5
Glukhov, Alexey V; Fedorov, Vadim V; Lou, Qing et al. (2010) Transmural dispersion of repolarization in failing and nonfailing human ventricle. Circ Res 106:981-91
Li, Wenwen; Ripplinger, Crystal M; Lou, Qing et al. (2009) Multiple monophasic shocks improve electrotherapy of ventricular tachycardia in a rabbit model of chronic infarction. Heart Rhythm 6:1020-7
Ripplinger, Crystal M; Lou, Qing; Li, Wenwen et al. (2009) Panoramic imaging reveals basic mechanisms of induction and termination of ventricular tachycardia in rabbit heart with chronic infarction: implications for low-voltage cardioversion. Heart Rhythm 6:87-97
Mowrey, K A; Cheng, Y; Tchou, P J et al. (2002) Kinetics of defibrillation shock-induced response: design implications for the optimal defibrillation waveform. Europace 4:27-39
Cheng, Yuanna; Mowrey, Kent A; Nikolski, Vladimir et al. (2002) Mechanisms of shock-induced arrhythmogenesis during acute global ischemia. Am J Physiol Heart Circ Physiol 282:H2141-51
Yamanouchi, Y; Cheng, Y; Tchou, P J et al. (2001) The mechanisms of the vulnerable window: the role of virtual electrodes and shock polarity. Can J Physiol Pharmacol 79:25-33
Al-Khadra, A; Nikolski, V; Efimov, I R (2000) The role of electroporation in defibrillation. Circ Res 87:797-804
Efimov, I R; Cheng, Y; Yamanouchi, Y et al. (2000) Direct evidence of the role of virtual electrode-induced phase singularity in success and failure of defibrillation. J Cardiovasc Electrophysiol 11:861-8
Cheng, Y; Nikolski, V; Efimov, I R (2000) Reversal of repolarization gradient does not reverse the chirality of shock-induced reentry in the rabbit heart. J Cardiovasc Electrophysiol 11:998-1007

Showing the most recent 10 out of 16 publications