The electrical treatment of arrhythmias includes cardioversion, defibrillation, stimulation to prevent arrhythmias and ablation of arrhythmogenic tissue. Little is known about the basic mechanisms of how electric stimulation halts or prevents arrhythmias and ablates tissue. Experimental techniques have been developed by us to study these basic mechanisms by determining the potential gradient and current density fields created throughout the heart by the electrical stimulus as well as by mapping the activation sequences immediately before and after the stimulus. These techniques will be used to accomplish the following specific aims.
Specific Aim #1 : To determine the basic mechanism by which a chock halts ventricular tachycardia and the shock field strength needed to halt ventricular tachycardia in animals. The mechanism by which cardioversion inadvertently induces fibrillation will also be determined. The optimum cardioversion electrode configurations will be determined for tachycardias arising from different cardiac regions.
Specific Aim #2 : To determine the mechanism and field characteristics with which a shock halts ventricular fibrillation in humans. High shock fields adjacent to cardiac defibrillation electrodes will be investigated to see if they cause post-shock conduction disturbances.
Specific Aim #3 : To determine the mechanisms by which inhibition and stimulation during the protective zone can prevent arrhythmias. An array of stimulating electrodes will be developed to create the required electrical field to prevent arrhythmia induction.
Specific Aim #4 : To determine if the amount and location of tissue necrosis during electrical ablation is a function of the electrical field strength. If so, the field strength causing ablation will be determined as a function of stimulus duration. Modeling and experimentation will be used to develop a multi-electrode catheter probe for insertion into the left ventricular cavity to create focused fields for ablating predictable known locations and amounts of myocardium. The effects of fiber orientation and shock waveform, e.g., monophasic, biphasic, and triphasic, will be determined as part of all four specific aims. Accomplishing these specific aims will be a large step forward in understanding the fundamental principles governing the response of the myocardium to externally applied electric fields and should lead to better therapies to halt and prevent ventricular tachyarrhythmias.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL044066-05
Application #
3362804
Study Section
Cardiovascular and Renal Study Section (CVB)
Project Start
1990-01-01
Project End
1994-05-15
Budget Start
1994-01-01
Budget End
1994-05-15
Support Year
5
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Duke University
Department
Type
Schools of Medicine
DUNS #
071723621
City
Durham
State
NC
Country
United States
Zip Code
27705
Idriss, S F; Wolf, P D; Smith, W M et al. (1999) Effect of pacing site on ventricular fibrillation initiation by shocks during the vulnerable period. Am J Physiol 277:H2065-82
Malkin, R A; Souza, J J; Ideker, R E (1997) The ventricular defibrillation and upper limit of vulnerability dose-response curves. J Cardiovasc Electrophysiol 8:895-903
Walcott, G P; Rollins, D L; Smith, W M et al. (1996) Effect of changing capacitors between phases of a biphasic defibrillation shock. Pacing Clin Electrophysiol 19:945-54
Zhou, X; Smith, W M; Rollins, D L et al. (1996) Transmembrane potential changes caused by shocks in guinea pig papillary muscle. Am J Physiol 271:H2536-46
Malkin, R A; Pilkington, T C; Ideker, R E (1996) Estimating defibrillation efficacy using combined upper limit of vulnerability and defibrillation testing. IEEE Trans Biomed Eng 43:69-78
Usui, M; Walcott, G P; Strickberger, S A et al. (1996) Effects of polarity for monophasic and biphasic shocks on defibrillation efficacy with an endocardial system. Pacing Clin Electrophysiol 19:65-71
Zhou, X; Ideker, R E; Blitchington, T F et al. (1995) Optical transmembrane potential measurements during defibrillation-strength shocks in perfused rabbit hearts. Circ Res 77:593-602
Usui, M; Walcott, G P; KenKnight, B H et al. (1995) Influence of malpositioned transvenous leads on defibrillation efficacy with and without a subcutaneous array electrode. Pacing Clin Electrophysiol 18:2008-16
Alt, E U; Fotuhi, P C; Callihan, R L et al. (1995) Endocardial carbon-braid electrodes. A new concept for lower defibrillation thresholds. Circulation 92:1627-33
KenKnight, B H; Eyuboglu, B M; Ideker, R E (1995) Impedance to defibrillation countershock: does an optimal impedance exist? Pacing Clin Electrophysiol 18:2068-87

Showing the most recent 10 out of 56 publications