The goal of this investigation is to achieve a safe, understandable, and precise means of modifying arrhythmogenic tissue via a catheter during a series of in-vitro tank and in-vivo canine experiments. Catheter mediated ablation of arrhythmogenic cardiac tissue using presently available techniques is, as yet, neither proven safe nor effective - especially for ventricular tachycardia or accessory pathways. One of the principle problems is the high pressure, high velocity shock waves generated from arcing of current during delivery of a standard defibrillator pulse resulting in barotraumatic cardiac rupture in some instances. The other problem with the present technique is poor control of tissue injury. This, we believe, results from poor understanding of the basic electrical factors mediating cell death. The focus of this investigation, therefore, will be on developing a better understanding of what type of electrical pulses generate shock waves and on identifying what electrical factors (i.e., energy, charge and/or voltage gradient) are responsible for tissue injury. A unique high energy, variable current waveform modulator capable of delivering synchronized pulses (singly or in bursts) with amplitudes of up to 50 Amps for periods of 1 microsec to 200msec will provide the means to complete the project. The pulses can be delivered synchronously with each heart beat for indefinite periods. Any shock waves that are generated will be monitored by a piezoelectric transducer capable of recording pressures with rise times as fast as 1.5 microsec for amplitudes of 2,000 PSI. The investigation first will identify in-vitro the optimal current waveform characteristics (pulse amplitude, pulse duration, number of pulses, pulse repetition interval, total bursting time, and duty factor) that will minimize creation of shock waves. The second phase will employ current modulation in a canine preparation to determine the relative effect of energy, charge, and/or voltage gradient on cell death. We expect to make catheter mediated ablation of arrhythmogenic tissue using electric pulses safe, predictable and understandable.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Unknown (R23)
Project #
5R23HL036170-02
Application #
3449208
Study Section
Surgery and Bioengineering Study Section (SB)
Project Start
1986-04-01
Project End
1989-03-31
Budget Start
1987-04-01
Budget End
1988-03-31
Support Year
2
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Washington
Department
Type
Schools of Medicine
DUNS #
135646524
City
Seattle
State
WA
Country
United States
Zip Code
98195
Marks, M L; Johnson, G; Hofer, B O et al. (1994) Biphasic waveform defibrillation using a three-electrode transvenous lead system in humans. J Cardiovasc Electrophysiol 5:103-8
Bardy, G H; Troutman, C; Johnson, G et al. (1991) Electrode system influence on biphasic waveform defibrillation efficacy in humans. Circulation 84:665-71
Bardy, G H; Sawyer, P L; Johnson, G W et al. (1990) Radio-frequency ablation: effect of voltage and pulse duration on canine myocardium. Am J Physiol 258:H1899-905
Bardy, G H; Allen, M D; Mehra, R et al. (1990) Transvenous defibrillation in humans via the coronary sinus. Circulation 81:1252-9
Dolack, G L; Callahan, D B; Bardy, G H et al. (1990) Signal-averaged electrocardiographic late potentials in resuscitated survivors of out-of-hospital ventricular fibrillation. Am J Cardiol 65:1102-4
Bardy, G H; Allen, M D; Mehra, R et al. (1990) An effective and adaptable transvenous defibrillation system using the coronary sinus in humans. J Am Coll Cardiol 16:887-95
Gartman, D M; Bardy, G H; Williams, A B et al. (1989) Direct surgical treatment of atrioventricular node reentrant tachycardia. J Thorac Cardiovasc Surg 98:63-71;discussion 71-2
Bardy, G H; Ivey, T D; Allen, M D et al. (1989) Evaluation of electrode polarity on defibrillation efficacy. Am J Cardiol 63:433-7
Bardy, G H; Sawyer, P L; Johnson, G W et al. (1989) Effect of voltage and charge of electrical ablation pulses on canine myocardium. Am J Physiol 257:H1534-42
Bardy, G H; Ivey, T D; Allen, M D et al. (1989) A prospective randomized evaluation of biphasic versus monophasic waveform pulses on defibrillation efficacy in humans. J Am Coll Cardiol 14:728-33

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