The goal of this study is to optimize catheter design for the cure of atrial fibrillation and ventricular tachycardia by endocardial radiofrequency (RF) ablation. It is estimated that currently in the USA about 2 million people are affected by some form of atrial fibrillation. Also, each year about 200,000 patients are treated for ventricular tachycardia. Atrial fibrillation, although itself not fatal, is a frequent cause of stroke and is linked to a high degree of cardiovascular mortality. Ventricular tachycardia is the main cause of sudden cardiac death, affecting particularly patients suffering from myocardial infarction. To cure cardiac dysrhythmias, radiofrequency current flows through an electrode on a catheter in contact with the endocardium to ablate undesired arrhythmia substrates. This research will improve the electrodes and improve the procedure. In vitro tests on myocardium will yield physical parameters of electric conductivity, and thermal conduction, capacity, and heat convection variation throughout the endocardium. In vivo swine tests will improve accuracy of most parameters. The parameters will be used to improve a 3-dimensional finite element computer model that simulates the electric power deposited, the myocardial temperature rise and the volume and distribution of the 50 degree Celsius contour that defines the lesion boundary. Further in vitro and in vivo tests will confirm the accuracy of the model. The model will predict lesion volumes resulting from proposed new electrodes. These are (1) uniform current density electrodes that prevent hot spots, steam generation """"""""popping"""""""" and coagulum formation; (2) noncontact electrodes that generate larger lesions; (3) needle electrodes that generate larger lesions; (4) long electrodes that generate linear lesions for curing atrial fibrillation; (5) balloon electrodes that permit large imprints; (6) cooled electrodes; and (7) other novel electrodes. The model will aid in the design of new electrodes. The model will also predict the lesion volume at each ablation site. These volume predictions will form guidelines for setting tip temperature to achieve desired lesion volume at each ablation site and thus enhance present ablation techniques.
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| Haemmerich, Dieter; Staelin, S T; Tsai, J Z et al. (2003) In vivo electrical conductivity of hepatic tumours. Physiol Meas 24:251-60 |
| Zhang, Jie; Tsai, Jang-Zern; Cao, Hong et al. (2003) Noncontact radio-frequency ablation for obtaining deeper lesions. IEEE Trans Biomed Eng 50:218-23 |
| Haemmerich, D; Wright, A W; Mahvi, D M et al. (2003) Hepatic bipolar radiofrequency ablation creates coagulation zones close to blood vessels: a finite element study. Med Biol Eng Comput 41:317-23 |
| Haemmerich, D; Ozkan, R; Tungjitkusolmun, S et al. (2002) Changes in electrical resistivity of swine liver after occlusion and postmortem. Med Biol Eng Comput 40:29-33 |
| Haemmerich, Dieter; Tungjitkusolmun, Supan; Staelin, S Tyler et al. (2002) Finite-element analysis of hepatic multiple probe radio-frequency ablation. IEEE Trans Biomed Eng 49:836-42 |
| Tungjitkusolmun, Supan; Haemmerich, Dieter; Cao, Hong et al. (2002) Modeling bipolar phase-shifted multielectrode catheter ablation. IEEE Trans Biomed Eng 49:10-7 |
| Cao, Hong; Speidel, Michael A; Tsai, Jang-Zern et al. (2002) FEM analysis of predicting electrode-myocardium contact from RF cardiac catheter ablation system impedance. IEEE Trans Biomed Eng 49:520-6 |
| Tsai, Jang-Zern; Will, James A; Hubbard-Van Stelle, Scott et al. (2002) In-vivo measurement of swine myocardial resistivity. IEEE Trans Biomed Eng 49:472-83 |
| Bin Choy, Young; Cao, Hong; Tungjitkusolmun, Supan et al. (2002) Mechanical compliance of the endocardium. J Biomech 35:1671-6 |
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