Abstract: The invention relates to an ablation catheter which controls the temperature and reduces the coagulation of biological fluids on a tip of a catheter, prevents the impedance rise of tissue in contact with the catheter tip, and maximizes the potential energy transfer to the tissue, thereby allowing an increase in the lesion size produced by the ablation. The ablation catheter includes a catheter body. The ablation catheter also includes a tip for monitoring electrical potentials, and applying electrical energy to a biological tissue. A fluid source is positioned at one end of the catheter for supplying a fluid flow through the catheter to the tip means. Passages are positioned within the tip in a variety of manners for directing the fluid flow through the tip means to the exterior surface of the tip to control the temperature and form a protective fluid layer around the tip. Monitoring structure is also positioned within the tip structure for measurement of the electrical potentials in a biological tissue.

Abstract: A method of targeting and ablating cardiac tissue wherein an ablation catheter is directed and positioned at a potential ablation site, and is energized to a catheter tip temperature of approximately 50 degrees centigrade while observing whether AP block occurs. If block occurs, the site is confirmed and treatment is then initiated at a higher ablation level, either immediately or at a later time. On the other hand, if block does not occur within a first time interval T.sub.1, illustratively five or ten seconds, at the lower targeting energy, the catheter is repositioned and another site evaluated.

Abstract: The invention relates to an ablation catheter which controls the temperature and reduces the coagulation of biological fluids on a tip of a catheter, prevents the impedance rise of tissue in contact with the catheter tip, and maximizes the energy transfer to the tissue, thereby allowing an increase in the lesion size produced by the ablation. The ablation catheter includes a tip for applying electrical energy to biological tissue. Passages are positioned within the tip in a variety of manners for directing a fluid flow through the tip to the exterior surface of the tip to control the temperature and form a protective fluid layer around the tip. Monitoring structure is also positioned within the tip for measurement of the electrical potentials in a biological tissue. Ablation electrode structure is also positioned within the tip for application of ablative energy to the biological tissue.