Method of using endocardial impedance for determining electrode-tissue contact

• US 5,673,704 A
• Filed: 05/28/1996
• Issued: 10/07/1997
• Est. Priority Date: 01/28/1994
• Status: Expired due to Fees

• Current Assignee: Charles D. Gottlieb, David S. Schwartzman, Francis E. Marchlinski, Isaac Chang, Kenneth R. Foster, Mark S. Mirotznik
• Original Assignee: Charles D. Gottlieb, David S. Schwartzman, Francis E. Marchlinski, Isaac Chang, Kenneth R. Foster, Mark S. Mirotznik
• Inventors: Schwartzman, David S., Chang, Isaac, Mirotznik, Mark S., Foster, Kenneth R., Marchlinski, Francis E., Gottlieb, Charles D.
• Primary Examiner(s): Bahr, Jennifer
• Assistant Examiner(s): HUANG, STEPHEN D
• Application Number:
  US08/654,197
• Time in Patent Office: 497 Days
• Field of Search: 128/637, 128/642, 128/662.06, 128/670, 128/692, 128/701, 128/713, 128/654, 128/672, 128/734, 606/41, 607/41, 607/99, 607/122
• US Class Current: 600/552
• CPC Class Codes: A61B 18/1402 Probes for open surgery
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 2018/00702 Power or energy
• CPC Class Codes: A61B 2018/00875 Resistance or impedance
• CPC Class Codes: A61B 2018/126 bipolar
• CPC Class Codes: A61B 2034/2051 Electromagnetic tracking systems
• CPC Class Codes: A61B 2090/065 for measuring contact or contact pressure
• CPC Class Codes: A61N 1/025 Digital circuitry features of electrotherapy devices, e.g. memory, clocks, processors
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/056 Transvascular endocardial electrode systems
• CPC Class Codes: A61N 1/40 Applying electric fields by inductive or capacitive coupling microwave apparatus A61N5/00; Applying radio-frequency signals

Abstract

A method of locating infarcted myocardial tissue in a beating heart includes the step of inserting an impedance measuring tip of a catheter into the chamber of the beating heart, particularly the left or right ventricle, and measuring the impedance of the endocardium at various locations within the chamber of the beating heart. The values measured are compared to impedance values with a predetermined range of values to identify an infarcted area of myocardium and distinguish such area from normal myocardium. The measurements are also compared to a range of values for an infarction border zone. In accordance with the invention, the infarction border zone may be located. The infarction border zone is a significant source of arrhythmia, and particularly of ventricular tachycardia. Further, in accordance with the methods of the present invention, the risk of arrhythmia in a beating heart may be substantially reduced or eliminated by ablating endocardium within the infarction border zone utilizing the same catheter tip. Impedance measurements may also be utilized to assess the adequacy of the electrode-tissue contact, particularly in a fluid filled body organ or cavity. Further, the effectiveness of the ablation of the tissue may be determined by determining the degree of heating of the tissue by measuring the change in impedance in the area of ablation.

Claims

1. A method for assessing adequacy of electrode-tissue contact in a fluid filled organ, comprising the steps of:

inserting an impedance measuring electrode mounted on a catheter into a fluid filled organ;

measuring a non-zero impedance numerical value when the electrode is in fluid to establish a measured base line impedance numerical value;

comparing the measured base line impedance numerical value to a predetermined non-zero range of numerical values of impedance for the fluid;

measuring impedance numerical values as the electrode comes into contact with organ tissue;

comparing measured impedance numerical values to a predetermined range of impedance numerical values of the organ tissue; and

determining the adequacy of electrode-tissue contact by comparing said measured impedance numerical values with said predetermined ranges of impedance numerical values.

2. A method in accordance with claim 1, wherein said inserting step comprises inserting the impedance measuring electrode into a chamber of a beating heart.

3. A method for assessing adequacy of electrode-tissue contact in a beating heart, comprising the steps of:

inserting an impedance measuring electrode mounted on a catheter into a blood vessel connected to the beating heart;

measuring the impedance in blood in a blood vessel outside of the beating heart;

positioning the catheter electrode using fluoroscopy at least one stable catheter placement site on endocardium;

measuring the impedance at said at least one stable catheter placement site with the catheter electrode placed against endocardium as monitored by fluoroscopy to determine a range of impedance values corresponding to adequate electrode-tissue contact; and

determining from said two measuring steps whether the electrode is in contact with the endocardium in subsequent placements based on said determined values.