The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 07, 2004
Filed:
Feb. 21, 2003
David Prutchi, Lake Jackson, TX (US);
Patrick J. Paul, Lake Jackson, TX (US);
Gregory R. Martin, Pearland, TX (US);
Intermedics Inc., Angleton, TX (US);
Abstract
A cardiac stimulator capable of measuring pacing impedance includes a tank capacitor for delivering charge to the heart via device leads, a shunt resistor, and high-impedance buffers for measuring pacing current through the shunt resistor. Soon after the leading edge of the stimulation pulse, the voltage across the shunt resistor, as sampled by a high-impedance buffer, indicates lead and cardiac tissue resistance. Just prior to opening the pacing switch to terminate the stimulation pulse, the voltage across the shunt resistor is sampled by a high-impedance buffer and held once again to allow the capacitance of the lead/heart tissue to be calculated. In alternative embodiments, a high-impedance buffer measures the voltage between the tank capacitor and ground immediately following the stimulation pulse to allow estimation of the lead/heart tissue capacitance. In one alternative embodiment, a look-up table is created in main memory and searched to find the closest lead/heart tissue capacitance estimate to any arbitrary degree of accuracy. In another alternative embodiment, the lead/heart tissue capacitance is estimated by successive approximation to any arbitrary degree of accuracy. When the lead/heart tissue capacitance and lead resistance have been determined, a plurality of parameters of importance for analyzing and optimizing a cardiac stimulation system may be calculated, such as the instantaneous current, the average current, the charge, and the energy delivered to the cardiac tissue.