Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Patent
1998-05-08
2000-10-31
Kamm, William E.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
600547, 607 1, A61N 100
Patent
active
061415855
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.
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Time Course of Transvenous Pacemaker Stimulation Impedance, Capture Threshold, and Electrogram Amplitude, Edward V. Platia and Jeffrey A. Brinker, Sep.-Oct. 1986, pp. 620-625, Washington, D.C.
Bioelectric Phonemena in Cardiac Pacing, M. Schaldach, 1987, pp. 0139-0142, Erlangen, West Germany.
Martin Gregory R.
Paul Patrick J.
Prutchi David
Evanisko George R.
Intermedics Inc.
Kamm William E.
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