Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Patent
1994-08-11
1996-11-26
Lateef, Marvin M.
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
607 17, 128734, 128901, A61N 1368
Patent
active
055780644
ABSTRACT:
An implantable, rate responsive pacemaker, sensitive to impedance changes in the heart as an indicator of cardiac stroke volume, wherein the baseline impedance is eliminated from the measurement of impedance. In one embodiment, an adaptively controlled, balanced bridge is utilized to eliminate the baseline. A Wein bridge is provided having a variable reactance whose impedance is controlled continuously. In another embodiment, an impedance measurement is modified by a signal conditioner providing an appropriate varying offset through the use of a sample and hold circuit and other signal modifying circuits prior to converting the impedance measurement to digital information. In a third embodiment, a sample and hold circuit may be used to provide digital information through an A to D converter to a microprocessor which directly controls a variable reactance. The end voltage of a pacing capacitor is used as an indication of a baseline impedance.
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Intermedics Inc.
Lateef Marvin M.
Merkling John R.
Schaetzle Kennedy J.
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