Method and apparatus for detecting cardiac capture
First Claim
1. A pacemaker system comprising:
- a body-implantable pulse generator;
at least one conductive lead having a distal end and a proximal end, said proximal end for coupling to said pulse generator and having at least one lead electrode disposed near said distal end for placement within a chamber of a patient'"'"'s heart, said lead having conductor means adapted to deliver stimulating pulses to said heart and to convey cardiac electrical signals from said electrode to said pulse generator;
a common electrode, coupled to said pulse generator;
said pulse generator comprising;
a control circuit having signal generating means for issuing control signals including an excitation control signal for timing excitation pulses, a capture detect window signal for timing a capture detect window, and at least one stimulation control signal for timing and controlling pulse width and amplitude for stimulation pulses;
a stimulation circuit, coupled to said control circuit and to said lead, responsive to said at least one stimulation control signal to generate a stimulation pulse having amplitude and pulse width determined by said at least one stimulation control signal;
an excitation circuit, coupled to said control circuit, said common electrode, and said lead, said control circuit being responsive to said excitation control signal to generate excitation pulses to be applied to said heart via said lead;
an impedance circuit, coupled to said control circuit and to said lead and responsive to assertion of said capture detect window signal following generation of a stimulation pulse by said stimulation circuit to derive a cardiac impedance signal reflecting a voltage differential between said lead electrode and said common electrode;
an impedance processing circuit, coupled to said impedance circuit and to said control circuit and responsive to said capture detect window signal to derive at least one morphology value reflecting morphology of said impedance signal so as to characterize said impedance signal with said morphology value;
wherein said control circuit comprises a control value reading circuit for reading at least one control value and comparator means to compare said at least one morphology value to said at least one control value to determine whether said stimulation pulse achieved cardiac capture.
0 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus for automatic determination of a pacemaker patient'"'"'s pacing stimulation threshold. Circuitry is provided in a pacemaker for obtaining a signal reflecting cardiac impedance, which is known to reliably reflect certain aspects of cardiac function. Circuitry is also provided for monitoring the cardiac impedance waveform during a predetermined capture detect window following delivery of stimulating pulses. One or more values are derived which characterize the morphology of the impedance waveform during the capture detect window associated with each stimulation pulse delivered. These values are compared to predetermined control values in order to assess whether a stimulation pulse has achieved cardiac capture. The assessment of whether cardiac capture has been achieved is also based partly upon the conventional sensing of atrial and/or ventricular cardiac signals occurring during the capture detect window. In one embodiment of the invention, the control values against which impedance waveform characterization values are compared are obtained by delivering a series of stimulation pulses having sufficient energy to ensure that capture is achieved, and by monitoring the impedance waveform during delivery of these pulses.
51 Citations
7 Claims
-
1. A pacemaker system comprising:
-
a body-implantable pulse generator; at least one conductive lead having a distal end and a proximal end, said proximal end for coupling to said pulse generator and having at least one lead electrode disposed near said distal end for placement within a chamber of a patient'"'"'s heart, said lead having conductor means adapted to deliver stimulating pulses to said heart and to convey cardiac electrical signals from said electrode to said pulse generator; a common electrode, coupled to said pulse generator; said pulse generator comprising; a control circuit having signal generating means for issuing control signals including an excitation control signal for timing excitation pulses, a capture detect window signal for timing a capture detect window, and at least one stimulation control signal for timing and controlling pulse width and amplitude for stimulation pulses; a stimulation circuit, coupled to said control circuit and to said lead, responsive to said at least one stimulation control signal to generate a stimulation pulse having amplitude and pulse width determined by said at least one stimulation control signal; an excitation circuit, coupled to said control circuit, said common electrode, and said lead, said control circuit being responsive to said excitation control signal to generate excitation pulses to be applied to said heart via said lead; an impedance circuit, coupled to said control circuit and to said lead and responsive to assertion of said capture detect window signal following generation of a stimulation pulse by said stimulation circuit to derive a cardiac impedance signal reflecting a voltage differential between said lead electrode and said common electrode; an impedance processing circuit, coupled to said impedance circuit and to said control circuit and responsive to said capture detect window signal to derive at least one morphology value reflecting morphology of said impedance signal so as to characterize said impedance signal with said morphology value; wherein said control circuit comprises a control value reading circuit for reading at least one control value and comparator means to compare said at least one morphology value to said at least one control value to determine whether said stimulation pulse achieved cardiac capture. - View Dependent Claims (2, 3, 4, 5, 6, 7)
-
Specification