Demand pacemaker using an artificial baroreceptor reflex

Claim 2

A cardiac pacemaker for stimulating a heart to beat at a rate which is variable in response to physiological need, comprising: a pulse generator for generating periodic electrical pulses at a rate determined by a rate input signal supplied to said pulse generator; a pacing lead for delivering said periodic electrical pulse generated by said pulse generator to said heart; means for sensing arterial blood pressure and generating a signal indicative of arterial blood pressure; and means for generating said rate input signal in response to said signal indicative of arterial blood pressure.

Claim 3

A cardiac pacemaker as defined in claim 1, wherein said pulse generator generates said periodic electrical pulses only in the absence of naturally occurring heartbeats.

Claim 4

A cardiac pacemaker as defined in claim 1, wherein said sensing means senses arterial blood pressure at the proximal axillary artery.

Claim 5

A cardiac pacemaker as defined in claim 2, wherein said sensing means is located externally of the proximal axillary artery.

Claim 6

A cardiac pacemaker as defined in claim 1, wherein said sensing means comprises: a transducer located externally about an artery for producing a variable output indicative of the stretch in the arterial wall caused by pressure change of blood within said artery.

Claim 7

A cardiac pacemaker as defined in claim 5, wherein said transducer is a strain detector device.

Claim 8

A cardiac pacemaker as defined in claim 5, wherein said transducer operates by measuring pulse transit time.

Claim 9

A cardiac pacemaker as defined in claim 1, wherein said generating means has as an input the signal generated by said sensing means, said generating means using a transfer function to produce said rate input signal in response to said signal generated by said sensing means.

Claim 10

A cardiac pacemaker as defined in claim 8, wherein said transfer function is nonlinear.

Claim 11

A cardiac pacemaker as defined in claim 8, wherein said transfer function is linear.

Claim 12

A cardiac pacemaker as defined in claim 10, wherein said rate input signal is commanded heart interval, and said transfer function produces a value of commanded heart interval which is equal to a first constant a times the signal indicative of arterial pressure, plus a second constant b.

Claim 13

A cardiac pacemaker as defined in claim 10, wherein said rate input signal is commanded heart rate, and said transfer function produces a value of commanded heart rate which is equal to a third constant c times the signal indicative of arterial pressure, plus a fourth constant d.

Claim 14

A cardiac pacemaker as defined in claim 1, wherein said generating means comprises: means for amplifying the signal indicative of arterial blood pressure, said amplifying means having a gain a and producing an amplified output; and means for summing said amplified output with a constant b to produce said rate input signal.

Claim 15

A cardiac pacemaker as defined in claim 13, additionally comprising: means for maintaining the long term resting heart rate at a predetermined rate.

Claim 16

A cardiac pacemaker as defined in claim 14, wherein said maintaining means comprises: means for generating an error signal between said predetermined rate and said rate input signal; and means for periodically resetting said constant b in response to said error signal.

Claim 17

A cardiac pacemaker as defined in claim 13, additionally comprising: means for filtering said signal indicative of blood pressure to minimize harmonics due to the pulsatile nature of the arterial pressure waveform.

Claim 18

A cardiac pacemaker as defined in claim 16, wherein said filtering means has a time constant of between 0.3 and 1.6 seconds.

Claim 19

A cardiac pacemaker as defined in claim 1, wherein said generating means produces a rate input signal corresponding to a heart rate of between 60 and 170 beats per minute.

Claim 20

A cardiac pacemaker as defined in claim 1, additionally comprising: means for maintaining the long term resting heart rate at a predetermined level.

Claim 21

A cardiac pacemaker for stimulating a heart to beat at a rate which is variable in response to physiological need, comprising: a pulse generator for generating periodic electrical pulses at a rate determined by a rate input signal supplied to said pulse generator; a pacing lead for delivering said periodic electrical pulse generated by said pulse generator to said heart; a transducer located about an artery for producing a variable output signal indicative of arterial blood pressure in response to the stretch in the arterial wall caused by pressure change of blood within said artery; means for amplifying the signal indicative of arterial blood pressure, said amplifying means having a gain a and producing an amplified output; and means for summing said amplified output with a constant b to produce said rate input signal.

Claim 22

A cardiac pacemaker for stimulating a heart to beat at a rate which is variable in response to physiological need, comprising: a pulse generator for generating periodic electrical pulses at a rate determined by a rate input signal supplied to said pulse generator; a pacing lead for delivering said periodic electrical pulse generated by said pulse generator to said heart; a transducer located about an artery for producing a variable output signal indicative of arterial blood pressure in response to the stretch in the arterial wall caused by pressure change of blood within said artery; means for amplifying the signal indicative of arterial blood pressure, said amplifying means having a gain a and producing an amplified output; and means for summing said amplified output with a constant b to produce said rate input signal.

Claim 23

A cardiac pacemaker for stimulating a heart to beat at a rate which is variable in response to physiological need, comprising: a pulse generator for generating periodic electrical pulses at a rate determined by a rate input signal supplied to said pulse generator; a pacing lead for delivering said periodic electrical pulse generated by said pulse generator to said heart; a transducer located about an artery for producing a variable output signal indicative of arterial blood pressure in response to the stretch in the arterial wall caused by pressure change of blood within said artery; means for amplifying the signal indicative of arterial blood pressure, said amplifying means having a gain a and producing an amplified output; means for summing said amplified output with a constant b to produce said rate input signal; and means for maintaining the long term resting heart rate at a predetermined rate.

Claim 24

A cardiac pacemaker for stimulating a heart to beat at a rate which is variable in response to physiological need, comprising: a pulse generator for generating periodic electrical pulses at a rate determined by a rate input signal supplied to said pulse generator; a pacing lead for delivering said periodic electrical pulse generated by said pulse generator to said heart; a transducer located about an artery for producing a variable output signal indicative of arterial blood pressure in response to the stretch in the arterial wall caused by pressure change of blood within said artery; means for amplifying the signal indicative of arterial blood pressure, said amplifying means having a gain a and producing an amplified output; means for summing said amplified output with a constant b to produce said rate input signal; and means for maintaining the long term resting heart rate at a predetermined rate.