Ventricular synchronised atrial pacemaker

Claim 2

A heart pacemaker comprising: atrial pacing pulse generator means (10, 12) for generating stimulating pulses adapted to be applied to the atrium at an atrial pacing rate; means (20) for sensing ventricular heart depolarizations; means (16, 40, 44) for timing the interval between atrial pacing pulses and ventricular depolarizations and for producing a clock signal when ventricular depolarizations occur out of synchronism with atrial pacing pulses; and atrial pacing rate adjusting means (64) responsive to the clock signal for adjusting the atrial pacing rate of the pulse generator means to restore atrial and ventricular synchrony.

Claim 3

A heart pacemaker as claimed in claim 1 wherein said sensing means comprises a ventricular sense amplifier (20) having first input means adapted to be coupled to the ventricle of the heart to receive electrical signals from the ventricle, amplifier means for amplifying and shaping sensed electrical signals and producing an output signal, and second input means (18) adapted to respond to said timing means for inhibiting the production of said output signal when the ventricular depolarizations occur in synchrony with atrial pacing pulses.

Claim 4

A heart pacemaker as claimed in claim 2 wherein said timing means (16) comprises: blanking window signal generating means (26, 28, 30) responsive to the generation of atrial stimulating pulses for producing a first blanking signal for a first predetermined interval for preventing the response of said ventricular sense amplifier means (20) to the generated atrial stimulating pulses and a second blanking signal over a subsequent second interval for preventing the response of said sense amplifier means to ventricular depolarizations triggered by the preceding atrial stimulating pulse; and means (32) for applying the first and second blanking signals to said second input means.

Claim 5

A heart pacemaker as claimed in claim 3 wherein said blanking window generating means further comprises means (28) responsive to the generation of the atrial stimulating pulses for separating the first and second intervals by a third interval representative of a physiological atrial-ventricular delay interval and means responsive to the atrial pacing rate for adjusting the third interval in inverse relation to the rate.

Claim 6

A heart pacemaker as claimed in claim 4, wherein said blanking window signal generating means further comprises: a first one-shot (26) set by the generation of the atrial stimulating pulse for the first interval; a second one-shot (28) set by the generating of the atrial stimulating pulse for the third interval; a third one-shot (30) set at the reset of the second one-shot for the second interval; and gate means (32) for coupling the set states of the first and third one-shots to said second input means of said ventricular sense amplifier (20).

Claim 7

A heart pacemaker as claimed in any preceding claim wherein said atrial pacing rate adjusting means (64) further comprises rate counter means (64) for storing a rate count and wherein said atrial pacing pulse generator means (10, 12) is responsive to the rate count stored in said rate counter means for establishing the atrial pacing rate.

Claim 8

A heart pacemaker as claimed in claim 6 wherein said atrial pacing rate adjusting means further comprises: means (64) for increasing the atrial pacing rate in response to the clock signal.

Claim 9

A heart pacemaker as claimed in claim 7 wherein said means for increasing the atrial pacing rate further comprises: first counter means (48) responsive to the clock signal for producing an up count signal; and said rate. counter means (64) is responsive to the clock signal and the up count signal for increasing the rate count to a higher count for establishing a high atrial pacing rate.

Claim 10

A heart pacemaker as claimed in claim 8 wherein said atrial pacing rate adjusting means further comprises means for decreasing an increased atrial pacing rate wherein: said first counter means (48) is responsive to the generation of an atrial pacing pulse for counting the number of atrial pacing pulses generated between clock signals; and said first counter means is responsive to the clock signal for resetting the count; and wherein said first counter means further comprises: selector means (62) responsive to a certain count in said first counter means for generating a down count signal and for producing an output signal, the selector means also comprising: logic means (56, 44) responsive to said output signal for producing a clock signal; and wherein said rate counter means (64) is responsive to the clock signal produced by the logic means and the down count signal for decreasing the rate count from a higher count to a lower count for establishing a lower atrial pacing rate.

Claim 11

A heart pacemaker as claimed in claim 9 wherein said first counter means (48) is responsive to said clock signal (46) for resetting the count in said first counter means to its initial count.

Claim 12

A heat pacemaker as claimed in any of claims 6 to 10 wherein said rate counter means further comprises: decoder means (54) responsive to the rate count for producing maximum and minimum rate control signals when the rate count reaches counts which establish maximum and minimum atrial pacing rates.

Claim 13

A heart pacemaker as claimed in claim 11 when dependent on claim 9 or 10, wherein said logic means (40, 56, 44) is responsive to said maximum and minimum rate control signals for inhibiting the production of clock signals in response to the ventricular sense amplifier means (20) and the selector means (62), respectively.