Patent GB-1496273-A (GB)
Title: Artificial cardiac pacemaker
IPC: A61B5/0402
Filed: 1975-03-06
Abstract: 1496273 Cardiac pacemakers DAINI SEIKOSHA KK 6 March 1975 [7 March 1974] 9458/75 Heading A5R A cardiac pacemaker comprises a circuit for detecting electrical signals produced by the heart, a generating circuit connected to the detecting circuit to be reset by an output signal of the latter, and an output circuit connected to the generating circuit for producing heart stimulating signals when no naturally occurring heart signal is detected by the detecting circuit, the detecting circuit, the generating circuit and the output circuit each being of complementary M O S integrated circuitry except for the capacitors thereof. A circuit 1 prevents the feedback of stimulating signals to an amplifier 2 through which spontaneous and stimulated heart signals are fed to a selective converter circuit 3 which inverts negative signals and interposes clock pulses from a circuit 15 to a responding signalpreventing circuit 4 The circuit 4 removes certain parts of the heart signals produced in response to artificial stimulation of the heart, (41), (42), Figs. 3A, E, F, (not shown). After passing through a low pass filter circuit 5, the output of which is in the form of pulses corresponding to spontaneous and stimulated QRS and T-wave signals, the signals reach a distinguishing circuit 7. Circuit 7 gives an output on line a in response to spontaneous heart signals, an output on line b in response to stimulated heart signals, and an output on line c in the absence of spontaneous and stimulated heart signals. If the signals reaching the distinguishing circuit 7 include spontaneous heart signals, a circuit 8 is triggered and operates a delay circuit 11 which resets the stimulating pulse generating circuit 12 for a predetermined time. In the event that another spontaneous heart signal is not conveyed to the circuit 7 in that time, the circuit 11 produces a signal which triggers the generating circuit 12 and a stimulating pulse is conveyed to the heart via the circuit 1. If another spontaneous heart signal is conveyed to the circuit 7 in that time, the circuit 11 is reset for operating a delay for a further period. When the heart is generating signals in response to the artificial stimulation, the distinguishing circuit 7 produces signals which are fed on line b to a circuit 9. After a predetermined number of stimulated heart pulses are received by the circuit 9, this circuit 9 produces an output pulse signals generated by the heart causing a level adjusting circuit 14 to produce a reduction of the current level of the stimulating pulses passing from the output circuit 13 to the heart via circuit 1. As long as the heart produces stimulated heart signals, the current level of the output stimulating pulses is successively reduced stepwise in this manner. A supplement output generating circuit 10 causes the adjusting circuit 14 to stepwise increase the current level of the output stimulating pulses in the event that the stimulating pulses fall below the threshold value necessary to stimulate the heart. The circuit 10 also causes a supplementary heart stimulating pulse to be generated by circuit 12 of increased current level and at a reduced time interval than usual from the preceding stimulating pulse. If the heart does not respond to the preceding stimulating pulse, (Figs. 3A, O).