| 摘要 |
1,267,493. Cardiac pacers. CORDIS CORP. 6 March, 1970 [10 March, 1969], No. 10762/ 70. Heading A5R. A cardiac pacer comprises an oscillator 1 which provides a pulsating signal, a nine-stage cyclically operated digital counter 3 which counts the pulsations of the oscillator and means for generating a cardiac stimulating potential when said counter reaches a predetermined count. The stimulating potential is terminated on the subsequent count. The pacer may be used in demand mode operation, when atrial potentials are not generated regularly, or in synchronous mode operation, when atrial signals are not transferred to the ventriclecommonly called A-V block. In demand mode operation the output electrode 6 and its corresponding flip flap 16 are used. Electrode terminals 6 and 10 may be connected to the same lead. When no ventricular signals are detected the input at D of the flip-flop 16 is high, and the oscillator runs indefinitely in cyclic mode so that when the count changes from 511 to zero the C9 output signal experiences a positive-going transition which is transferred to input C, thus allowing the transfer of the signal at D to Q. This signal is passed through an amplifier 21 to electrode 6 and applied to the ventricle. Between counts zero and 255 the output signal at C9 is low, i.e. input at D of flip-flop 17 is low and therefor, even if a cardiac signal is detected by input electrode 10 and passed to input C, there is no transfer of signal in flip-flop 17 and consequently the counter is not reset. This period stimulates the refractory delay of the heart. Between counts 256 and 511 the C9 output signal is high and consequently a cardiac signal causes the counter to be reset. Simultaneously the output signal from Q of flip-flop 17 goes low, i.e. input at D of flipflop 16 is low, and therefor even though C9 experiences a positive-going transition there is no output signal at Q of the flip-flop 16. In synchronous mode operation output electrode 9 and its corresponding flip-flop 18 are used. Outputs C8 and C9 of the counter 3 are combined to give a high signal only between counts zero and 127, this signal is connected to input D of flip-flop 18. Output C7, connected to input C, experiences positive-going transitions on counts 64, 192, 320 and 448, but only the transition on count 64 will cause a transfer of signal since this is the only transition that occurs when the input signal at D is high. Accordingly a cardiac stimulating potential is generated and applied to the atrium from electrode terminal 9 on each count of 64 and terminated on the subsequent count of 65. The pacer may incorporate circuitry, Fig. 2, not shown, including a two-stage counter, for detecting electronic noise in the environment and preventing the pacer from operating undesirably in response to the noise. |
