Cardiac pacing apparatus with electromagnetic interference protection

• US 4,091,818 A
• Filed: 08/03/1976
• Issued: 05/30/1978
• Est. Priority Date: 08/03/1976
• Status: Expired due to Term

• Current Assignee: Pennsylvania Research Corporation
• Original Assignee: Research Corporation
• Inventors: Brownlee, Robert R., Tyers, G. Frank O.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/711,254
• Time in Patent Office: 665 Days
• Field of Search: 128/419 PG, 128/421, 128/422, 128/423
• US Class Current: 607/9
• CPC Class Codes: A61N 1/37 Monitoring; Protecting
• CPC Class Codes: A61N 1/3718 Monitoring of or protection against external electromagnetic fields or currents
• CPC Class Codes: G01R 29/0814 Field measurements related to measuring influence on or from apparatus, components or humans EMC, EMI and similar testing in general G01R31/001, e.g. in ESD, EMI, EMC, EMP testing, measuring radiation leakage; detecting presence of micro- or radiowave emitters; dosimetry; testing shielding; measurements related to lightning

Abstract

A cardiac pacing apparatus of the type having a first signal processing channel which functions in the demand mode is disclosed including a second signal processing channel for detecting electromagnetic interference and causing the pacing apparatus to revert to a safe operating rate in the presence of such interference. In a preferred embodiment, the second signal processing channel has an enhanced high-frequency response with respect to that of the first signal processing channel in order to optimize interference detection. The second channel may receive an input from either a conventional cardiac sensing and pacing electrode, or else a second electrode, remote from the heart, may be provided for interference detection. When electromagnetic interference is detected by the second signal processing channel, an override of the conventional demand pacer inhibit function occurs and the pacing apparatus is switched to a safe operating rate, which may be either an appropriate predetermined fixed rate or a rate-limited rate synchronous with the detected electromagnetic interference. In an alternate embodiment, the gain of the second signal processing channel is reduced with respect to that of the first channel, and the pacing apparatus is switched to a safe operating rate upon the detection of electromagnetic interference having an amplitude level above that of natural cardiac signals.

Claims

1. An improved cardiac pacing apparatus of the type having first electrode means for sensing and pacing connectable to the heart;

a first signal processing channel including means for generating artificial heart stimulating pulses at a predetermined rate and applying said pulses to said first electrode means, first bandpass amplifier means having an input connected to said first electrode means for detecting natural heart stimulating pulses, said artificial heart stimulating pulses and electromagnetic interference, and producing a detection signal having a rate in accordance therewith, and first control means, responsive to said detection signal and having an output operatively coupled to said means for generating artificial heart stimulating pulses, for continuously inhibiting the generation of said artificial pulses whenever the rate of said detection signal exceeds said predetermined rate;

wherein the improvement comprises a second signal processing channel including;

second bandpass amplifier means for detecting electromagnetic interference and producing a blocking signal in accordance therewith, said second bandpass amplifier means having an enhanced high frequency response with respect to the high frequency response of said first bandpass amplifier means to enhance the relative sensitivity of said second bandpass amplifier means to the higher frequency spectral components of said electromagnetic interference; and

second control means, responsive to said blocking signal and having an output operatively coupled to said first control means, for preventing said first control means from inhibiting the generation of said artificial heart stimulating pulses whenever said blocking signal is produced, thereby causing the generation of artificial heart stimulating pulses at said predetermined rate whenever electromagnetic interference is detected by said second bandpass amplifier means.

2. An improved cardiac pacing apparatus as in claim 1, wherein said second bandpass amplifier means has a detecting input connected to said first electrode means in common with said first bandpass amplifier means, and wherein said second bandpass amplifier means has a reduced low frequency response with respect to said first bandpass amplifier means to render said second amplifier means substantially insensitive to natural cardiac signals.

3. An improved cardiac pacing apparatus as in claim 1, further comprising second electrode means remote from the heart for detecting electromagnetic interference and providing an input to said second bandpass amplifier means.

4. An improved cardiac pacing apparatus as in claim 1, wherein said means for generating artificial heart stimulating pulses at a predetermined rate comprises rate control means operatively coupled to the output of said second control means for selectably and momentarily switching said predetermined rate from a first, lower rate in the absence of an electromagnetic interference detection to a second, higher rate whenever said second control means is activated by a blocking signal from said second bandpass amplifier means for detecting electromagnetic interference.

5. An improved cardiac pacing apparatus of the type having a first electrode means for sensing and pacing connectable to the heart;

a first signal processing channel including means for generating artificial heart stimulating pulses at a predetermined rate and applying said pulses to said first electrode means, first bandpass amplifier means having an input connected to said first electrode means for detecting natural heart stimulating pulses, said artificial heart stimulating pulses and electromagnetic interference, and producing a detection signal having a rate in accordance therewith, and first control means, responsive to said detection signal and having an output operatively coupled to said means for generating artificial heart stimulating pulses, for continuously inhibiting the generation of said artificial pulses whenever the rate of said detection signal exceeds said predetermined rate;

wherein the improvement comprises a second signal processing channel including;

second bandpass amplifier means for detecting electromagnetic interference and producing a second detection signal in accordance therewith, said second bandpass amplifier means having an enhanced high frequency response with respect to the high frequency response of said first bandpass amplifier means to enhance the relative sensitivity of said second bandpass amplifier means to the higher frequency spectral components of said electromagnetic interference; and

second control means, responsive to said second detection signal and having a rate-limited output operatively coupled to said means for generating artificial heart stimulating pulses, for triggering said generating means at a rate in accordance with the rate of said second detection signal but at a rate no higher than a predetermined maximum rate, thereby causing the generation of rate-limited artificial heart stimulating pulses whenever electromagnetic interference is detected by said second bandpass amplifier means.

6. An improved cardiac pacing apparatus as in claim 5, wherein said second bandpass amplifier means has a detecting input connected to said first electrode means in common with said first bandpass means, and wherein second bandpass amplifier means has a reduced low frequency response with respect to said first bandpass amplifier means to render said second amplifier means substantially insensitive to natural cardiac signals.

7. An improved cardiac pacing apparatus as in claim 5, further comprising second electrode means remote from the heart for detecting electromagnetic interference and providing an input to said second bandpass amplifier means.

8. An improved cardiac pacing apparatus of the type having first electrode means for sensing and pacing connectable to the heart;

a first signal processing channel including means for generating artificial heart stimulating pulses at a predetermined rate and applying said pulses to said first electrode means, first amplifier means having an input connected to said first electrode means for detecting natural heart stimulating pulses, said artificial heart stimulating pulses and electromagnetic interference, and producing a detection signal having a rate in accordance therewith, and first control means, responsive to said detection signal and having an output operatively coupled to said means for generating artificial heart stimulating pulses, for continuously inhibiting the generation of said artificial pulses whenever the rate of said detection signal exceeds said predetermined rate;

wherein the improvement comprises a second signal processing channel including;

second amplifier means, for detecting electromagnetic interference having an amplitude level above that of natural heart stimulating pulses and producing a blocking signal in accordance therewith, the gain of said second amplifier means being reduced with respect to the gain of said first amplifier means sufficiently to render said second signal processing channel insensitive to natural heart stimulating pulses; and

second control means, responsive to said blocking signal and having an output operatively coupled to said first control means, for preventing said first control means from inhibiting the generation of said artificial heart stimulating pulses whenever said blocking signal is produced, thereby causing the generation of artificial heart stimulating pulses at said predetermined rate whenever electromagnetic interference having an amplitude level above that of natural heart stimulating pulses is detected by said second amplifier means.

9. An improved cardiac pacing apparatus of the type having first electrode means for sensing and pacing connectable to the heart;

a first signal processing channel including means for generating artificial heart stimulating pulses at a predetermined rate and applying said pulses to said first electrode means, first amplifier means having an input connected to said first electrode means for detecting natural heart stimulating pulses, said artificial heart stimulating pulses and electromagnetic interference, and producing a detection signal having a rate in accordance therewith, and first control means, responsive to said detection signal and having an output operatively coupled to said means generating artificial heart stimulating pulses, for continuously inhibiting the generation of said artificial pulses whenever the rate of said detection signal exceeds said predetermined rate;

wherein the improvement comprises a second signal processing channel including;

second amplifier means for detecting electromagnetic interference having an amplitude level above that of natural heart stimulating pulses and producing a second detection signal in accordance therewith, the gain of said second amplifier means being reduced with respect to the gain of said first amplifier means sufficiently to render said second signal processing channel insensitive to natural heart stimulating pulses; and

second control means, responsive to said second detection signal and having a rate-limited output operatively coupled to said means for generating artificial heart stimulating pulses, for triggering said generating means at a rate in accordance with the rate of said second detection signal but at a rate no higher than a predetermined maximum rate, thereby causing the generation of rate-limited artificial heart stimulating pulses whenever electromagnetic interference having an amplitude level above that of natural heart stimulating pulses is detected by said second amplifier means.