IL42616A

IL42616A - Rechargeable cardiac pacemaker

Info

Publication number: IL42616A
Application number: IL42616A
Authority: IL
Original assignee: Univ Johns Hopkins
Priority date: 1972-06-28
Filing date: 1973-06-27
Publication date: 1976-10-31
Also published as: FR2190403B1; GB1419533A; CA1020633A; DE2331499A1; FR2190403A1; GB1419531A; CH578355A5; AU5742673A; CH583569A5; GB1419532A; ZA734385B; CH583570A5; IL42616A0; NL7308947A; IT985803B; JPS4964283A

Abstract

1419531 Heart pacemaker JOHNS HOPKINS UNIVERSITY 28 June 1973 [28 June 1972] 30787/73 Heading A5R [Also in Divisions H2 and H3] An implantable heart pacer includes a rechargeable battery 19, Figure 3, a stimulating pulse generator 10, 11, 12, and means 20 for coupling alternating magnetic input recharging energy to the battery 19 from a source external to the patient, an inner shield 13 encompassing the pulse generator and constructed of a material effective to shield the pulse generator from said alternating magnetic input energy and' sources of electromagnetic energy, and a second shield 18 encompassing the coupling means 20 battery 19 and the pulse generator to form a hermetic shield against body fluids and constructed of a material effective to permit the coupling of recharging energy by said coupling means to battery 19 from said source without substantial alternation. Shield 13 may be made of specified thickness pure nickel or pure gold and shield 18 may be made of specified thickness stainless steel, titanium, glass or ceramic. Shields 13, 18 are in the form of open sided cans, with their contents encapsulated therein and the open sides engaged on and sealed to shoulders 16, 17 of a cap 15, which may be of pure nickel and receives one end of a co-axial catheter electrode unit 21. A continuous outer coating 27 of one or more layer of plastics is provided. The Pacer Circuitry comprises a ferrite core transformer 20, Fig. 1a, 1b, receiving the charging energy to charge single-cell nickel-cadmium battery 19 via current monitoring resistor 32, current linking FET 31 and resistor 33. Resistor 32 is coupled to voltage controlled oscillator 35 which feeds winding 39 to give an externally detectable signal having a frequency dependent on the charging current. Charging current through resistor 33 increases the intrinsic pulse rate of the stimulating pulse generator giving a second means to monitor battery charging. In the absense of spontaneous heart beats the pulse generator is free running at about 72 ppm. A capacitor 45 charges via transformer 12 and resistors 44, 42 until transistor 40 and therefore transistor 41 turn on connecting capacitor 45 to the power supply in the opposite sense to its connection during said charging and about 1 m.sec later transformer 12 saturates current through capacitor 45 decreases and transistors 40, 41 turn off, each such cycle giving in the secondary of transformer 12 a stimulating pulse comprising a positive going part, coupled to electrode 55 by transistor 49, followed by a negative going part coupled to electrode 55 by transistor 50, transistor 49, 50 only conducting when an output pulse appears in transformer 12 secondary. Heart beats are amplified by transistors 56, 57, 58 in an input amplifier. When the output of the input amplifier exceeds a threshold transistor 61 and thereby transistors 63, 62 turn on, transistors 62 maintaining transistor 63 on for a fixed interval after the input to transistor 61 disappears determined by R-C circuit 67, 68 and typically equal to 100 m.secs, whereby a 100 m.sec wide pulse appears on the collector of transistor 63. This pulse turns transistor 64 on the discharge capacitor 70. Transistor 65 conducts and thus transistor 66 turns on until capacitor 70 charges to a level sufficient to turn off transistor 65 and thereby 66, this time delay typically being 200 m.sec whereby the output of one-shot circuit 65-66 is a negative going pulse whose leading edge corresponds to the start of an R- wave and which is (100 + 200) = 300 m.sec long. This 300 m.sec output pulse at the collector of transistor 66 will be extended beyond 300 m.sec for as long as pulses less than 300 m.sec apart are detected. Thus this circuit prevents the pacer being inhibited by normally timed T-waves and by spacious noise signals exceeding 200 p.p.m., the stimulating pulse generator only being inhibited by the leading edge of the output pulse on transistor 66 collector. This leading edge momentarily turns on transistor 73 and is coupled to a one-shot circuit comprising transistors 75, 76 whereby these transistors conduct and capacitor 77 charges until it reaches a level at which transistors 75, 76 turn off, the output at transistor 75 collector being a negative going square wave of 500 m.secs duration whereby transistors 46 conducts for 500 m.secs and discharges timing capacitor 45 in the stimulating pulse generator, a further 500 m.secs then being required following turn-off of transistor 46 before generation of the next stimulating pulse. Thus following a spontaneous heart beat the pacer waits for 500 + 500 m.sec = 1 sec. and only then generates a pulse if no further spontaneous beat occurs, (<SP>5</SP>/ 6 sec. being the normal waiting period between successive stimulating pulses). Thus in general if the heart is beating at between about 60 and 180 beats/min the power remains inhibited. The stimulating pulse is also coupled from transistor 41 collector via capacitor 78 and resistor 79 to turn on transistor 81 whereby the heart beat resulting from the stimulating pulse will not operate the pulse inhibitor 73, 75, 76, 46. Closure of a magnetic reed switch 82 produces a fixed rate mode of operation at 72 stimulating pulses/min. [GB1419531A]

Claims

42616/2 . CLAIMS i

1. In a human tissue stimulator adapted to be implanted in the body of a patient and including a rechargeable battery, means for coupling alternating magnetic input recharging energy to said battery from an external source, and electronic circuitry powered by said battery for generating stimulating pulses and \ applying them to the patient's tissue to be stimulated, the improvement comprising telemetry means rendered effective when recharging energy is being coupled to said battery for providing an indication external of the patient's body that said recharging is taking place, said telemetry means including a means operably connected to said coupling means to receive operating energy only during recharging of said battery for generating an output .telemetry signal indicative that recharging of said battery is taking place, said output telemetry signal generating means being responsive to the magnitude of recharging current being applied to said battery to cause the output signal to indicate whether or not said battery is being recharged at an acceptable recharging current level.

2. The human tissue stimulator according to Claim 1 wherein the generating means included in said telemetry means is an electrical signal generating means rendered effective only -when recharging of said battery is taking place to generate an output electrical telemetry signal capable of being received external of the patient's body.

3. The human tissue stimulator according to Claim 2 wherein said coupling means is an inductive coupling means comprising a first winding means wound on a core member and disposed within the patient's body for inductively coupling energy from said external source to' said battery in order to recharge said battery, and wherein the output electrical telemetry signal from said signal generating means is connected to a second wind

4. The human tissue stimulator according to Claim 1 wherein the generating means included in said telemetry means is an oscillator circuit means whose output signal frequency is proportional to the magnitude of recharging current being applied to said battery, said output frequency signal from said oscillator means being connected to said coupling means for transfer external of the patient's body.

5. The human tissue stimulator according to Claim 1 wherein the output telemetry signal generated by said generating means indicates whether or not said battery is being recharged at an acceptable recharging current level.

6. The human tissue stimulator according to Claim 1 further including: first shield means disposed and fabricated of a material effective to shield both said electronic circuitry and said telemetry signal generating means from said alternating magnetic input recharging energy and sources of magnetic interference, said coupling means being disposed external to said first shield means; and second shield means surrounding said first shield means, said electronic circuitry, said telemetry signal generating means, and said coupling means to form an outer hermetic seal for said human tissue stimulator and being fabricated of a material effective to provide minimum attenuation of the coupling by said coupling means of said recharging energy and of said output telemetry signal.

7. The human tissue stimulator according to Claim 6 wherein said first shield means surrounds said electronic 42616/2

8. In a human tissue stimulator according to Claim 1 wherein the stimulator is a cardiac pacemaker and wherein the electronic circuitry powered by said battery generates heart \ stimulating pulses and applies them to the patient's heart.

9. The cardiac pacemaker according to Claim 8 further including means for monitoring the beating of the patient's heart for inhibiting said electronic pulse generating circuitry when said heart is beating naturally without the application of said stimulating pulse.

10. The cardiac pacemaker according to Claim 8 wherein the generating means included in said telemetry means is an electrical signal generating means rendered effective only when recharging of said battery is taking place to generate an output electrical telemetry signal capable of, being received external of the patient's body.

11. The cardiac pacemaker according to Claim 10 wherein said coupling means is an inductive coupling means comprising a first winding means wound on a core member and disposed within the patient's body for inductively coupling energy from said external source to said battery' in order to recharge said battery, and wherein the output electrical telemetry signal from said signal generating means is connected to a second winding means on said core member for inductive coupling to receiving means external of the patient's body. 1 12. The cardiac pacemaker according to Claim 8 2 wherein the generating means included in said telemetry means is

12. N 3 an oscillator circuit means whose output signal frequency is \ 4 · proportional to the magnitude of recharging current being applied 5 to said battery, said output frequency signal from said oscillato 6 means being connected to said coupling means for transfer externa 7 of the patient's body. 1

13. The cardiac pacemaker according to Claim 8 wherein 2 the output telemetry signal generated by said generating means 3 indicates whether or not said battery is being recharged at an 4 acceptable recharging current level. 1

14. The cardiac pacemaker according to Claim 8 2 further including: first shield means disposed and fabricated 3 ;of a material effective to shield both said electronic circuitry and said telemetry signal generating means from said alternating 5 magnetic input recharging energy and sources of magnetic inter- 6 "ference, said coupling means being disposed external to said 7 first shield means; and second shield means surrounding said 8 first shield means, said electronic circuitry, said telemetry 9 signal generating means, and said, coupling means to form an 10 outer hermetic seal for said pacemaker and being fabricated of 11 a material effective to provide minimum attenuation of the . 12 coupling by said coupling means of said recharging energy and 13 of said output telemetry signal. 1

15. The cardiac pacemaker according to Claim 14 2 wherein said first shield means surrounds said electronic circuit 4261 /2

16. In a cardiac pacemaker according to Claim 8 further comprising: a first inner shield means disposed between said electronic circuitry and said external source and constructed of a material effective to shield said circuitry from said alternating magnetic input recharging energy and sources of magnetic interference, said coupling means being disposed external to said first shield means; and a second outer shield means encompassing said coupling means, said battery and said electronic circuitry to form a hermetic shield against body fluids and constructed of a material effective to permit the coupling of recharging energy by said coupling means to said battery from said external source without substantial attenuation.

17. The cardiac pacemaker according to Claim 16 wherein said first shield means encompasses said electronic circuitry to form a second hermetic seal.

18. The cardiac pacemaker according to Claim 16 wherein said first inner shield means is constructed of a material characterized by relatively high magnetic permeability and low electrical resistivity and said second outer shield means is constructed of a material characterized by relatively high electrical resistivity and low magnetic permeability.

19. The cardiac pacemaker according to Claim 18 wherein said first inner shield means is fabricated of nickel having a thickness greater than substantially 0.127 millimeter.

20. The cardiac pacemaker according to Claim 18 wherein said second outer .shield means is fabricated of stain-

21. The cardiac pacemaker according to Claim 18 wherein said second outer shield means is fabricated of titanium having a thickness substantially within the range 0.0762 to 0.508 millimeter.

22. The cardiac pacemaker according to Claim 18 wherein said second outer shield means is glass.

23. The cardiac pacemaker according to Claim 18 wherein said second outer shield means is ceramic.

24. The cardiac pacemaker according to Claim 16 wherein said coupling means is an inductive coupling means.

25. The cardiac pacemaker according to Claim 18 wherein said inductive coupling means comprises a first winding means disposed within the patient's body and adapted to induc-tively couple energy from said external source to said battery in order to recharge said battery.

26. The cardiac pacemaker according to Claim 16 wherein said pacemaker is of the demand inhibited type including means for monitoring the heart beat of the patient and inhibiting said electronic circuitry in order to prevent the generation thereby of said heart stimulating pulse when said heart is beatin naturally at an acceptable rate without application of said heart stimulating pulses. 42616/2

27. The rechargeable demand inhibited cardiac pacemaker according to Claim 26 further including a coaxial catheter means terminating at a pair of electrodes adapted to be disposed at a preselected location in the patient's heart for applying the heart stimulating pulses generated by said elec-tronic circuitry and for sensing the electrical R-wave signal emanating from the patient's heart when the heart beats.

28. The cardiac pacemaker according to Claim 16 wherein: said first shield means is a substantially rectangular hollow metallic can having one end open and adapted to receive and have encapsulated therein said electronic circuitry; said second shield means is a substantially rectangular hollow metallic can having one end open and adapted to receive and have encapsulated therein said rechargeable battery, said coupling means and said first metallic can; and further including a unitary end cap member adapted to be attached to and cover the open end of each of said first and second can members.

29. The cardiac pacemaker according to Claim 28 wherein said end cap member is formed with first and second shoulder portions configured to mate with and seal respectively the open end of said first and second metallic cans. 4261 6/2 '

30. The cardiac pacemaker according to Claim 8 wherein said electronic circuitry includes a first electronic circuit portion for generating output heart stimulating pulses for application to a patient's heart and a second electronic circuit portion for monitoring the patient's heart beat and inhibiting the generation by said first electronic circuit of said heart stimulating pulses in the presence of an acceptable beat rate, and catheter means terminating at electrode means1 adapted to be disposed at a preselected location in the patient's heart for applying the heart stimulating pulses generated by said first electronic circuit portion and for sensing the electrical R-wave signal emanating from the patient's heart when the heart beats; and switching means ,£or selectively connecting said electronic pulse generating circuit portion to said catheter means only when an output pulse is being generated by said pulse generating circuit portion.

31. The cardiac pacemaker according to Claim 30 v/herein said catheter means is a coaxial catheter and wherein said rechargeable battery supplies operating voltage to said first and second electronic circuit portions; and means for iriductively coupling said alternating magnetic recharging energy to said battery from said external source.

32. The cardiac pacemaker according to Claim 31 wherein said electronic pulse generating circuitry includes a step-up output transformer having primary and secondary windings for increasing the amplitude of each heart stimulating pulse rior to a lication thereof to the atient's hear.t. 4261 6/2

33. The cardiac pacemaker according to Claim 30 wherein said switching means comprises a bipolar' transistor switching gate circuit connected electrically between the secondary winding of said output transformer and said catheter means, said switching gate being closed only when an output heart stimulating pulse is being generated by said pulse generating circuitry and appears at the secondary winding of said output transformer.

34. The cardiac pacemaker according to Claim 32 wherein said switching means comprises a bipolar transistor switching gate circuit connected electrically between the secondary winding of said output transformer and said catheter means, said switching gate being closed only when an output heart stimulating pulse is being generated by said pulse generating circuitry and appears at the secondary winding of said output transformer.

35. The cardiac pacemaker according to Claim 31 wherein said telemetry signal generating means is connected to said inductive coupling means to receive operating power only during recharging of said battery* for generating an output telemetry signal indicative that recharging of said battery is taking place, said output telemetry signal being connected to said inductive coupling means to be inductively coupled external of the patient's body; first shield means disposed and fabricated of a material effective to shield both of said first and second electronic circuit portions and said telemetry si nal eneratin means from said alternatin ma netic in u 42616/2 I CLAIM 35 continued signal generating means, and said inductive coupling means to form an outer hermetic seal for said pacemaker and being fabricated of a material effective to provide minimum attenuation of the inductive coupling by said inductive coupling means of said recharging energy and of said output telemetry signal.

36. The cardiac pacemaker according to Claim 35 wherein: said telemetry signal generating means is an oscillator circuity means operably connected to said inductive coupling means to receive operating voltage only during recharging of said battery for generating an output electrical signal whose existence provides an indication that recharging of said battery is taking place and whose frequency is proportional to the magni-tude of recharging current being applied to said battery, said output frequency signal from said oscillator means being connected to said inductive coupling means to be inductively coupled external of the patient's body; and said first shield means surrounds said first and second electronic circuit portions and said oscillator means to form a second inner hermetic seal for said pacemaker unit.

37. The cardiac pacemaker according to Claim 36 wherein said electronic pulse generating circuitry includes a step-up output transformer having primary and secondary windings for increasing the amplitude of each heart stimulating pulse prior to application thereof to the patient's heart. 42616/2 '

38. The cardiac pacemaker according to Claim 36 wherein said switching means comprises a bipolar transistor switching gate circuit connected electrically between the secondary winding of said output transformer and said catheter means, said switching gate being closed only when an output heart stimulating pulse is being generated by said pulse generati circuitry and appears at the secondary winding of said output transformer.

39. The cardiac pacemaker according to Claim 37 Λ wherein said switching means comprises a bipolar transistor switching" gate circuit connected electrically between the secondary winding of said output transformer and said catheter means, said switching gate being closed only when an output heart stimulating pulse is being generated by said pulse generating circuitry and appears at the secondary winding of said output transformer.

40. The cardiac pacemaker according to Claim 30 wherein said second electronic circuit portion includes circuit means to prevent said first electronic circuit portion from being inhibited by pulse signals and noise occurring at greater than a predetermined rate corresponding to a predetermined maximu acceptable natural heart rate. For fhe Applicants