Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/18—Applying electric currents by contact electrodes
  • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
  • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
  • A61N1/362—Heart stimulators
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
  • A61N1/00—Electrotherapy; Circuits therefor
  • A61N1/18—Applying electric currents by contact electrodes
  • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
  • A61N1/36—Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
  • A61N1/372—Arrangements in connection with the implantation of stimulators

Definitions

• the invention described relates to a pacemaker in which paraphysiological operation is produced by virtue of the circadian design principle adopted.
• a circadian rhythm persists in heartbeat even in the event of total atrioventricular stoppage. Circadian rhythm is also manifest in variations of the normal atrioventricular sequence.
• the heart of a donor will retain circadian rhythm in its beat notwith ⁇ standing the absence of sympathetic connections.
• the regular, natural pacemaking characteristic of the heart can undergo circadian variation resulting from disturbances such as a concentration of hydro- cortisone and catecholamine, electrolytic changes, and above all, direct influence from the nervous system.
• dynamic ECG Helter
• the object of the invention described herein is that of embodying a pacemaker that will permit of producing a circadian rhythm in heartbeat exogenously, and of ensuring that the circadian variation produced is commensurate with the overall pattern of endogenous biorhythmic factors normally influencing heartbeat, physical exercise excluded.
• pacemaker There are several models of pacemaker commercially available, in effect, that are not synchronized with spontaneous physiological atrial activity, such act ⁇ ivity being either non-existent, or unreliable. At all events, conventional pacemakers are designed to generate a minimum number of beats per minute, beneath which the rate must not drop. Minimum bpm is fixed in VVI types, and is program- mable at preset levels in externally controlled VVIM types. In DVI , VDD and DDD types, the disappearance or significant weakening of the atrial signal is compensated by emission of a fixed, preset bpm by the pulse generator; in this instance, however, bpm neither follows nor takes account of bioryhthm.
• pace ⁇ maker which vary heartbeat according to biological or metabolic parameters such as pH value, temperat ⁇ ure and breathing; heartbeat is varied only when the individual expends physical or mental effort, whilst minimum bpm remains a fixed quantity that does not adapt to chronobiological requirements.
• a fixed minimum can constitute a hazard to the individual, especially during the night when reduced biological activity would dictate a lower heartbeat rate ' ; this is particularly the case in patients suffering from disease of the sinoatrial node .
• a pacemaker which not only is sensitive to triggered physiological change, such as would be produced by physical effort, but also responds to biorhythmic variation in the state of the individual.
• One of the advantages obtained with a pacemaker ac ⁇ cording to the invention consists in the fact that it can be embodied simply by connection of a sine wave pulse ' generator to the input of the clock of a conventional pacemaker; the signal produced by such a device, covering a 24 hour period and variable in amplitude, will thus be integrated with that of the cloc.k generator.
• fig 1 shows the natural curve traced by chronobio- logically induced circadian variation in heartbeat
• fig 2 shows the stimulus curve, produced by a pace- maker according to the invention, relating solely to chronobiologically induced circadian variation in heartbeat
• fig 3 is the block diagram illustrating a pacemaker according to the invention
• fig 4 is a detailed block diagram of the block de ⁇ noted 1 in fig 3
• fig 5 is the block diagram of a programmable pace ⁇ maker according to the invention.
• the pacemaker disclosed is suitable for all current methods of producing cardiac stimulus, and is defin ⁇ able as paraphysiological, inasmuch as it takes ac ⁇ count of circadian rhythm in an individual's heart ⁇ beat.
• embodiment of a circuit that will reproduce the periodic, circadian type of variation encountered in heartbeat is made possible by virtue of the fact that such variation can be considered as a sine wave (fig 1).
• Fig 3 is a basic block diagram of the pacemaker as described herein, which implements one of the simpl ⁇ est of cardiac stimulus methods, namely VVI and AAI , that is, ventricular or auricular 'on demand' .
• the pacemaker stimulates the ventricle (or the auricle) , and is inhibited whenever the muscular depolarizat ⁇ ion signal, amplified by the block denoted 5, rises above the preset bpm dictated by a clock generator 2 and divider 3.
• a circadian pacemaker use is made of a VC0 (voltage controlled oscillator) the clock frequency of which can be varied by appli ⁇ cation of a voltage.
• the input stage of the clock 2 may be in receipt of a signal representing variation in biological or metabolic parameters (pH value, or breathing &c.) from the block denoted 11.
• the sine wave signal with its period of 24 hours, will thus vary the beats per minute between preset maximum and minimum levels, which are dictated by the sine wave generated by block 1 and the clock frequency emitted by block 2.
• Phase of the sine wave is adjusted such as to respond to the normal chronological conditions illustrated in the graph of fig 1.
• fig 4 illustrates a digital generator.
• the clock frequency may be produced by a quartz type generator giving a period of 4.12msec, and utilizing a 20-stage binary divider.
• the block denoted 9 ampli ⁇ fies and adjusts the sine wave of fig 2 in order to vary amplitude commensurately with the physiological characteristics of the individual.
• the circuit in question can be integrated without difficulty adopting CMOS techno ⁇ logy, by virtue of its digital operation.
• the sine wave illustrated in fig 2 provides a sufficiently accurate approximation of the circadian rhythm in heartbeat
• the effective curve can be ap ⁇ proached yet further by varying the value of the re ⁇ sistances R , which may be achieved by calculation, n where a mathematical equation representing the curve is made available, or by experimenting with the re ⁇ sistance settings on a trial-and-error basis.
• Fig 5 illustrates a development of fig 3, * in which one has the standard programming options fo'r cardiac stimulus parameters as already featured in program ⁇ mable pacemakers: mean bpm is varied by the block denoted 14, and pulse width by the block denoted 15; amplitude of the signal fed into the circuit 20 pro ⁇ ducing the output pulses is varied by the block de ⁇ noted 16; a block denoted 17 alters the sensitivity threshold.
• the implanted pacemaker can be programmed utilizing any of the methods currently employed; moreover, the identification code can remain the same as those al ⁇ ready in use.
• Bpm can be programmed by way of the pacemaker's VC0 , and maximum permissible variation between F and max
• Phase can be adjusted at the moment of implanting a pacemaker according to the invention, for instance, by accelerating the clock frequency 6 (fig 4) until coincident with the value dictated by the sine wave at that particular instant.

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• Health & Medical Sciences (AREA)
• Radiology & Medical Imaging (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Heart & Thoracic Surgery (AREA)
• Cardiology (AREA)
• Electrotherapy Devices (AREA)

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• 1985
  • 1985-06-05 IT IT03457/85A patent/IT1202151B/it active
• 1986
  • 1986-05-26 WO PCT/IT1986/000039 patent/WO1986007270A1/en unknown
  • 1986-05-26 EP EP86903542A patent/EP0222870A1/en not_active Withdrawn

Non-Patent Citations (1)

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