Apparatus for electrically stimulating the heart

Abstract

Abstract 1416197 Heart stimulators L RUBIN 28 Nov 1972 [13 Dec 1971] 54988/72 Heading A5R [Also in Division G1] A heart stimulator 9 comprises a heart pacemaker 11, which is preferably of the demand type responsive to an output of a heart beat analyser and control unit 12 to produce pacing pulses whenever the natural heart beats stop or occur at too low a rate, and a defibrillator 10 connected to another output of unit 12 to produce a defibrillating pulse whenever a predetermined average rate of occurence in a predetermined period of QRS pulses of greater than a predetermined length is exceeded. A transmission gate .40, which may include amplifying and filtering means, is connected to pass heart beat pulses only in the absence of pacing and defibrillating pulses. A pulse shaper 41 gives an output pulse B for each R wave and shaper 42 gives output pulses C having leading and trailing edges occuring in phase with all zero crossings of the detected heart signal A. A pulse duration detector 43 gives an output pulse D having an amplitude dependent on the duration of the respective input pulse C and a shaper 44 gives an output pulse E for each pulse D of greater than a predetermined height. A flip-flop 45 gives output pulses F having leading edges in phase with the start of the R waves and trailing edges in phase with the S points, pulses F yielding output pulses G from one-shot 47 of fixed height and length and with leading edges in phase with the start of the R waves. AND gate 61 gives an output pulse H each time a QRS complex of longer than a preset time, e.g. 120 m.sec, occurs, the H pulses being inverted and connected to AND gate 62, receiving pulses I from F. pulse trailing edge detector 64, gate 62 giving a pulse J for each QRS complex shorter than the preset time (120 m.sec.). A flip-flop 63 is connected so that if it is in the reset state it will be set by the first occurence of a normal QRS complex (shorter than 120 m.sec) and if it is in the set state it will be reset by the first abnormal QRS (longer than 120 m.sec.). An integrator 65 and threshold detector 66 are connected to give an output pulse each time all the QRS pulses are abnormal in a given time interval, e.g. 10 secs. A pulse rate detector 50 and threshold detector 55 give an output whenever the output K of detector 50 exceeds a predetermined level, the output K building up gradually to said level during said time interval of e.g. 10 sees if both the QRS complexes occur at greater than said predetermined average rate and they are all longer than 120 m.sec. Thus AND gate 70 activates defibrillator 10 at the expiry of said 10 second time interval whenever during said interval all QRS complexes are of abnormally high repetition rate and abnormal length. Alternatively control unit 12 may be constructed to activate defibrillator 10 if instead of all QRS complexes being abnormally long in said 10 second period, all but, for example, two or three are abnormally long. An electrode structure may be attached to a catheter which is connected to the implanted stimulator 9, said structure comprising a distal tip electrode (30), Fig. 3 (not shown), at the right ventricle apex spaced from an electrode (31) also in the2right ventricle, electrode (31) being in turn spaced from an electrode (32) in the right atrium, electrodes (30), (31), (32) being connected to terminals 14, 15. 16 respectively of stimulator 9.

Inventors

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