Patent GB-1505130-A (GB)
Title: Systems for detecting information in an artificial cardiac pacemaker
IPC: A61N1/378
Filed: 1975-05-06
Abstract: 1505130 Checking the battery level of a pacemaker in a patient DAINI SEIKOSHA KK 6 May 1975 [7 May 1974 8 May 1974 14 May 1974] 18983/75 HeadingsGlG G1N(E) and G1U In a device for checking the battery level of a pacemaker A in a patient without draining any appreciable power from the battery, some form of energy (electromagnetic, light, sound or mechanical) is transmitted to the pacemaker by a suitable supply 1 that is outside the body. The transmitted energy is then received by a suitable transducer circuit or energy receiver 2 inside the body. The received energy is converted to electrical energy and save embodiments use a capacitor to store the energy. The derived electrical energy then supplies an "energy charging circuit" that produces some kind of regular variable electrical wave form (sinusoidal, sawtooth &c.) The electric waveform is modulated (in accordance with the pacemaker battery level) by an information generator 3. The information generator may also be supplied with energy from the energy receiver 2, Fig.2 (not shown). The modulated waveform is supplied to an information transmitter 5 which changes the waveform to corresponding electromagnetic, light, sound or mechanical energy forms that are transmitted outside the body and received by an indicator 6 that may actuate a red or a green light (or emit a particular sound) depending upon the battery level. The energy supplier and energy receiver. The energy supplier 1 may comprise a high frequency generator 27, Fig.3, and a transmitter 28, or, be an analogous system for sound or light. The energy receiver within the pacemaker has a resonance circuit comprising a coil for receiving the electric waves and a capacitor 30. The resulting high frequency, induced voltage is half-wave rectified by diodes 31, 32 and applied to charge a capacitor 33. An associated transducer 34 acts as a switch and is connected so that until the charge in the capacitor reaches a certain level no voltage appears on terminals 2T 1 , 2T 0  so that when the energy supplier 1 has stopped transmitting the capacitor is allowed to discharge, thereby providing further energy. Other arrangements are described, Fig.4 (not shown), involving a transformer and no capacitor. Analogens arrangements, Figs.5, 6-1, 6-2, 7 and 8 (not shown), are described which utilize light sound and mechanical energy forms. "Clockwork" energy storage. In Fig.9, a reciprocating device 96, reciprocates a sliding rod 97 having a feed pawl 98 engaging a rachet wheel 99 on the shaft of which is a spiral spring 100 which acts as.an energy store. A pawl 101 prevents reverse rotation of the wheel 99 and the energy stored in the spring may be released through the shaft 102 by disengagement of the pawl 101. A further "clockwork" device, Fig.10 (not shown), comprises two rotating wheels each having a magnet attached to its surface. When the "outside" wheel is positioned near the "inside" pacemaker wheel the rotation of the outside wheel will induce rotations of the inside wheel whose energy can be stored on a spiral spring somewhat as before. Battery information generator. The pacemaker battery 111, Fig. 11, is connected as shown to a high resistance potentiometer 112 and 113, the junction point of which is connected to the gate of a F.E.T. 114 connected as shown to a transistor 116. The design of the circuit is such that when the battery level is low the F.E.T. 114, and then the transistor 116, are turned on providing an output across the terminals 3T 1 , 3T 0 . A further circuit, Fig.12 (not shown), is disclosed in which the individual cells of the battery have an associated transistor and diode circuit. All the circuits of the cells being connected together to give a total output. Energy charging and transmitting means. Several energy charging means are described which rely on modulation of a waveform produced by an oscillator. In Fig.15, a switching transistor 150 operates a switch in response to the output information generating means 3. In the ON state of the transistor, high frequency oscillations of a frequency determined by the inductance of coil 152 and the capacitors 153, 154 appears. Various modifications, Figs. 13, 16, 17, 18 and 19 (not shown), are disclosed dealing with various types of energy transmission. Indicators. The indicator receives a modulated electric waveform from the pacemaker. It may comprise a high frequency amplifier 211, Fig.21, including a resonance circuit 212, 213 the output being detected by a detector 214 feeding two low pass filters 215, 216. One filter passes an audio frequency wave which is present in the absence of battery information being transmitted and the other filter is designed to pass the audio frequency which is present when there is information. The outputs of the filters are amplified by power amplifiers 217, 218 and fed to different indicators 219, 220 e.g. a red or green lamp. Various modifications, Figs.20, 22, 23, 24, 25 and 26 (not shown), are disclosed involving different forms of circuits and responsive to different types of energy.