GB2206797A

GB2206797A - Cardiac pacemaker

Info

Publication number: GB2206797A
Application number: GB08813533A
Authority: GB
Inventors: Lorraine Anne Mcmillan
Original assignee: Thales Optronics Ltd
Current assignee: Thales Optronics Ltd
Priority date: 1987-07-11
Filing date: 1988-06-08
Publication date: 1989-01-18
Also published as: GB8813533D0; GB8716395D0

Abstract

A cardiac pacemaker 10 comprises a light source 11, a catheter 12 releasably connected to source 11 and terminating in a tip 14 adapted to be inserted into the right ventricle of a patient's heart. An optical fibre 15 extends along the catheter 12. Source 11 comprises a semi-conductor light emitting device such as a laser or light-emitting diode operating in the near infra red. Tip 14 comprises external electrodes 22, 23 for driving the patient's heart connected to a solar cell 16 which is illuminated by light emergent from the fibre 15. <IMAGE>

Description

CARDIAC PACEMAXERS This invention relates to cardiac pacemakers.

Cardiac pacemakers are well known for use in intensive care wards for the temporary stabilisation of a patient's heartbeat. Such pacemakers comprise a catheter which is inserted into the heart via a vien in the patient's arm or leg, the catheter terminating in a tip at which two electrodes are presented, the electrodes being spaced apart so as to be capable of location in the apex of the right ventricle of the heart. The electrodes are connected via wires extending along the catheter to a pulse generator which is arranged to pulse the electrodes with a current above the threshold current of the heart in order to keep the heart beating.

The known form of cardiac pacemaker suffers from the disadvantage that it cannot be electrically isolated or freed of possible earth leakage and any electrical noise which is picked up by the wires within the catheter is transmitted to the patient's heart, which may endanger the patient's life. Such electrical noise may emanate from interference on the mains supply feeding the pulse generator or radio frequency interference emanating from other equipment within the near vicinity of the patient or electro-static charges emanating from nursing staff. Numerous precautions are taken to minimise these disadvantages, all of which are dangerous and some are lethal, but it has not proved possible hitherto to ensure that such dangers are eliminated.

It is an object of the present invention to provide a new and improved form of cardiac pacemaker.

According to the present invention a cardiac pacemaker comprises a light source capable of emitting pulses of light, a catheter including an optical fibre coupled to the output of said light source, the catheter terminating in a tip having two electrodes adapted to sit in the apex of the right ventricle of the heart, said tip housing a solar cell connected to said electrodes with the end of the optical fibre arranged to illuminate the solar cell.

By virtue of the present invention the pacemaker is isolated from the electrical mains supply and is immune to electro-magnetic interference and radio frequency pickup since there are no electrical leads within the catheter and likewise transfer of electrostatic charges from nursing staff is eliminated. Additionally, where defibrillation is required the pacemaker of the present invention need not be removed from the patient's body, unlike prior art pacemakers.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawing, in which: Fig 1 illustrates a cardiac pacemaker in accordance with the present invention; Fig. 2 schematically illustrates a first form of a first detail of the Fig. 1 pacemaker; Fig. 3 illustrates a second form of the first detail.

Fig. 4 illustrates a first form of a second detail of the Fig. 1 pacemaker; and Fig. 5 illustrates a second form of the second detail.

As is shown in the drawing a cardiac pacemaker 10 comprises a light source 11, a catheter 12 releasably connected to source 11 by a connector 13, the catheter 12 terminating in a tip 14 which is adapted to be inserted into the right ventricle of a patient's heart, and within the catheter 12 there is an optical fibre 15 which may be a single fibre or a thin fibre bundle depending on the space constraints imposed by the catheter 12.

The light source 11 includes a semi-conductor light emitting device such as a laser or light emitting diode associated with pulse control circuitry for adjustment of power frequency and pulse length and can be mains powered. Control of the source 11 is effected by a feedback mechanism with the feedback signal taken directly from the semi-conductor device or by the arrangement shown in Fig. 2 or, alternatively, by the arrangement shown in Fig. 3. In Fig. 2 the feedback signal is taken from a star coupler 18 and delivered to a monitor circuit 19 which provides the feedback signal to the semi-conductor device pulser 20, in this instance the semi-conductor device being a laser. Fibre 15 delivers the pulse output signal to the catheter tip 14.

In the arrangement of Fig. 3 catheter 12 comprises a thin bundle of fibres 15 one of which is used to provide a light pulse reflection from the catheter tip 14 which reflection is delivered to the monitor circuit 19 to produce the feedback signal for the pulser 20.

Figs. 4 and 5 illustrate alternative forms of the catheter tip 14 each of which is provided with a pair of electrodes 22, 23, exteriorly presented on the tip 14 and internally connected to a solar cell 16 via electrical leads 16A, 16B. In the Fig. 4 arrangement the optical fibre 15 terminates with the fibre end spaced from the cell 16 by a distance which enables the light emitted from the fibre to illuminate substantially the entirety of the cell 16 being related to the diameter of the cell and the numerical aperture of the fibre whereas in the Fig. 5 arrangement the end of the fibre 15 abuts cell 16 and although illuminating only a small area thereof good collection efficiency is achieved by provision of an annular electrode on the surface of the cell which extends into peripheral abutment with the fibre.In this connection it will be appreciated that each face of the solar cell is provided with a collecting electrode conveniently deposited photolithographically.

It is preferred that the semi-conductor device of the source 11 operates in the near infra-red. The use of of such semi-conductor diodes enables the associated electronic control equipment to be compact and reliable.

The solar cell 16 is conveniently a miniature cell having an area of about 1.25mum; or smaller which is effected by edge-machining and polishing so as to fit the catheter tip 14 which conveniently is about lOmm in length and has a diameter of about 2.4mm. The cell 16 may of course be formed as a bank of individual cell elements eletrically connected in parallel to provide the required electrical output power and arranged optically in series. Such an arrangement enables miniaturised cell elements of about O.25mm2 in area to be used. To facilitate insertion of the catheter tip its free end 17 is rendered dome-like or bulbous.

Claims

1. A cardiac pacemaker comprises a light source capable of emitting pulses of light, a catheter including an optical fibre coupled to the output of said light source, the catheter terminating in a tip having two electrodes adapted to sit in the apex. of the right ventricle of the heart, said tip housing a solar cell connected to said electrodes with the end of the optical fibre arranged to illuminate the solar cell.

2. A cardiac pacemaker as claimed in claim 1, wherein the light source operates in the near infra red.

3. A cardiac pacemaker as claimed in either preceding claim, wherein the light source includes a semi-conductor light emitting device with associated pulse control circuitry for adjustment of power, frequency and pulse length.

4. A cardiac pacemaker as claimed in claim 3, wherein control of the light emitting device is effected by a feedback signal derived optically from the light output of the device.

5. A cardiac pacemaker as claimed in any preceding claim, wherein the optical fibre end adjacent the solar cell is spaced from the cell by a distance which enables the light emitted from the fibre to illuminate substantially the entirety of the cell.

6. A cardiac pacemaker as claimed in any one of claims 1 to 4, wherein the optical fibre end adjacent the solar cell abuts one surface of the cell and collection of the electrical output from the cell is effected by an annular electrode on the surface of the cell which electrode extends into peripheral abutment with the abutting fibre end.

7. A cardiac pacemaker as claimed in any preceding claim, wherein the solar cell comprises a plurality of cell elements electrically connected in parallel to provide the required electrical output power.

8. A cardiac pacemaker as claimed in claim 1, and substantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings