Implantable defibrillator arrangement

#1. Field of the Invention

#The present invention is directed to an implantable defibrillator arrangement, and in particular such an arrangement making use of a capacitor and an inductance for generating an electrical defibrillation pulse.

#2. Description of the Prior Art

#FIG. 1 is a schematic diagram of a first embodiment of a defibrillator arrangement having first and second housings, constructed in accordance with the principles of the present invention.

#FIG. 2 is a schematic diagram showing a further embodiment of a current divider circuit in the second housing in portion of a defibrillator arrangement constructed in accordance with the principles of the present invention.

#FIG. 3 is a schematic diagram of a third embodiment of a second housing forming an electrode, in a portion of a defibrillator arrangement constructed in accordance with the principles of the present invention.

#An implantable defibrillator 1 is shown in FIG. 1, the defibrillator 1 being of the conventional type for generating monophase defibrillation pulses. The defibrillator 1 includes a capsule housing 2, adapted for in vivo implantation in a patient, containing a capacitor 3. The capacitor 3 is connected via a switch arrangement 5, controllable by a control unit 4, either to a voltage source 6 or to two externally accessible electrode terminals 7 and 8. The electrode terminals 7 and 8 are connected via electrode leads 9 and 10 to two electrodes 12 and 13 placed at a heart 11. An inductance 14 is connected in the path of the electrode lead 9, the inductance 14 being contained in a second, separate housing 15. The housing 15 has a terminal 16 which is connected via a first section 18 of the electrode 9 to the output terminal 7 of the defibrillator 1. The housing 15 also has a terminal 17 which is connected via a second section 19 of the electrode lead 9 to the electrode 12.

#The housings 2 and 15 each consist of tissue-compatible material, for example titanium, and the terminals 7, 8, 16 and 17 are in the form of insulated bushings extending through the metal housing. The separate housing 15, however, may alternatively consist of plastic, for example silicone, in order to more simply integrate the housing 15 into the electrode lead 9. The housing 15 may have a shape other than shown in the drawing, to facilitate implantability.

#As long as the capacitor 3 is connected to the voltage source 6 via the switch arrangement 5, it will be charged to a prescribed charging voltage. For releasing an electrical defibrillation pulse to the heart 11, the capacitor 3 is briefly connected by the switch arrangement 5 to the electrodes 12 and 13 via the inductance 14. This causes the generation of a biphase current pulse in the form of a highly attenuated oscillation. The shape of the current pulse is defined by the values for the capacitance of the capacitor 3, the inductance 14, and the impedance of the heart tissue between the electrodes 12 and 13. Because the value for the impedance of the heart tissue between the electrodes 12 and 13 changed dependent on the size and arrangement of the electrodes at the heart 11, the defibrillation pulse supplied to the heart 11 can deviate from a pulse shape which is considered optimum with respect to defibrillation effectiveness. This deviation can be counteracted in a simple manner by selecting a suitable value for the inductance 14, so that the second, separate housing 15 having the selected inductance 14 must merely be initially implanted together with the defibrillator 1, or can be implanted in a patient as a replacement, or addition to, an existing defibrillator arrangement. Because the separate housing 15 can have relatively small dimensions, it can be implanted at a location in the body which is easily accessible for replacement.