Screw-in electrode probe for cardiologocal application

#The present invention relates to a screw-in electrode probe for cardiological application.

#Screw-in electrode probes are known from public prior uses or may also be inferred from US 2002/0188340 A1 or US 2003/0144722 A1. They have an oblong electrode body made of an electrically insulating material, a rotatable electric supply line running in the electrode body, and an electrode head situated at the distal end of the electrode body. The latter is provided with the housing from which a corkscrew-like screw-in electrode may be screwed into cardiac tissue through rotation around its coil axis with corresponding axial displacement. For this purpose, the screw-in electrode is seated coaxially on a shaft which is in turn connected in its axial extension to the supply line for the electrode—typically a coiled wire—running in the electrode body. A torque may be transmitted to the shaft via the supply line, through a corresponding pitch provider, the shaft is then rotated around its longitudinal axis and axially displaced in order to screw the screw-in electrode actively into the cardiac tissue or retrieve it therefrom again.

#Depending on the application, it may be necessary, for reasons of signal or stimulation technology, to produce an electrical connection between the electrically conductive housing, which is made of metal, and the screw-in electrode itself, so that both elements are at the same electrical potential. This is typically implemented by a contact spring, for which different embodiments and installation possibilities are known through public prior use. It is to be ensured in principle in connection with the active fixing and the rotation of the screw-in electrode, with its shaft, and the simultaneous axial displacement connected thereto that the contact spring is also capable of compensating for radial displacements in addition to the axial movement of shaft and screw-in electrode. For this purpose, welding both ends of a type of clock spring, as is used for the balance wheel of a clock, for example, to the shaft and/or the housing is known. Because of the filigree configuration of this spring, this assembly step is relatively complex and sensitive in regard to the reliability of the contact connections. Furthermore, this type of spring requires a relatively large installation space, since the displacement path, which must cover the fixed connection points of the clock spring on the housing and shaft in relation to one another, is comparatively large, specifically two rotations at an axial displacement of 2 mm, for example. This path must be provided by the length of the spring leg without building up a noticeable counter tension during the rotation and axial displacement of the screw-in electrode.

#FIG. 1 shows a schematic axial section through the electrode head of a screw-in electrode probe, and

#FIG. 2 shows a section along section line II/II in FIG. 1.

#As shown in FIG. 1 in particular, a screw-in electrode for cardiological application has an oblong, tubular electrode body 1 made of an electrically insulating material. Various supply lines to electrodes (not shown in greater detail), such as the ring electrodes at a distance to the distal end 2 of the probe, are housed therein.

#At the distal end 2 of the electrode body 1 itself, an electrode head, identified as a whole by 3, is provided, which has a corkscrew-like screw-in electrode 4 which may be anchored in cardiac tissue. This electrode is rotatable in an essentially cylindrical housing 5 on a shaft 6 around its coil axis 7 and is mounted so it is axially displaceable in this direction. A bush 8 is provided on the housing 5 for connecting the electrode body 1 to the housing 5, onto which the lumen 9 of the electrode body 1 is pushed and fixed in a suitable way there. A conduction coil 10, which is permanently mechanically and electrically connected to the shaft 6, is guided in this lumen 9 of the electrode body 1 from the proximal end of the electrode probe. Via the conduction coil 10, electrical pulses may be guided for delivery via the screw-in electrode 4 or electrocardiological measuring signals may be guided from the screw-in electrode 4. In addition, the conduction coil 10 is so torsion-proof that a torque may be transmitted via it from the proximal end of the electrode probe to the shaft 6 for its rotation around the coil axis 7. The axial advance of the screw-in electrode 4 is caused via a pitch provider, which is integrated in the housing 5 but is not shown separately here.

#A contact spring, which is implemented as an essentially planar spiral spring 11, is provided to produce an electrical contact between the assembly made of screw-in electrode 4 and shaft 6 with the housing 5. The plane of extension of this spiral spring 11 is directed orthogonally to the coil axis 7, so that the leg ends 12, 13 of the spiral spring 11 are each supported at approximately the same height on the inner wall of the housing 5 and the lateral surface of the shaft 6, respectively. There is no rigid connection between the leg ends 12, 13 and the above-mentioned components of the electrode head, so that a sliding contact exists between spiral spring 11 and shaft 6 or housing 5, respectively. As may be seen from FIG. 2, the leg length of the spiral spring 11 is dimensioned in such way that it rotates around the shaft 6 under radial tension, the wrap angle U being at least 360°, preferably—as shown here—approximately 450°, however. Because of the system shown and described, both leg ends 12, 13 of the spiral spring 11 exert a spreading force F, which ensures a clean contact connection between the elements connected thereto. Therefore, both the axial displacement A of the screw-in electrode 4 using shaft 6 during anchoring and also radial play R occurring in this case may be compensated for without impairing the spring force F and thus the contact provided between the connected elements.