Pacemaker-electrode

Abstract

A transvenous unipolar electrode for permanent pacing of the heart with protruding wire hooks to fix it to the myocardium with an electrode tip comprising a hollow cylinder, in which a bolt, bearing the wire hooks is movable with the aid of a stylet within the hollow electrode from one end position, in which the wire hooks are completely lying within the hollow cylinder, to a second end position, in which the wire hooks are outside the cylinder in the working position.

Description

FIELD OF THE INVENTION

The present invention relates to a transvenous unipolar electrode for permanent pacing with hooks at the tip of the electrode which can be moved out to fix it within the myocardium.

BACKGROUND OF THE INVENTION

Catheter electrodes transvenously brought into the heart have the advantage over epicardial electrodes in that they are introduced without thoracotomy and so diminish greatly the operation risks. In order to avoid the loss of contact between the intravenous electrode and the myocardium and to reach a secure fixation within the myocardium, a pacemaker-electrode was recently developed which has barbs at the tip of the electrode (Deutsche Medizinische Wochenschrift 95 (1970), pp 2026 - 2028). This special electrode ends in two wire barbs of approximately 1 cm length which form, together with a wire loop, the proper electrode tip. The wires are bent backwards. The insertion of the electrode is performed with the aid of a guide-catheter (12 F-size) which is brought into the right ventricle. To determine a favourable position of the electrode by measuring the stimulation threshold, the electrode tip is partially moved outside the guide-catheter in such a way that the barbs remain locked. If a favourable position has been reached, the electrode is pushed forward to release the barbs and to hook them into the tissue.

This well-known special electrode is not without problems. Firstly, the technique of insertion is rendered more difficult in that the proper electrode needs a guide-catheter of a relatively large diameter which is in turn inserted by a normal heart catheter (7 F-size) into the right ventricle. Therefore the implantation requires considerably more time than a normal transvenous electrode. Secondly, the system is relatively stiff so that complications such as perforation of the thin wall of the right ventricle or the inability to find a favourable position may occur.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an electrode which combines the simple technique of insertion and localisation of a normal transvenous electrode with the possibility of locking the hooks in the myocardium. According to the present invention this is solved in such a way that the electrode-tip consists of a hollow cylinder in which a bolt carrying the hooks can be moved from one end position to another. In the first position the hooks are completely within the cylinder and in the other they are outside it forming bent hooks.

According to the present invention the construction of the electrode tip with its hidden hooks in such that a guide catheter is no longer needed. The most favourable electrode position can be determined in the same way as is usual in the transvenous manner. If the correct position is found, the bolt within the cylinder is moved forward with the aid of a stylet which is pushed through the hollow electrode lead. The hooks protrude out from the opening of the cylinder, then due to their own elasticity, spring up independently and so fix the electrode tip at the predeterminated position.

According to a further feature of the present invention the hooks do not have the form of backward bent barbs but are arranged with their whetted peaks towards the opening of the cylinder in a way that they spring out side-way due to their own tension.

The wire hooks are suitably formed by winding a piece of wire in the middle in such a way that the pretension involved brings the bolt into its second position automatically after the release of the peaks of the hooks from the hollow cylinder.

According to a further feature of the present invention the outer surface of the cylinder is protected by an electrical isolation layer. This isolation of the surface insures that in measuring the threshold a position of the electrode is found in which the electrode tip is nearly perpendicular to the excitable tissue. Thus the probability that the two wire hooks are actually anchored in the myocardium, is considerably increased. This is another disadvantage of the already existing electrode which involves a certain risk of being only anchored at one side and thus becoming loose.

BRIEF DESCRIPTION OF THE DRAWING

The invention will become more readily apparent from the following description of a preferred embodiment thereof shown, by way of example in the accompanying drawing, in which:

FIG. 1 is a schematic representation of the electrode tip with the hooks inside the cylinder, in longitudinal section,

FIG. 2 is a schematic representation of the electrode tip with the hooks outside the cylinder, in longitudinal section and

FIG. 3 is a cross-section of the electrode tip according to line III -- III .

The electrode catheter 1 is fabricated in the usual way of a wound metal wire which connects electrically the electrode tip 2 with the pacemaker. The electrode tip 2 comprises a metalic hollow cylinder 3, in which the catheter 1 is firmly inserted. The electrical connection is established in a suitable way. The hollow cylinder 3 has at its free end internally a protruding edge 4, which serves as a stop for the bolt 5. The bolt 5 may freely move within the hollow cylinder 3. The anterior part 5a of the bolt has a reduced diameter so that it fits within the protruding edge 4 of the hollow cylinder 3.

Within the bolt 5, 5a, a slit-like opening 6 in which the wire hooks 7 are arranged, is raised. The wire hooks 7 are formed into a loop with two peaks of equal length and wound in the middle. The wound part 7a is placed on a pin 8 which is arranged in a adequate drilled hole in the bolt 5. The wire hooks 7a consist of a highly elastic material which is body compatible and are so pretensioned that they press their free ends against the anterior part of the hollow cylinder 3 and thus fix the bolt 5 in its end position, demonstrated in FIG. 1.

In FIG. 2 the electrode tip is demonstrated in the working position of the bolt 5. The bolt 5 lies with its part 5a in the ring-shaped protruding edge 4 of the cylinder 3. The wire hooks 7 protrude out of the opening in a way that they are nearly perpendicular to the axis of the hollow cylinder 3. They are pressed against the internal edge 4a of the opening of the hollow cylinder and thus fix the bolt 5 in this end position.

The electrode tip 2 is surrounded by an electrical isolation layer 10 formed by a body compatible synthetic material in the same way as is the catheter 1. This isolation layer 10 covers the whole surface of the electrode tip up to its front side. This isolation allows a position to be found, by measuring the stimulation threshold, in which the whole front side of the tip is in contact with the myocardium. Thus the electrode tip is nearly perpendicular to the exitable tissue where by the probability of penetration of both hooks into the myocardium is greatly increased. Moreover, this measure leads to an electrode with low current drain.

After having found a favourable position by measuring the stimulation threshold, the bolt 5 is moved forward by a stylet within the hollow catheter 1.

If the position of the electrode tip proves after fixation to be unfavourable, the hooks 7 can be compressed by a flexible catheter which is pushed over the catheter 1. Thus the electrode may be withdrawn without fear of any injury to the papillary muscles or veins.

Claims

We claim:

1. A transvenous unipolar electrode for permanent pacing of the heart comprising a tip portion, said tip portion including wire hook means for fixing the tip portion to the myocardium, an electrically conductive hollow cylinder having an opening at one end, a catheter means wound into a hollow spiral and secured in said cylinder in the region of the other end thereof for connecting said tip portion to a pacemaker, said tip portion and catheter means being electrically conductive, said tip portion being secured in said one end of said hollow cylinder, an electrical insulation layer at least on the outer surface defined by said one end of said hollow cylinder, securing means for said wire hook means movable from one end position in which the wire hook means lie completely within said hollow cylinder, to a second end position in which the wire hook means are outside of said cylinder in the hooked or working position, said wire hook means being pretensioned and having end portions directed towards the opening of said hollow cylinder in said one end position and arranged within said hollow cylinder and, when said securing means is moved into said second position said hook means spring open sideways to project laterally to said hollow cylinder due to pretension of said hook means.

2. An electrode for a pacemaker as claimed in claim 1, wherein said hook means are a piece of resilient wire wound in the middle and attached to said securing means at said wound section, said wire hook means being under pretension such that after the tip of said wire hook means protrudes from said one end of said hollow cylinder, said wire hook means forces said securing means into said second position.