Background of the invention At present the electrodes on intravascular leads pertaining to the field of pacing systems and the like normally are placed in the auricle of the right atrium and in the apex of the right ventricle. For different reasons it has however become desirable to place the electrodes in other locations in the heart. One example is placement in the coronary sinus in order to reach the left side of the heart.

For these reasons efforts have been made in order to achieve thin and highly flexible leads that for instance easily can be introduced into the coronary sinus and into the peripheral veins on the outside of the heart.

One example of such a lead is disclosed in US Patent No 5,935,159. In this design the conductors in the lead in some embodiments are placed longitudinally on the envelope surface of a core. In one embodiment, shown in Fig 8 in this patent, the longitudinal conductors are separated by longitudinal flanges formed integrally with the core. A longitudinal lumen for a guiding stylet is located at the center of the core.

A similar lead having integral flanges extending helically along the core is disclosed in US Patent No 5,968,087. In this design conductors are wound helically around the core inbetween the helical flanges. Flanges and conductors are then embedded in the outer sheath or insulation, see particularly Figs 3 and 4 in this patent.

The object of the invention is to design a lead, which is thin, which is easy to manufacture, and which is highly flexible.

Short description of the inventive concept The above object is achieved by means of a lead having the features set out in the characterizing portion of the appended main claim. Preferred embodiments are set forth in the dependent claims.

Short description of the appended drawings Fig 1 shows a cross-section of a lead according to the invention; Fig 2 shows a longitudinal part section of a lead according to the invention.

Detailed description of a preferred embodiment As can be seen in Fig 1, the lead comprises a lead body 1. The lead body comprises an inner, cylindrical core 2 with an inner lumen 3 for a guiding stylet 7. The lead body 1 further comprises a protective, insulating sheath 6 of a polymer material as is well known in the art of pacer leads.

Conductors 4 are wound helically around the core. It is preferred that the conductors 4 are made of material in the form of strands, since this increases the flexibility of the lead.

Each conductor is separated from the adjacent conductors 4 by means of a cable or wire 5 made of an insulating, soft material. This cable 5 preferably is wound around the core together with the conductors. The diameter of the cable preferably is the same as the diameter of the conductors. It should however be noted that the insulating cables could have larger or smaller diameters as long as the requirement that the conductors are separated from each other is met.

The cables 5 preferably also are made of material in the form of strands. The number of conductors may vary from one conductor and upwards.

The conductors 4 further are covered individually by an insulating layer 8 that preferably is made of PTFE. The use of a low friction material such as PTFE will minimise the

friction between the conductors 4 on one hand and the core 2 and the cables or wires 5 on the other hand.

The above design with separate insulating cables separating adjacent conductors from each other will result in a thin, flexible cable. The flexibility is improved by the fact that the conductors, the core and the cables all have the possibility to move slightly relative to each other, particulary if the conductors are covered with a low- friction material.