New material for implantable cardiac leads

Cardiac function management devices, including implantable pacemakers and implantable defibrillators, include at least 1 cardiac lead having an electrode for making contact with a portion of the heart. It has been previously shown that the braided multifilament wire electrodes have a high failure rate both for sensing of spontaneous heart activity and for safe heart stimulation. Therefore, it is desirable to have cardiac leads made of materials with mechanical and electrical properties to insure safe pacemaker function. We have developed a new fiber material suitable for implantable cardiac leads with superior high modulus, high mechanical strength, and excellent electrical conductivity.

Methods

The material comprises poly(p-phenylene benzobisoxazole) fibers plated with gold by using an electroless plating method. Due to the difficulty in plating gold directly on organic and inorganic fibers, gold plating was carried out on the surface of silver-plated fibers.

Results

The morphology of plated fibers was studied by x-ray diffraction, scanning electron microscopy with energy dispersive spectroscopy, and electrochemical polarization measurements. It was found that gold was uniformly plated on the poly(p-phenylene benzobisoxazole) fiber, and the gold-plated fibers have good corrosion resistance. The electrical conductivity of the gold-plated fibers was higher than 4 × 104 S/cm, and its tensile strengths and Young moduli were greater than 1.9 and 130 GPa, respectively, when estimated in terms of a single-fiber strand.

Conclusions

The metal-clad polymer fibers have advantages over conventional metal cardiac leads in flexibility, weight savings, mechanical strength, durability, and tailored electrical conductivity. Therefore, the combined engineering properties of the new fiber afford implantable cardiac lead applications at reduced diameter while having higher strength. Furthermore, the new fiber can be terminated just like a regular metal wire with the choice of ultrasonic bonding, crimping, or band connection.