Pacemaker

Pacemaker

Submit a 1 to 1-1/2 page write-up on the case study addressing: the following points-

  • What is a pace maker and what are the leads for it? 4-5 lines
  • What materials were used initially for the leads? 4-5 lines
  • What was the undesirable effect of those materials? 3-4 lines
  • What was the new material used? Was it helpful in addressing the problem? How?6-8 lines
  • Any update on the leads technology?3-4 lines

 

Case Study:

An individual may require an artificial pacemaker to regulate their heartbeat. The pacemaker is an implanted device which monitors heartbeat and provides electrical simulation to the muscles of the heart, resulting in muscle contraction when needed. The pacemaker is connected to the appropriate heart muscles through pacemaker leads, electrically conductive wires which are fed to the heart through the vasculature.

The pacemaker leads require insulation. Initially poly(dimethyl siloxane) (PDMS) or polyethylene was used as the insulator for the leads. However, both of these materials resulted in a fibrous endocardial reaction. Furthermore, PDMS has low tensile modulus and poor tear resistance.

What properties were required of the biomaterials?

A successful insulator for pacemaker leads would not elicit a fibrous reaction from the heart, and would have high tensile strength and resistance to tearing allowing for thinner lead insulations to be produced.

What polymeric biomaterial is used?

In 1978 polyurethane was introduced as a lead insulator. Although not as flexible as PDMS, the PU had superior tensile properties and tear resistance. This allowed much thinner lead insulations to be fabricated without compromising handling properties. The thinner insulation allows multiple leads to be inserted per vein, enabling sequential pacing. Furthermore, the PU surface has lower friction in contact with blood and tissue than the PDMS surface, allowing easier insertion of the leads.

The search for the optimum lead insulation material is not over yet, however.  In the 1980s it was found that metal-induced oxidation from lead metals resulted in undesired degradation of the polyurethane insulation. Lower ether content in the polyurethane was one solution to this problem, although this results in higher modulus insulation. In subsequent years there have been changes in the material used for the lead wire, and silicone rubber remains in use as well as polyurethanes for pacemaker insulation. Research is underway to find more biostable polyurethanes for this application.

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