In my previous article, The Basics of Heart Failure, it was mentioned that a ventricular-assist device (VAD) is the primary treatment for heart failure. Dr. William Wagner (who also contributed to the positive displacement pump technology previously mentioned) believes that there is much room for improvement in the biocompatibility of VADs. he spoke at the BMES conference of infection and thrombosis (blood clotting) problems upon implantation of VADs into patients.

Infection due to VADs can be caused by the biomaterial used, poor sterile technique, device failure, and percutaneous line design. Shear forces caused by excessive bleeding upon implantation of the device can also cause infection, and infection leads to tissue necrosis.

Thrombosis and thromboembolism are problems that all devices face when coming into contact with blood. To avoid this issue, surgeons use drugs like Heparin or Coumadin to avoid coagulation when devices come into direct contact with the blood.

Many scientists believe that nothing can be solved unless it can be quantified. Infection and thrombosis (believe it or not) can be crudely measured through microembolic signals (MES). Dr. Wagner suggested that scientists should get more out of animal models by analyzing MES, explants, and gross neurological health more thoroughly to minimize plately aggregation and avoid thrombosis. An example of a thoroughly tested device that has been underway for 30 years is the Heartmate II, which is implanted in the chest to aid the heart in pumping (shown in the figure above). This device can be used as a treatment method for patients with severe heart failure, or as a bridge until a transplant is available. When tested in calves, this device showed a spike in platelet aggregation (which is expected and normal) and then a steady decrease in aggregation due o microaggregates leaving the implant site. In previous VADs, the platelet aggregation spiked and then didn’t decline at a steady enough rate for thrombosis to cease. Another research project underway by EvaHeart to improve the downfalls of VADs is to replace bovine (cow) with ovine (sheep) products due to this superior configuration of ovine tissue (methacryloyloxyethyl phosphorylcholine).

-Amy

This entry was posted on Sunday, August 15th, 2010 at 9:11 am and is filed under Cardiovascular Engineering, Health. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.