Mechanical Circulatory Support can be categorized in many ways: internal vs. external, pneumatic vs. electric, pulsatile vs. non-pulsatile, uni-ventricular vs. biventricular and ventricular assist vs. total artificial heart, and on and on. Each individual system may hold one or more features (i.e. there are internal electric non-pulsatile ventricular assist devices and internal, electric pulsatile total artificial hearts). Currently the intrigue focuses around the pulsatile vs. non-pulsatile issue. For more information on each, please click on the appropriate image.
All of this technology certainly does have limitations, however, but advances have given us smaller portable controller/drivers, lower rates of thromboembolism and more advances are on the horizon. The most common problems involve bleeding, thromboembolism, and infection. Device failure is obviously a concern, but occurrences are rare. Patients are constantly achieving new milestones of days on a device that continually tests the fortitude of these devices. These devices have a difficult job to perform, pumping the equivalent of 350 liters of water/hour (or 5 bathtubs full) to a height of 6 feet, in a hostile environment (blood is corrosive and prone to clotting). Eventually everything wears out, as will these devices, but there are methods for dealing with this. Novacor for example has developed a highly sophisticated failure model, which predicts pump failure as far as three to six months in advance.
Hundreds of patients have been supported for
over a year on many of these devices. Many patients have broken
the 2, 3, and 4 years barriers. New systems, currently in
clinical trials, which are totally implanted should reduce
the rates of infection by removing the percutaneous driveline
from the equation. Better blood contacting surfaces will reduce
the occurrences of thromboembolism. New devices may make it
possible to drastically extend the time of support, which
will then be in direct competition with cardiac transplant
survival rates. Inevitably, all of these improvements will
have positive affects not only on the patient's survival but
maybe more importantly on the patient's quality of life.
