LONG-TERM RELIABILITY TESTING OF THE HEARTMATE?? II LVAD

Abstract

The HeartMate II (HM II) is an axial flow LVAD currently undergoing clinical trials in the U.S. and in Europe. The blood pump and internal components have been designed for long-term use in humans with chronic advanced heart failure. The various features of the HM II that influence operating life (bearing wear, internal seal mechanisms, percutaneous cable integrity) are being evaluated in a long term in-vitro test designed to challenge the system under simulated physiological conditions. Presently, life tests of nine HM II blood pumps are ongoing. Each pump is submerged in a vessel of 37° C saline and operated in a pulsatile mock circulatory loop with an active ventricle. The pumps are operated at three different speeds, 8000, 12000, and 15000 RPM, with each condition maintained for approximately one week at a time. As of Jan 1, 2005, a total of 21.3 pump years have been accumulated, with no failures. Three pumps have been running for over 3.2 years, and four more for over 2.5 years. Upon inspection of one of the longest running pumps at 2.7 years, net bearing wear was 0.00030 inch. Based on this wear rate, that device will operate for approximately 9 years before reaching the maximum allowable wear limit. This figure is consistent with previous test results of multiple development units. The life test results are consistent with clinical results to date in which 34 pumps have been implanted in humans for a total run time of 10.3 years without pump failure. The longest ongoing patient has been supported for well over a year, and ongoing or explanted devices have shown no signs of bearing wear issues.