LONG-TERM, IN VITRO RELIABILITY TESTING FOR LVADS INTENDED FOR DESTINATION THERAPY:

PURPOSE A crucial characteristic of LVADs intended for heart failure destination therapy is long-term device reliability. Accordingly, reliability was the primary impetus for the basic features of the Thoratec HeartMate® 111, including its magnetically-levitated rotor to obviate mechanical bearings, implanted control electronics to reduce electrical wire count, and single-fault tolerant architecture to maintain operation even in the event of component failure. METHODS Five prototype LVADs were placed in test loops topologically similar to the cardiovascular system, including a pulsatile pump to simulate native ventricular contractility. The pumps were immersed in 37C saline, which also serves in this ongoing test as the circulating fluid. The flow conditions are changed according to a regular, periodic schedule among 3 cases: high flow (1OLpm, 11OmmHg), 'design point' (7Lpm, 140mmHg), and low flow (7Lpm, 70mmHg). This time-terminated study will be evaluated at 5 years, seeking to establish 80% reliability with 60% confidence, with the provision that units will be subsequently run to failure. RESULTS: All 5 test units continue to operate 24 months after the protocol started, without incident and with no apparent change in power consumption or pressure-flow characteristic. OUTLOOK To prove clinical readiness, a second in vitro test of 10 LVADs, similar in construction but built to official assembly, process, and inspection procedures, will imminently begin to lend statistical power to the reliability assessment.