Low Bearing Wear in Explanted HeartMate II Left Ventricular Assist Devices After Chronic Clinical Support

Abstract

The primary objective of this study was to evaluate bearing wear during clinical use of the HeartMate II (HMII) left ventricular assist device. Bearings obtained from HMII pumps explanted after clinical use in the Destination Therapy and Bridge to Transplantation clinical trials were analyzed for wear using surface profilometry. Geometric profile variations measured on the inlet bearing ball were used to calculate the wear. Bearing wear was normalized to the total pump support duration to obtain an annualized bearing wear rate. Bearing life was estimated assuming a linear wear rate, as the time to reach a wear limit of 25 µm, which includes a 3× safety factor, to ensure that there is no contact between the rotor blades and the blood bore housing. One hundred and eighty-three bearings from left ventricular assist devices implanted in 181 patients were analyzed. Average age of the patients was 56.3 ± 14.6 years, 76% were male, 46% had an ischemic etiology of heart failure. Mean support duration for the pumps was 363 ± 349 days (median: 238, range: 1-1,621 days). Sixty pumps (33%) were explanted at heart transplantation, 20 (11%) after device replacement, 6 (3%) for ventricular recovery, 94 (51%) after patient death, and 3 (2%) were explanted for other reasons. Mean bearing wear was 0.59 ± 0.37 µm (median: 0.46 µm [5-95% interval: 0.25-1.48]). The median bearing wear rate for patients supported for at least 1 year was 0.30 [5-95% interval: 0.09-0.94] µm/yr. The 5-95% limits of the bearing wear rate corresponded to an estimated bearing life between 27 and 269 years. The pump having the highest bearing wear rate (1.46 µm/yr) had an estimated bearing life of at least 17 years. HMII bearing wear is extremely small, with an estimated bearing life well in excess of 17 years; it is not a limiting factor for long-term support with the HMII left ventricular assistive system.

Circulatory support exceeding five years with a continuous-flow left ventricular assist device for advanced heart failure patients

“…Analysis of the explanted LVAD (Fig. 2 ) showed a clean pump with no accumulated thrombus and very low bearing wear of 0.381 μm over 5.46 years (.070 μm/year) consistent with estimated bearing life of well over 17 years of support as previously reported [ 4 ]. In addition, the outflow conduit is clean and without pannus formation in the outflow conduit (Fig.…”

Ventricular assist device use in congenital heart disease with a comparison to heart transplant

“…The long-term durability of pediatric devices is largely unknown, though many larger pediatric patients are supported with adult devices with known excellent long-term durability [88]. The VAD would have to experience a significant reduction in adverse events, most notably CVEs, though with increased postoperative experience this is being accomplished [53].…”

Current Options and Practices in Long-Term Ventricular Assist Devices

“…It sits within a surgically created pocket, though it is small, with a displaced volume of 63 ml, which allows its utilization in smaller patients [28]. It was designed to have only one moving part to increase durability, with the bearing wear on explanted devices having been tested with an estimated life of [27 years [32]. It has been extensively studied and shows fewer adverse events and superior overall survival compared to the pulsatile devices for both BTT and DT with a 2-year survival of 68 versus 55 % [22,29].…”