Acoustic Analysis of a Mechanical Circulatory Support

Abstract

Mechanical circulatory support technology is continually improving. However, adverse complications do occur with devastating consequences, for example, pump thrombosis that may develop in several parts of the pump system. The aim of this study was to design an experimental clot/thrombosis model to register and analyze acoustic signals from the left ventricular assist device (LVAD) HeartMate II (HMII) (Thoratec Corporation, Inc., Pleasanton, CA, USA) and detect changes in sound signals correlating to clots in the inflow, outflow, and pump housing. Using modern telecom techniques, it was possible to register and analyze the HMII pump-specific acoustic fingerprint in an experimental model of LVAD support using a mock loop. Increase in pump speed significantly (P < 0.005) changed the acoustic fingerprint at certain frequency (0–23 000 Hz) intervals (regions: R1–3 and peaks: P1,3–4). When the ball valves connected to the tubing were narrowed sequentially by ∼50% of the inner diameter (to mimic clot in the out- and inflow tubing), the frequency spectrum changed significantly (P < 0.005) in P1 and P2 and R1 when the outflow tubing was narrowed. This change was not seen to the same extent when the lumen of the ball valve connected to the inflow tube was narrowed by ∼50%. More significant (P < 0.005) acoustic changes were detected in P1 and P2 and R1 and R3, with the largest dB figs. in the lower frequency ranges in R1 and P2, when artificial clots and blood clots passed through the pump system. At higher frequencies, a significant change in dB figs. in R3 and P4 was detected when clots passed through the pump system. Acoustic monitoring of pump sounds may become a valuable tool in LVAD surveillance.

Acoustic Characterization of Axial Flow Left Ventricular Assist Device Operation In Vitro and In Vivo

“…When the inflow graft was occluded in vitro, a trend of curve mirroring with reduction in amplitude was observed, as shown in Figure 4. This supports the findings of Hubbert et al 22 who detected a similar pattern when ball valves were used to occlude the inflow and outflow conduits. The similarities between these in vitro changes because of partial occlusion and the effect of thrombus in vivo may be related to the location of the thrombus at the inflow stator of the pump, upstream of the impeller in patient A, and within the inflow tract and device housing in patient B.…”

“…In 2003, Tanishiro et al 20 showed that arterial sound can be used to detect malrotation in centrifugal LVADs in an in vitro setup, and in 2007, Slaughter et al 21 showed that acoustic changes predicted impending device malfunction in the pulsatile HeartMate XVE. Recently, Hubbert et al 22 showed significant differences in HeartMate II acoustics when inflow and outflow tubing were subject to artificial stenosis and when artificial clots were passed through the pump, and Kaufmann et al 23 showed that thrombus formation in HeartWare ventricular assist device pumps was associated with telltale changes in acoustic spectra. Similar data collection techniques were used in all studies, although particular equipment differed.…”

731 Acoustic Analysis of a Mechanical Circulatory Support

“…The overall increases in amplitude due to increase in speed are similar to those seen in a previous study (9). With each increase in pump speed, significant changes were detected in regions R1-R3 and in P1, P3, and P4, but not P2.…”

“…To our knowledge, there is no article published, apart from abstracts, on acoustic data from continuous flow devices (4,9).…”

Epidermal mechano-acoustic sensing electronics for cardiovascular diagnostics and human-machine interfaces

“…Additional biomedical applications include monitoring of mechanical circulatory support devices, such as those that augment dysfunctional ventricular pump function and serve as important temporary or permanent alternatives to heart transplantation ( 47 ). The latest continuous-flow left ventricular assist devices (LVADs) offer improved durability and hemodynamic restoration, though with the limitation of adverse events, including a loss of pump function due to pump thrombosis or other mechanical failure ( 48 ).…”