Acoustic Spectral Analysis for Determining Pump Thrombosis in Rotary Blood Pumps

Implantation of rotary blood pumps is an established treatment for end-stage heart failure. Anticoagulation is routinely used for reducing pump thrombosis, but this severe complication still occurs in 5-8% of patients. In 105 patients, the sound produced by the left ventricular assist device HeartWare HVAD was prospectively and sequentially recorded. The acoustic spectra calculated by runtime fast Fourier transformation were investigated. Results were compared with respect to patients without thrombotic complications (97 patients) and those with signs of pump thrombosis (8 patients). All eight pumps exchanged were opened and investigated. Thrombus formation was confirmed in all eight exchanged pumps. The existence of a sound peak with the threefold frequency of the pump speed correlated with the presence of thrombi inside the pump (p < 0.001). An increase in the sound amplitude of the rotary frequency of approximately 75% compared to previous measurements also denotes pump thrombosis. Analysis of the acoustic spectrum of the HVAD pump can be used as a reliable method to detect pump thrombosis. The appearance of third harmonics indicates the presence of thrombotic particles independently of previous baseline measurements. The goal of this study is to define and validate such a method.