A Novel Method of Predicting Aortic Valve Opening through LVAD Power Waveform Analysis

Abstract

Purpose Aortic valve opening (AVO) during left ventricular assist device (LVAD) support has important clinical implications in preventing thrombosis and leaflet fusion causing chronic regurgitation. Assessment of AVO has become part of routine LVAD care. Traditionally, this has been done with transthoracic echocardiography (TTE) but that technology is costly and not always readily available, especially as patients are increasingly released back to their communities. This study investigates the use of LVAD power waveform analysis as a faster and inexpensive method of evaluating AVO in LVAD patients. Methods and Materials Waveforms were collected from HeartMate II LVAD controllers and saved in The Artificial Heart Program database. Waveforms were then matched with corresponding TTE reports to determine AV status. A LabView program was used to filter and analyze these power waveforms and output characteristics of each wave. These characteristics were then stratified into AV opened or AV closed groups. Averages of parameters for each group were taken and compared using a two-tailed Student’s t-test. Results 492 AV closed waveforms were obtained from 39 patients and 168 AV opened waveforms were obtained from 19 patients. Patients with open AV are shown to have higher average wave amplitudes, and took a larger percentage of time to reach max amplitude as shown by the skewness which is a measure of wave asymmetry. Conclusions We describe an innovative and inexpensive method of detecting significant differences between open and closed AV. Further study is needed to create and validate a user interface in LabView to input an unknown waveform and be able to predict AVO within a reliable accuracy level. AV Closed (n=492) AV Open (n=168) Waveform Characteristics μ ± μ ± p-values Baseline Current (mA) 303 77 305 83 0.85 Amplitude (mA) 139 37 160 50 Skewness 0.07 0.41 -0.08 0.44 Table 1 μ: mean, ±: standard deviation