BIO29: Investigating EVAHEART2 Speed Modulation Using Computational Hemodynamic Analysis

Study: Hemodynamic optimization is a current unmet clinical need of LVAD therapy for end-stage heart failure patients. Understanding the LVAD pressureflow relationship and the interaction of the pump with the patient cardiovascular system is essential to designing custom LVAD speed modulation waveforms to optimize hemodynamic performance. This study focuses on investigating the EVAHEART 2 LVAD towards designing optimal pump speed modulation (PSM) algorithms. Methods: A custom designed hemodynamic lumped parameter model (HM) incorporating the EVAHEART 2 pressureflow curves, cardiac chambers and the systemic and pulmonary circulations was developed and used in this study (Fig 1a). Several PSM waveforms were designed and tested to evaluate their influence on the mean arterial pressure (MAP), cardiac output (CO) and to encourage aortic valve (AV) flow for representative heart failure patients. Baseline speeds were varied from 1600 – 2200 RPM in increments of 50 RPM. For each baseline speed, the variation in the following parameters were analyzed: (i) PSM ratio (reduced speed/ baseline speed), (ii) PSM duration ranging from 3 – 7 seconds, (iii) native ventricle contractility and (iv) patient MAP, ranging from 65 – 85 mmHg. Results: PSM waveforms were investigated for several baseline speeds. For a baseline speed of 1800 RPM, the AV did not open at baseline, and also at PSM settings varying from PSM ratios of 80% (reduced speed of 1440 RPM) to PSM ratio of 95% (reduced speed of 1710 RPM). AV flow did occur for three out of five cardiac cycles at a PSM ratio of 75% (reduced speed of 1350 RPM). With the PSM occurring once every 25 seconds, lasting for a duration of 5 seconds, the flow through the AV was just over 0.2 L/min (Fig 1d). At a lower baseline speed of 1700 RPM, a PSM ratio of 80% (reduced speed 1360 RPM) encouraged the AV to open for four times out of five cardiac cycles, allowing for more than 0.2 L/min to flow through the AV (Fig 1b and c). Increased PSM duration, higher native LV contractility and lower patient MAP strongly influenced the PSM hemodynamics and AV openings for the over 1500 cases analyzed. Conclusions: This study of the EVAHEART 2 LVAD is the first to focus on leveraging PSM to enhance pulsatility and encourage AV flow. Our analysis indicates that increasing the PSM duration and utilizing a lower baseline speed provided the optimal conditions to allow for AV flow. Increased AV opening frequency can help wash out blood potentially stagnating in the aortic root, thereby reducing thrombogenicity and improving patient outcomes.