Calculation of VAD Cardiac Cycle Volume Using HeartWare Waveform

Purpose An increasing number of heart failure patients are being supported by a ventricular assist device (VAD). Historically, assessment of a patient's hemodynamic status and optimization of VAD performance has been conducted using right heart catheterization and/or echocardiography. The HeartWare HVAD flow waveform displays the blood flow rate through the VAD using a flow estimation algorithm. Our hypothesis is the flow waveform can be utilized to calculate blood volume that is processed by the VAD. Methods An image of the HVAD waveform was obtained for five patients (66 ± 13.1 years, 80% male, 60% Caucasian, MAP 81.4 ± 16.9 mmHg, LVEF 22.0 ± 7.1 %, 2560 ± 40 rpms) while hemodynamic measurements were recorded. A program was written that analyzed the waveform image and calculated blood flow through the VAD by applying integration over a cardiac cycle (Figure 1). Stroke volume measured by hemodynamic monitoring was used to determine the percentage of blood flow going through the VAD versus native heart contribution. Results Average stroke volume calculated using measured hemodynamics was 71.0 ± 15.7 mL and VAD cardiac cycle volume was 36.8 ± 7.1 mL giving an average contribution of 52.0% VAD versus 48.0% native heart for the patient cohort. Figure 2 illustrates the results for each patient. Conclusion VAD cardiac cycle volume can aid in quantifying the contribution of the VAD and the workload of the native heart. This algorithm can be utilized as a new metric in optimizing VAD function, improving patient hemodynamics and assessing for myocardial recovery.