Comparison of Intraoperative Doppler Flow Measurements and Algorithmic Flow Estimations in Patients Undergoing Durable Left Ventricular Assist Device Implantation

INTRODUCTION: Left ventricular assist devices (LVAD) have become an established therapy for end-stage heart failure over the last three decades. In currently available devices, the blood flow is estimated using a power consumption algorithm. In this study, intraoperative direct LVAD flow measurement with an ultrasonic flow probe was analyzed. METHODS: As part of our routine evaluation of optimal LVAD flow, intraoperative direct flow measurement at the outflow graft was performed using a 14-mm ultrasonic flow probe. Direct LVAD flow measurements were performed at different speed levels: 4400 rpm, 4800 rpm, 5200 rpm, and the optimal flow setting before chest closure. In twenty consecutive patients who underwent a durable LVAD implantation via median sternotomy in our institution between January and April 2025, direct flow measurement was compared with the estimated flow provided by the device. RESULTS: Median age was 63 [60;68] years, 17 (85%) were male, 8 (40%) had a history of acute myocardial infarction. Temporary mechanical circulatory support with a microaxial flow pump was necessary in 8 (40%) patients prior to durable LVAD implantation. Destination therapy was indicated in 12 (60%) cases. Mean flows at 4400 rpm were 2.9 ± 0.3 and 3.4 ± 0.4 L/min calculated by the pump and measured by the probe, respectively. Mean difference between the measurements was 0.56 L/min (95% CI [0.40, 0.70], p < 0.001). Mean flows at 4800 rpm were 3.5 ± 0.3 and 4.1 ± 0.5 L/min, respectively. Mean difference between the measurements was 0.55 L/min (95% CI [0.33, 0.77], p < 0.001). Mean flows at 5200 rpm were 4.2 ± 0.3 and 4.7 ± 0.5 L/min, respectively. Mean difference between the measurements was 0.53 L/min (95% CI [0.40, 0.70], p = 0.001). Mean optimal speed for patients was 5400 rpm, mean difference between the measurements was 0.49 L/min (95% CI [0.23, 0.74], p = 0.001). CONCLUSION: LVAD flow measured with an ultrasonic flow probe shows significantly higher results (approximately +0.5 L/min) compared to the flow estimated by the device. The difference remains constant at different LVAD speed modes. Intraoperative flow measurement employing an ultrasonic flow probe is a valuable tool for hemodynamic evaluation during implantation of a durable LVAD.