Redefining Normal Outflow Cannula Velocity Reference Values for Each Left Ventricular Assist Device

Abstract

2D transthoracic echocardiography (TTE) remains an integral component of imaging left ventricular assist devices (LVAD) and determining proper functionality of these devices. Despite relying heavily on transthoracic echocardiography, little is known about standardization of echocardiographic values and measurements pertinent to different types of devices (i.e. HeartMate II (HMII), Heartmate 3 (HM3), or HeartWare HVAD). We identified 216 patients with HM3, HM2, and HVAD left ventricular assist devices. For each patient, we identified all transthoracic echocardiograms that had been performed post-LVAD implantation (n=489 TTEs). Peak outflow cannula velocities were measured using continuous wave Doppler from the right sternal border position on the chest (most co-axial to flow). Patients with incomplete continuous Doppler waveforms were excluded. Peak velocities were different for all three LVADs. The mean peak velocity for the HMII (n=289) was 1.74±0.575 m/s, the mean peak velocity for the HM3 (n=113) was 1.54±0.458 m/s and the mean peak velocity for the HVAD (n=87) was 2.07±0.762 m/s. The mean peak velocity for the HeartMate 2 was significantly different than the HeartMate 3 (p=0.0013). Similarly, the HeartMate 2 velocity was also different than the HeartWare HVAD (p=0.000011). When the mean peak velocities of the HeartMate 3 were compared with the HeartWare HVAD, statistical significance was also found (p=0.0000000039). Mean peak outflow cannula velocities differ significantly in each of today's most commonly used LVADs. Different reference standards should be considered for each LVAD type.