A Novel Echocardiographic Window for the Evaluation of the Outflow Graft in HeartMate 3 Left Ventricular Assist Devices

Abstract

Interrogation of the left ventricular assist devices (LVAD) outflow graft with trans thoracic echocardiography (TTE) is often limited by poor windows. We describe a novel subcostal TTE approach to assess the outflow graft in patients with HeartMate 3 LVAD. The outflow graft was visualised using a shallow subcostal window with the probe tilted almost parallel to the abdominal wall. This new subcostal window was compared to the right parasternal window. The velocity time integral (VTI) of the Doppler between the artificial pulse every 2 seconds was used to calculate total pump flow (litres per minute) = VTI x cross-sectional area of outflow graft x 30 'beats per minute'. Pump parameters were recorded at the same time. 35 consecutive patients with HeartMate 3 LVAD were included (Age: 53±4 years; 89% males; body mass index 26±1kg/m2).The outflow graft could be visualised in 28/35 patients (80%) with this subcostal window compared to 12/35 (34%) patients with parasternal window (p<0.05). The colour Doppler and VTI of a patient with normal and partially occluded outflow graft are shown in FIGURE 1a, 1b and 1c respectively. The latter shows high velocity Doppler compared to normal. The calculated pump flow correlated with the displayed pump flow (R2=0.69, p<0.001), but agreement on the Bland-Altman plot is modest [FIGURE 2]. 'Pulsatility' based on the ratio of s and d flow on Doppler correlated with the displayed pulse index (R2=0.52, p<0.001). A novel shallow subcostal echocardiographic window can interrogate the LVAD outflow graft in patients with HeartMate 3 LVAD.