Screening for Outflow Cannula Malfunction of Left Ventricular Assist Devices (LVADs) With the Use of Doppler Echocardiography: New LVAD-Specific Reference Values for Contemporary Devices

Abstract

Background Echocardiographic assessment of left ventricular assist devices (LVADs) is used as a screening tool to evaluate the integrity and mechanics of the pump and circuit. We aimed to 1) establish the normal range and upper reference limit of peak velocity of the outflow cannula for the modern era of LVADs and 2) assess the clinical performance of the currently cited and newly proposed reference limits in patients with continuous-flow LVADs as a screening tool for cannula malfunction. Methods LVAD outflow peak CW velocities were measured with the use of Doppler transthoracic echocardiography (TTE) in 57 patients with LVADs (44 with Heartmate II (HM2), 13 with Heartware (HW)). The average velocity and the upper and lower normal reference limits (defined as ±2 standard deviations from the mean) for each LVAD type was calculated. The upper reference limit was then used as a screening threshold for cannula malfunction. Results The average outflow cannula peak velocity for the normal HM2 cohort was 1.86 ± 0.44 m/s with upper and lower reference limits of 2.73 m/s and 0.98 m/s, respectively. The average outflow cannula peak velocity for the normal HW cohort was 2.36 ±0.53 m/s with upper and lower reference limits of 3.42 m/s and 1.3 m/s, respectively, which was significantly higher than the HM2 cohort (P = .004). Conclusions In both HM2 and HW LVADs, the average peak outflow velocity and reference limit for the normal population, as measured by Doppler TTE, was markedly higher than the currently used LVAD reference limits of 2 m/s and are significantly different between devices. Patients with peak outflow velocities above our upper reference limits should be evaluated for LVAD outflow cannula malfunction.

Outflow graft obstruction after left ventricular assist device implantation: a retrospective, single‐centre case series

“…2 Reports suggest that adequate echocardiographic images of the outflow graft can be obtained in >90%. 3 However, our echocardiographic success rate was only 71%, and the pressure gradient estimated was significantly lower than by catheterization. Thus, additional testing must be considered if the clinical suspicion remains high.…”

“…Therefore, the rapidity with which flow drops does not distinguish between inflow and outflow cannula problems as proposed elsewhere 2 . Reports suggest that adequate echocardiographic images of the outflow graft can be obtained in >90% 3 . However, our echocardiographic success rate was only 71%, and the pressure gradient estimated was significantly lower than by catheterization.…”

Percutaneous treatment of left ventricular assist device outflow graft obstruction

“…The 2015 American Society of Echocardiography 10 guidelines recommended screening for outflow graft obstruction for velocities greater than 2 m/s. Conversely, independent investigations have reported device specific doppler velocities with average velocities for Heartmate II were 1.86 ± 0.44 m/s and for Heartware 2.36 ± 0.53 m/s 11 …”

Percutaneous Management of Outflow Graft Obstruction in Patients With Continuous Flow Left Ventricular Assist Devices

“…Although there are limited data for the use of multi-imaging modalities for the diagnosis of LVAD dysfunction, prior studies have shown that transthoracic Doppler echocardiography can be used as a screening method to assess for OGO ( 4 ). Moreover, transesophageal echocardiography is suitable in the overall assessment of LVADs and can provide information for device position, ventricular function, valvular structure and hemodynamics, thrombus, aortic root anatomy, and inflow and outflow graft angulation.…”