Outflow Graft Narrowing of the Heartmate 3 Left Ventricular Assist Device: Incidence, Imaging Findings, and Outcomes

Purpose Outflow graft narrowing or occlusion has been reported in patients with the HeartMate 3 (HM3) left ventricular assist device (LVAD) due to accumulation of biodebris external to the graft. This study assesses the impact of HM3 LVAD outflow graft narrowing on clinical outcomes and left ventricular unloading. Methods A single-center retrospective cohort study was performed among patients who received a HM3 LVAD between November, 2014 and August, 2019. All patients with a Computed Tomography Angiography (CTA) or Computed Tomography (CT) with IV contrast sufficient to evaluate the outflow graft lumen were included in this analysis. A significant narrowing was defined as a hypodensity of 4mm or greater. Results Of 165 patients who received a HM3 LVAD, 46 (28%) had qualifying imaging. Fourteen patients (30%) had any hypodensity in the outflow graft, and 10 (22%) had a significant narrowing. Median (interquartile range) hypodensity was 4.5mm (3.25 to 5.75). 12 patients had asymmetric hypodensity (example shown in Figure), 2 had circumferential hypodensity, and 1 had complete obstruction. Median distance from the pump exit to the start of narrowing was 5mm (0 to 12mm), length of narrowing was 29mm (22 to 49mm), and diameter of the outflow bend relief at most narrow area of lumen was 14mm (14 to 15mm). 41 (89%) patients had a transthoracic echocardiogram (TTE) done within 35 days of imaging, with the majority (37) having a TTE within two weeks of CT imaging. Death at one year post LVAD occurred in 0 patients with narrowing vs 2 (6%) in those without narrowing (p=0.48). Mean decrease in left ventricular end diastolic diameter compared to pre-LVAD TTE was 12% in patients with narrowing vs 19% in those without narrowing (p=0.34). Conclusion HM3 patients with outflow graft narrowing due to external compression by biodebris have similar outcomes and no difference in left ventricular unloading compared to patients without outflow graft narrowing. Additional analysis with a larger population is warranted.