Thrombus on the inflow cannula of the HeartWare HVAD: an update

Glass, Carolyn; Christakis, Alexander; Fishbein, Gregory A.; Watkins, Jaclyn C; Strickland, Kyle C.; Mitchell, Richard N.; Padera, Robert F.

doi:10.1016/j.carpath.2018.09.002

Cited by 32 publications

(37 citation statements)

References 14 publications

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“…The cause of this apparent increased stroke risk in HVAD recipients remains unclear. However, a recently published pathologic series suggested that the inflow cannula of the HVAD may be a potential culprit . Glass et al reported that among 24 HVADs implanted in 22 BTT patients (two received biventricular support) which were subsequently explanted during heart transplant, 23 devices (96%) revealed thrombi on the inner cannula, with a preponderance of thrombi occurring at the smooth‐sintered interface of the cannula.…”

Section: Discussionmentioning

confidence: 99%

Stroke risk following implantation of current generation centrifugal flow left ventricular assist devices

et al. 2019

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Background and Aim: Stroke remains a significant complication of left ventricular assist device (LVAD) therapy. We performed a single-center retrospective study evaluating patients undergoing first-time HeartWare HVAD (Methods: Exclusion criteria were age <18 and preoperative ECMO. The primary endpoint was stroke-free survival. Stroke was defined as new neurological deficits persisting >24 hours with corresponding radiographic evidence. Risk factors evaluated included demographics, medical comorbidities, heart failure etiology, LVAD indication, INTERMACS profile, and device type. Univariate predictors (P < .15) and variables clinically suspected to raise stroke risk were entered in a multivariate hazard regression model, specified using backward selection of covariates and accounting for competing risks of transplant/LVAD exchange.Results: A total of 163 HVAD and 84 HM3 patients were analyzed. Median follow up (until death, censoring for transplant/LVAD removal, or end of follow up) was 1.2 years in HVAD patients and 1.4 years in HM3 patients. Stroke occurred in 24 HVAD patients (15 ischemic, 9 hemorrhagic) and 6 HM3 patients (4 ischemic, 2 hemorrhagic). One-year stroke-free survival was 76.8% for HVAD and 84.3% for HM3. Thirty-day mortality following stroke was 41.7% for HVAD and 66.7% for HM3; 54.2% of HVAD strokes were disabling compared to 83.3% of HM3 strokes. Age, LVAD indication, and device type were associated (P < .15) with stroke on univariate analysis. On multivariate analysis, the HVAD was associated with significantly higher stroke risk (hazard ratio, 2.57; 95% confidence interval, 1.02-6.44; P = .045).Conclusions: Different LVAD models appear to be associated with significantly different stroke risks. K E Y W O R D S Left ventricular assist device, Stroke, Cardiovascular research Stroke remains a devastating complication of left ventricular assist device (LVAD) therapy and a leading cause of death during LVAD support. 1 LVAD patients who experience a stroke have decreased life expectancy and diminished quality of life; those who are transplant candidates see a significant reduction in their chances of receiving a heart transplant. 2 Data from the MOMENTUM 3 trial suggests that patients who receive the centrifugal flow Heartmate 3 device (HM3; Abbott Inc, Chicago, IL) experience a significantly lower risk of stroke compared to patients who receive the axial flow Heartmate II device (HM2; Abbott Inc). 3 In contrast, data from the Heartware HVAD ADVANCE and ENDURANCE trials showed an increased risk of stroke for the HVAD compared to the HM2. 4,5 However, differences in clinical trial design (such as inclusion and exclusion criteria, the combination of both destination therapy [DT] and bridge to transplant [BTT] subjects in the MOMENTUM 3 trial, and adverse event definition) preclude the direct comparison of their results. Recently, Mahr et al compared a combined subset of ADVANCE and ENDURANCE trial subjects that represented a similar mix of

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Section: Discussionmentioning

confidence: 99%

Stroke risk following implantation of current generation centrifugal flow left ventricular assist devices

et al. 2019

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“…Hypertension, diabetes, and thrombocytopenia are all risk factors for thrombus formation in heart failure patients, which are not accounted for in the mock circulatory loop studies. Long‐term remodeling is another significant challenge for predicting outcomes from in vitro studies, including the formation of pannus at the inflow cannula and LV volume reduction due to reverse remodeling . Thus, any trends indicated by experimental measurements must be validated with clinical outcomes.…”

Section: Discussionmentioning

confidence: 99%

“…Long-term remodeling is another significant challenge for predicting outcomes from in vitro studies, including the formation of pannus at the inflow cannula and LV volume reduction due to reverse remodeling. 2,3,8,9,22,54,55 Thus, any trends indicated by experimental measurements must be validated with clinical outcomes.…”

Section: Limitationsmentioning

confidence: 99%

Reducing regional flow stasis and improving intraventricular hemodynamics with a tipless inflow cannula design: An in vitro flow visualization study using the EVAHEART LVAD

et al. 2019

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Due to the high stroke rate of left ventricular assist device (LVAD) patients, reduction of thrombus has emerged as an important target for LVAD support. Left ventricular blood flow patterns with areas of flow stasis and recirculation are associated with platelet aggregation, which is worsened by exposure to high shear stress. Previous reports of intraventricular thrombus in LVAD patients have identified the outside of the LVAD inflow cannula as a nidus for LV thrombus formation. Previous studies of LVAD inflow cannula design have shown a region of low blood velocity and pulsatility at the apex, adjacent to the cannula. One unresolved question is whether the standard practice of inserting the LVAD inflow cannula several mm into the LV could be revised to reduce thrombus formation. To address this, a “tipless” inflow cannula was designed for the EVAHEART LVAS, and assessed in a mock circulatory loop of the LVAD‐supported heart. Customized transparent silicone models of a dilated LV were connected to the EVAHEART LVAS at the apex with a clear polycarbonate inflow cannula for flow visualization using particle image velocimetry (PIV). The “tipless” cannula was inserted flush with the endocardial border and did not protrude into the LV. This condition was compared to the standard cannula position with a 1‐cm insertion into the LV. The Pre‐LVAD condition corresponded to a severe heart failure patient (ejection fraction of 24%) with a dilated LV (180 mL). LVAD support was provided at speeds of 1.8 and 2.3 krpm. At the lower LVAD speed, 63% of the flow passed through the LVAD, with the remainder ejecting through the aortic valve. When LVAD speed was increased, nearly all flow (98%) left the LV through the LVAD. Both LVAD speed conditions produced a vortex ring similar to the Pre‐LVAD condition in diastole. However, the protruding inflow cannula interrupted the growth and restricted the movement of the vortex, and produced areas of low velocity and pulsatility adjacent to the cannula. The tipless cannula exhibited an uninterrupted pattern of the mitral jet toward the LV apex, which allowed the diastolic vortex to grow and aid in the washout of this region. In addition, the tipless cannula increased aortic valve flow, which reduces stasis in the left ventricular outflow tract. The EVAHEART LVAS tipless inflow cannula design improved regional velocity, pulsatility, and vortex formation compared to the standard protruding design, which all reduce the risk of thrombus formation. The clinical significance of the differences observed in the flow field will be dependent on other factors such as the cannula material and surface characteristics, as well as the patients' coagulation status.

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“…In the apical region, wedge thrombus formation around the cannula was attributed to the combined effect of the altered flow field and geometric obstruction. 20,25,49 Second, rotary LVADs draw blood from the apex throughout the entire cardiac cycle, disrupting native vortex formation.…”

Section: Introductionmentioning

confidence: 99%

“…27 These thrombi may detach and are a considerable contributor towards the adverse events associated with LVAD therapy. 20 To investigate the ventricular flow patterns in LVAD patients, imaging modalities that enable visualization of these flow fields in vivo are required. The typical method of using phase contrast 4D MRI for flow field visualization 9,34 cannot be applied in LVAD patients due to the ferromagnetic parts.…”

Section: Introductionmentioning

confidence: 99%

Ventricular Flow Field Visualization During Mechanical Circulatory Support in the Assisted Isolated Beating Heart

et al. 2019

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Thrombus on the inflow cannula of the HeartWare HVAD: an update

Cited by 32 publications

References 14 publications

Stroke risk following implantation of current generation centrifugal flow left ventricular assist devices

Stroke risk following implantation of current generation centrifugal flow left ventricular assist devices

Reducing regional flow stasis and improving intraventricular hemodynamics with a tipless inflow cannula design: An in vitro flow visualization study using the EVAHEART LVAD

Ventricular Flow Field Visualization During Mechanical Circulatory Support in the Assisted Isolated Beating Heart

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