Left Ventricular Assist Device Outflow Research Articles

In Vivo Testing of a Second-Generation Prototype Accessory for Single Transapical Left Ventricular Assist Device Implantation.

A new accessory was developed to allow implantation of left ventricular assist devices (LVADs) without requiring an anastomosis to the ascending aorta. The accessory combines the LVAD inflow and outflow into a dual-lumen device. Initial prototypes encountered reduced pump performance in vitro, but a second-generation prototype successfully addressed this issue. This feasibility study aimed to demonstrate the anatomic fit, safe implantation, and hemodynamic effectiveness of the LVAD with the accessory. The accessory was implanted in ten female pigs (104 ± 13 kg). Following sternotomy and apical coring under cardiopulmonary bypass, a balloon catheter was retrogradely inserted and exteriorized through the coring site, where it was inflated within the distal third of the outflow graft. It was utilized to pull the accessory's outflow across the aortic valve. After LVAD attachment, the catheter was removed. Echocardiography revealed no relevant valve regurgitation post-implantation. During ramp testing, pump flow increased from 3.7 ± 1.2 to 5.4 ± 1.2 L/min. Necropsy confirmed correct accessory placement in nine animals. No valve lesions or device thrombosis were observed. The accessory enabled LVAD implantation without compromising pump performance. Future work includes design refinements for implantation without cardiopulmonary bypass and long-term testing in a chronic heart failure model.

Influence of LVAD Cannula Outflow Graft Flow Rate and Location on Fluid-Particle Interactions and Thrombi Distribution: A Primary Numerical Study.

A left ventricular assist device (LVAD) supports hemodynamics in heart failure patients. To deepen the understanding of hemodynamic changes and the movement of thrombi in the aorta, we examined three distinct LVAD blood flow rates across two implantation sites using the theory of computational fluid dynamics. Our findings revealed the complex dynamics of blood flow during cardiac systole under various scenarios. We also analyzed thrombi residence time and flow probabilities into aortic branches. Simulation results indicate that thrombi distribution in the aorta is significantly influenced by the location of the LVAD outflow graft and the flow rate. When the LVAD outflow graft is implanted into the ascending aorta, higher flow rates may reduce the risk of cerebral thrombosis. However, lower flow rates may reduce the risk of cerebral thrombosis while it is implanted into the descending aorta. The study may offer valuable insights into the LVAD implantation about the risk of cerebrovascular embolism.

A Clinicopathological Case of Left Ventricular Assist Device Outflow Graft Stenosis.

A Clinicopathological Case of Left Ventricular Assist Device Outflow Graft Stenosis.

Robotically assisted outflow graft anastomosis in minimally invasive left-ventricular assist device implantation: feasibility, surgeon comfort, and operative times in an anatomical study.

Upper hemi-sternotomy is a common approach for outflow graft anastomosis to the ascending aorta in minimally invasive left-ventricular assist device implantation. Right mini-thoracotomy may also be used, but use of robotic assistance has been reported only anecdotally. The aim of our study was to confirm the feasibility of robotically assisted suturing of the outflow graft anastomosis and to assess performance metrics for the robotic suturing part of the procedure. The procedure was carried out in eight cadaver studies by two surgeons. The assist device pump head was inserted through a left-sided mini-thoracotomy and the outflow graft was passed toward a right-sided second interspace mini-thoracotomy through the pericardium. After placement of a partial occlusion clamp on the ascending aorta, a longitudinal aortotomy was performed and the outflow graft to ascending aorta anastomosis was carried out robotically. The procedure was feasible in all eight attempts. The mean outflow graft anastomotic time was 20.1 (SD 6.8) min and the mean surgeon confidence and comfort levels to complete the anastomoses were 8.3 (SD 2.4) and 6.9 (SD2.2), respectively, on a ten-grade Likert scale. On open inspection of the anastomoses, there was good suture alignment in all cases. We conclude that suturing of a left-ventricular assist device outflow graft to the human ascending aorta is very feasible with good surgeon comfort. Anastomotic times are acceptable and suture placement can be performed with appropriate alignment.

Percutaneous endovascular intervention for left ventricular assist device outflow graft obstruction: A single-center experience

BackgroundOutflow graft obstruction (OGO) is an uncommon yet life-threatening complication in patients with left ventricular assist devices (LVADs). In this retrospective, single-center case series, we identify the baseline demographics and presenting features of patients who develop LVAD OGO and the procedural details and outcomes surrounding percutaneous endovascular intervention (PEI). MethodsWe conducted a retrospective review of patients with LVADs at our institution between January 2010 and February 2023 who developed OGO and were treated with PEI. Details of the PEI including procedure time, fluoroscopy time, contrast use, stent size, number of stents, change in gradient, and change in flow after intervention were collected. ResultsA total of 12 patients who had 14 cases of OGO were identified from January 2010 to February 2023. The average age at presentation was 64.78 years. Nine of the 14 cases occurred in male patients. Eleven of the 14 cases occurred with Heartware devices (2 recurrences), 2 in Heartmate 2 and 1 in Heartmate 3. Notable procedural details include a mean procedure time of 90.86 min and mean contrast use of 162.5 mL. The initial gradient across the OGO was reduced by an average of 72 %, to a mean post-PEI of 11.57 mmHg. The average number of stents to achieve this gradient was around 2.08, with the most common stent diameter being 10 mm. Thirty-day mortality after PEI was 7 % (1/14) in this high-risk patient population. ConclusionIn our single-center experience, PEI can be a safe and effective treatment for LVAD OGO.

Influence of the Outflow Graft Angular Position on the Outcomes in Patients With a Left Ventricular Assist Device.

This study aimed to explore the potential impact of the angular position of the outflow graft on thromboembolic events and aortic valve regurgitation in people with a left ventricular assist device (LVAD). We analyzed contrast computed tomography (CT) data of patients with LVAD implantation between 2016 and 2021. Three-dimensional reconstructions of the outflow graft and aortic arch were performed to calculate the horizontal (azimuth) angle and vertical (polar) angle, as well as the relative distance between the outflow graft, aortic valve, and brachiocephalic artery. Among 59 patients (median age 57, 68% male), a vertical angle ≥107° correlated significantly with increased cerebrovascular accidents (hazard ratio [HR]: 5.8, 95% confidence interval [CI]: 1.3-26.3, p = 0.022) and gastrointestinal bleeding (HR: 3.4, 95% CI: 1.0-11.2, p = 0.049) during a median 25 month follow-up. No significant differences were found between the vertical angle and aortic valve regurgitation or survival. The horizontal angle and relative distance did not show differences regarding clinical adverse events. This study emphasizes the importance of the LVAD outflow graft angular position to prevent life-threatening thromboembolic events. This study suggests the need for prospective research to further validate these findings.

Left Ventricular Assist Device With External Iliac Artery Outflow Graft Anastomosis.

Durable left ventricular assist devices (LVADs) are a cornerstone therapy for patients with end-stage heart failure, and thus efforts to develop techniques that facilitate their use in an expanded population of patients are critical. Although the preferred outflow graft anastomosis site is the ascending aorta, alternative sites have been described including the descending thoracic and supraceliac abdominal aorta, as well as the innominate and axillary arteries. However, these vessels can be unfavorable targets in the setting of atherosclerosis, aneurysm, insufficient caliber, dissection, or complicated anatomy due to prior interventions. We present the case of a patient undergoing destination therapy LVAD implantation who had a complex surgical history leaving these targets unviable and thus necessitating selection of an alternative site. In this case, the right external iliac artery was successfully used for LVAD outflow graft anastomosis.

Percutaneous Stenting of a Stenotic Berlin Heart Outflow Cannula Graft in a 2 Year Old Child.

Left ventricular assist device (LVAD) outflow obstruction is a rare complication of long-term LVAD support. We present the first case of successful percutaneous stent implantation in a pediatric patient with LVAD outflow obstruction.

Abstract 13623: In Silico Comparison of Pressure Head Loss for Outflow Variations of a Novel LVAD Accessory Compared to Generic LVAD Pump Outflow

Introduction: Left ventricular assist device (LVAD) implantation is a treatment option for end-stage heart failure, requiring a sternotomy. A novel accessory, redirecting the outflow via the left ventricular apex into the ascending aorta, allows for LVAD implantation via left thoracotomy. Pressure distribution within accessory designs is unknown. Our goal was to compare three different outflow designs with a generic LVAD outflow (Control) to optimize the accessory’s outflow design. Hypothesis: We hypothesize that the LVAD accessory leads to higher pressure head loss than Control and that there are relevant differences among varied designs. Methods: Volume models of the LVAD accessory variations (A–C) and Control were created using computer aided design. Computational fluid dynamics (CFD) was used to simulate blood flow through the accessories and generic outflows. A verification study was performed to optimize numerical parameters. Pressure head loss (mmHg) was calculated for each outflow while changing the LVAD flow rate continuously (2–7 L/min). Pressure loss was compared by mean differences (MD). Results: Pressure head loss increased with higher LVAD flow rate among all groups. Addressing the accessories’ outflow designs, Design B revealed the lowest increase in pressure loss revealing a mean slope of 2.3 mmHg/L/min compared to 4.6 and 3.0 for Design A and C. Referring to a flow rate of 5.5 L/min, a common flow rate among clinical LVAD patients, and comparing pressure head loss with Control, we found an additional pressure loss of 15.5, 6.4 and 8.3 mmHg in Design A, B and C, respectively. Conclusion: There is a trade off between fitting the outflow design to the cardiac geometry and the pressure head loss. Continued optimization of the LVAD accessory could allow minimally invasive LVAD implantation with minimal changes in LVAD performance. Potential compromise between improved design and performance renders CFD an important tool for medical device development.

Intra-aortic band impairs transapical device implantation in a pig: a case report

BackgroundAnatomic anomalies in the ascending aorta may impair the implantation and testing of cardiovascular devices in humans and animal models.Case presentationWe present the rare case of an intra-aortic band in a German Landrace pig. During terminal animal testing, the band hindered the implantation of a left ventricular assist device (LVAD) with transventricular outflow graft across the aortic valve. After lower partial sternotomy, epicardial echocardiography displayed an intraluminal echogenic structure at the sinotubular junction causing unspecific flow turbulences. Under cardiopulmonary bypass, coring of the left ventricular apex was performed. Due to strong resistance in the proximal aorta, accurate positioning of the transventricular LVAD outflow graft was impossible. After euthanasia, necropsy revealed a fibrous band located at the sinotubular junction, dividing the lumen of the ascending aorta.ConclusionsThe occurrence of an intra-aortic band represents an extremely rare case of a most likely congenital anomaly. Awareness of such anomalies is important for planning and performing animal testing. Perioperative echocardiography may help to either remove such anomalies or allow discontinuing the procedure prior to device implantation.

The Impact of Left Ventricular Assist Device Outflow Graft Positioning on Aortic Hemodynamics: Improving Flow Dynamics to Mitigate Aortic Insufficiency.

Heart failure is a global health concern with significant implications for healthcare systems. Left ventricular assist devices (LVADs) provide mechanical support for patients with severe heart failure. However, the placement of the LVAD outflow graft within the aorta has substantial implications for hemodynamics and can lead to aortic insufficiency during long-term support. This study employs computational fluid dynamics (CFD) simulations to investigate the impact of different LVAD outflow graft locations on aortic hemodynamics. The introduction of valve morphology within the aorta geometry allows for a more detailed analysis of hemodynamics at the aortic root. The results demonstrate that the formation of vortex rings and subsequent vortices during the high-velocity jet flow from the graft interacted with the aortic wall. Time-averaged wall shear stress (TAWSS) and oscillatory shear index (OSI) indicate that modification of the outflow graft location changes mechanical states within the aortic wall and aortic valve. Among the studied geometric factors, both the height and inclination angle of the LVAD outflow graft are important in controlling retrograde flow to the aortic root, while the azimuthal angle primarily determines the rotational direction of blood flow in the aortic arch. Thus, precise positioning of the LVAD outflow graft emerges as a critical factor in optimizing patient outcomes by improving the hemodynamic environment.

The Relation Between Viscous Energy Dissipation and Pulsation for Aortic Hemodynamics Driven by a Left Ventricular Assist Device.

Left ventricular assist device (LVAD) provides mechanical circulatory support for patients with advanced heart failure. Treatment using LVAD is commonly associated with complications such as stroke and gastro-intestinal bleeding. These complications are intimately related to the state of hemodynamics in the aorta, driven by a jet flow from the LVAD outflow graft that impinges into the aorta wall. Here we conduct a systematic analyses of hemodynamics driven by an LVAD with a specific focus on viscous energy transport and dissipation. We conduct a complementary set of analysis using idealized cylindrical tubes with diameter equivalent to common carotid artery and aorta, and a patient-specific model of 27 different LVAD configurations. Results from our analysis demonstrate how energy dissipation is governed by key parameters such as frequency and pulsation, wall elasticity, and LVAD outflow graft surgical anastomosis. We find that frequency, pulsation, and surgical angles have a dominant effect, while wall elasticity has a weaker effect, in determining the state of energy dissipation. For the patient-specific scenario, we also find that energy dissipation is higher in the aortic arch and lower in the abdominal aorta, when compared to the baseline flow without an LVAD. This further illustrates the key hemodynamic role played by the LVAD outflow jet impingement, and subsequent aortic hemodynamics during LVAD operation.

Application of 1,000 fps High-Speed Angiography to In-Vitro Hemodynamic Evaluation of Left Ventricular Assist Device Outflow Graft Configurations.

Left ventricular assist device (LVAD)-induced hemodynamics are characterized by fast-moving flow with large variations in velocity, making quantitative assessments difficult with existing imaging methods. This study demonstrates the ability of 1,000 fps high-speed angiography (HSA) to quantify the effect of the surgical implantation angle of a LVAD outflow graft on the hemodynamics within the ascending aorta in vitro . High-speed angiography was performed on patient-derived, three-dimensional-printed optically opaque aortic models using a nonsoluble contrast media, ethiodol, as a flow tracer. Outflow graft configuration angles of 45° and 90° with respect to the central aortic axis were considered. Projected velocity distributions were calculated from the high-speed experimental sequences using two methods: a physics-based optical flow algorithm and tracking of radio-opaque particles. Particle trajectories were also used to evaluate accumulated shear stress. Results were then compared with computational fluid dynamics (CFD) simulations to confirm the results of the high-speed imaging method. Flow patterns derived from HSA coincided with the impingement regions and recirculation zones formed in the aortic root as seen in the CFD for both graft configurations. Compared with the 45° graft, the 90° configuration resulted in 81% higher two-dimensional-projected velocities (over 100 cm/s) along the contralateral wall of the aorta. Both graft configurations suggest elevated accumulated shear stresses along individual trajectories. Compared with CFD simulations, HSA successfully characterized the fast-moving flow and hemodynamics in each LVAD graft configuration in vitro , demonstrating the potential utility of this technology as a quantitative imaging modality.

Durable Left Ventricular Assist Device Outflow Graft Obstructions: Clinical Characteristics and Outcomes.

We report on the clinical course and management of patients supported with durable implantable LVADs who developed outflow graft obstructions at a large academic center. We performed a retrospective review of patients receiving LVAD support from 2012 through 2020. Patients who developed an outflow graft obstruction diagnosed by computed tomography angiography (CTA) or angiogram were identified, and patient characteristics and outcomes were reported. Of the 324 patients supported by LVAD at our institution, 11 patients (3.4%) were diagnosed with outflow graft obstructions. The most common presentation was low flow alarms, which was present in 10/11 patients, and the remaining patient presented with lightheadedness. Patients had minimal LDH elevation with 8/11 presenting with less than 2-fold the upper limit of normal. Transthoracic echocardiograms were not diagnostic, but CTA enabled non-invasive diagnoses in 8/11 of the patients. Three patients with extrinsic compression of the outflow graft successfully underwent endovascular stent placement, and three patients with outflow cannula kinks received supportive care. Of the five patients diagnosed with intraluminal thromboses, one received a heart transplant, one underwent an outflow graft revision, and three received supportive care due to comorbidities. Outflow graft obstructions remain a rare, but serious complication. The true prevalence of this entity is likely underestimated due to the non-specific clinical presentation. CTA is a pivotal non-invasive diagnostic step. Patients with external compression were successfully treated with endovascular stenting.

Outflow cannula alignment in continuous flow left ventricular devices is associated with stroke.

We sought to evaluate whether differences in left ventricular assist device (LVAD) canula alignment are associated with stroke. There is a paucity of clinical data on contribution of LVAD canulae alignment to strokes. We conducted a retrospective analysis of patients who underwent LVAD implantation at Houston Methodist hospital from 2011 to 2016 and included those who had undergone cardiac computed tomography (CT) with contrast. LVAD graft alignment using X-ray, echocardiography, and cardiac CT was evaluated. The primary outcome was stroke within 1 year of LVAD implantation. Of the 101 patients that underwent LVAD Implantation and cardiac CT scan during the study period, 78 met inclusion criteria. The primary outcome occurred in 12 (15.4%) patients with a median time to stroke of 77 days (interquartile range: 42-132 days). Of these, 10 patients had an ischemic and two had hemorrhagic strokes. The predominant device type was Heart Mate II (94.8%). Patients with LVAD outflow cannula to aortic angle lesser than 37.5° and those with outflow graft diameter of anastomosis less than 1.5 cm (assessed by cardiac CT) had significantly higher stroke risk (p < 0.001 and p = 0.01 respectively). In HMII patients, a lower LVAD speed at the time of CT scan was associated with stroke. Further studies are needed to identify optimal outflow graft configuration to mitigate stroke risk.

Quantitative Assessment of Aortic Hemodynamics for Varying Left Ventricular Assist Device Outflow Graft Angles and Flow Pulsation.

Left ventricular assist devices (LVADs) comprise a primary treatment choice for advanced heart failure patients. Treatment with LVAD is commonly associated with complications like stroke and gastro-intestinal (GI) bleeding, which adversely impacts treatment outcomes, and causes fatalities. The etiology and mechanisms of these complications can be linked to the fact that LVAD outflow jet leads to an altered state of hemodynamics in the aorta as compared to baseline flow driven by aortic jet during ventricular systole. Here, we present a framework for quantitative assessment of aortic hemodynamics in LVAD flows realistic human vasculature, with a focus on quantifying the differences between flow driven by LVAD jet and the physiological aortic jet when no LVAD is present. We model hemodynamics in the aortic arch proximal to the LVAD outflow graft, as well as in the abdominal aorta away from the LVAD region. We characterize hemodynamics using quantitative descriptors of flow velocity, stasis, helicity, vorticity and mixing, and wall shear stress. These are used on a set of 27 LVAD scenarios obtained by parametrically varying LVAD outflow graft anastomosis angles, and LVAD flow pulse modulation. Computed descriptors for each of these scenarios are compared against the baseline flow, and a detailed quantitative characterization of the altered state of hemodynamics due to LVAD operation (when compared to baseline aortic flow) is compiled. These are interpreted using a conceptual model for LVAD flow that distinguishes between flow originating from the LVAD outflow jet (and its impingement on the aorta wall), and flow originating from aortic jet during aortic valve opening in normal physiological state.

Emergent In Situ Fenestration in the Ascending Aorta for the Endovascular Repair of a Large Pseudoaneurysm: A Technical Note

Purpose: The purpose of this article is to describe an emergent in situ fenestration (ISF) technique in the ascending aorta for the endovascular repair of a large pseudoaneurysm using a trans-septal needle device through direct right common carotid artery access, in a patient with left ventricular assist device (LVAD). Technique: We performed, in a multidisciplinary team-work approach, an emergent ISF to correct the displacement of a physician-modified thoracic endograft released in the ascending aorta to correct a large anastomotic pseudoaneurysm in a patient who underwent ascending aorta replacement and subsequent LVAD implantation. We used a trans-septal needle device inserted through a direct access to the right carotid artery and performed an ISF to restore the patency of the outflow ostium of the LVAD. Window was then completed and stabilized with a nitinol balloon expandable covered stent graft obtaining an effective exclusion of the anastomotic aortic aneurism and the regular patency of the LVAD outflow graft with no signs of leaks. Conclusions: Multidisciplinary teamwork approach can be crucial in challenging procedures where an alternative approach may lead to problem solving. The ISF technique may be a valid option to adopt in emergency cases in which no other technical solutions are suitable. Clinical Impact The endovascular approach has become more and more frequent for the treatment of vascular pathologies, getting increasingly refined and complex. Thereby the chance of incurring intraprocedural troubles has grown and bailout strategies should always be present. In situ fenestration is a technique to be aware of and that could help you recover from difficult situations. We report a possible rescue maneuver that can be applied also in arduous anatomies such as the ascending aorta. Moreover, we would like to highlight the importance of a multidisciplinary working environment that can enrich our everyday practice accomplishing effective and unexpected solutions.

Percutaneous management of left ventricular assist device outflow graft obstruction.

Percutaneous management of left ventricular assist device outflow graft obstruction.

The Effect of Spiral Inducing Chamber to Left Ventricular Assist Device Outflow Cannula

The rise of heart failure in the setting of shortage heart donor had brought to the emergence of development of left ventricular assist device (LVAD). However, patients are still encountering severe complications such as stroke and device thrombosis due to the hemodynamic changes. This study aimed to compare the hemodynamic characteristic between the standard and spiral LVAD outflow cannula. Two different anastomosis sites (2cm and 3cm) from sino-tubular junction are used and a spiral inducing chamber is attached to the cannula to promote spiral flow. The result showed that spiral LVAD cannula exhibit a lower output velocity with 37% percentage difference and lower region of low WSS value.

Cerebral protection during percutaneous intervention for left ventricular assist device outflow graft obstruction.

Left ventricular assist devices (LVAD) outflow graft obstruction is an uncommon complication but carries significant morbidity and mortality. Here we provide a case series of patients with LVAD intrinsic outflow graft obstruction who are deemed to be a high surgical risk for pump exchange and, therefore, underwent percutaneous intervention with the concomitant use of neuroprotective device-Sentinel cerebral protection system(CPS)(Boston Scientific) to prevent embolic stroke. We retrospectively analyzed patients who underwent LVAD placement in our institution and developed LVAD outflow graft obstruction. The diagnosis of LVAD outflow graft obstruction was confirmed by utilizing various cardiac imaging modalities such as echocardiography and/or computed tomography angiography. All patients were treated with percutaneous intervention and a catheter-based CPS. From a total of 501 LVAD implants in our institute, 6 (1.2%) patients with LVAD outflow graft obstruction who underwent percutaneous treatment were included; 4 patients with HeartMate-IIILVAD, 1patient with HeartMate-II LVAD, and 1patient with HeartWare (HVAD). The median age of patients was 56.5 years at the time of LVAD implantation. The median time from the LVAD implantation to the episode of LVAD outflow obstruction was 1343 days. Utilization of Sentinel CPS resulted in the capture and removal of thrombus/debris in all patients. Percutaneous intervention of LVAD outflow graft obstruction is less invasive than surgical pump exchange and an acceptable alternative in properly selected patients. In our experience, utilization of a catheter-based CPScan help in reducing the incidence of periprocedural embolic events.