Left Ventricular Assist Device Outflow Graft Research Articles

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.

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.

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.

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.

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.

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.

Heart Mate 3 Pump Thrombosis After Ventricular Tachycardia Ablation: Pushing the Boundaries of Hemocompatibility

<h3>Introduction</h3> The risk for pump thrombosis (PT) following ventricular tachycardia (VT) ablation in HeartMate II and HeartWare HVAD left ventricular assist devices (LVADs) has been described previously; however, it is unknown whether Heart Mate 3 (HM3) LVADs are also at increased risk of PT following VT ablation. <h3>Case Report</h3> A 51-year-old male with non-ischemic cardiomyopathy status post HM3 LVAD as destination therapy, VT on mexiletine and quinidine with previous VT ablation, and amiodarone-induced thyrotoxicosis presented to the emergency room in VT storm after multiple defibrillator shocks. He underwent successful endocardial/epicardial VT ablation of seven VT morphologies, ethanol ablation of the coronary sinus branch, as well as coil embolization of two left circumflex branches that fed the culprit territory. Target ACT was achieved throughout the procedure and he was bridged to warfarin with a therapeutic INR upon discharge. Two weeks later, he presented with low flow LVAD alarms, a subtherapeutic INR, and an elevated lactate dehydrogenase concerning for PT. Despite volume resuscitation and pressors, he required initiation of venoarterial extracorporeal membrane oxygenation (VA-ECMO), intra-aortic balloon pump, and underwent a LV outflow tract aortogram. Thrombus was noted in the LVAD outflow graft and the LVAD flow was 0 liters per minute. Thrombolytics were not given due to the patient's tenuous status and need for emergent pump exchange, so decision was made to turn off the LVAD to prevent a cardioembolic event while he was supported by VA-ECMO. Transthoracic echocardiogram confirmed PT with a large thrombus extending out of the inflow cannula. The patient was deemed not to be a surgical candidate given a high operative mortality after worsening shock, liver failure, and bacteremia. His family proceeded with comfort care and support was withdrawn. <h3>Summary</h3> While PT is rare with HM3 LVADs even with lower intensity anticoagulation, there may be a higher risk of PT after VT ablation.

LVAD Outflow Graft Stenosis

Introduction Left Ventricular Assist Device (LVAD) outflow graft obstruction is a known long-term complication, etiologies for obstruction include thrombosis, kinking as well as external compression. Here we present a clinical case presenting with low LVAD flows due to external compression of the outflow graft with marked improvement after surgical intervention. Case Report A 60-year-old woman with chronic systolic heart failure secondary to non-ischemic cardiomyopathy with a HeartWare LVAD implanted 2018 presented with one month of low flows prior to admission. She was in atrial fibrillation (AF) with rapid ventricular response and volume overloaded. Despite AF rhythm control and volume optimization, flows never returned to prior baseline (Figure A). Gated cardiac CT demonstrated narrowing within the bend relief down to 3.7mm. During an echo guided ramp study aortic valve opening frequency decreased only minimally with speed up titration with slight improvement in flows. Ventriculography was significant for narrowing of the proximal outflow graft with most contrast exiting through LVOT, however, a kink in the outflow tract vs external compression could not be distinguished (Figure B). Percutaneous stenting was deemed to be too high-risk due to the proximity to the rotor blade. In the OR, fibrinous tissue between the outflow graft and the externally reinforced goretex graft covering the strain relief was identified. Via a limited left subcostal incision, the goretex graft was sharply opened from distal end to proximal end resulting in immediate LVAD flow normalization (Figures C and D). The patient discharged home on post-operative day 5. Summary Mechanical LVAD outflow graft obstructions can be catastrophic and addressing its causes requires a multidisciplinary approach. Here we present a case where a symptomatic, mechanical outflow graft obstruction was identified via multimodal imaging. The mechanical obstruction was ultimately amendable to a minimally invasive surgical approach and avoided pump exchange or even cardiac transplant. Left Ventricular Assist Device (LVAD) outflow graft obstruction is a known long-term complication, etiologies for obstruction include thrombosis, kinking as well as external compression. Here we present a clinical case presenting with low LVAD flows due to external compression of the outflow graft with marked improvement after surgical intervention. A 60-year-old woman with chronic systolic heart failure secondary to non-ischemic cardiomyopathy with a HeartWare LVAD implanted 2018 presented with one month of low flows prior to admission. She was in atrial fibrillation (AF) with rapid ventricular response and volume overloaded. Despite AF rhythm control and volume optimization, flows never returned to prior baseline (Figure A). Gated cardiac CT demonstrated narrowing within the bend relief down to 3.7mm. During an echo guided ramp study aortic valve opening frequency decreased only minimally with speed up titration with slight improvement in flows. Ventriculography was significant for narrowing of the proximal outflow graft with most contrast exiting through LVOT, however, a kink in the outflow tract vs external compression could not be distinguished (Figure B). Percutaneous stenting was deemed to be too high-risk due to the proximity to the rotor blade. In the OR, fibrinous tissue between the outflow graft and the externally reinforced goretex graft covering the strain relief was identified. Via a limited left subcostal incision, the goretex graft was sharply opened from distal end to proximal end resulting in immediate LVAD flow normalization (Figures C and D). The patient discharged home on post-operative day 5. Mechanical LVAD outflow graft obstructions can be catastrophic and addressing its causes requires a multidisciplinary approach. Here we present a case where a symptomatic, mechanical outflow graft obstruction was identified via multimodal imaging. The mechanical obstruction was ultimately amendable to a minimally invasive surgical approach and avoided pump exchange or even cardiac transplant.

LVAD Outflow Graft Compression Presenting as Pump Thrombosis

<h3>Introduction</h3> Pump thrombosis is a serious adverse event in patients with left ventricular assist devices (LVAD). Pump thrombosis is a complication of LVAD implantation, affecting approximately five percent of patients. It often presents with clinically significant hemolysis, device alarms and can progress to heart failure and cardiogenic shock. We present a case of a patient with a Heartmate II LVAD who presented with a rising LDH that led to investigation to diagnose a potential pump thrombosis. <h3>Case Report</h3> The patient is a 73 year old male who was implanted with a HeartMate II LVAD as destination therapy (DT) for ischemic cardiomyopathy (ICM). Approximately 3 years after implant, the patient was noted to have a markedly elevated LDH on routine lab work. After 8 months of event-free observation, the patients LDH trended up again and the plasma free hemoglobin level was also elevated. An ECHO with limited ramp study was performed. The power and flow responded appropriately however LVEDD showed no applicable change. To further investigate a potential thrombosis, a CT angiogram was obtained. The CT demonstrated a significant obstruction to the outflow graft within the bend relief. The initial intervention was a balloon angioplasty of the outflow graft. The angioplasty was technically successful, and the balloon fully expanded. A repeat CT 2 weeks later showed the obstruction was still present. Interestingly, the patient remained asymptomatic and his LDH normalized. The decision was made to continue observation. Six months later, his LDH was noted to be increasing. A repeat CT showed that the outflow obstruction was worsening. The outflow graft appeared to be at least 90% obstructed. Again, the patient was taken to the OR for an intervention. Balloon angioplasty was repeated to predilate the lesion. Three endovascular stents were placed in the outflow graft within the bend relief. Completion angiogram confirmed the stents to be fully expanded with no residual obstruction. There were no complications from the procedure. The patient remains event-free 8 months later. <h3>Summary</h3> In conclusion, the patient demonstrated signs of pump thrombosis mediated by an extrinsic compression of the outflow graft. In this case, the problem was treated with angioplasty with excellent result. The patient remains under surveillance but has been event-free for one year.

Outflow Graft Narrowing of the HeartMate 3 Left Ventricular Assist Device

BackgroundIn patients with the HeartMate 3 (HM3, Abbott) left ventricular (LV) assist device (LVAD), outflow graft narrowing has been reported as a result of accumulation of biodebris either internal or external to the graft. This study describes the prevalence, imaging findings, and clinical outcomes associated with HM3 LVAD outflow graft narrowing. MethodsA single-center retrospective cohort study was performed in patients who received an HM3 LVAD between November 2014 and July 2019. All patients with a computed tomographic (CT) angiogram or a CT scan with intravenous contrast sufficient to evaluate the outflow graft lumen were included. Narrowing was defined as a hypodensity of ≥3 mm. ResultsOf 165 HM3 LVAD recipients, 46 (28%) had qualifying imaging. Outflow graft narrowing was present in 33% (15/46). One patient had complete obstruction requiring emergency surgery, whereas 14 patients had a median hypodensity of 4.5 mm (interquartile range, 3.3-5.8 mm). The presence of outflow graft narrowing was significantly associated with a longer duration of LVAD support (588.2 ± 277.5 days vs 131.5 ± 170.9 days; P < .0001). One-year survival after identification of narrowing was 93%, with death occurring in 1 patient with complete obstruction. LV unloading (mean percent decrease in LV end-diastolic diameter at time of CT imaging vs pre-LVAD) was 16.7% vs 17.7% in patients with and without narrowing, respectively (P = .86). ConclusionsAmong patients with adequate imaging, one-third have evidence of narrowing. Outflow graft narrowing secondary to biodebris was more likely to be found in HM3 LVAD recipients with longer duration of LVAD support. There was no significant difference in LV unloading between patients with and without narrowing.

Computational Fluid Dynamics Study of Cerebral Thromboembolism Risk in Ventricular Assist Device Patients: Effects of Pulsatility and Thrombus Origin.

This study investigates the hypothesis that by surgically manipulating the outflow graft (OG) implantation during ventricle assist device placement, it may be possible to reduce the risk of cerebral embolism. We investigate this hypothesis using a computational approach on a patient-specific basis under fully pulsatile hemodynamics with a multiscale computational fluid dynamics model incorporating a coupled Eulerian-Lagrangian scheme that effectively tracks emboli in the fluid domain. Blood is modeled as a non-Newtonian fluid based on the hematocrit level. Preliminary flow analysis shows that depending on the anastomosis angle the left ventricular assist device (LVAD) can enhance the flow to the cerebral circulation by nearly 31%. Z-test results suggest that unsteady-flow modeling ought to be an integral part of any cardiovascular simulation with residual ventricular function. Assuming unsteady-flow conditions, a shallow LVAD outflow graft anastomosis angle is the most optimal if thrombi are released from the aortic-root reducing cerebral embolization incidence to 15.5% and from the ventricle to 17%, while a more pronounced anastomosis angle becomes advantageous when particles originate from the LVAD with an embolization rate of 16.9%. Overall, computations suggest that a pronounced LVAD anastomosis angle is the better implementation. Unsteady modeling is shown to be necessary for the presence of significant antegrade aortic-root flow which induces cyclical flow patterns due to residual pulsatility. On the other hand, depending on thrombus origin and ventricular assist devices (VAD) anastomosis angle there is a strong tradeoff in embolization rates.

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

AimsOutflow graft obstruction is a poorly described complication following left ventricular assist device (LVAD) surgery. We sought to define the incidence of LVAD outflow graft obstruction and assess clinical outcomes with a percutaneous treatment strategy.Methods and resultsFrom January 2012 to October 2020, 322 patients with LVAD were managed at our institution. Patients with LVAD outflow graft obstruction were identified by cardiac computed tomography with angiography and invasive haemodynamic assessment and were subsequently treated with percutaneous intervention. Poisson regression was used to analyse time‐dependent differences in the incidence of LVAD outflow graft obstruction. Kaplan–Meier analysis was used to estimate survival. Twenty patients (6.2%) developed haemodynamically significant LVAD outflow graft obstruction at a rate of 0.03 events per patient‐year. Outflow graft obstruction presented a median of 33 (26–49) months after surgery. Patients presented with low estimated LVAD pump flow (95%), heart failure (90%), or both (85%), and 59% developed cardiogenic shock prior to intervention. The most common aetiology identified by cardiac computed tomography with angiography was external compression of the outflow graft (78%). On presentation, the median peak gradient in the outflow graft was 78 (64–100) mmHg. Outflow graft stenting was 100% successful with no in‐hospital mortality, and it reduced the peak outflow graft gradient to 10 (2–17) mmHg (P < 0.001). Outflow graft stenting was durable with two patients (10%) requiring a repeat procedure over a median follow‐up of 13 (7–20) months and did not impact survival.ConclusionsLeft ventricular assist device outflow graft obstruction is a relatively common and underappreciated cause of recurrent heart failure and LVAD dysfunction. Outflow graft stenting can be achieved with low morbidity and provides a long‐term solution to this complication.

Less Invasive HeartMate 3 Left Ventricular Assist Device Implantation under Deep Hypothermic Circulatory Arrest for Severely Calcified Aorta

Introduction Left ventricular assist devices (LVADs) such as the HeartMate 3 (HM3) are becoming more frequently implanted in those with end-stage heart failure. We present one such patient with prior sternotomies and severely calcified ascending aorta in whom we planned a less invasive LVAD implantation via redo hemi-sternotomy and left thoracotomy with short-term deep hypothermic circulatory arrest (DHCA) to avoid cross-clamping of the aorta. Case Report A 70 year old male with history of two prior cardiac surgeries and heart failure presented in cardiogenic shock requiring temporary mechanical support with Impella CP. He continued to require increasing doses of inotropes and pressors; therefore, he was approved for high risk LVAD placement. A preoperative 4D CT scan revealed severely calcified ascending aorta with only a small area of focal sparing. First, a left anterior thoracotomy in the fifth intercostal space and redo upper hemi-sternotomy was performed. The LVAD outflow graft was positioned through the thoracotomy and brought up to the ascending aorta via the right pleural space, which was opened from the hemi-sternotomy. After initiation of cardiopulmonary bypass, the patient was cooled to 28°C with selective antegrade cerebral perfusion via the right axillary artery and systemic perfusion was temporarily arrested. DHCA was achieved. The LVAD outflow graft was then anastomosed to the aorta after which circulation was restarted and the patient rewarmed. The HM3 LVAD was then implanted in the LV apex and the rest of the operation was completed successfully. Summary Placing an LVAD via thoracotomy has theoretical advantages over a median sternotomy. Surgical trauma is minimized leading to less postoperative bleeding, improved maintenance of the chest stability, earlier recovery, and less cost. Additionally, there might be a reduction in post-operative right heart failure since the pericardium remains intact. Data from the LATERAL study and ELEVATE registry support the safety of this approach. While data support the safety of DHCA in other aortic arch procedures, there are only two case reports of DHCA for LVAD implantation. Our unique case validates the safety of LVAD implantation via thoracotomy and highlights the use of preoperative CT as well as DHCA in placement of an LVAD in a patient with severely calcified ascending aorta.

Simultaneous Multi-Vascular Bed Imaging in a Patient Supported by a Continuous-Flow LVAD

<h3>Introduction</h3> Patients supported with left ventricular assist devices (LVADs) are burdened by frequent hemocompatibility-related adverse events related to patient-pump interactions. These predominantly vascular events include stroke, gastrointestinal bleeding, and pump thrombosis. Our center performs routine, invasive hemodynamic ramp speed titrations in LVAD patients to determine the optimal rotational speed after implantation. We sought to interrogate changes in vascular hemodynamics during an exercise ramp study to understand the influence of pump speed and exercise on outflow graft and cerebrovascular flow. <h3>Case Report</h3> A 71-year-old male patient supported by Heartware HVAD operating at a baseline speed of 2700 RPM presented for LVAD ramp and exercise study with vascular imaging. A right heart catheterization, echocardiography with Doppler imaging of the patient's LVAD outflow graft, and vascular Doppler of the left common carotid artery and middle cerebral artery were performed. The patient's LVAD operating speed was reduced to 2400 RPM and then increased stepwise to a maximum speed of 3000 RPM. At each increment of operating speed, Doppler imaging was attempted and right heart catheterization was repeated. After reviewing data from the ramp study, the patient's operating speed was set to 2900 RPM and then a staged exercise protocol with bicycle ergometer was performed. Pertinent findings of vascular imaging include a blunting of peak systolic to end-diastolic velocity ratio in vascular beds with incremental speed increase and partial recovery of pulsatility with exercise (Figure). <h3>Summary</h3> This case demonstrates the influence LVAD speed adjustment and exercise have on carotid artery and outflow graft pulsatility. With exercise the outflow graft and carotid artery peak systolic and end-diastolic velocities were similar to those at the lowest LVAD pump speed, suggesting that intrinsic contractility and native LV unloading was restored with exercise despite a higher pump speed.

Performing under Pressure: Invasive Hemodynamics to Diagnose and Guide Treatment of LVAD Outflow Graft Stenosis

<h3>Introduction</h3> Left ventricular assist device (LVAD) outflow graft obstruction (OGO) is difficult to diagnose. We describe 4 consecutive cases of OGO diagnosed with invasive hemodynamics in the cardiac catheterization lab. <h3>Case Report</h3> Patients 1 (66 male, ischemic cardiomyopathy (ICM), HeartMate II), 2 (38 male, non-ischemic cardiomyopathy (NICM), HeartMate 3), 3 (20 female, NICM, HVAD), and 4 (66 male, ICM, HeartMate 3) were included. Patients 1, 2, and 4 were admitted with decompensated heart failure. Patient 3 was admitted with stroke-like symptoms. All 4 had concern for LVAD pump malfunction, and Patient 3 initially received catheter-directed thrombolytics via the left ventricle due to initial concern for pump thrombosis. Initial hemodynamics in Patients 1, 2, and 4 showed elevated biventricular filling pressures with low cardiac output. Computed tomography angiography (CTA) in Patients 1, 3, and 4 indicated OGO via kinking, stenosis, and thrombus, respectively. CTA was deferred in Patient 2 due to acute kidney injury. All 4 patients underwent invasive hemodynamic testing for initial, or confirmatory, diagnosis of OGO. Gradients from the proximal to distal outflow graft were measured as 30, 80, 40, and 9 mmHg in patients 1-4, respectively. Next, percutaneous versus surgical treatment was determined by a multi-disciplinary team. Patients 1 and 3 underwent successful deployment of a Viabahn stent, 8 × 79 mm and 9 × 59 mm, respectively, in the outflow graft with post-procedural gradients of 0 mmHg. Patients 2 and 4 underwent surgical correction. Patient 2 was found to have an outflow graft twist 3 cm from the connection and was untwisted with a 120 degree turn. Patient 4 was found to have compression of the outflow graft 6 cm from the connection, resolved with removal of yellow fibrin materials covering around the graft. <h3>Summary</h3> Invasive hemodynamics can be used to diagnose, and guide treatment of suspected LVAD OGO. There were no significant clinical events on 3-7 months follow-up post-procedure.