Left Ventricular Assist Device Outflow Research Articles

Echocardiographic Assessment of Left Ventricular Assist Device Outflow Velocity During Percutaneous Decommissioning

Left ventricular assist devices (LVADs) have been used as an effective therapeutic option in patients with advanced heart failure, either as a bridge to transplantation or, in some patients, as a bridge to recovery. LVAD withdrawal with ventricular recovery represents the optimal outcome for patients previously implanted with an LVAD. In this E-Challenge, the authors present a case of percutaneous decommissioning of an LVAD, in which TEE provided critical, real-time perioperative evaluation. The authors also review the current perspectives on LVAD decommissioning in terms of patient selection and surgical techniques.

A New Strategy for Left Ventricular Assist Device Outflow Graft Interrogation Using Ultrasound Contrast

Interrogation of the outflow graft (OTG)-ascending aorta anastomosis is an integral part of the transthoracic echocardiographic (TTE) evaluation of left ventricular assist devices (LVADs) as it is important to confirm patency of this communication. However, it can be challenging to image the OTG anastomosis on TTE. Ultrasound enhancing agents (UEAs) have been used successfully to enhance visualization of endocardial borders and intracardiac masses.1-3 We hypothesized that UEAs would improve OTG detection, optimize the alignment of Doppler velocity signals with graft flow, and enable more meaningful peak velocity measurements across the anastomosis of the OTG to the ascending aorta.

Treatment of outflow graft stenosis in left ventricular assist device patients: Endovascular approach

Left ventricular assist device outflow graft stenosis is a rare, but a lethal complication. Device replacement or thrombolytic treatments are associated with serious mortality and morbidity. Implantation of covered stents is a less invasive option. Herein, we represent a successful stent placement of two cases with outflow graft stenosis, which we performed by leaving the stents on the aortic side of the anastomosis line 5 to 10 mm. This treatment option can be used reliably in cases of stenosis of the outflow graft with part of the stent leaving the aorta.

From bench to bedside: Impact of left ventricular assist device outflow conduit anastomosis position on outcome.

Continuous flow left ventricular assist devices (LVADs) have become a valuable therapy for end-stage heart failure. In vitro research highlighted a role of outflow cannula position on the pattern of blood flow in the aorta. However, the clinical effects of the alterations of flow remain unclear. We investigate short- and long-term outcomes of patients implanted with Jarvik 2000 LVAD, according to the ascending (Group 1) versus descending (Group 2) outflow graft connection to the aorta in a multicenter study. From May 2008 to October 2014, 140 consecutive end-stage heart failure patients underwent Jarvik 2000 LVAD implantation in 17 Italian centers. According with a preliminary multivariate analysis, we selected the 90 patients implanted in the four high-volume centers to avoid bias (Group 1 n=39, Group 2 n=51). Among the groups, no differences were recorded in the hospital mortality and the main complications occurring after LVAD implantation were similar. In multivariable analysis, the ascending aorta outflow cannula position and higher creatinine at discharge were significant predictors for long-term survival. Postimplant hemolysis was more pronounced in descending aorta outflow graft anastomosis. Outflow graft anastomosis to the ascending aorta is associated with better long-term survival, independent of age and perfusion techniques, reflecting the previous in vitro results.

Endovascular repair of left ventricular assist device outflow graft defect

Outflow graft complications after left ventricular assist device placement are infrequent but highly morbid. In this case report, we describe endovascular repair of multiple outflow graft defects with external hemorrhage in a complex patient using overlapping stent grafts. This approach successfully stopped the outflow graft hemorrhage and temporized the patient for subsequent cardiac transplantation.

Left Ventricular Assist Device Outflow Cannula Obstruction: Importance of Multimodality Imaging

One of the dreaded complications of left ventricular assist device implantation is mechanical obstruction of the device secondary to pump thrombosis or mechanical outflow cannula obstruction. We describe a case of outflow cannula obstruction caused by kinking and twisting of the outflow graft after surgical manipulation of the pump. (Level of Difficulty: Beginner.)

Left ventricular assist device outflow graft obstruction development in the original bend relief.

Left ventricular assist device outflow graft obstruction development in the original bend relief.

Use of patient-specific computational models for optimization of aortic insufficiency after implantation of left ventricular assist device

ObjectiveAortic incompetence (AI) is observed to be accelerated in the continuous-flow left ventricular assist device (LVAD) population and is related to increased mortality. Using computational fluid dynamics (CFD), we investigated the hemodynamic conditions related to the orientation of the LVAD outflow in these patients. MethodWe identified 10 patients with new aortic regurgitation, and 20 who did not, after LVAD implantation between 2009 and 2018. Three-dimensional models of patients' aortas were created from their computed tomography scans. The geometry of the LVAD outflow graft in relation to the aorta was quantified using azimuth angles (AA), polar angles (PAs), and distance from aortic root. The models were used to run CFD simulations, which calculated the pressures and wall shear stress (rWSS) exerted on the aortic root. ResultsThe AA and PA were found to be similar. However, for combinations of high values of AA and low values of PA, there were no patients with AI. The distance from aortic root to the outflow graft was also smaller in patients who developed AI (3.39 ± 0.7 vs 4.07 ± 0.77 cm, P = .04). There was no significant difference in aortic root pressures in the 2 groups. The rWSS was greater in AI patients (4.60 ± 5.70 vs 2.37 ± 1.20 dyne/cm2, P < .001). Qualitatively, we observed a trend of greater perturbations, regions of high rWSS, and flow eddies in the AI group. ConclusionsUsing CFD simulations, we demonstrated that patients who developed de novo AI have greater rWSS at the aortic root, and their outflow grafts were placed closer to the aortic roots than those patients without de novo AI.

A Novel Echocardiographic Window for the Evaluation of the Outflow Graft in HeartMate 3 Left Ventricular Assist Devices

Interrogation of the left ventricular assist devices (LVAD) outflow graft with trans thoracic echocardiography (TTE) is often limited by poor windows. We describe a novel subcostal TTE approach to assess the outflow graft in patients with HeartMate 3 LVAD. The outflow graft was visualised using a shallow subcostal window with the probe tilted almost parallel to the abdominal wall. This new subcostal window was compared to the right parasternal window. The velocity time integral (VTI) of the Doppler between the artificial pulse every 2 seconds was used to calculate total pump flow (litres per minute) = VTI x cross-sectional area of outflow graft x 30 'beats per minute'. Pump parameters were recorded at the same time. 35 consecutive patients with HeartMate 3 LVAD were included (Age: 53±4 years; 89% males; body mass index 26±1kg/m2).The outflow graft could be visualised in 28/35 patients (80%) with this subcostal window compared to 12/35 (34%) patients with parasternal window (p<0.05). The colour Doppler and VTI of a patient with normal and partially occluded outflow graft are shown in FIGURE 1a, 1b and 1c respectively. The latter shows high velocity Doppler compared to normal. The calculated pump flow correlated with the displayed pump flow (R2=0.69, p<0.001), but agreement on the Bland-Altman plot is modest [FIGURE 2]. 'Pulsatility' based on the ratio of s and d flow on Doppler correlated with the displayed pulse index (R2=0.52, p<0.001). A novel shallow subcostal echocardiographic window can interrogate the LVAD outflow graft in patients with HeartMate 3 LVAD.

Outflow Cannula Systolic Slope as a Predictor of Myocardial Recovery Leading to Successful LVAD Decommission: A Case Series

In patients implanted with durable left ventricular assist device (LVAD), the incidence of myocardial recovery leading to device explant or decommission is low, and reliable predictors of myocardial recovery remain lacking. Here, we investigate the potential of outflow cannula systolic slope as a non-invasive predictor of successful LVAD liberation amongst select cohort of patients with high recovery potential. We first identified a cohort of patients with high recovery likelihood by querying all LVAD patients at our institution who underwent reverse ramp test, a protocol developed to assess native myocardial contractility with sequential LVAD turn-down to minimal support. We then queried all echocardiographic studies of these patients within one year of the reverse ramp tests. In the subset of patients with adequate Doppler images of the outflow cannula, the systolic slope, a load-independent marker of contractility, was measured as previously described, and the clinical outcomes were correlated. Between September 1, 2015 and August 23, 2019, a total of 10 patients underwent reverse ramp test at our institution per published protocol. Of these, 4 patients had adequate echocardiographic window of the LVAD outflow cannula, and the systolic slope was calculated. 3 of the 4 patients had outflow cannula systolic slope of <1200 cm/s2 (813 ±148 cm/s2, range 651-1010 cm/s2; top figure), and none was able to achieve sustainable recovery (1 was bridged to transplant, 1 remains on LVAD support, and 1 was deceased). 1 out of the 4 patients had outflow cannula systolic slope >1200 cm/s2 (1788 cm/s2), and she underwent successful percutaneous decommission of her LVAD device (bottom figure). In a small case series of 4 patients from reverse ramp database with available echocardiographic images of the outflow cannula, high systolic slope value (>1200 cm/s2) identified the patient with clinical recovery leading to successful LVAD decommission.

Transcervical LVAD Outflow Graft Implantation as Sternotomy Free Procedure: Proof-of-Concept

Minimally invasive methods to implant left ventricular assist devices (LVAD) have emerged as alternatives to the classic median sternotomy as they have been shown to decrease bleeding and periprocedural complications, plus speed up recovery and make future sternotomies easier. While implantation of a centrifugal LVAD within the LV apex can be performed via a left thoracotomy, the outflow graft anastomosis to ascending aorta is still routinely done via upper hemi-sternotomy which, although limited, has some of the above disadvantages. We present a technique of transcervical outflow graft implantation which completely avoids sternotomy. This is a proof-of-concept implantation performed on a cadaveric model. The procedure is facilitated by a novel access system (CoreVista® Retractor, CardioPrecision Ltd, Glasgow UK) designed for surgery via a transcervical approach. This device comprises a frame fixed to the operating table to which a disposable transcervical retractor with inbuilt illumination modes used for the different steps of the procedure is attached plus an HD display offering optimal views. The technique can be broken down into a number of reproducible steps: transverse neck incision, retractor insertion, sternal elevation, illumination, dissection of anterior mediastinum and exposure of aorta. The outflow graft is pulled into the field and, after trimming to avoid kinking, a side clamp is placed on the aorta and the graft is sutured in continuous fashion. This is greatly aided by the retractor illumination and HD visualisation on-screen. Sutures are tied, clamp released, haemostasis confirmed, retractor removed and the small neck incision closed. This proof of concept demonstrates that a sternotomy-free implantation of a LVAD is feasible and should prove reproducible with the help of the novel transcervical access system. The approach may also be suitable for implantation of an axial flow pump without the current limitations imposed by access vessel size.

Impact of turbulent blood flow in the aortic root on de novo aortic insufficiency during continuous-flow left ventricular-assist device support.

Severe aortic insufficiency (AI) after implantation of continuous-flow left ventricular-assist device (LVAD) affects device performance and outcomes. However, the mechanism for the occurrence and progression of AI has not been elucidated. We investigated the impact of nonphysiological retrograde blood flow in the aortic root on AI after LVAD implantation. Blood flow pattern was analyzed in patients with and without AI (n = 3 each) who underwent LVAD implantation, by computational fluid dynamics with patient-specific geometries, which were reproduced using electrocardiogram-gated 320-slice computed tomographic images. The total volume of retrograde blood flow during one cardiac cycle (716±88 mL) was higher and the volume of slow blood flow (<0.1 cm/s) (0.16 ± 0.04cm3 ) was lower in patients with AI than in those without AI (360 ± 111 mL, P =.0495, and0.49 ±0.08 cm3 , P =.0495, respectively). No significant difference in wall shear stress on the aortic valve was observed between the groups. Patients with AI had a perpendicular anastomosis at the distal ascending aorta and the simulation in the modified anastomosis model of patients with AI showed that the retrograde blood flow pattern depended on the angle and position of anastomosis. Computational fluid dynamics revealed strong retrograde blood flow in the ascending aorta and aortic root in patients with AI after LVAD implantation. The angle and position of LVAD outflow anastomosis might impact retrograde blood flow and de novo AI after LVAD implantation.

Computed Tomography and Fluoroscopic Angiography in Management of Left Ventricular Assist Device Outflow Graft Obstruction

A decrease in pump flow in patients with left ventricular assist devices (LVADs) is a life-threatening complication that results in severe heart failure. The main cause, besides right ventricular failure, is outflow graft (OG) obstruction. Through combined use of computed tomography angiography (CTA

Percutaneous Deactivation of Left Ventricular Assist Devices

Left ventricular assist device (LVAD) deactivation may be considered in cases of left ventricular recovery, pump thrombosis, infection, and end-of-life palliation. Surgical pump explantation remains the principal method, but percutaneous deactivation presents a safe and effective alternative. We have developed a formal program for percutaneous LVAD deactivation within our advanced heart failure program including patient selection criteria, preprocedure testing, a procedural algorithm, and a postprocedure care plan. Patient selection for percutaneous LVAD deactivation required review by an interdisciplinary heart transplant team including reason for deactivation, cardiac function, surgical risk, and patient preference. All candidates underwent LVAD ramp studies with both transthoracic echocardiography and right heart catheterization assessment. Deactivation was performed under general anesthesia with transesophageal echocardiography guidance. Three Amplatzer Vascular Plug IIs (Abbott, St. Paul, MN) were deployed in the LVAD outflow cannula with the proximal edge of the third plug aligned with the aortic anastomosis of the graft as guided by angiography and 3-dimensional transesophageal echocardiography. In a separate procedure, the LVAD drive line was transected below the skin, which was closed surgically over the driveline stump. Anticoagulation was continued for at least 3 months. Since initiation in January 2017, our program has performed 7 percutaneous LVAD deactivation procedures. All procedures have been successful, 5 of the patients remain medically managed, and 2 have proceeded to heart transplant. Percutaneous LVAD deactivation provides an alternative to surgical explantation. A percutaneous LVAD deactivation program is an important component of an advanced heart failure program.

Magnetic Resonance Imaging Based Flow Field and Lagrangian Particle Tracking From a Left Ventricular Assist Device.

This study explores the optimal left ventricular assist device (LVAD) cannula outflow configuration in a patient-specific replica of the aorta. The volumetric velocity field is measured using phase-contrast magnetic resonance imaging (PC-MRI) under a physiologically relevant steady flow. The effect of the LVAD outflow graft insertion site and anastomosis angle on the transport of embolic particles to cranial vessels is studied by solving the particle equation of motion for spheres in the range of 0.1-1.0 mm using the measured three-dimensional (3D) velocity field. Results show that for a given aorta anatomy, it is possible to design the cannula graft location and terminal curvature so that the probability of embolic transport to the cranial vessels is significantly minimized. This is particularly important since the complex flow pattern in each cannula case affects the embolic trajectories differently, and hence the common assumption that particles distribute by the volumetric flow division does not hold.

Percutaneous Intervention for Left Ventricular Assist Device Outflow Obstruction

Left ventricular assist devices (LVADs) are used to support patients with advanced systolic heart failure (HF). These patients might develop LVAD dysfunction and consequent HF symptoms. Occasionally, outflow graft obstruction is responsible for LVAD dysfunction. Here, we describe percutaneous techniques to repair the outflow graft and avoid re-sternotomy.

Left Ventricular Assist Device Outflow Graft Obstruction: A Case Series.

Dysfunction of different components within continuous-flow (CF) left ventricular assist device (LVAD) systems may cause adverse cardiovascular and end-organ sequelae. Outflow graft obstruction is a recognized type of LVAD component dysfunction. Ten patients were admitted and treated for LVAD outflow graft obstruction. Two of these patients subsequently developed recurrent outflow graft obstruction requiring reintervention; however, each reoccurrence was at a different site than the original obstruction. Thus, a total of 12 cases of obstruction were analyzed. The most common reasons for hospital admission were low flow LVAD alarms or decompensated heart failure. Presentation with outflow graft obstruction occurred an average of 3.0 years after LVAD implantation. Patients underwent echocardiographic evaluation at the time of admission. Left ventricular assist device component dysfunction was suspected based on echocardiographic findings, and follow-up contrast studies were used to establish the specific diagnosis of outflow graft stenosis. The majority of stenotic lesions (10/12) were treated percutaneously with balloon angioplasty and stenting with balloon-expandable endovascular prostheses. Postintervention, all patients had significant improvement in LVAD flow rates.

Association of LVAD Outflow Cannula Position with Stroke Risk

Background Stroke remains a major cause of morbidity and mortality in patients with left ventricular assist devices (LVAD). Although several studies have delineated clinical risk factors for development of stroke, it is not entirely clear whether changes in position/orientation of the LVAD cannula impact incidence of subsequent stroke. Hypothesis We hypothesized that variations in surgical implant techniques for LVAD inflow and outflow cannula positions impact the subsequent risk of stroke. Methods We conducted a retrospective review of all patients that underwent LVAD implantation at our institute between 2011 and 2016. All patients that underwent multi detector cardiac computed tomography (MDCT) were included in the analysis. Patients with non-contrast CT scans and poor imaging quality were excluded. Baseline demographic as well as clinical parameters were obtained for all patients. Inflow and outflow cannula positions were assessed by various MDCT parameters outlined in table 1. The incidence of stroke from time of implantation to one year post-LVAD implantation was obtained. Results A total of 311 continuous-flow LVADs were implanted at our hospital from 2011-2016, of which 75 patients met inclusion criteria for the study. The study population was predominantly HM II with only 3 HVAD and 1 HM 3 patients. 11 patients had stroke within 1 year of LVAD implantation. There were no significant differences in baseline demographic or clinical characteristics between patients that had stroke versus those that did not. Patients with stroke had more acute angulation of outflow cannula relative to the aorta compared to patients without stroke (42⁰ versus 65⁰ respectively, p= 0.026). In addition, patients with stroke had a smaller diameter of anastomosis of the outflow cannula compared to those without stroke (1.3 cm versus 1.5 cm respectively, p= 0.013). The inflow cannula position did not impact incidence of stroke. Conclusions Our study shows that LVAD outflow cannula orientation and size of anastomosis portend a higher risk of subsequent stroke. Therefore, it is imperative to optimize LVAD surgical implant techniques and device manufacturing to allow larger anastomosis site and less acute angulation of the outflow cannula.

TAVR Thrombosis in Patient Supported with Durable Left Ventricular Assist Device

Introduction Aortic incompetence (AI) is very common complication after continuous flow left ventricular assist device (LVAD) implantation, and can result in increased symptoms for LVAD patients. Recent advances in Transcatheter Aortic Valve Replacement (TAVR) technology has resulted in this becoming a potential therapeutic avenue for LVAD patients with AI. We report a case of TAVR implantation in a patient supported with a LVAD complicated by thrombosis. Case Report A 61-year-old female presented with STEMI. She was treated with primary PCI, but had progressive cardiogenic shock and was placed on VA-ECMO. Due to high PRA, she was unable to be listed for primary transplantation and underwent implantation of a Heartware LVAD (Medtronic) as bridge to decision. Her post-operative course was complicated by recurrent GI bleeding. Over the following 12 months, she was noted to have worsening AI on routine echocardiography, with worsening symptoms that persisted despite hemodynamic and echocardiographic-guided LVAD optimization. After heart team review, her anatomy was deemed appropriate for TAVR and she underwent implant of a 26mm Evolut Pro (Medtronic). The procedure was complicated by post-implant complete heart block on POD #4 requiring pacemaker implantation. She was discharged from the hospital, however over the next 3 months had recurrent episodes of low flow alarms that continued despite LVAD speed and medication optimization. A transthoracic echocardiogram did not reveal any abnormalities, although it was unable to visualize the TAVR leaflets. A multiphase 4D CT Angiogram was performed to rule out LVAD outflow graft obstruction, which revealed extensive hypoattenuating leaflet thickening involving all 3 leaflets of the TAVR with absent leaflet motion consistent with thrombosis of the prosthetic valve leaflets (See Figure). She was started on intravenous anticoagulation (unfractionated heparin), but this had to be ceased due to hemodynamically significant GI bleeding requiring multiple transfusions. LVAD speed was also attempted to be increased to minimize risk of aortic valve opening, but this was unable to be continued due to recurrent low flow LVAD alarms. Repeat imaging 3 months later showed continual thrombosis, and she has remained stable while awaiting transplantation. Summary We describe a novel complication of TAVR in LVAD patients. This case highlights the major diagnostic and management dilemmas that should be considered as this management strategy becomes more widespread in this patient population.

Pulsatile Conduit Pressure Gradients in the HeartWare HVAD.

We evaluated mean, peak, and instantaneous pressure gradients across the outflow conduit in a pulsatile mock circulation loop which incorporated Heartware HVADs for left ventricular (LV) and right ventricular (RV) support. Steady-state 50 Hz measurements of left ventricular assist device (LVAD) flow (Q) and pressures within the proximal and distal outflow conduit were obtained at varying pump speed, LV contractility, hematocrit (HCT), heart rate (HR), and conduit diameter and length. Experiments were conducted using polyvinyl chloride (PVC) tubing and results confirmed in HVAD Gelweave conduit. Conduit diameter was negatively and nonlinearly associated with mean and peak gradient in both the PVC and HVAD conduits. There were no significant differences between the PVC and HVAD conduits in terms of mean Q, systolic dQ/dt, mean conduit gradient, or peak gradient. Across the 10 mm HVAD conduit, mean gradient correlated linearly with mean Q, systolic dQ/dt, HCT, and conduit length (r = 0.91), whereas peak gradient correlated with mean Q, systolic dQ/dt, and conduit length (r = 0.93). A nonlinear model to determine instantaneous gradient was highly predictive (r = 0.83) across a range of pump and circulatory conditions. In summary, hemodynamically significant pressure gradients are observed across the LVAD outflow conduit under physiologic conditions, which may result in diminished pump flow.