Surgical technique influences HeartMate II left ventricular assist device thrombosis

Temporarily Reversing Warfarin With Low-Dose 4-Factor Prothrombin Complex Concentrate in Left Ventricular Assist Device Patients Undergoing an Invasive Procedure

BACKGROUND

American Association for Thoracic Surgery and The International Society for Heart and Lung Transplantation (AATS/ISHLT) guidelines recommend warfarin in patients with continuous-flow left ventricular assist devices (LVADs) to reduce the risk of device thrombosis and systemic embolization. Left ventricular assist device patients often undergo elective and emergent procedures that require interrupted anticoagulation. Data and experience vary on the optimal strategy to rapidly reverse warfarin in LVAD patients when an emergent procedure is planned.

OBJECTIVE

The purpose of this study was to describe the use of 4-factor prothrombin complex concentrate (PCC4) for warfarin reversal in patients with LVADs undergoing elective and emergent procedures.

METHODS

This retrospective, single-center, cohort review describes the use of PCC4 in patients with LVADs who require warfarin reversal for elective or emergent procedures. The primary outcome was a composite incidence of pump thrombosis, venous thromboembolism, and ischemic stroke within 30 days of PCC4 administration.

RESULTS

In total, 14 patients received 17 administrations of PCC4. One patient received 3 administrations, and 1 other patient received 2 administrations during separate encounters. The median dose was 500 units or 6.6 units/kg (range = 4.2-14.1 units/kg). Of the PCC4 administrations, 82% (14/17) were for low bleed risk procedures and 76% (13/17) were for elective procedures. There were no cases of pump thrombosis, venous thromboembolism, or stroke within 30 days of the procedure.

CONCLUSIONS AND RELEVANCE

Low-dose PCC4 appears to be a safe and effective temporary reversal strategy for patients with LVADs undergoing low-bleed risk elective procedures.

Preoperative anatomical landmarks and longitudinal HeartMate 3 pump position in X-rays: Relevance for adverse events

BACKGROUND

Left ventricular assist device (LVAD) malposition has been linked to hemocompatibility-related adverse events (HRAEs). This study aimed to identify preoperative anatomical landmarks and postoperative pump position, associated with HRAEs during LVAD support.

METHODS

Pre- and postoperative chest X-ray measures (≤14 days pre-implantation, first postoperative standing, 6, 12, 18, and 24 months post-implantation) were analyzed for their association with HRAEs over 24 months in 33 HeartMate 3 (HM3) patients (15.2% female, age 66 (9.5) years).

RESULTS

HM3 patients with any HRAE showed significantly lower preoperative distances between left ventricle and thoracic outline (dLVT) (25.3 ± 10.2 mm vs. 40.3 ± 15.5 mm, p = 0.004). A ROC-derived cutoff dLVT ≤ 29.2 mm provided 85.7% sensitivity and 72.2% specificity predicting any HRAE during HM3 support (76.2% (>29.2 mm) vs. 16.7% (≤29.2 mm) freedom from HRAE, p < 0.001) and significant differences in cardiothoracic ratio (0.58 ± 0.04 vs. 0.62 ± 0.04, p = 0.045). Postoperative X-rays indicated lower pump depths in patients with ischemic strokes (9.1 ± 16.2 mm vs. 38.0 ± 18.5 mm, p = 0.007), reduced freedom from any neurological event (pump depth ≤ 28.7 mm: 45.5% vs. 94.1%, p = 0.004), and a significant correlation between pump depth and inflow cannula angle (r = 0.66, p < 0.001). Longitudinal changes were observed in heart-pump width (F(4,60) = 5.61, p < 0.001).

CONCLUSION

Preoperative X-ray markers are associated with postoperative HRAE occurrence. Applying this knowledge in clinical practice may enhance risk stratification, guide therapy optimization, and improve HM3 recipient management.

Tailoring left ventricular assist device cannula implantation using coupled multi-scale multi-objective optimization

BACKGROUND

The frequent occurrence of thromboembolic cerebral events continues to limit the widespread implementation of Ventricular Assist Devices (VAD) despite continued advancements in VAD design and anti-coagulation treatments. Recent studies point to the optimal positioning of the outflow graft (OG) as a potential mitigator of post implantation thromboembolism.

OBJECTIVE

This study aims to examine the tailoring of the OG implantation orientation with the goal of minimizing the number of thrombi reaching the cerebral vessels by means of a formal shape optimization scheme incorporated into a multi-scale hemodynamics analysis.

METHODS

A 3-D patient-specific computational fluid dynamics model is loosely coupled in a two-way manner to a 0-D lumped parameter model of the peripheral circulation. A Lagrangian particle-tracking scheme models and tracks thrombi as non-interacting solid spheres. The loose coupling between CFD and LPM is integrated into a geometric shape optimization scheme which aims to optimize an objective function that targets a drop in cerebral embolization, and an overall reduction in particle residence times.

RESULTS

The results elucidate the importance of OG anastomosis orientation and placement particularly in the case that studied particle release from the OG, as a fivefold decrease in cerebral embolization was observed between the optimal and non-optimal implantations. Another case considered particle release from the ventricle and aortic root walls, in which optimal implantation was achieved with a shallow insertion angle. Particle release from all three origins was investigated in the third case, demonstrating that the optimal configurations were generally characterized by VAD flow directed along the central lumen of the aortic arch. Because optimal configurations depended on the anatomic origin of the thrombus, it is important to determine, in clinical studies, the most likely sites of thrombus formation in VAD patients.

Comparing left ventricular assist device inflow cannula angle between median sternotomy and thoracotomy using 3D reconstructions

BACKGROUND

Left ventricular assist device (LVAD) implantation via thoracotomy has many potential advantages compared to conventional sternotomy, including improved inflow cannula (IFC) positioning. We compared the difference in IFC angles, postoperative, and long-term outcomes for patients with LVADs implanted via thoracotomy and sternotomy.

METHODS

A single-center, retrospective analysis of 14 patients who underwent thoracotomy implantation was performed and matched with 28 patients who underwent sternotomy LVAD implantations for a total of 42 patients. Inclusion required a minimum LVAD support duration of 30 days and excluded concomitant procedures. A postoperative CT-chest was used to measure the angle the between the IFC and mitral valve in two-dimensions and results were compared with three-dimensional reconstruction using the same CT chest. Outcome data were extracted from medical records.

RESULTS

There was no significant difference in gender, INTERMACS score, BMI, or age between the two groups. Median cardiopulmonary bypass time was longer in the thoracotomy group compared to the sternotomy group, 107 min (86-122) versus 76 min (56-93), p < 0.01. 3D reconstructions revealed less deviation of the IFC away from the mitral valve in devices implanted via thoracotomy compared to sternotomy, median (IQR) angle 16.3° (13.9°-21.0°) versus 23.2° (17.9°-26.4°), p < 0.01. Rates of pump thrombosis, stroke, and gastrointestinal bleeding were not significantly different.

CONCLUSIONS

Devices implanted via thoracotomy demonstrated less deviation away from mitral valve. However, there was no difference in morbidity between the two approaches. 3D reconstruction of the heart is an innovative technique to measure angulation and is clinically advantageous when compared to 2D imaging.

The Impact of Intrapericardial versus Intrapleural HeartMate 3 Pump Placement on Clinical Outcomes

Background

The integrated design of the HeartMate 3 (Abbott Laboratories, Chicago, IL, USA) affords flexibility to place the pump within the pericardium or thoracic cavity. We sought to determine whether the presence of a left ventricular assist device (LVAD) in either location has a meaningful impact on overall patient outcomes.

Methods

A retrospective cohort study was conducted of all 165 patients who received a HeartMate 3 LVAD via a median sternotomy from November 2014 to August 2019 at our center. Based on operative reports and imaging, patients were divided into intrapleural (n=81) and intrapericardial (n=84) cohorts. The primary outcome of interest was in-hospital mortality, while secondary outcomes included postoperative complications, cumulative readmission incidence, and 3-year survival.

Results

There were no significant between-group differences in baseline demographics, risk factors, or preoperative hemodynamics. The overall in-hospital mortality rate was 6%, with no significant difference between the cohorts (9% vs. 4%, p=0.20). There were no significant differences in the postoperative rates of right ventricular failure, kidney failure requiring hemodialysis, stroke, tracheostomy, or arrhythmias. Over 3 years, despite similar mortality rates, intrapleural patients had significantly more readmissions (n=180 vs. n=117, p<0.01) with the most common reason being infection (n=68/165), predominantly unrelated to the device. Intrapleural patients had significantly more infection-related readmissions, predominantly driven by non-ventricular assist device-related infections (p=0.02), with 41% of these due to respiratory infections compared with 28% of intrapericardial patients.

Conclusion

Compared with intrapericardial placement, insertion of an intrapleural HM3 may be associated with a higher incidence of readmission, especially due to respiratory infection.

Simple left ventricular apical cannulation for temporary mechanical circulatory support

Surgical management of cardiogenic shock, utilizing mechanical circulatory support, can provide a bridge to recovery, bridge to decision making and/or bridge to transplantation. Despite extracorporeal membrane oxygenation (ECMO) being a reliable, temporary form of support, intracardiac thrombosis is a devastating complication of veno-arterial ECMO. The use of a temporary left ventricular assist device (LVAD), although not immune to thrombosis, helps reduce intracardiac thrombosis, maintaining flow through the heart but importantly allowing for concurrent venting and drainage of the left ventricle. We demonstrate a technique for LV apical cannulation, as a part of a temporary LVAD circuit, aiming to prevent thrombotic complications secondary to cannula angulation.

Inflow cannula position as risk factor for stroke in patients with HeartMate 3 left ventricular assist devices

Background

A relation between the left ventricular assist device inflow cannula (IC) malposition and pump thrombus has been reported. This study aimed to investigate if the pump position, derived from chest X‐rays in HeartMate 3 (HM3) patients, correlates with neurological dysfunction (ND), ischemic stroke (IS), hemorrhagic stroke (HS) and survival.

Methods

This analysis was performed on routinely acquired X‐rays of 42 patients implanted with a HM3 between 2014 and 2017. Device position was quantified in patients with and without ND from frontal and lateral X‐rays characterizing the IC and pump in relation to spine, diaphragm or horizontal line. The primary end‐point was freedom from stroke and survival one‐year after HM3 implantation stratified by pump position.

Results

The analysis of X‐rays, 33.5 (41.0) days postoperative, revealed a significant smaller IC angle of HM3 patients with ND versus no ND (0.1° ± 14.0° vs. 12.9° ± 10.1°, p = 0.005). Additionally, the IC angle in the frontal view, IS: 4.1 (20.9)° versus no IS: 13.8 (7.5)°, p = 0.004 was significantly smaller for HM3 patients with IS. Using receiver operating characteristics derived cut‐off, IC angle <10° provided 75% sensitivity and 100% specificity (C‐statistic = 0.85) for predicting IS. Stratified by IC angle, freedom from IS at 12 months was 100% (>10°) and 60% (<10°) respectively (p = 0.002). No significant differences were found in any end‐point between patients with and without HS. One‐year survival was significantly higher in patients with IC angle >10° versus <10° (100% vs. 71.8%, p = 0.012).

Conclusions

IC malposition derived from standard chest X‐rays serves as a risk factor for ND, IS and worse survival in HM3 patients.

3D Holographic Virtual Surgical Planning for a Single Right Ventricle Fontan Patient Needing Heartmate III Placement

A 15 year old female with hypoplastic left heart syndrome status post Norwood with Sano modification, bidirectional Glenn and extracardiac conduit Fontan developed severe right ventricular (RV) systolic dysfunction. Due to symptomatic heart failure, she underwent assessment for ventricular assist device (VAD) placement as a bridge-to-cardiac transplantation strategy. To evaluate her atypical anatomy, a chest computed tomography (CT) was uploaded into an EchoPixel True3D (Santa Clara, CA) view portal along with an accurately scaled 3D surface model of the HeartMate III (HM3) device. The surgeon then manipulated the position of the HM3 to evaluate multiple potential device positions in relation to anatomic features such as the intraventricular septum, tricuspid valve annulus, and RV muscle bundles. The patient was taken to the operating room and the HM3 device was placed just anterior to the RV apex as virtually planned. She had an uneventful postoperative course, underwent cardiac transplantation on postoperative day (POD) 63 and is doing well now 19 months post-transplantation.

Left Ventricular Flow Dynamics with the HeartMate3 Left Ventricular Assist Device: Effect of Inflow Cannula Position and Speed Modulation

Improper left ventricular assist device (LVAD) inflow cannula (IC) positioning creates areas of stasis and low pulsatility that predispose thromboembolism, but may be mitigated with LVAD speed modulation. A mock loop study was performed to assess the sensitivity of left ventricle (LV) flow architecture to IC position and speed modulation during HeartMate3 support. System pressure, flow, and the time-resolved velocity field were measured within a transparent silicone LV for three IC angles and three IC insertion depths at matched levels of cardiac function and LVAD speed. Inflow cannula angulation towards the septum increased the resistance to LVAD flow as well as increasing the size and energy of the counter-clockwise (CCW) vortex. Apical velocity was reduced compared to IC angulation towards the mitral valve, but regional pulsatility was maintained across all angles and LVAD speeds. Increased IC protrusion decreased LVAD flow resistance, increasing velocity within the IC but reducing flow and pulsatility in the adjacent apical region. Increasing LVAD flow resistance improves aortic valve opening and strengthens the CCW vortex which directs inflow towards the septum, producing higher blood residence time and shear activation potential. Despite this impact on flow architecture, pulsatility reduction with increased LVAD speed was minimal with the HeartMate3 speed modulation feature.

Serial assessment of HeartMate 3 pump position and inflow angle and effects on adverse events

OBJECTIVES

This study analyses the position of the HeartMate 3 left ventricular assist device on serial radiographs to assess positional change and possible correlation with adverse events.

METHODS

We retrospectively analysed 59 left ventricular assist device recipients who had serial chest radiographs at 1 month, 6 months and 12 months post-implantation between November 2014 and June 2018. We measured pump angle, pump-spine distance and pump-diaphragm depth and investigated their relationship to a composite outcome of heart failure readmission, low flow alarms, stroke or inflow/outflow occlusion requiring surgical repositioning through recurrent event survival modelling.

RESULTS

Between 1 and 6 months, the absolute pump-spine distance changed by 10.00 mm (P < 0.01) and the absolute pump-diaphragm depth changed by 18.80 mm (P < 0.01). These parameters did not change significantly between 6 and 12 months post-implantation. Pump angle did not change significantly over any period. Twenty-six patients experienced the composite outcome; in these patients, the median 1-month pump angle was 66.2° (interquartile range 54.5-78.0) as compared to 59.0° (interquartile range 47.0-65.0) in the 33 patients who did not have adverse events (P = 0.04). Pump depth and pump-spine distance at 1 month were not associated with the composite outcome. Change in pump depth between 1 and 6 months [hazard ratio (HR) 1.019; 95% confidence interval (CI) 1.000-1.039] and between 6 and 12 months (HR 1.020; 95% CI 1.000-1.040) were weakly associated with the composite outcome.

CONCLUSIONS

Larger pump angles are associated with the composite outcome of position-related adverse events. Pump depth movement is weakly associated with the composite outcome.

Pump position and thrombosis in ventricular assist devices: Correlation of radiographs and CT data

Malpositioning of left ventricular assist devices (LVAD) is a risk factor for thrombosis, but its identification from clinical imaging remains challenging. X-rays and CT scans were analyzed and parameters identified that correlated to pump thrombosis. Retrospective imaging data of patients (n = 115) with HeartmateII (HMII) or HVAD were analyzed in two groups (pump-thrombosis PT, n = 15 vs matched control group NT, n = 15) using routine X-rays and CT scans. In CT, directional deviations of the inflow cannula in three-chamber and two-chamber view (α and β angles) were identified. In HVAD PT frontal radiographs showed reduced pump body area and smaller minor axis (PT 41.3 ± 4.8 mm vs NT 34.9 ± 6.0 mm, p = 0.026), and in the lateral radiographs the visibility of the inflow cannula served as a predictive parameter for PT. In HMII patients, no parameters were associated with PT. The angle α differed significantly (NT −1.2 ± 7.5°, PT −22.0 ± 4.7°, p = 0.006) in HVAD patients. Further, correlations of x-ray parameters with CT angles α and β showed that radiographs can be used to identify malpositioned pumps. Well-aligned inflow cannula positions are essential. HVAD patients with a posterior rotation of the inflow cannula have a higher risk of pump thrombosis. This risk can reliably be identified from routine radiographs.

Inflow Cannula Position Influences Improvement in Mitral Regurgitation After Ventricular Assist Device Implantation

Significant residual mitral regurgitation (MR) after left ventricular assist device (LVAD) implantation has been associated with increased morbidity and mortality. The effect of cannula position on improvement of preexisting MR has yet to be evaluated. Consecutive patients who underwent centrifugal LVAD implantation with >mild preoperative MR and without concomitant mitral repair were reviewed. Left ventricular assist device position was determined by the angle between actual and ideal inflow cannula on computed tomography. The magnitudes of angles (anterior and lateral angle) were added to form an LVAD position assessment (LVADpa). Mitral regurgitation was numerically classified, and improvement in MR was determined by difference in MR preoperatively to MR >1 month postoperatively with a median of 162 (interquartile range: 78-218) days. The primary analysis examined the relationship between LVADpa and postoperative MR. Forty-one patients were identified with >mild preoperative functional MR. Mean age was 51 ± 13 years with an ejection fraction of 16 ± 4%. Overall, MR improved from moderate-severe preoperatively to mild postoperatively (p < 0.001). On multivariable analysis, higher LVADpa deviation was associated with greater postoperative MR (odds ratio [OR] = 2.29, p = 0.005) and higher 1-month pulsatility index was associated with lower postoperative MR (OR = 0.47, p = 0.011). Inflow cannula position during centrifugal LVAD implantation is an important determinant of postoperative MR.

Understanding the influence of left ventricular assist device inflow cannula alignment and the risk of intraventricular thrombosis

BACKGROUND

Adverse neurological events associated with left ventricular assist devices (LVADs) have been suspected to be related to thrombosis. This study aimed to understand the risks of thrombosis with variations in the implanted device orientation. A severely dilated pulsatile patient-specific left ventricle, modelled with computational fluid dynamics, was utilised to identify the risk of thrombosis for five cannulation angles. With respect to the inflow cannula axis directed towards the mitral valve, the other angles were 25° and 20° towards the septum and 20° and 30° towards the free wall.

RESULTS

Inflow cannula angulation towards the free wall resulted in longer blood residence time within the ventricle, slower ventricular washout and reduced pulsatility indices along the septal wall. Based on the model, the ideal inflow cannula alignment to reduce the risk of thrombosis was angulation towards the mitral valve and up to parallel to the septum, avoiding the premature clearance of incoming blood.

CONCLUSIONS

This study indicates the potential effects of inflow cannulation angles and may guide optimised implantation configurations; however, the ideal approach will be influenced by other patient factors and is suspected to change over the course of support.

Mechanical Blood-Immersed Bearings in Continuous-Flow Rotary Blood Pumps

Mechanical blood-immersed bearings have been used in many continuous-flow rotary blood pumps to reduce friction between relatively moving parts, but their use has been associated with a significant incidence of pump thrombosis. As newer cardiac assist devices with more advanced bearings become available, the rate of pump thrombosis will likely decrease. Nevertheless, it is important to understand the design limitations of mechanical bearings as pumps utilizing them are still in use as chronic support devices and especially in the acute setting for temporary support devices. A properly designed journal bearing should support the spinning rotor with no surface-to-surface contact between the bearing and journal surfaces. The journal continuously undergoes orbital motion within the bearing, which can be "stable" or "unstable." Unstable orbital motion causes the journal to move progressively off-center until it collides with the bearing, and even minor variations in manufacturing can create off-design operation and dynamic instability of the journal. Since blood is the lubricant in most clinically-used rotary blood pumps, lubricant viscosity can vary abruptly in response to changes in hematocrit or plasma protein concentration. Additionally, shear stress from the high-speed rotor can cause hemolysis and plasma protein denaturation. We reviewed theoretical design and operating principles of mechanical bearings and discuss why the phenomenon of mechanical bearing thrombosis may be an inherent design issue dependent on variables that are beyond the control of clinicians.

HeartWare Ventricular Assist Device Cannula Position and Hemocompatibility-Related Adverse Events

BACKGROUND

HeartWare ventricular assist device (HVAD) cannula position is associated with hemodynamics and heart failure readmissions. However, its impact on hemocompatibility-related adverse events (HRAEs) remains uncertain.

METHODS

HVAD patients were followed for 1 year after index hospitalization, when cannula coronal angle was quantified from chest x-ray film. Invasive right heart catheterization and transthoracic echocardiography were performed. One-year occurrences of each HRAE were compared between those with and without a cannula coronal angle of greater than 65 degrees.

RESULTS

Among 63 HVAD patients (median age 60 years, 63% male), 10 (16%) had a cannula coronal angle greater than 65 degrees. The wide-angle group had elevated intracardiac pressures and lower pulmonary artery pulsatility index (P < .05). They also had reduced right ventricular function by echocardiography. Freedom from HRAEs tended to be lower in the wide-angle group (24% vs 62%; P = .11). The rate of gastrointestinal bleeding was significantly higher in the greater than 65 degrees group (0.90 events/year vs 0.40 events/year; P = .013). The rates of stroke and pump thrombosis were statistically comparable irrespective of cannula angle (P > .05).

CONCLUSIONS

HVAD cannula coronal angle was associated with reduced right ventricular function and HRAEs. Prospective studies evaluating surgical techniques to ensure optimal device positioning and its effects on HRAEs are warranted.

Left Ventricular Assist Device Outflow Graft Obstruction: A Complication Specific to Polytetrafluoroethylene Covering. A Word of Caution!

Pump thrombosis is an established complication of left ventricular assist devices (LVADs). Outflow graft obstruction has been previously described as one cause of LVAD thrombosis. We identified four cases of outflow graft obstruction that were attributed to a commonly applied polytetrafluoroethylene (PTFE) covering of the outflow graft. In this set of patients, the outflow graft was obstructed by a thrombus which formed between the outflow graft and its external PTFE covering, leading to impingement of the outflow graft. Patients typically presented after a median duration of 26 months (range 23-41 months) of support with gradual increase of heart failure symptoms and low pump flows. Computed tomography angiography was found to be the best diagnostic modality. Treatments included surgical LVAD replacement as well as percutaneous intraluminal stenting of the outflow graft. Our findings indicate that PTFE graft covering of the LVAD outflow graft can lead to graft occlusion and should be reconsidered as a potentially harmful modification to the approved device implant technique.

Limited Efficacy of Thrombolytics for Pump Thrombosis in Durable Left Ventricular Assist Devices

BACKGROUND

This study reports a single-center experience with thrombolytics for left ventricular assist device (LVAD) pump thrombosis.

METHODS

Adults undergoing continuous-flow LVAD implantation between 2004 and 2018 at a single center were reviewed and those with pump thrombosis were identified. Primary outcomes included 1-year survival and success rates of thrombolytic therapy. Secondary outcomes included posttreatment adverse events, freedom from major bleeding at 1 year, and freedom from stroke at 1-year follow-up.

RESULTS

A total of 341 patients underwent LVAD implantation and 10.8% (n = 37) developed pump thrombosis. Of those 37, 26 received initial thrombolytic therapy (70.2%), 5 underwent direct pump exchange (13.5%), and 6 received only intravenous heparin owing to presentation with acute stroke or severe multiorgan failure (16.2%). Successful treatment was achieved in 11.5% of patients receiving thrombolytics (n = 3). Early adverse events after thrombolytic therapy included major bleeding in 11.5% (n = 3) and new stroke in 7.7% (n = 2). Most patients undergoing thrombolytic therapy underwent subsequent device exchange (69.2%; n = 18). Overall survival in patients with pump thrombosis after treatment was 96.8% at 30 days, 78.9% at 90 days, and 63.1% at 1 year. Freedom from major bleeding and stroke at 1 year was 74.2% and 87.2%, respectively.

CONCLUSIONS

In this single-center experience of thrombolytics for pump thrombosis in LVAD patients, there was limited efficacy; most patients required subsequent pump exchange. Combined with the risk for major bleeding or stroke with thrombolysis, this underscores the importance of further refining patient selection for direct pump exchange in those presenting with pump thrombosis.

Association of Inflow Cannula Position with Left Ventricular Unloading and Clinical Outcomes in Patients with HeartMate II Left Ventricular Assist Device

The relationship between the HeartMate II left ventricular assist device (LVAD) position and pump thrombosis has been reported. However, further clinical implications of device position are unknown. This study aimed to investigate optimal device position for better left ventricular (LV) unloading and patient prognosis. Patients undergoing a ramp test with right heart catheterization after HeartMate II LVAD implantation were enrolled to this study. Device position was quantified from the chest X-ray obtained at the time of the ramp test: (1) inflow cannula angle relative to horizontal line, (2) pump angle relative to spine, (3) pump depth, (4) angle between inflow cannula and pump, and (5) angle between pump and outflow graft. LV unloading was assessed by pulmonary capillary wedge pressure at set LVAD speed. Fifty-four patients (60 years old and 34 male [63%]) were enrolled. Nobody experienced device malfunction during the study period. Increased LV unloading (i.e., lower pulmonary capillary wedge pressure) was associated with a narrower inflow cannula angle relative to horizontal line. Inflow cannula angle <75° was associated with higher 1 year heart failure readmission-free survival rate (p < 0.05, hazards ratio 7.56 [95% confidence interval 2.32-24.7]). In conclusion, HeartMate II LVAD inflow cannula position was associated with LV unloading and patient prognosis. Prospective studies to ensure optimal device positioning and target better clinical outcomes are warranted.

Telecardiographic measurements for device migration: A useful tool for follow-up

OBJECTIVE

Pump thrombosis in left ventricular assist device (LVAD) patients is an important cause of mortality and morbidity. Inflow cannula migration is a predisposing factor for pump thrombosis. Telecardiographic measurements can be used to follow up apical cannula deviation. In this study, we aimed to evaluate the migration of the inflow cannulas in patients with LVADs using angle measurements on telecardiograms.

METHODS

Twenty-three patients who were implanted left ventricular assist devices in our clinic between February 2013 and April 2016 were included in our study. During the first year of follow-up, changes in angle measurements on postoperative 1^st, 3^rd, 6^th, and 12^th month telecardiograms were compared against the incidence of device thrombus and serum Lactate Dehydrogenase (LDH) levels.

RESULTS

Patients who were diagnosed with device thrombosis had more change in inflow cannula angles than patients without device thrombus (p<0.05 at 6^th and 12^th months). Patients with higher LDH values had more parallel angular changes at all intervals, and the change in angle was statistically significant at 3^rd, 6^th and 12^th months (p<0.05).

CONCLUSION

This study shows that it is possible to track the migration of inflow cannulas in patients with left ventricular heart failure using telecardiograms. The correlation between angle change and LDH levels and embolic events may suggest that telecardiographic follow up of angles may be a useful tool for ventricular assist devices teams for early detection of thrombus.

The Effect of Inflow Cannula Angle on the Intraventricular Flow Field of the Left Ventricular Assist Device-Assisted Heart: An In Vitro Flow Visualization Study

Previous studies have identified left ventricular assist device (LVAD) inflow cannula (IC) malposition as a significant risk for pump thrombosis. Thrombus development is a consequence of altered flow dynamics, which can produce areas of flow stasis or high shear that promote coagulation. The goal of this study was to measure the effect of IC orientation on the left ventricle (LV) flow field using a mock circulatory loop, and identify flow-based indices that are sensitive measures of cannula malposition. Experimental studies were performed with a customized silicone model of the dilated LV and the EVAHEART Centrifugal LVAS (Evaheart, Inc.; Houston TX). The velocity field of the LV midplane was measured for a transparent IC oriented parallel to and rotated 15° toward the septum under matched hemodynamic conditions. Vortex structures were analyzed and localized stasis calculated within the IC and combined with a map of normalized pulsatile velocity. The velocity fields revealed increased apical stasis and lower pulsatility with a small angulation of the IC. A significant change in vortex dynamics with the angled IC was observed, doubling the size of the counterclockwise (CCW) vortex while reducing the kinetic energy provided by LVAD support. A significant decrease in average and systolic velocities within the IC was found with cannula angulation, suggesting an increased resistance that affects primarily systolic flow and is worsened with increased LVAD support. These common echocardiographic indices offer the opportunity for immediate clinical application during ramp study assessment. Optimized IC positioning may be determined preoperatively using imaging techniques to develop patient-specific surgical recommendations.

Food and Drug Administration Malfunction Recalls of Left Ventricular Assist Devices

Left ventricular assist devices (LVADs) are being increasingly implanted given the increasing prevalence of patients with advanced heart failure stages. However, they are not exempt from device malfunctions. A PubMed search for the key words (left ventricular assist device malfunction) (ventricular assist system malfunction) was performed. We identified 28 publications in the US Food and Drug Administration (FDA) website database that addressed LVAD malfunction. Twenty-nine FDA recalls were identified regarding LVAD malfunctions: 17 regarding HeartWare ventricular assist device, six for HeartMate II, three for HeartMate 3, and three for total artificial heart. Mechanisms involved in LVAD malfunction include battery malfunction, loose driveline connector, malfunction of the system controller, loose power supply connector ports, malfunction of the driveline splice kit, problems with the percutaneous lead connection, disconnection of the bend relief and outflow graft and outflow graft occlusion among others. Multiple mechanisms could be linked to LVAD malfunction. However, multiple device modifications have been developed over the past decade to avoid recurrent malfunctions. Constant improvements and research in biotechnology are needed to prevent these complications. It remains to be seen if newer generation devices will lead to improved patient outcomes over the long term.

Outcomes following left ventricular assist device exchange

INTRODUCTION

Left ventricular assist device (LVAD) exchange has been historically associated with a significant risk of morbidity and mortality. It is unknown, however, whether these outcomes have improved. We aimed to compare clinical outcomes following LVAD exchange to those following initial LVAD implant in a contemporary patient cohort.

METHODS

A total of 115 LVAD patients were enrolled between 2014 and 2017 and followed for 1 year. Of these, 15 patients (54.5 ± 13.3 years old, 87% male) underwent LVAD exchange at 277 (IQR 191-597) days following LVAD implantation and 100 patients (57.5 ± 12.3 years old, 76% male) did not undergo an LVAD exchange (non-exchange group).

RESULTS

One-year survival rate following LVAD exchange tended to be higher than the non-exchange patients (93% vs 76%, P = .15). Readmission rates for each comorbidity did not significantly differ between the two groups (P > .05 for all) except for the higher rate of pump thrombosis in the LVAD exchange group (P < .05).

DISCUSSION

LVAD exchange cohorts seem to have comparable clinical outcome with the non-exchange cohorts.

CONCLUSION

LVAD exchange might be an increasingly appropriate therapeutic option for the management of pump thrombosis, although careful monitoring for recurrent pump thrombosis is required.

Chest radiographs of cardiac devices (Part 2): Ventricular assist devices

Heart failure is considered a worldwide pandemic affecting 26 million people globally. Patients who are unfit or waiting for cardiac transplantation may benefit from alternate mechanical support therapies using ventricular assist devices. It is not uncommon for radiologists, especially those working in institutions with a high volume of cardiac transplantations, to be presented with radiographs containing these devices. The role of the radiologist is not only to accurately identify these devices, but also to evaluate for any complications.

Left Ventricular Assist Device Inflow Cannula Angle and Thrombosis Risk

BACKGROUND

As heart failure prevalence continues to increase in the setting of a static donor supply, left ventricular assist device (LVAD) therapy for end-stage heart failure continues to grow. Anecdotal evidence suggests that malalignment of the LVAD inflow cannula may increase thrombosis risk, but this effect has not been explored mechanistically or quantified statistically. Our objective is to elucidate the impact of surgical angulation of the inflow cannula on thrombogenicity.

METHODS AND RESULTS

Unsteady computational fluid dynamics is used in conjunction with computational modeling and virtual surgery to model flow through the left ventricle for 5 different inflow cannula angulations. We use a holistic approach to evaluate thrombogenicity: platelet-based (Lagrangian) metrics to evaluate the platelet mechanical environment, combined with flow-based (Eulerian) metrics to investigate intraventricular hemodynamics. The thrombogenic potential of each LVAD inflow cannula angulation is quantitatively evaluated based on platelet shear stress history and residence time. Intraventricular hemodynamics are strongly influenced by LVAD inflow cannula angulation. Platelet behavior indicates elevated thrombogenic potential for certain inflow cannula angles, potentially leading to platelet activation. Our analysis demonstrates that the optimal range of inflow angulation is within 0±7° of the left ventricular apical axis.

CONCLUSIONS

Angulation of the inflow cannula >7° from the apical axis (axis connecting mitral valve and ventricular apex) leads to markedly unfavorable hemodynamics as determined by computational fluid dynamics. Computational hemodynamic simulations incorporating Lagrangian and Eulerian metrics are a powerful tool for studying optimization of LVAD implantation strategies, with the long-term potential of improving outcomes.

Novel Formula to Calculate Three-Dimensional Angle Between Inflow Cannula and Device Body of HeartMate II LVAD

BACKGROUND

The acute angle between inflow cannula and device body of HeartMate II left ventricular assist device (LVAD) (Abbott, Pleasanton, California) is associated with device thrombosis. However, most studies utilized two-dimensional (2D) angle obtained from chest roentgenogram (CXR), which is unlikely accurate. We aimed to create and validate a formula to estimate actual three-dimensional (3D) angle.

METHODS

We retrospectively reviewed the cohort undergoing HeartMate II LVAD implantation between 2008 and 2016. A formula for calculating 3D angles of the LVAD inflow cannula relative to the device body was mathematically derived, using simple 2D measurements from CXR.

RESULTS

The cohort included consecutive 275 patients with HeartMate II (median age: 60 [25% quartile: 51, 75% quartile: 68] years). There was no significant difference between the calculated 3D angles (from formula) and actual 3D angles (from computed tomography) from the subset group with 3D computed tomography (n = 28) (71.7° ± 13.4° vs 71.1° ± 11.5°, P = .858). Among all participants, the calculated 3D angle (from formula) was 74.4° ± 14.2°, which was significantly larger than the 2D projected angle (from CXR) (65.2° ± 11.3°, P < .001). There was no statistical difference in the calculated 3D angles (from formula) between patients with/without device thrombosis, hemorrhagic stroke, ischemic stroke, or mortality (P > .05 for all).

CONCLUSIONS

We established a novel formula to mathematically calculate actual 3D angles between inflow cannula and device body of HeartMate II. The formula would help investigators to validate their findings of the relationship between 2D projected angle (from CXR) and device thrombosis.

Prothrombotic activity of cytokine-activated endothelial cells and shear-activated platelets in the setting of ventricular assist device support

BACKGROUND

We systematically analyzed the synergistic effect of: (i) cytokine-mediated inflammatory activation of endothelial cells (ECs) with and (ii) shear-mediated platelet activation (SMPA) as a potential contributory mechanism to intraventricular thrombus formation in the setting of left ventricular assist device (LVAD) support.

METHODS

Intact and shear-activated human platelets were exposed to non-activated and cytokine-activated ECs. To modulate the level of LVAD-related shear activation, platelets were exposed to shear stress patterns of varying magnitude (30, 50, and 70 dynes/cm², 10 minutes) via a hemodynamic shearing device. ECs were activated via exposure to inflammatory tumor necrosis factor-α (TNF-α 10 and 100 ng/ml, 24 hours), consistent with inflammatory activation recorded in patients on LVAD circulatory support.

RESULTS

Adhesivity of shear-activated platelets to ECs was significantly higher than that of intact/unactivated platelets, regardless of the initial activation level (70 dynes/cm² shear-activated platelets vs intact platelets: +80%, p < 0.001). Importantly, inflammatory activation of ECs amplified platelet prothrombinase activity progressively with increasing shear stress magnitude and TNF-α concentration: thrombin generation of 70 dynes/cm² shear-activated platelets was 2.6-fold higher after exposure and adhesion to 100 ng/ml TNF-α‒activated ECs (p < 0.0001).

CONCLUSIONS

We demonstrated synergistic effect of SMPA and cytokine-mediated EC inflammatory activation to enhance EC‒platelet adhesion and platelet prothrombotic function. These mechanisms may contribute to intraventricular thrombosis in the setting of mechanical circulatory support.

Left Ventricular Assist Devices: How Do We Define Success?

Despite the growing acceptance of left ventricular assist device (LVAD) therapy to improve survival and quality of life in heart failure (HF) patients, uncertainties persist regarding the definition of a successful implant. We sought to define an innovative approach to assess success and subsequently compare preoperative variables affecting outcomes. From January 2007 to 2015, 278 patients underwent LVAD implantation. Median age at implant was 62 years and 81% patients were males. Indication for support was bridge-to-transplantation in 36% patients and the etiology of HF was ischemic in 49% patients. Based on clinically relevant and accepted standards, we defined successful LVAD implant as someone who was alive or transplanted at 2 years, had two or less readmissions in the first year, had no major adverse events in the first year, and had a New York Heart Association class of ≤ II at 6 months. Follow-up was obtained for a median of 1.7 years for a total of 605 patient-years-of-support. Based on our criteria, 81/278 (29%) patients were defined as having a successful implant. Univariate predictors of LVAD failure included destination therapy indication (hazard ratio [HR] = 2.11 [1.24, 3.58]), ischemic cardiomyopathy (HR = 1.73 [1.02, 2.94]), and a higher left ventricular ejection fraction (HR = 1.54 [1.07, 2.22]). After multivariable analysis, only destination therapy indication (HR = 2.2 [1.28, 3.78]) was found to be independently predictive of success failure. Despite an overall trend toward improved outcomes on device therapy, our criteria classified only one-third of patients as successful. Continued improvements in adverse event profiles, appropriate patient selection, and optimal time of implantation, together hold the key to improve outcomes after LVAD therapy.

Surgical Implantation of Intracorporeal Devices: Perspective and Techniques

Surgical maneuvers for implantation of a continuous-flow ventricular assist device are revolutionary concepts that have been associated with a reduction in pump-related complications. With the advancement of technology, surgical implant strategy continues to evolve, incorporating less-invasive approaches into the armamentarium of the experienced surgeon.

Left Ventricular Assist Device Inflow Cannula Position May Contribute to the Development of HeartMate II Left Ventricular Assist Device Pump Thrombosis

Background

Pump thrombosis (PT) is a dreaded complication after left ventricular assist device (LVAD) implantation. Problems with inflow cannula (IC) position may precipitate thrombus development. We sought to determine if IC position contributes to the development of PT.

Methods

We conducted a retrospective review of 76 HeartMate II LVAD implants. The angle of the IC (AIC) to the horizontal plane was measured on chest x-rays. Patients who developed PT (PT group) were compared to the remaining patients (control group).

Results

The mean age at implantation was 56 ± 14 years, and 82% of the patients were male. Ten patients (13%) developed PT. Six (60%) required device exchange, and 4 (40%) were managed with anticoagulation and/or thrombolysis. The median AIC for all patients at implantation was 59° (range, 38°-98°; 25th-75th interquartile range, 50°-75°). In the PT group, the median AIC was larger at the time of PT diagnosis compared to implantation (70° vs 60°, P = 0.005). In the control group, the median AIC was also larger at follow-up compared to implantation (61° vs 58°, P < 0.001) although to a lesser degree than in the PT group. No difference was seen in the median AIC between the PT group and the control group at implantation (60° vs 58°, respectively; P = 0.668) or at follow-up (70° vs 61°, respectively; P = 0.309). However, the median AIC at follow-up in the PT group was significantly larger than the median AIC at implantation in the control group (70° vs 58°, respectively; P = 0.014).

Conclusion

The HeartMate II LVAD IC position contributes to the development of PT. Regular monitoring of cannula position may help identify patients at risk for this problem.

Role of computed tomography angiography for HeartMate II left ventricular assist device thrombosis

INTRODUCTION

Device thrombosis is one of the most devastating complications of HeartMate II left ventricular assist devices. The purpose of this study is to assess the anatomical properties that the inflow and outflow computed tomography angiography provides in assessing for left ventricular assist device thrombosis, as well as their impact on clinical management and postoperative outcomes.

METHODS

Between April 2010 and December 2016, 22 patients who received a HeartMate II left ventricular assist device implantation were readmitted for suspected device thrombosis and underwent a computed tomography angiography for workup. Left ventricular assist device-associated anatomy was assessed, including outflow abnormality on computed tomography angiography (contrast filling defect), inflow abnormalities on computed tomography angiography (space at inflow, M-I angle), and inflow abnormalities on chest X-ray (inflow angulation, pump pocket depth).

RESULTS

Computed tomography angiography revealed an outflow filling defect in three patients (14%) resulting in change in surgical approach from subcostal pump exchange to resternotomy pump and outflow graft exchange. Inflow graft malpositioning was identified in four patients, with the inflow abutting the left ventricular wall and obstructing the cannula opening. On computed tomography angiography assessment, mean space at inflow was 5.3 ± 1.6 mL and M-I angle was 35.6° ± 6.6°. Chest X-ray evaluation revealed mean inflow angle and pump pocket depth of 75.7° ± 13.4° and 110.2 ± 26.6 mm, respectively.

CONCLUSION

Computed tomography angiography provides a noninvasive assessment of the outflow graft and inflow cannulas in left ventricular assist device patients. Findings on computed tomography angiography reveal possible mechanical etiologies of thrombosis and may be useful for determining the surgical management of device thrombosis patients.

Ventricular Assist Device Implantation Configurations Impact Overall Mechanical Circulatory Support System Thrombogenic Potential

Ventricular assist devices (VADs) became in recent years the standard of care therapy for advanced heart failure with hemodynamic compromise. With the steadily growing population of device recipients, various postimplant complications have been reported, mostly associated with the hypershear generated by VADs that enhance their thrombogenicity by activating platelets. Although VAD design optimization can significantly improve its thromboresistance, the implanted VAD need to be evaluated as part of a system. Several clinical studies indicated that variability in implantation configurations may contribute to the overall system thrombogenicity. Numerical simulations were conducted in the HeartAssist 5 (HA5) and HeartMate II (HMII) VADs in the following implantation configurations: 1) inflow cannula angles: 115° and 140° (HA5); 2) three VAD circumferential orientations: 0°, 30°, and 60° (HA5 and HMII); and 3) 60° and 90° outflow graft anastomotic angles with respect to the ascending aorta (HA5). The stress accumulation of the platelets was calculated along flow trajectories and collapsed into a probability density function, representing the "thrombogenic footprint" of each configuration-a proxy to its thrombogenic potential (TP). The 140° HA5 cannula generated lower TP independent of the circumferential orientation of the VAD. Sixty-degree orientation generated the lowest TP for the HA5 versus 0° for the HMII. An anastomotic angle of 60° resulted in lower TP for HA5. These results demonstrate that optimizing the implantation configuration reduces the overall system TP. Thromboresistance can be enhanced by combining VAD design optimization with the surgical implantation configurations for achieving better clinical outcomes of implanted VADs.

Quantitative Assessment of Inflow Malposition in Two Continuous-Flow Left Ventricular Assist Devices

BACKGROUND

We previously investigated preoperative variables associated with qualitative inflow cannula malposition in the HeartMate II (Thoratec-Abbott, Abbott Park, IL) continuous-flow left ventricular assist device. In this report, we assess inflow cannula malposition quantitatively in recipients of both the HeartMate II and the HeartWare (Medtronic-HeartWare, Minneapolis, MN) and examine its association with device thrombosis.

METHODS

Malposition was quantified based on angular deviation from a hypothetic ideal inflow cannula position in two orthogonal computed tomography imaging planes. Ideal position lies on a line from the apex to the center of the mitral valve. Positive anterior plane angulation indicates deviation toward the superior free wall; negative, toward the inferior wall. Positive lateral plane angulation indicates deviation toward the septum; negative, toward the lateral wall. Device thrombosis was assessed based on clinical criteria.

RESULTS

Fifty-four HeartMate II patients and 68 HeartWare patients were analyzed. Inflow cannula deviation was significantly higher for HeartMate II than for HeartWare (anterior plane angle 36.7 ± 16.8 versus -18.7 ± 11.6 degrees, p < 0.001; lateral plane angle 23.7 ± 20.1 versus 0.2 ± 15.0 degrees, p < 0.001. Pump thrombosis occurred in 31% of HeartMate II patients and 2.9% of HeartWare patients (p < 0.001). In a multivariate model, HeartMate II and increasing inflow cannula deviation toward the septum were associated with higher thrombosis risk (odds ratio 1.35 per 10-degree increase).

CONCLUSIONS

We found distinct device-dependent differences in inflow cannula positioning and thrombosis, with HeartWare showing both less malposition and less thrombosis. Malposition toward the ventricular septum may contribute to pump thrombosis through a vicious cycle of suction events, low flow, and speed reduction.