Survival After Orthotopic Heart Transplantation in Patients Undergoing Bridge to Transplantation With the HeartWare HVAD Versus the Heartmate II

Clinical Outcomes of Cardiac Transplantation in Heart Failure Patients with Previous Mechanical Cardiocirculatory Support

Objectives: Heart failure (HF) remains a significant public health issue, with heart transplantation (HT) being the gold standard treatment for end-stage HF. The increasing use of mechanical circulatory support, particularly left ventricular assist devices (LVADs), as a bridge to transplant (BTT), presents new perspectives for increasingly complex clinical scenarios. This study aimed to compare long-term clinical outcomes in patients in heart failure with reduced ejection fraction (HFrEF) receiving an LVAD as BTT to those undergoing direct-to-transplant (DTT) without mechanical support, focusing on survival and post-transplant complications. Methods: A retrospective, single-center study included 105 patients who underwent HT from 2010. Patients were divided into two groups: BTT (n = 28) and DTT (n = 77). Primary endpoints included overall survival at 1 and 7 years post-HT. Secondary outcomes involved late complications, including organ rejection, renal failure, cardiac allograft vasculopathy (CAV), and cerebrovascular events. Results: At HT, the use of LVADs results in longer cardiopulmonary bypass and cross-clamping times in the BTT group; nevertheless, surgical complexity does not affect 30-day mortality. Survival at 1 year was 89.3% for BTT and 85.7% for DTT (p = 0.745), while at 7 years, it was 80.8% and 77.1%, respectively (p = 0.840). No significant differences were observed in the incidence of major complications, including permanent dialysis, organ rejection, and CAV. However, a higher incidence of cerebrovascular events was noted in the BTT group (10.7% vs. 2.6%). Conclusions: LVAD use as BTT does not negatively impact early post-transplant survival compared to DTT. At long-term follow-up, clinical outcomes remained similar across groups, supporting LVADs as a viable option for bridging patients to transplant.

Heartware ventricular assist device versus HeartMate II versus HeartMate III in advanced heart failure patients: A systematic review and meta-analysis

Objective

Ventricular assist device is one of the treatment options for heart failure patients. Therefore, the purpose of this review is to aid in clinical decision-making of exchanging previous older ventricular assist device models to the newest one, HM3.

Methods

The search was conducted across several databases until February 25, 2023, and was registered with the ID of CRD42023405367. Risk of bias was performed using Cochrane Risk of Bias 2.0 and the Newcastle Ottawa Scale. In order to rank and evaluate the pooled odds ratios and mean differences with 95% confidence intervals, we employed conventional and Bayesian network meta-analysis converted to surface under the cumulative ranking.

Results

A total of 49 studies with 31,105 patients were included in this review. HM3 is the best device exchange choice that causes the lowest risk of mortality (HM3 (99.98) > HM2 (32.43) > HVAD (17.58)), cerebrovascular accidents (HM3 (99.99) > HM2 (42.41) > HVAD (7.60)), other neurologic events beside cerebrovascular accident (HM3 (91.45) > HM2 (54.16) > HVAD (4.39)), pump thrombosis (HM3 (100.00) > HM2 (39.20) > HVAD (10.80)), and bleeding (HM3 (97.12) > HM2 (47.60) > HVAD (5.28)). HM3 is also better than HM2 in hospital admissions (OR: 1.90 (95% CI: 1.15-3.12)). When complications were present, HM2 or Heartware ventricular assist devices exchange to HM3 lowered the mortality rate compared to exchanging it to the same device type.

Conclusion

HM3 is the best device for all six outcomes. Exchange from Heartware ventricular assist devices or HM2 to HM3 rather than the same ventricular assist device type is recommended only if a complication is present.

Resistance valves in circulatory loops have a significant impact on in vitro evaluation of blood damage caused by blood pumps: a computational study

Background: Hemolysis and its complications are major concerns during the clinical application of blood pumps. In-vitro circulatory testing loops have been employed as the key procedure to evaluate the hemolytic and thrombogenic performance of blood pumps during the development phase and before preclinical in-vivo animal studies. Except for the blood damage induced by the pump under test, blood damage induced by loop components such as the resistance valve may affect the accuracy, reproducibility, and intercomparability of test results. Methods: This study quantitatively investigated the impact of the resistance valve on in vitro evaluation of blood damage caused by blood pumps under different operating points. A series of idealized tubing models under the resistance valve with different openings were created. Three pumps - the FDA benchmark pump, the HeartMate 3 LVAD, and the CH-VAD - were involved in hypothetical tests. Eight operating points were chosen to cover a relatively wide spectrum of testing scenarios. Computational fluid dynamics (CFD) simulations of the tubing and pump models were conducted at the same operating points. Results and Conclusion: Overall, hemolysis and platelet activation induced by a typical resistance valve are equivalent to 17%-45% and 14%-60%, respectively, of those induced by the pump itself. Both ratios varied greatly with flow rate, valve opening and pump models. Differences in blood damage levels between different blood pumps or working conditions can be attenuated by up to 45%. Thus, hemolysis and platelet activation induced by the resistance valve significantly affect the accuracy of in-vitro hemocompatibility evaluations of blood pumps. A more accurate and credible method for hemocompatibility evaluations of blood pumps will benefit from these findings.

A novel model for hemolysis estimation in rotating impeller blood pumps considering red blood cell aging

For blood pumps with a rotating vane-structure, hemolysis values are estimated using a stress-based power-law model. It has been reported that this method does not consider the red blood cell (RBC) membrane's shear resistance, leading to inaccurate estimation of the hemolysis value. The focus of this study was to propose a novel hemolysis model which can more accurately predict the hemolysis value when designing the axial flow blood pump. The movement behavior of a single RBC in the shear flow field was simulated at the mesoscale. The critical value of shear stress for physiological injury of RBCs was determined. According to the critical value, the equivalent treatment of RBC aging was studied. A novel hemolysis model was established considering the RBC's aging and the hemolysis' initial value. The model's validity was verified under the experimental conditions of shear stress loading and the conditions of the shear flow field of the blood pump. The results showed that compared with other hemolysis models for estimating the hemolysis value of blood pumps, the novel hemolysis model proposed in this paper could effectively reduce the estimation error of the hemolysis value and provide a reference for the optimal design of rotary vane blood pumps.

Risk of Renal Dysfunction Following Heart Transplantation in Patients Bridged with a Left Ventricular Assist Device

Acute renal failure (ARF) and chronic kidney disease (CKD) are associated with short- and long-term morbidity and mortality following heart transplantation (HT). We investigated the incidence and risk factors for developing ARF requiring hemodialysis (HD) and CKD following HT specifically in patients with a left ventricular assist device (LVAD). We examined the International Society for Heart and Lung Transplantation (ISHLT) Thoracic Transplant Registry for heart transplant patients between January 2000 and June 2015. We compared patients bridged with durable continuous-flow LVAD to those without LVAD support. Primary outcomes were ARF requiring HD before discharge following HT and CKD (defined as creatinine >2.5 mg/dl, permanent dialysis, or renal transplant) within 3 years. There were 18,738 patients, with 4,535 (24%) bridged with LVAD support. Left ventricular assist device patients had higher incidence of ARF requiring HD and CKD at 1 year, but no significant difference in CKD at 3 years compared to non-LVAD patients. Among LVAD patients, body mass index (BMI) (odds ratio [OR] = 1.79, p < 0.001), baseline estimated glomerular filtration rate (eGFR) (OR = 0.43, p < 0.001), and ischemic time (OR = 1.28, p = 0.014) were significantly associated with ARF requiring HD. Similarly, BMI (hazard ratio [HR] = 1.49, p < 0.001), baseline eGFR (HR = 0.41, p < 0.001), pre-HT diabetes mellitus (DM) (HR = 1.37, p = 0.011), and post-HT dialysis before discharge (HR = 3.93, p < 0.001) were significantly associated with CKD. Left ventricular assist device patients have a higher incidence of ARF requiring HD and CKD at 1 year after HT compared with non-LVAD patients, but incidence of CKD is similar by 3 years. Baseline renal function, BMI, ischemic time, and DM can help identify LVAD patients at risk of ARF requiring HD or CKD following HT.

HVAD versus heartmate III bridge to heart transplantation: Waitlist and posttransplant outcomes

BACKGROUND

This study compared outcomes of patients bridged with either the Heartware HVAD or Heartmate 3 (HM3) device to orthotopic heart transplantation (OHT).

METHODS

The United Network of Organ Sharing registry was queried to perform two separate analyses of adult, isolated OHT candidates bridged with HVAD or HM3. First, waitlist outcomes were compared among patients waitlisted 1/1/2015-3/20/2020. Second, posttransplant survival was compared among those transplanted 1/1/2015-3/20/2020.

RESULTS

Two thousand two hundred fifty-five candidates were waitlisted within the study period, 1587 (70.4%) bridged with HVAD and 668 (29.6%) with HM3. At 1 year from waitlisting, cumulative incidence of OHT higher in the HVAD cohort (p < .001). During the same time period, 2643 patients underwent OHT, 2154 (81.5%) with prior HVAD and 489 (18.5%) with HM3. Yearly proportions of patients bridged with HM3 increased across the study period and decreased for HVAD (p < .001). HM3-bridged recipients had shorter waitlist times, longer graft cold ischemic times, and experienced a higher rate of posttransplant dialysis requirement. Unadjusted and risk-adjusted posttransplant mortality rates were similar between both groups.

CONCLUSIONS

Posttransplant survival is equivalent regardless of device type used for bridging. However, HM3 patients had lower likelihood of reaching transplantation, which may be a reflection of the recent heart allocation policy changes.

Posttransplant Long-Term Outcomes for Patients with Ventricular Assist Devices on the Heart Transplant Waitlist

Ventricular assist devices (LVADs) are commonly used in end-stage heart failure for mechanical circulatory support as a bridge to heart transplantation. However, LVADs' long-term effects on posttransplant survival are unknown. We sought to compare long-term mortality after transplantation for patients with and without LVADs. Using the Organ Procurement and Transplantation Network database, we investigated LVADs' impact on long-term (3 month, 1 year, 2 years, 5 years, and 8 years) posttransplant mortality risk for all heart transplant recipients between 2010 and 2019. Time-to-event regression analysis quantified mortality risk by LVAD status in both unconditional and conditional survival analyses. Of 20,113 transplant recipients, 8,999 (45%) had a LVAD while on the waitlist. Among those who died after transplantation, patients with LVADs on average died sooner (1.8 years) than patients without LVADs (3.0 years; p < 0.01). On multivariable analysis, patients with LVADs had a 44% higher mortality risk within the first 3 months posttransplant (HR = 1.44, p = 0.03). There was no significant difference in mortality risk between patients who did and did not have pretransplant LVADs after 1, 2, and 5 years of posttransplant conditional survival. While LVAD patients have a survival disadvantage in the first year posttransplant, conditional survival analysis demonstrated no difference in mortality risk between patients with and without LVADs beyond 1 year of follow up. Of the patients who died posttransplant, patients with LVADs on average died sooner than patients without LVADs.

The Design and Evaluation of a Portable Extracorporeal Centrifugal Blood Pump

In recent years, blood pumps have become the bridge to heart transplantation for patients with heart failure. Portability and wearability of blood pumps should be considered to ensure patient satisfaction in everyday life. To date, the focus has been on the development of portable and wearable peripheral components, little attention has been paid to the portable and wearable performance of the blood pump itself. This study reported a novel design of a wearable and portable extracorporeal centrifugal blood pump. Based on an in-house centrifugal maglev blood pump, the wearable and portable blood pump was designed with parallel inlet and outlet pipes to improve the wearable performance. A ring cavity was set at the inlet to convert the circumferential velocity of the inlet pipe to an axial velocity. The hydraulic and hemolytic performance of the baseline and portable blood pumps were analyzed and compared. Compared with the baseline pump, the hydrodynamic and hemolytic performance of the portable pump has been maintained without serious degradation. The results of this study will improve the life quality of patients with heart failure, and enhance the clinical benefits of artificial heart.

Intraventricular flow visualization in different heart failure stages with blood pump support in a mock circulatory loop

The intraventricular blood flow changed by blood pump flow dynamics may correlate with thrombosis and ventricular suction. The flow velocity, distribution of streamlines, vorticity, and standard deviation of velocity inside a left ventricle failing to different extents throughout the cardiac cycle when supported by an axial blood pump were measured by particle image velocimetry (PIV) in this study. The results show slower and static flow velocities existed in the central region of the left ventricle near the mitral valve and aortic valve and that were not sensitive to left ventricular (LV) failure degree or LV pressure. Strong vorticity located near the inner LV wall around the LV apex and the blood pump inlet was not sensitive to LV failure degree or LV pressure. Higher standard deviation of the blood velocity at the blood pump inlet decreased with increasing LV failure degree, whereas the standard deviation of the velocity near the atrium increased with increasing intraventricular pressure. The experimental results demonstrated that the risk of thrombosis inside the failing left ventricle is not related to heart failure degree. The "washout" performance of the strong vorticity near the inner LV wall could reduce the thrombotic potential inside the left ventricle and was not related to heart failure degree. The vorticity near the aortic valve was sensitive to LV failure degree but not to LV pressure. We concluded that the risk of blood damage caused by adverse flow inside the left ventricle decreased with increasing LV pressure.

On the Optimization of a Centrifugal Maglev Blood Pump Through Design Variations

Centrifugal blood pumps are usually designed with secondary flow paths to avoid flow dead zones and reduce the risk of thrombosis. Due to the secondary flow path, the intensity of secondary flows and turbulence in centrifugal blood pumps is generally very high. Conventional design theory is no longer applicable to centrifugal blood pumps with a secondary flow path. Empirical relationships between design variables and performance metrics generally do not exist for this type of blood pump. To date, little scientific study has been published concerning optimization and experimental validation of centrifugal blood pumps with secondary flow paths. Moreover, current hemolysis models are inadequate in an accurate prediction of hemolysis in turbulence. The purpose of this study is to optimize the hydraulic and hemolytic performance of an inhouse centrifugal maglev blood pump with a secondary flow path through variation of major design variables, with a focus on bringing down intensity of turbulence and secondary flows. Starting from a baseline design, through changing design variables such as blade angles, blade thickness, and position of splitter blades. Turbulent intensities have been greatly reduced, the hydraulic and hemolytic performance of the pump model was considerably improved. Computational fluid dynamics (CFD) combined with hemolysis models were mainly used for the evaluation of pump performance. A hydraulic test was conducted to validate the CFD regarding the hydraulic performance. Collectively, these results shed light on the impact of major design variables on the performance of modern centrifugal blood pumps with a secondary flow path.

Experimental investigation of the influence of the hydraulic performance of an axial blood pump on intraventricular blood flow

Blood flow inside the left ventricle (LV) is a concern for blood pump use and contributes to ventricle suction and thromboembolic events. However, few studies have examined blood flow inside the LV after a blood pump was implanted. In this study, in vitro experiments were conducted to emulate the intraventricular blood flow, such as blood flow velocity, the distribution of streamlines, vorticity and the standard deviation of velocity inside the LV during axial blood pump support. A silicone LV reconstructed from computerized tomography (CT) data of a heart failure patient was incorporated into a mock circulatory loop (MCL) to simulate human systemic circulation. Then, the blood flow inside the ventricle was examined by particle image velocimetry (PIV) equipment. The results showed that the operating conditions of the axial blood pump influenced flow patterns within the LV and areas of potential blood stasis, and the intraventricular swirling flow was altered with blood pump support. The presence of vorticity in the LV from the thoracic aorta to the heart apex can provide thorough washing of the LV cavity. The gradually extending stasis region in the central LV with increasing blood pump support is necessary to reduce the thrombosis potential in the LV.

A two-phase flow approach for modeling blood stasis and estimating the thrombosis potential of a ventricular assist device

Thrombosis and its related events have become a major concern during the development and optimization of ventricular assist devices (VADs, also called blood pumps), and limit their clinical use and economic benefits. Attempts have been made to model the thrombosis formation, considering hemodynamic and biochemical processes. However, the complexities and computational expenses are prohibitive. Blood stasis is one of the key factors which may lead to the formation of thrombosis and excessive thromboembolic risks for patients. This study proposed a novel approach for modeling blood stasis, based on a two-phase flow principle. The locations of blood residual can be tracked over time, so that regions of blood stasis can be identified. The blood stasis in an axial blood pump is simulated under various working conditions, the results agree well with the experimental results. In contrast, conventional hemodynamic metrics such as velocity, time-averaged wall shear stress (TAWSS), and relative residence time (RRT), were contradictory in judging risk of blood stasis and thrombosis, and inconsistent with experimental results. We also found that the pump operating at the designed rotational speed is less prone to blood stasis. The model provides an efficient and fast alternative for evaluating blood stasis and thrombosis potential in blood pumps, and will be a valuable addition to the tools to support the design and improvement of VADs.

Use of durable left ventricular assist devices for high-risk patients: Korean experience before insurance coverage

Background

Left ventricular assist devices (LVADs) were not covered by the Korean national insurance until September 2018, and they were implanted at the patient’s own or a third party’s expense. However, there have been no reports on using an LVAD without insurance coverage or manufacturer support.

Methods

We reviewed 23 patients who underwent durable LVAD implantation at our institution from August 2012 to September 2018. Patients with temporary LVADs using extracorporeal or paracorporeal circulation were excluded. The available devices were the HeartMate II^TM (HMII) and HeartWare^TM Ventricular Assist Device (HVAD). The primary outcome was 30-day mortality. The secondary outcomes were postoperative complications and late mortality.

Results

The mean age of the patients was 68.7±9.9 years. The study sample comprised six female (26.1%) and 17 male (73.9%) patients. All patients had modifiable (bridge to candidacy) or unmodifiable absolute (destination therapy) contraindications for heart transplantation (HT). Among the patients in this study, 12 (52.2%) had ischemic cardiomyopathy and 11 (47.8%) had non-ischemic cardiomyopathy. Nine patients (39.1%) had temporary mechanical circulatory support such as extracorporeal membrane oxygenation or a temporary LVAD in place preoperatively. The average duration of LVAD support was 618.6±563.2 days (range, 59–2,285 days). There was no 30-day mortality. Four patients (17.4%) underwent HT. Six patients (26.1%) underwent re-exploration for postoperative bleeding, and one patient (4.3%) had a disabling stroke after discharge. The estimated survival rates at 12 and 24 months were 89.2% and 68.8%, respectively.

Conclusions

All patients who received LVADs before insurance coverage had contraindications for HT. The overall outcomes were comparable with those reported in the international registry.

The predictive value of preimplant pulmonary function testing in LVAD patients

BACKGROUND

The predictive value of preoperative pulmonary function testing (PFT) in left ventricular assist device (LVAD) patients remains unknown. This study evaluates the relationship between abnormal PFTs and postimplant outcomes in LVAD patients.

METHODS

LVAD implants from January 2004 to December 2018 at a single institution were included. Patients were stratified based on the presence of abnormal preoperative PFTs, and the primary outcome was respiratory adverse events (AE). Secondary outcomes included 1-year overall postimplant survival, and complications including bleeding, renal failure, thromboembolism, and device malfunction.

RESULTS

The total of 333 patients underwent LVAD implant, 46.5% (n = 155) with normal PFTs and 53.5% (n = 178) with abnormal PFTs. Patients with abnormal PFTs were noted to have higher rates of respiratory AEs (25.9% vs. 15.1%, p = .049). In multivariable analysis, the impact of PFTs was most significant when forced expiratory volume in 1 s/forced expiratory volume (FEV1/FVC) ratio was less than 0.5 (hazard ratio [HR] 16.32, 95% confidence interval [CI], 1.70-156.78). The rates of other AEs including bleeding, renal failure, right heart failure, and device malfunction were similar. One-year overall postimplant survival was comparable between the groups (56.8% vs. 68.8%, p = .3183), though patients in the lowest strata of FEV1 (<60% predicted) and FEV1/FVC (<0.5) had elevated risk-adjusted hazards for mortality (HR 2.63, 95% CI, 1.51-4.60 and HR 18.92, 95% CI, 2.10-170.40, respectively).

CONCLUSIONS

The presence of abnormal preoperative PFTs is not prohibitory for LVAD implantation although it can be used for risk stratification for respiratory AEs and mortality, particularly in patients with severely reduced metrics. The importance of careful patient selection should be underscored in this higher risk patient subset.

A 3-dimensional-printed left ventricle model incorporated into a mock circulatory loop to investigate hemodynamics inside a severely failing ventricle supported by a blood pump

Intraventricular blood stasis is a design consideration for continuous flow blood pumps and might contribute to adverse events such as thrombosis and ventricular suction. However, the blood flow inside left ventricles (LVs) supported by blood pumps is still unclear. In vitro experiments were conducted to imitate how the hydraulic performance of an axial blood pump affects the intraventricular blood flow of a severe heart failure patient, such as velocity distribution, vorticity, and standard deviation of velocity. In this study, a silicone model of the LV was constructed from the computed tomography data of one patient with heart failure and was 3D printed. Then, intraventricular flow was visualized by particle image velocimetry equipment within a mock circulation loop. The results showed that the axial blood pump suctions most of the blood in a severely failing LV, there was an altered flow status within the LV, and blood stasis appeared in the central region of the LV. Some blood may be suctioned from the aortic valve to the blood pump because the patient's native heart was severely failing. Blood stasis at the LV center may cause thrombosis in the LV. The vortex flow near the inner wall of the LV can thoroughly wash the left ventricular cavity.

Sex-Based Heart Transplant Outcomes After Bridging With Centrifugal Left Ventricular Assist Devices

BACKGROUND

Prior studies demonstrated that female sex is associated with an increased mortality after orthotopic heart transplantation (OHT). The impact of sex on OHT outcomes after bridging with newer-generation durable left ventricular assist devices (LVADs) remains unclear.

METHODS

The United Network for Organ Sharing database was queried to study OHT recipients bridged with a newer-generation LVAD (ie, HeartMate III or HeartWare) between 2010 and 2018. The primary outcome was mortality at 30 and 90-days and 1-year. Secondary outcomes included rates of posttransplant complications. Propensity score matching and Cox multivariable analysis were used to assess comorbidity-adjusted sex differences in outcomes.

RESULTS

A total of 3010 patients (76.7% male) bridged with newer-generation LVADs underwent OHT. After adjusting for relevant covariates, both age and heart failure etiology, but not sex, were independent predictors of mortality. In the matched cohorts, sex did not affect posttransplant outcomes, including renal failure, cerebrovascular events, allograft rejection, functional status, or mortality (all P > .05). Survival at 1-year after OHT was 90.5% in males and 92.8% in females (P = .058).

CONCLUSIONS

Among 3010 OHT recipients, matched females bridged with newer-generation HeartWare or HeartMate III LVADs have comparable posttransplant outcomes compared with males. Furthermore, survival at 1-year follow-up was not affected by sex; instead, it was driven by well-established risk factors including increased age, worse preoperative renal function, and heart failure etiology. These data suggest that considerable progress has been made in mitigating sex differences in heart failure outcomes in the modern era.

Effects of implanting a long-term left ventricle assist device on post-transplant outcomes

BACKGROUND

An increasing number of patients are receiving left ventricle assist devices as a bridge to heart transplantation. The aim of this study was to determine the difference between patients who received transplants from a left ventricle assist device and those who underwent heart transplantation without a prior left ventricle assist device implantation.

MATERIAL AND METHODS

The study included patients who underwent heart transplantation in our institute between January 2010 and November 2018. The following clinical variables were evaluated: donor characteristics, patient's pre-transplant demographical data, post-transplant data, and patient survival. Cardiac allograft vasculopathy progression was prospectively examined (after 1 month and 12 months after heart transplantation) by coronary optical coherence tomography. We were interested in the difference in 1- and 5-year survival between the left ventricle assist device and non-left ventricle assist device groups.

RESULTS

A total of 248 patients were identified; out of them, 48 patients received a left ventricle assist device before heart transplantation, whereas 200 had transplants with no prior left ventricle assist device implantation. There were no significant differences in any donor characteristics. The mean duration of cardiopulmonary bypass time in the non-left ventricle assist device group was 156 versus 175 min in the left ventricle assist device group (p = 0.009), blood loss was 650 versus 1045 mL (p < 0.001), the need to implant an extracorporeal membrane oxygenation was 10% versus 23% (p = 0.02). There was no difference in cardiac allograft vasculopathy progression between the groups 1 year after heart transplantation (p = 0.528). The 1- and 5-year survival, according to Kaplan-Meier, was 80% and 70% in the left ventricle assist device group, compared to 80% and 73%, respectively, in the non-left ventricle assist device group (Log-rank test: p = 0.945).

CONCLUSION

Our results indicate that patients undergoing heart transplantation from left ventricle assist devices suffer significantly more from intraoperative and post-operative complications; however, only insignificant cardiac allograft vasculopathy progression and survival differences between the two groups were observed.

Platelet adhesion emulation: A novel method for estimating the device thrombosis potential of a ventricular assist device

Device thrombosis inside ventricular assist devices remains a limitation to their long-term clinical use. Thrombosis potential exists in almost all ventricular assist devices because the device-induced high shear stress and vortices can activate platelets, which then aggregate and adhere to the surfaces inside the ventricular assist device. To decrease the device thrombosis potential of long-term use of ventricular assist devices, a methodology entitled platelet adhesion emulation for predicting the thrombosis potential and thrombosis position inside the ventricular assist devices is developed. The platelet adhesion emulation methodology combines numerical simulations with in vitro experiments by correlating the structure of the flow passage components within the ventricular assist device with the platelet adhesion to estimate the thrombosis potential and location, with the goal of developing ventricular assist devices with optimized antithrombotic performance. Platelet adhesion emulation is aimed at decreasing the device thrombus potential of ventricular assist devices. The platelet adhesion emulation effectiveness is validated by simulating and testing an axial left ventricular assist device. The blood velocity relative to the surfaces of the flow passage components is calculated to estimate the platelet adhesion potential, indicating the probability of thrombus formation on the surfaces. Platelet adhesion emulation experiments conducted in a mock circulation loop with pump prototypes show the distribution of platelet adhesion on the surfaces. This methodology of emulating the device thrombosis distribution indicates the potential for improving the component structure and reducing the device thrombosis of ventricular assist devices.

Numerical investigation of the influence of a bearing/shaft structure in an axial blood pump on the potential for device thrombosis

Adverse events caused by flow-induced thrombus formation around the bearing/shaft of an axial blood pump remain a serious problem for axial blood pumps. Moreover, excessive anticoagulation with thrombosis around the bearing potentially increases the risk of postoperative gastrointestinal bleeding. The purpose of this study is to analyze the influence of the bearing structure on the thrombosis potential of an axial blood pump. The bearing/shaft structure was embedded into an axial blood pump numerical model. The numerical simulation and analysis are focused on the low wall shear stresses, recirculation, and residence time close to the bearing region to evaluate the potential for thrombosis around the bearing. Then, the flow field near the blood pump bearing was tested via in vitro particle image velocimetry experiments to verify the numerical results. The simulation results showed that after embedding the bearing/shaft structure a recirculation zone appeared in the outlet guide vane bearing/shaft region, the residence time increased 11-fold in comparison to the pump without the bearing/shaft structure, the scalar shear stress in the shaft surface was less than 7.8 Pa, and the stress accumulation was less than 0.10 Pa s. The numerical results showed that platelets that flow through the bearing region are exposed to significantly lower wall shear stress and a longer residence time, leading to activated platelet adhesion. The reduced stress accumulation and increased time in the bearing region lead to increased platelet activation.

Noteworthy Literature Published in 2017 for Thoracic Transplantation Anesthesiologists

Thoracic organ transplantation constitutes a significant proportion of all transplant procedures. Thoracic solid organ transplantation continues to be a burgeoning field of research. This article presents a review of remarkable literature published in 2017 regarding perioperative issues pertinent to the thoracic transplant anesthesiologists.

Cannula and Pump Positions Are Associated With Left Ventricular Unloading and Clinical Outcome in Patients With HeartWare Left Ventricular Assist Device

BACKGROUND

Cannula and pump positions are associated with clinical outcomes such as device thrombosis in patients with HeartMate II; however, clinical implications of HVAD (HeartWare International, Framingham, Massachusetts) cannula position are unknown. This study aims to assess the relationship among cannula position, left ventricular (LV) unloading, and patient prognosis.

METHODS AND RESULTS

Twenty-seven HVAD patients (60.0 ± 12.6 years of age and 19 males [70%]) underwent ramp test. Device position was quantified from chest X-ray parameters obtained at the time of the hemodyamic ramp test: (1) cannula coronal angle, (2) pump depth, (3) cannula sagittal angle, and (4) pump area. Lower cannula coronal angle was associated with LV unloading (as measured by smaller LV diastolic dimension and lower pulmonary capillary wedge pressure). Smaller pump area was associated with LV dynamic unloading, as assessed by steeper negative slopes of LV diastolic dimension and pulmonary capillary wedge pressure during incremental rotational speed change. Cannula coronal angle ≤65° was associated with reduced heart failure readmission rate (hazard ratio, 10.33; P = .007 by log-rank test).

CONCLUSION

HVAD cannula and pump positions are associated with LV unloading and improved clinical outcomes. Prospective studies evaluating surgical techniques to ensure optimal device positioning and its effects on clinical outcomes are warranted.

Noteworthy Literature Published in 2016 for Thoracic Organ Transplantation Anesthesiologists

This article is first in the series to review the published literature on perioperative issues in patients undergoing thoracic solid organ transplantations. We present recent literature from 2016 on preoperative considerations, organ preservation, intraoperative anesthesia management, surgical techniques, postoperative complications, and the impact of perioperative management on short- and long-term outcomes that are pertinent to thoracic transplantation anesthesiologists.