Resilience-Oriented Approach to the Control of Ventricular Assist Devices

Context: Advanced heart failure (AHF) poses a global challenge, where heart transplantation is a treatment option but limited by donor scarcity. Proposal: This study aims to enhance the performance of ventricular assist devices (VADs) in the face of adverse events (AEs) using a resilience-based approach. The objective is to develop a method for integrating resilience attributes into VAD control systems, employing dynamic risk analysis and control strategies. Results: The outcomes include a resilient control architecture enabling anticipatory, regenerative, and degenerative actions in response to AEs. A method of applied resilience (MAR) based on dynamic risk management and resilience attribute analysis was proposed. Conclusion: Dynamic integration between medical and technical teams allows continuous adaptation of control systems to meet patient needs over time, improving reliability, safety, and effectiveness of VADs, with potential positive impact on the health of heart failure patients.

Treatment of gastrointestinal bleeding in left ventricular assist devices:A comprehensive review

Left ventricular assist devices(LVAD)are increasingly become common as life prolonging therapy in patients with advanced heart failure.Current devices are now used as definitive treatment in some patients given the improved durability of continuous flow pumps.Unfortunately,continuous flow LVADs are fraught with complications such as gastrointestinal(GI)bleeding that are primarily attributed to the formation of arteriovenous malformations.With frequent GI bleeding,antiplatelet and anticoagulation therapies are usually discontinued increasing the risk of life-threatening events.Small bowel bleeds account for 15%as the source and patients often undergo multiple endoscopic procedures.Treatment strategies include resuscitative measures and endoscopic therapies.Medical treatment is with octreotide.Novel treatment options include thalidomide,angiotensin converting enzyme inhibitors/angiotensinⅡreceptor blockers,estrogen-based hormonal therapies,doxycycline,desmopressin and bevacizumab.Current research has explored the mechanism of frequent GI bleeds in this population,including destruction of von Willebrand factor,upregulation of tissue factor,vascular endothelial growth factor,tumor necrosis factor-α,tumor growth factor-β,and angiopoetin-2,and downregulation of angiopoetin-1.In addition,healthcare resource utilization is only increasing in this patient population with higher admissions,readmissions,blood product utilization,and endoscopy.While some of the novel endoscopic and medical therapies for LVAD bleeds are still in their development stages,these tools will yet be crucial as the number of LVAD placements will likely only increase in the coming years.

Comprehensive review of hemolysis in ventricular assist devices

Ventricular assist devices(VADs)have played an important role in altering the natural history of end-stage heart failure.Low-grade hemolysis has been traditionally described in patients with VADs,indicating effective device functionality.However,clinically significant hemolysis could be crucial in terms of prognosis,calling for prompt therapeutic actions.The absence of solid and widely approved diagnostic criteria for clinically significant hemolysis,render the utilization of hemolysis laboratory markers challenging.Hemolysis incidence varies(5%-18%)depending on definition and among different VAD generations,being slightly higher in continuous-flow devices than in pulsatile devices.Increased shear stress of red blood cells and underlying device thrombosis appear to be the main pathogenetic pathways.No certain algorithm is available for the management of hemolysis in patients with VADs,while close clinical and laboratory monitoring remains the cornerstone of management.Imaging examinations such as echocardiography ramp test or computed tomography scan could play a role in revealing the underlying cause.Treatment should be strictly personalized,including either pharmacological(antithrombotic treatment)or surgical interventions.

Utility and correlation of known anticoagulation parameters in the management of pediatric ventricular assist devices

AIM To assess utility and correlation of known anticoagulation parameters in the management of pediatric ventricular assist device(VAD). METHODS Retrospective study of pediatric patients supported with a Berlin EXCOR VAD at a single pediatric tertiary care center during a single year.RESULTS We demonstrated associations between activated thro-mboplastin time(a PTT) and R-thromboelastography(R-TEG) values(rs = 0.65, P < 0.001) and between anti-Xa assay and R-TEG values(rs = 0.54, P < 0.001). The strongest correlation was seen between a PTT and anti-Xa assays(rs = 0.71, P < 0.001). There was also a statistically significant correlation between platelet counts and the maximum amplitude of TEG(rs = 0.71, P < 0.001). Importantly, there was no association between dose of unfractionated heparin and either measure of anticoagulation(a PTT, anti-Xa or R-TEG value). CONCLUSION This study suggests that while there is strong correlation between a PTT, anti-Xa assay and R-TEG values for patients requiring VAD support, there is a lack of relevant correlation between heparin dose and degree of effect. This raises concern as various guidelines continue to recommend using these parameters to titrate heparin therapy.

To ventricular assist devices or not:When is implantation of a ventricular assist device appropriate in advanced ambulatory heart failure?

Advanced heart failure has been traditionally treated via either heart transplantation,continuous inotropes,consideration for hospice and more recently via left ventricular assist devices(LVAD).Heart transplantation has been limited by organ availability and the futility of other options has thrust LVAD therapy into the mainstream of therapy for end stage heart failure.Improvements in technology and survival combined with improvements in the quality of life have made LVADs a viable option for many patients suffering from heart failure.The question of when to implant these devices in those patients with advanced,yet still ambulatory heart failure remains a controversial topic.We discuss the current state of LVAD therapy and the risk vs benefit of these devices in the treatment of heart failure.

Evolvement of left ventricular assist device： the implications on heart failure management

Heart failure （HF） is a potentially fatal disease that affects increasing number of people worldwide. Although heart transplant is the ＂gold standard＂ therapy for HF, due to the limited availability of organs, many patients died when waiting for the transplant. Left ventricular assist device （LVAD）, as a mechanical circulatory support, has become a new light for patients with HF. With the technical advancements, LVADs work not only as a bridge to transplant, but also assist heart recovery and even as a destination therapy in long-term treatment. This observation paper reviewed the development of LVAD and its clinical roles. The challenges and possible solutions in nursing care for pa- tients with LVAD at different stage of implantation were discussed. The healthcare professionals could obtain a better understanding about the LVAD treatment for HF patients.

Optimal timing of same-admission orthotopic heart transplantation after left ventricular assist device implantation

AIM To investigate the impact of timing of same-admission orthotopic heart transplant(OHT) after left ventricular assist device(LVAD) implantation on in-hospital mortality and post-transplant length of stay.METHODS Using data from the Nationwide Inpatient Sample from 1998 to 2011, we identified patients 18 years of age or older who underwent implantation of a LVAD and for whom the procedure date was available. We calculated in-hospital mortality for those patients who underwent OHT during the same admission as a function of time from LVAD to OHT, adjusting for age, sex, race, household income, and number of comorbid diagnoses. Finally, we analyzed the effect of time to OHT after LVAD implantation on the length of hospital stay post-transplant.RESULTS Two thousand and two hundred patients underwent implantation of a LVAD in this cohort. One hundred and sixty-four(7.5%) patients also underwent OHT duringthe same admission, which occurred on average 32 d(IQR 7.75-66 d) after LVAD implantation. Of patients who underwent OHT, patients who underwent transplantation within 7 d of LVAD implantation("early") experienced increased in-hospital mortality(26.8% vs 12.2%, P = 0.0483) compared to patients who underwent transplant after 8 d("late"). There was no statistically significant difference in age, sex, race, household income, or number of comorbid diagnoses between the early and late groups. Post-transplant length of stay after LVAD implantation was also not significantly different between patients who underwent early vs late OHT. CONCLUSION In this cohort of patients who received LVADs, the rate of in-hospital mortality after OHT was lower for patients who underwent late OHT(at least 8 d after LVAD implantation) compared to patients who underwent early OHT. Delayed timing of OHT after LVAD implantation did not correlate with longer hospital stays post-transplant.

EXPERIMENTAL STUDY OF RIGHT VENTRICULAR ASSIST IN ACUTE RIGHT VENTRICULAR FAILING

The efficacy of right atrial-pulmonary artery (RA-PA) bypass during acute right ventricular failure (RVF) produced by pulmonary artery constriction in dogs was examined in this study Control group (n=7) was supported with conventional volume loading and inotropic therapy. In the experimental animals (n=8) , RA-PA bypass was initiated 5 min. after the onset of severe RVF. Three control animals died from refractory ventricular fibrillation within one hour of RVF. No animals in the experimental group died within two hours of RA-PA bypass , but the histological study of the lungs in these animals demonstrated peribronchial , perivascular and intraalveolar hemorrhage. Light microscopic and electron microscopic examination of the myocardial specimens of the right ventricular free wall displayed the myocardial structures and ultrastructures were maintained effectively with RA-PA bypass while irreversible myocardial injuries occurred in the control animals after two hours of RVF with conventional therapy. During the 2 hours of RA-PA bypass, the hemodynamic indices were also maintained better when compared to the control animals. It may be concluded , a roller pump right ventricular assist device effectively unloads the acute failing right ventricle, maintains systemic cardiac output , and significantly reverses the myocardial ischemia during right ventricular failure, but RA-PA bypass may induce pulmonary hypertension due to increased pulmonary vascular resistance secondary to pulmonary edema and interstitial hemorrhage.

Computational fluid dynamics of left ventricular assist device under unsteady flow

Left ventricular assist device( LVAD) in this study is a mechanical tool that is used to support blood flow in the patient with heart disease. It supports left ventricle by building up the pressure to the pump outlet connected to the aorta. This pump was designed based on the magnetic driven centrifugal pump with a unique small washout hole constructed inside the impeller to generate the washout flow passage to prevent the stagnation at the region underneath and around the rotor. Computational fluid dynamics( CFD) was adopted in this study to assess the performance and optimize the design to avoid recirculation and high shear stress which is the main cause of stagnation and blood damage. Transient simulation was used for this study due to the asymmetric design of the washout hole and the complication of the bottom support of the impeller that has a risk of thrombosis,also,it was used to predict the variation of hydraulic performance caused by the rotation of the impeller and pulsed flow at the pump inlet. The simulation results show no excessive stress and no recirculation observed within the computational domain; in addition,the research result also provides information for further optimization and development to the pump.

Subacute gastric perforation caused by a left ventricular assist device

This case report describes a rare complication of a left ventricular assist device (LVAD). A patient with ischemic cardiomyopathy had an LVAD placed due to intractable congestive heart failure following a large anterior myocardial infarction. The patient developed chronic bacteremia and multiple septic episodes. A gastric endoscopy revealed perforation of the anterior wall of the stomach by the LVAD. Gastric acid related erosions were present on the metallic surface suggesting prolonged exposure. This is the second case report of this rare complication and the first case report of a subacute course.

Effects of medically generated electromagnetic interference from medical devices on cardiac implantable electronic devices: A review

As cardiac implantable electronic devices(CIED)become more prevalent,it is important to acknowledge potential electromagnetic interference(EMI)from other sources,such as internal and external electronic devices and procedures and its effect on these devices.EMI from other sources can potentially inhibit pacing and trigger shocks in permanent pacemakers(PPM)and implantable cardioverter defibrillators(ICD),respectively.This review analyzes potential EMI amongst CIED and left ventricular assist device,deep brain stimulators,spinal cord stimulators,transcutaneous electrical nerve stimulators,and throughout an array of procedures,such as endoscopy,bronchoscopy,and procedures involving electrocautery.Although there is evidence to support EMI from internal and external devices and during procedures,there is a lack of large multicenter studies,and,as a result,current management guidelines are based primarily on expert opinion and anecdotal experience.We aim to provide a general overview of PPM/ICD function,review documented EMI effect on these devices,and acknowledge current management of CIED interference.

Simultaneous ramp right heart catheterization and echocardiography in a Reliant Heart left ventricular assist device

Many clinicians caring for patients with continuous flow left ventricular assist devices(CF-LVAD) use ramp right heart catheterization(RHC) studies to optimize pump speed and also to troubleshoot CF-LVAD malfunction. An investigational device,the Reliant Heart Heart Assist 5(Houston,TX),provides the added benefit of an ultrasonic flow probe on the outflow graft that directly measures flow through the CF-LVAD. We performed a simultaneous ramp RHC and echocardiogram on a patient who received the above CF-LVAD to optimize pump parameters and investigate elevated flow through the CF-LVAD as measured by the flow probe. We found that the patient's hemodynamics were optimized at their baseline pump speed,and that the measured cardiac output via the Fick principle was lower than that measured by the flow probe. Right heart catheterization may be useful to investigate discrepancies between flow measured by a CF-LVAD and a patient's clinical presentation,particularly in investigational devices where little clinical experience exists. More data is needed to elucidate the correlation between the flow measured by an ultrasonic probe and cardiac output as measured by RHC.

Cardiac rehabilitation in a heart failure patient after left ventricular assist device insertion and subsequent heart transplantation:A case report

BACKGROUND Insertion of a left ventricular assist device(LVAD)and heart transplantation(HT)improve the survival of patients with heart failure.In addition,cardiac rehabilitation(CR)further increases the functional capacity.This case report describes a successful case of CR after LVAD insertion and subsequent HT.CASE SUMMARY In the present case,during the LVAD insertion period,peak oxygen consumption(VO2)increased by 12.16%after CR.HT was performed 7 mo after the LVAD insertion,and the patient participated in phases I and II CR.The peak VO2 increased from 17.24 to 22.29 m L/kg/min.This improvement was more significant than that reported in previous studies on CR after LVAD insertion or HT.The patient’s quality of life also improved.The total average score of the short form-36 questionnaire increased from 29.5 points at admission to 53.3 points 9 mo after HT.CONCLUSION A tailored CR program after LVAD insertion or HT may improve the patients’quality of life and increase survival.

Effects of left ventricular assist device on pulmonary functions and pulmonary hemodynamics:A meta-analysis

BACKGROUND Given current evidence,the effect of left ventricular assist device(LVAD)implantation on pulmonary function tests remains controversial.AIM To better understand the factors contributing to the changes seen on pulmonary function testing and the correlation with pulmonary hemodynamics after LVAD implantation.METHODS Electronic databases were queried to identify relevant articles.The summary effect size was estimated as a difference of overall means and standard deviation on a random-effects model.RESULTS A total of four studies comprising 219 patients were included.The overall mean forced expiratory volume in one second(FEV1),forced vital capacity(FVC)and diffusion lung capacity of carbon monoxide(DLCO)after LVAD implantation were significantly lower by 0.23 L(95%CI:0.11-0.34,P=00002),0.18 L(95%CI:0.03-0.34,P=0.02),and 3.16 mmol/min(95%CI:2.17-4.14,P<0.00001),respectively.The net post-LVAD mean value of the cardiac index was significantly higher by 0.49 L/min/m2(95%CI:0.31-0.66,P<0.00001)compared to pre-LVAD value.The pulmonary capillary wedge pressure and pulmonary vascular resistance were significantly reduced after LVAD implantation by 8.56 mmHg(95%CI:3.78-13.35,P=0.0004),and 0.83 Woods U(95%CI:0.11-1.55,P=0.02),respectively.There was no significant difference observed in the right atrial pressure after LVAD implantation(0.61 mmHg,95%CI:-2.00 to 3.32,P=0.65).Overall findings appear to be driven by studies using HeartMateII devices.CONCLUSION LVAD implantation might be associated with a significant reduction of the spirometric measures,including FEV1,FVC,and DLCO,and an overall improvement of pulmonary hemodynamics.

Right Ventricular Failure Following Left Ventricular Assist Device Implantation

Left ventricular assist device (LVAD) is being used increasingly in recent years for end stage heart failure as a bridge to transplant (BTT) and also as a destination therapy (DT). Patients with end stage heart failure have some degree of elevated pulmonary capillary wedge pressure, causing right ventricular hypertrophy which in due course leads to decreased dilatation of the RV and fall in cardiac output & severe tricuspid regurgitation (TR) presenting with features of RV failure (RVF). Implantation of LVAD improves left heart function at the cost of right ventricular output with an incidence of 25%-30%. RVF may lead to impaired LVAD flow, difficulty in weaning from cardio-pulmonary bypass (CPB), decreased tissue perfusion and multi-organ failure. In this article we comprehended the pathophysiology leading to RVF post LVAD implantation and its preoperative predictors and the various treatment modalities for managing RVF post LVAD implantation.

Recovery after acute kidney injury requiring kidney replacement therapy in patients with left ventricular assist device: A metaanalysis

BACKGROUND Acute kidney injury(AKI)is a common and severe complication after left ventricular assist device(LVAD)implantation with an incidence of 37%;13%of which require kidney replacement therapy(KRT).Severe AKI requiring KRT(AKI-KRT)in LVAD patients is associated with high short and long-term mortality compared with AKI without KRT.While kidney function recovery is associated with better outcomes,its incidence is unclear among LVAD patients with severe AKI requiring KRT.AIM To identify studies evaluating the recovery rates from severe AKI-KRT after LVAD placement,which is defined by regained kidney function resulting in the discontinuation of KRT.Random-effects and generic inverse variance method of DerSimonian-Laird were used to combine the effect estimates obtained from individual studies.METHODS A total of 268 patients from 14 cohort studies that reported severe AKI-KRT after LVAD were included.Follow-up time ranged anywhere from two weeks of LVAD implantation to 12 mo.Kidney recovery occurred in 78%of enrollees at the time of hospital discharge or within 30 d.Overall,the pooled estimated AKI recovery rate among patients with severe AKI-KRT was 50.5%(95%CI:34.0%-67.0%)at 12 mo follow up.Majority(85%)of patients used continuous-flow LVAD.While the data on pulsatile-flow LVAD was limited,subgroup analysis of continuous-flow LVAD demonstrated that pooled estimated AKI recovery rate among patients with severe AKI-KRT was 52.1%(95%CI:36.8%-67.0%).Metaregression analysis did not show a significant association between study year and AKI recovery rate(P=0.08).There was no publication bias as assessed by the funnel plot and Egger's regression asymmetry test in all analyses.RESULTS A total of 268 patients from 14 cohort studies that reported severe AKI-KRT after LVAD were included.Follow-up time ranged anywhere from two weeks of LVAD implantation to 12 mo.Kidney recovery occurred in 78%of enrollees at the time of hospital discharge or within 30 d.Overall,the pooled estimated AKI recovery rate among patients with severe AKI-KRT was 50.5%(95%CI:34.0%-67.0%)at 12 mo follow up.Majority(85%)of patients used continuous-flow LVAD.While the data on pulsatile-flow LVAD was limited,subgroup analysis of continuous-flow LVAD demonstrated that pooled estimated AKI recovery rate among patients with severe AKI-KRT was 52.1%(95%CI:36.8%-67.0%).Metaregression analysis did not show a significant association between study year and AKI recovery rate(P=0.08).There was no publication bias as assessed by the funnel plot and Egger's regression asymmetry test in all analyses.CONCLUSION Recovery from severe AKI-KRT after LVAD occurs approximately 50.5%,and it has not significantly changed over the years despite advances in medicine.

Anesthesia management of a patient undergoing implantation of a left ventricular assist system:A case report

BACKGROUND Heart failure is generally regarded as a progressive and irreversible medical condition.The EVAHEART is an implantable left ventricular assist system.CASE SUMMARY We report the anesthesia management of a 56-year-old male patient with dilated cardiomyopathy undergoing an EVAHEART implantation.Transesophageal echocardiography is crucial to ensure the correct positioning of the device and the proper aortic valve outflow.Because the continuous blood flow device functions best under low systemic and pulmonary vascular resistance,milrinone is the preferred drug.Our patient was accompanied by pulmonary hypertension,so during the operation,nitric oxide was used to reduce pulmonary artery pressure.CONCLUSION The cardiac output achieved by the patient with the assistance of EVAHEART can reach 4 L/min,which of course depends on the front load,rear load,and pump speed.

Heart and Lung Mechanical Assist Devices are Comprehensively Tested by the New Hybrid Simulators

Two applications of the hybrid simulators have been presented as examples: nonpulsatile VAD interaction with lumped parameters cardiovascular system numerical model and respirator interacting with the Dubois numerical model of obstructive lung diseases. The results of simulations showed how the tested assist devices change biological system - assist device characteristics in the course of heart or lungs diseases and how it influences pressure and flow in a particular point of cardiovascular or respiratory system numerical model.

Combined Application of Circulatory Assist Devices Following Cardiac Arrest in Patients after Cardiac Surgery

Objectives To evaluate retrospectively the potential benefits of combined utilization of various assisted circulation devices in cardiac arrest patients who did not respond to conventional cardiopulmonary cerebral resuscitation （CPCR）. Methods Assisted circulation devices, including emergency cardiopulmonary bypass （ECPB）, intra-aortic balloon pump （IABP）, and left ventricular assist device （LVAD）, were applied to 16 adult patients who had cardiac arrest 82 rain-56 h after open heart surgery and did not respond to 20 rain or longer conventional CPCR. ECPB was applied to 2 patients, ECPB plus IABP to 8 patients, ECPB plus IABP and LVAD to 6 patients. Results One patient recovered fully and one patient died. Of the other 14 patients, 13 resumed spontaneous cardiac rhythm and one did not; none of them could be weaned from ECPB. Further treatment of the 14 patients with combinations of assisted circulation devices enabled 6 patients to recover. One of the 7 recovered patients died of reoccurring cardiac arrest after 11 days; the other 6 were discharged in good condition and were followed up for 3-49 months （mean =22 months）. Of the 6 discharged patients one suffered cerebral embolism during LVAD treatment, resulting in mild limitation of mobility of the right limbs ; the other 5 never manifested any central nervous system complications. There was no late deaths giving a 37.5% （6/16） long-term survival rate. Conclusions ECPB could effectively reestablish blood circulation and oxygen supply, rectify acidosis, and improve internal milieu. The combined utilization of ECPB, IABP, and LVAD reduces the duration of ECPB, improves the incidence of recovery, and offers beneficial alternatives to refractory cardiac arrest patients.