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.

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.

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.

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.

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.

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.

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.

Clinical application of BVS5000 left ventricular assist device in heart failure patients

Background Mechanical ventricular assistance is an important therapeutic method for severe heart failure patients. A variety of ventricular assist devices have been designed for use, The purpose of this report was to describe the experience of using Abiomed BVS5000 as a means of left ventricular support as a clinical treatment for heart failure patients. Methods From February 2004 to April 2006, 12 male patients were supported with Abiomed BVS5000 left ventricular assist device （LVAD） at Fu Wai Hospital. The average age was （55.2±9.6） years （range 39 to 68 years）. The mean body surface area was （1.76±0.1） m^2 （range 1.6 to 1.9 m^2 ）. Devices were inserted for post-cardiotomy shock after coronary artery bypass graft in 11 patients （92%） and in 1 dilated cardiomyopathy patient for acute cardiogenic shock. Modified cannulation methods by inserting the arterial cannulae in femoral artery and inserting the venous cannula in left atrium through a segment of bovine jugular vein were used in 7 patients. In this way, the device could be taken off without re-sternotomy when support was finished. A comparison was made between the modified method and routine left atrium-to-ascending aorta cannulating method. Results The median duration of support was 5 （3-43） days, with support flow rate of 3.8-4.5 L/min. There were 9 （75%） patients weaned from support and 8 （67%） patients discharged from the hospital. Four （33%） patients were dead. The most common morbidity was adverse neurological events. There is no statistical difference between modified and routine method on average in BVS5000 support duration, in assisted flow rate, in mechanical ventilation duration, in the intensive care unit stay and thoracic drainage. Conclusions The Abiomed BVS5000 is valuable to support patients with acute cardiogenic shock for short-term use. By the modified cannulating method, the weaning procedure can be effectively simplified. Optimization of inserting indication remains challenging and attributes to a successful assist program.

Investigation on hydrodynamic lubrication of bearings in a left ventricular assisted device

Formations of clots were found inside the hydrodynamic bearings of the left ventricular assisted devices (LVADs) and caused tremendous risks to the long-term use of these devices. For the hydrodynamic bearings used in the LVAD, not only the lubrication status but also the motion of the blood cells in the bearing will take great effect on the performance of the device. Based on the analysis of the hydrodynamic pressures distribution and the flowing trajectory of red blood cells in the lubrication film, the bearing is designed in a region where enough hydrodynamic pressure is generated to float the rotor to reduce the wear, and the entrainment of red blood cells in the gap of the bearing can be prevented to avoid the formation of clots.

Perioperative Nursing Management of an Animal Model of Axial Flow Blood Pump Implantation

This study aimed to explore the characteristics of perioperative nursing of experimental goats using self-made axial-flow blood pump implantation and provided theoretical nursing knowledge and practice-based evidence for the clinical application of domestically manufactured artificial cardiac pumps. Methods: Seven experimental goats were used in this study, three for pre-testing and four for the formal experiments. According to the surgical requirements for axial-flow blood pump implantation into the cardiac apex, we creatively designed and made a series of highly practical animal surgical instruments including a composite disassemblable bed for experimental animal transferring and monitoring, a multifunctional animal surgery bed, and portable medical supporting equipment. We also applied for two national invention patents and one utility model patent. Active measures were taken to ensure careful preparation before surgery, close collaboration during surgery, and effective management of complications after surgery. Results: Two of the four experimental goats died during surgery because of a massive hemorrhage caused by distal anastomotic failure and air embolism-induced cardiac arrest caused by air leakage from the outlet into the heart due to poor connection of the auxiliary pressure tap (used to measure left ventricular pressure). The mean survival time of the remaining three experimental goats was 22.7 hours. Conclusion: This study was the first to systematically and comprehensively investigate the perioperative nursing management of axial-flow blood pump implantation using animal models. These findings could greatly promote further clinical applied nursing research of self-made artificial cardiac pump implantation in experimental goats.

Long-term assist device patients admitted to ICU: Tips and pitfalls

Left ventricular assist device(LVAD)therapy is well-established in the treatment of end-stage cardiac failure.Indications are bridge to transplant(BTT),bridge to candidacy(BTC),bridge to recovery(BTR),and destination therapy(DT).The durability and adverse event(AE)rate of LVADs have improved over the years.However,due to donor shortage,the duration of support in the BTT population has increased tremendously;similarly,DT patients are on the device for a long time.Consequently,the number of readmissions of long-term LVAD patients has increased.In cases of severe AEs,intensive care unit(ICU)treatment can be necessary.Infectious complications are the most common AE.Furthermore,embolic or hemorrhagic strokes can occur due to foreign surfaces,acquired von Willebrand syndrome,and anticoagulation treatment.Another consequence of the coagulative status,in combination with the continuous flow,are gastrointestinal bleeding events.Moreover,in most patients,an isolated LVAD is implanted,and this involves the risk of late right heart failure.Adjustment of pump speed and optimization of the volume status can help solve this issue.Malignant arrhythmias,pre-existing or de novo after LVAD implantation,can be a life-threatening AE.Antiarrhythmic medical therapy or ablation are potential treatment options.As for specific LVADs,the Medtronic HeartWare TM ventricular assist device(HVAD)is not manufactured and distributed currently;however,4000 patients are still on the device.Pump thrombosis can occur,wherein thrombolytic therapy is the first-line treatment option.Additionally,the HVAD can fail to restart after controller exchange due to technical issues,and precautions must be taken.The Momentum 3 trial showed superior survival without pump exchange or disabling stroke in patients treated with the HeartMate 3■(HM3;Abbott,Abbott Park,IL,USA)device in comparison to the HeartMate II(HMII).However,in a few cases,a twisted graft or bio debris formation between the outflow graft and bend relief could be observed,causing outflow graft obstruction.Patients on LVADs are still heart failure patients,in many cases with comorbidities.Therefore,many situations can occur requiring ICU treatment.Ethical aspects should always be the focus when taking care of these patients.

Anesthetic management for the patients with cardiac transplant

With the advancement of medical technique and application of the new immunosuppressant agents, cardiac transplantation has become an effective treatment for end-stage heart disease caused by different reasons. The orthotopic procedure has been performed in many countries nowadays. Whether it is successful or not mainly depends on harvesting the denoted heart, operative technique and perioperative management.

Initial hydrodynamic study on a new intraaortic axial flow pump: Dynamic aortic valve

Rotary blood pumps have been researched as implantableventricular assist devices for years. To further reduce the complex of implanted axial pumps, the authors proposed a new concept of intraaortic axial pump, termed previously as "dynamic aortic valve (DAV)". Instead of being driven by an intraaortic micro-electric motor, it was powered by a magnetic field from outside of body. To ensure the perfusion of coronary artery, the axial flow pump is to be implanted in the position of aortic valve. It could serve as either a blood pump or a mechanical valve depending on the power input. This research tested the feasibility of the new concept in model study. A column, made from permanent magnet, is jointed to an impeller in a concentric way to form a "rotor-impeller". Supported by a hanging shaft cantilevered in the center of a rigid cage, the rotor-impeller can be turned by the magnetic field in the surrounding space. In the present prototype, the rotor is 8 mm in diameter and 15 mm in length, the impeller has 3 vanes with an outer diameter of 18 mm. The supporting cage is 22 mm in outer diameter and 20 mm in length. When tested, the DAV prototype is inserted into the tube of a mock circuit. The alternative magnetic field is produced by a rotating magnet placed side by side with the rotor-impeller at a distance of 30 mm. Once the alternative magnetic field is presented in the surrounding space, the DAV starts to turn, leading to a pressure difference and liquid flow in the tube. The flow rate or pressure difference is proportioned to rotary speed. At the maximal output of hydraulic power, the flow rate reached 5 L/min against an afterload of 100 mmHg. The maximal pressure difference generated by DAV at a rotation rate of 12600 r/min was 147 mmHg. The preliminary results demonstrated the feasibility of "DAV", further research on this concept is justifiable.