Ventricular assist devices pdf

Bleeding : This is the most frequent complication after VAD implantation and coagulopathy is common. Minimizing CPB times, meticulous surgical technique, autologous blood transfusion, and normothermia are standard. Early re-exploration reduces the excessive use of blood and associated products, which risk transfusion-related lung injury. Platelet consumption via the device and the risk of spontaneous intracerebral haemorrhage translate into early platelet transfusion.

TEG and laboratory results guide blood products' administration. Tamponade : The impending signs of tamponade are decreasing flows on the VAD, increasing central venous pressure, reduced mean arterial pressure with escalation of inotropic support and metabolic acidosis with oliguria. It is corrected by immediate surgical decompression.

RV failure : The risks and implications of RV failure have been previously discussed. Fluid overload : Fluid overload can be due to massive transfusion of blood and blood products or mobilization of oedema fluid with higher cardiac outputs. Early haemofiltration is recommended with removal of fluid if cardiovascularly stable. Vasoplegia : This may be secondary to the use of phosphodiesterase inhibitors or systemic inflammatory response syndrome. Despite the risks to the RV and renal axis, high-dose norepinephrine and vasopressin may be required to optimize organ perfusion.

Haemodynamic instability : Post-LVAD insertion, the interventricular septum is entrained leftwards towards the inflow cannula when the ventricles are underfilled. This differs from septal deviation seen with RV failure or high pump speeds. TOE is crucial to determine the need for further fluid challenges and adjustment of pump speeds.

Gastrointestinal and hepatic dysfunction : First-generation VADS, in the intraperitoneal position produced frequent upper GI pressure symptoms on the stomach and intestines, but this is rarely seen with second- and third-generation devices.

Ileus is common and managed with prokinetics. Enteral feeding is advocated as soon as gut function is resumed. Liver dysfunction is common in patients with chronic heart failure. Close monitoring of liver enzymes and withdrawal of hepatotoxic drugs limits further damage.

Warfarin therapy should be monitored closely with impaired liver synthetic function. Infection : Antibiotic prophylaxis is continued according to hospital infection control policy.

Preoperative malnutrition and invasive support and also the VAD itself contribute to postoperative infections. Successful long-term VAD management depends on comprehensive care from a multidisciplinary team, including patient, family, and care workers, with education and support being key components of outpatient survival.

There are excellent outcomes for VAD patients who are managed in an outpatient capacity. Medical management includes INR optimization with warfarin varies by device, typically 1. Hypertension reduces VAD support and increases the risk of cerebral events and thus must be controlled. Aspirin is commonly prescribed for its anti-platelet action. Of these, spontaneous intracerebral haemorrhage is by far the most serious incidence 1—1.

Fluid balance can also be a challenge to avoid the risks of both fluid overload and dehydration Table 3. Preoperative optimization for VAD patients requiring non-cardiac surgery. Device management is vitally important. Specific peripherals and components exist for outpatient use. Components include system controller and battery packs with back-ups. Emergency power pack, power base unit, and accessories such as stabilization belt and holster belt are also included.

Patients must keep the backup controller, charged spare batteries, battery clips with cables, and emergency ID card with them at all times. System alerts and alarms must be learnt and appropriate actions be taken.

Meticulous percutaneous lead care and immobilization as well as exit site wound management can reduce the number of hospital readmissions and risk of further procedures. There is a wide range of user manual support and device documentation that families must be knowledgeable of.

There must be a h contact support network to cover all emergencies, questions, and technical support. Anaesthesia for non-cardiac procedures in VAD patients can be performed by general anaesthetists, with cardiac support from perfusionist or VAD nurse, preferably in a VAD centre. Patients may be from intensive care units but are often ambulatory and in good condition.

Table 3 highlights optimization of patients to ensure the safest passage through the perioperative period. Anticoagulation must be continued but balanced against the bleeding risk for the surgery proposed.

A possible solution is the titrated administration of fresh-frozen plasma without fully reversing anticoagulation plus the use of antifibrinolytics, for example, tranexamic acid. Strict aseptic technique and prophylactic antibiotics are required for all invasive procedures.

Invasive haemodynamic monitoring is not mandatory and may prove challenging, with arterial cannulation often necessitating ultrasound guidance in the absence of pulsatile flow. Central venous and pulmonary artery monitoring are warranted for surgery with large fluid shifts, as is TOE.

The RV needs meticulous attention to prevent sudden failure and must be supported. Bipolar electrocautery is unlikely to interfere with VAD operation. Drivelines and cannulae should be excluded from the surgical field as fluid contamination may lead to plastic degradation and device malfunction.

Effective teamwork is the key to successful outcome of these patients. Similar figures are seen post-myocardial infarction.

With VAD support, the heart can be volume offloaded, which limits deterioration in ventricular compliance from over-distension and reduces myocardial work. Reducing cardiac inflammation and sympathetic drive can prevent myocyte death and contractile dysfunction, promoting a return to normal cellular, electrical, neurohormonal and functional indices.

Reverse remodelling can be seen in chronic heart failure, with a chance for explantation but recovery after more than 2—3 months of VAD support is unlikely. Potential candidates for heart transplantation must be free from ventilatory support and potential recipients should meet all the usual selection criteria before transplantation is undertaken.

Cardiac transplantation with VAD in situ is a highly skilled procedure because of the complexity of cannulae positions and thus femoral or axillary CPB is often instituted. The same haemodynamic considerations of VAD implantation must be applied. Previous aprotinin use risks anaphylaxis on subsequent exposure.

Weaning VAD support for explantation requires assessment of residual ventricular function with minimal pump support. However, adequate reduction in pump flows for reliable native heart function is generally not possible, because of thrombus formation, thus explantation may fail. Design improvements in current VAD systems include totally implantable devices with transcutaneous energy transmission systems, which eliminate the need for a driveline insertion site and also designs allowing more acceptable side-effect profiles for thromboembolism, infection, and device failure.

In addition, there are two total artificial hearts in clinical use, which involve explantation of the native heart and replacement with the device. These are the CardioWest total artificial heart Syncardia Inc. The latter organization also produces the Impella Fig.

Further detail on these devices can be found on their respective websites www. The Impella circulatory support system placed through the aortic valve into the LV. Courtesy of Abiomed.

Finally, with more devices in production, there is a need for regulation. Google Scholar. Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation.

Close mobile search navigation Article Navigation. Volume This article was originally published in. History and classification. Patient selection. Anaesthesia for VAD insertion. Outpatient management. Anaesthesia for VAD patients. Recovery, weaning, and transplantation. The future. Declaration of interest. Ventricular assist devices.

Consultant in Cardiothoracic Anaesthesia. Tel: Fax: E-mail: p. Oxford Academic. Select Format Select format. Key points. Open in new tab Download slide. Pump mechanism. Type of support.

EU approvals. Weight g. Open in new tab. Table 2 Contraindications to VAD implantation. Table 3 Preoperative optimization for VAD patients requiring non-cardiac surgery. Extra-corporeal membrane oxygenation for treating severe cardiac and respiratory disease in adults: part 1—overview of extracorporeal membrane oxygenation. Google Scholar Crossref. Search ADS. Evaluation for a ventricular assist device: selecting the appropriate candidate.

Google Scholar PubMed. Relationship between renal function and left ventricular assist device use. Mechanical Circulatory Support Options for the Failing Right Ventricle Vary by Clinical Scenario Broadly defined as impaired RV filling or emptying in the absence of overt heart failure HF symptoms [1], RV dysfunction arises in the setting of concomitant left ventricular LV dysfunction, cardiomyopathies, lung disease, congenital heart dis- ease, PH, and hepatic failure [2, 3].

RV failure is typically characterized by a com- bination of low cardiac output and elevated central venous pressures CVP [4], and elevated RV end diastolic pressure EDP [3], underfilling of the LV and variable LVEDP, which clinically can manifest with systemic hypotension, fatigue, organ hypoperfusion, peripheral edema, and ascites [5].

The initial goals of management of the patient with RV failure are to optimize RV preload, contractility, and afterload [6]. Both hypervolemia and hypovolemia can challenge RV function and reduce cardiac output [6, 7]. Volume removal strategies include diuresis and ultrafiltration [3, 6]. Vasopressors such as norepinephrine and vasopressin can be used to maintain systemic pressures above pulmonary arterial pres- sures [6, 7].

Intravenous prostacyclins such as epoprostenol and treprostinil, as well as inhaled therapies such as nitric oxide iNO , iloprost, treprostinil, and even inhaled milrinone can reduce pulmonary vascular resistance PVR and RV afterload [7].

RVADs have traditionally been used to support the RV after acute myocardial infarction MI , myocarditis, or in the setting of post-cardiac surgery RV failure, such as after cardiotomy, in acute or chronic rejection after heart transplant, or after left ventricular assist device implantation LVAD [5—7].

Adverse events include thromboembolism, bleeding, and infection [3]. In select cases with appropriate therapy and support, RV dysfunction tends to be more reversible than left sided failure [2], permitting shorter duration of support. In patients with fulminant myocarditis, or after cardiotomy and LVAD implanta- tion, biventricular support is associated with worse outcomes, in part related to increased severity of disease with manifestations of multiorgan system dysfunction [3].

RV volume and wall stress increase postoperatively, as the LV is decompressed and the septum shifts leftward [4, 8]. In select patients, preemptive RVAD at the time of LVAD implantation has been shown to lead to better outcomes in terms of survival to dis- charge and 1 year survival [10]. In general, although virtually all patients have echocardiographic manifestations of RV dysfunction after LVAD implantation, the incidence of frank acute RV failure requiring device therapy has diminished with increasing use of continuous-flow devices as compared to pulsatile devices and with more aggressive medical therapy.

In those patients with PH and medically refractory RV failure, RVADs should be cautiously considered as there is at least a theoretical risk that the high flow and pressure generated in a remodeled pulmonary vascular bed may damage the pulmo- nary microcirculation [6] and lead to pulmonary hemorrhage [13]. Newer continuous-flow pumps may be safer in this regard.

ECLS, which incorporates an oxygenator blood pump, provides an alternative route to maintain cardiac output in a patient with a failing RV [7] while minimizing this risk [6]. This will be addressed in the ECLS section.

Thus, approaches to device therapy in the setting of chronic RV failure need to be distinct from those in the biventricular heart failure population and must be individualized based on the pathology. To meet these requirements, modifications to LVADs include outlet banding that increases resistance to flow [8], constrictors [14], lower pump speed [9], and the use of spacers to shorten inflow cannulas that are placed in the RV [14]. Such adaptations minimize the risk of pul- monary overcirculation, ventricular suction events, and thrombosis [8].

Inflow cannulas can be placed in either the right atrium RA or RV. RV cannula- tion maximizes RV unloading and reduces thrombus risk in severe dysfunction when there is little expectation of recovery [15]. However, it has been associated with higher scar formation and suction events compared to LV cannulation [8]. If temporary support is required, RA cannulation [8] might allow for higher rates of pulmonary valve opening, lower RV stroke work, and eventual RV recovery [15].

However, RA cannulation has also been used in pulsatile devices for longer support as a bridge to transplantation [8]. Both pulsatile and continuous-flow devices are currently used for RV support. Unlike pulsatile devices, continuous-flow assist devices empty the ventricle in both systolic and diastole [8]. They are smaller and contain fewer moving parts compared to pulsatile devices, with improved durability [8]. However, with decreased sensitiv- ity to preload, continuous-flow devices are more susceptible to suction events [8].

Concerns about infection risk, quality of life, hemolysis, and thrombosis have traditionally caused delays in referral for RV support [9] and are being addressed in more recent device designs. RVADs Vary in Terms of Implantation Technique, Flow Rates, and Complications MCSD are available in configurations ranging from extracorporeal, in which the pumps are external to the body and connected via cannulas that are tunneled out of the body, to implantable, in which the pumps are internal with only a control cable tunneled out of the body.

Technologies have evolved from pulsatile pumps that are either electrically or pneumatically driven to continuous-flow pumps that work via an inline turbine or a centrifugally oriented rotor. For support of the left ventricle, most pumps utilized today are continuous-flow pumps due to the smaller size and greater device longevity. However, many of these newer devices are not yet approved for RV or biventricular support. Extracorporeal Support Extracorporeal pumps are designed for short-term mechanical support.

Outcomes are gener- ally poor but better than would otherwise be expected in such cases of multiorgan failure and reflects the inherent high risk in this population [16—19]. It uses a magnetic suspended impeller [3, 9] Fig. The lack of bearings and seals minimizes friction and wear over time, thus reducing thermal damage to blood cells and lowering rates of hemolysis and thrombo- sis [16]. In a retrospective review of 29 patients, this pump was used for the treatment of RV failure after cardiotomy, transplantation, and LVAD implantation.

The mean duration of support was 8. Other adverse events include bleeding and thromboembolism [4]. Adapted with permission from Noon et al. Two configurations, one with outflow cannula in jugular vein left and the other with cannulae in the right heart and PA right.

Adapted with permission from CardiacAssist Inc. RVAD alone, and from 1 to 22 days for biventricular support. Only one RVAD patient was successfully weaned off support, and eight off biventricular support [17]. It is a large device that significantly restricts mobility and requires re-operation to remove [9].

The mean duration of support was 5. Fifty percent of patients receiving an RVAD and Percutaneously Implanted Extracorporeal Devices Both devices that are currently available for percutaneous implantation are indi- cated for short-term use, only.

A recent review [19] included 46 patients in whom the pVAD percutaneous and surgical approach was used for isolated RV as well as biven- tricular support. The mean duration of support was 4. Mean flow provided was 4.

It is a small device, with a diameter of 6. Advantages over the Centrimag and AB include a much smaller surface area exposed to blood [2], but the device relies on mechanical bearings which increase the risk of hemolysis and thrombosis [9].

As a result, it is presently approved for only 10 days of support [9]. Paracorporeal Support The options for paracorporeal support are comprised of pneumatic pulsatile devices.

As a bridge to transplantation and recov- ery [3, 9], it has been used for univentricular or biventricular support in over 4, patients since Fig. The AB Abiomed Inc. Duration of support can last up to months [16]. It can generate flows of up to 5—6. It can provide ambulatory support for up to 10 h [9], and has been demonstrated to provide biventricular support for up to days Fig. In a multicenter clinical trial of 29 patients, 15 received biventricular support using the IVAD.

Of the 14 bridge to transplant candidates, eight patients survived: one was weaned off support, and the other seven were transplanted [24].

With dual controllers, the Heartware system has been increasingly used as an alternative to the total artificial heart. Such dual support can provide successful physiologic levels of support and can alter flows to respond to changes in preload and afterload [26]. The duration of support has ranged from 7 days [26] to 4 months [25].

Complications include suc- tion events causing RA collapse [26]. With such biventricular support, RVAD flows have been set lower than systemic output, to avoid overloading the LV [8]. However, some investigators point out that adapting LVADs for RV support— specifically by reducing pump speeds beyond design specifications—increases thrombosis risk [8].

This miniature pump, which weighs 25 g, has a pressure gradient of 70—80 mmHg and can generate flows up to 4. The Circulite system is currently undergoing revision. Case reports of patients in florid cardiogenic shock have also described significantly elevated pulmonary pressures with and without associated pulmonary hemorrhage after RVAD implantation [13, 28].

Indeed, a computer simulation of the cardiovascular system in PAH and RV dysfunction incorporating a continuous-flow micropump showed that, while left sided filling and cardiac output improved with mechanical support, pulmonary arterial pressures and PCWP rose significantly [27].

However, the increase in pulmonary arterial pres- sures could be mitigated by setting lower RVAD flow rates with continued improve- ment of the systemic hemodynamics Fig. Such a system has been shown to be feasible in animal models. It includes both an axial flow pump and a low resistance gas exchanger, with the VAD cannula placed in the RA appendage and the outflow graft anastamosed to the PA. The device successfully provided hemodynamic support for 14 days in healthy sheep [29].

The circuit connects the PA and LA, and it does not yet incorporate a blood pump. The total impedance of the TAL in parallel with the native pulmonary circulation is less than the native system alone, thus decreasing pulmonary resistance and RV afterload.

More blood can be diverted to the TAL when the PA is banded, but this is at the expense of increased overall impedance and afterload. More recently, the successful use of a paracorporeal artificial lung PAL has been described in patients with PH and RV failure [31, 32]. The Novalung, which does not incorporate a blood pump, connects the PA and LA and has been demonstrated to generate flows of 3.

In a retrospective review of patients with PAH who were listed for lung transplantation, the incorporation of ECLS strategy with select patients receiving the Novalung, was shown to reduce mortality and time on the waiting list for transplantation [33]. In particular, transfer of patients to centers where cardiac support device therapies have been established in a timely fashion is advisable. ECLS may include traditional femoral [38] vs. Novalung Extracorporeal AV removal of CO2 can be accomplished with newer generations of low resistance membrane oxygenators Avecor, Quadrox-D, Novalung and smaller canulas [40].

While the Novalung does not require a pump for CO2 removal, a centrifugal pump is added into the circuit in hypoxic patients. Support for PAH patients who are dying from RV failure necessitates both support of the heart and gas exchange with effective RV unloading. Furthermore, the Novalung pulmonary artery to left atrium pumpless configuration effectively unloads the RV, bypasses the venous occlusion and may be the most effective support for the patient with PVOD.

The underlying pulmonary hypertension allows for sufficient generated force in the pulmonary artery to func- tion as the driving force for the system [41] along with a canula size which is a determining factor of flow.

The oxygenator circuit is placed in parallel to the native pulmonary circuit and overall PVR is thus decreased. There are institutions that pre- fer this mechanical support to that of long-term ECMO configurations although most often a temporary peripheral ECMO is placed for hemodynamic stabilization prior to LAD central implantation.

Earlier reports included parallel circuits to be assured of patency but device exchanges have been performed without problems for patients who are awaiting transplant for weeks. Countless contributions and collaborative efforts to deal with issues such as massive hemolysis, plasma leakage, artificial lung technology, membrane oxygenators, prolonged bypass support, and silicone mem- brane oxygenator have paved the wave to our modern use of it.

Robert Bartlett is responsible for bringing this technology to the neonates [42] and the onset of its burgeoning success in the neonatal ICU. The introduction of ECMO in adult patients has been much slower. Coincident with its development was the worldwide H1N1 pandemic and need for specialized centers which could provide ECMO support for primary respiratory failure in previously healthy patients.

In the current era, innova- tions in cannula design, next generation centrifugal pump technology, membrane construction, and now anticoagulation protocols have demonstrated the feasibility of prolonged support with a durable device. It was essential to eliminate the massive transfusion requirements and risks of hemorrhage previously inherent in adult ECMO support. Traditional concerns of femoral cannulation include both a decreased upper extremity and importantly cerebral oxygenation, for which we require monitoring of upper extremity arterial saturation and the need for antegrade superficial femoral perfusion catheter due to risk of limb ischemia and lack of mobi- lization.