HeartWare HVAD for the Treatment of Patients With Advanced Heart Failure Ineligible for Cardiac Transplantation: Results of the ENDURANCE Destination Therapy Trial

Management of hypertension in patients supported with continuous flow left ventricular assist devices

PURPOSE OF REVIEW

Hypertension remains one of the most common clinical problems leading to devastating postleft ventricular assist device (LVAD) implant complications. This study reviews the pathophysiology of hypertension in the setting of continuous flow LVAD support and provides an update on currently available antihypertensive therapies for LVAD patients.

RECENT FINDINGS

The true prevalence of hypertension in the LVAD population remains unknown. Effective blood pressure (BP) control and standardization of BP measurement are key to prevent suboptimal left ventricular unloading, pump malfunction and worsening aortic regurgitation. Angiotensin-converting enzyme inhibitors (ACEI), angiotensin receptor blockers (ARB), beta blockers and mineralocorticoid receptor antagonists (MRA) are the preferred antihypertensive agents because of their additional potential benefits, including optimization of haemodynamics, prevention of stroke, gastrointestinal bleed and in some patients myocardial recovery. Angiotensin receptor-neprilysin inhibition (ARNI) may be a well tolerated and effective therapy for BP control especially among CF-LVAD patients with resistant hypertension. Similarly, sodium glucose co-transporter 2 inhibitors (SGLT2i) should be considered in the absence of contraindications.

SUMMARY

Hypertension is very common post-LVAD implant. Heart failure guideline directed medical therapies, including ACEI, ARB, beta blockers and MRA, are the preferred antihypertensive agents to improve post-LVAD outcomes.

High Right Ventricular Afterload Is Associated with Impaired Exercise Tolerance in Patients with Left Ventricular Assist Devices

Patients with left ventricular assist device (LVAD) have poor exercise tolerance. We aimed to characterize relationship between right ventricular (RV) afterload and exercise capacity, RV reserve, and adaptation to load. Twelve well-compensated LVAD subjects underwent right heart catheterization at rest and during symptom-limited exercise. Cardiopulmonary exercise tests were also performed. Hemodynamics were compared with age- and sex-matched subjects with pulmonary arterial hypertension (PAH) and normal non-athletes. Hemodynamic changes were expressed as Δ(exercise - rest). At rest, LVAD subjects had normal biventricular pressures and cardiac output (CO). On exercise, despite similar increases in pulmonary artery wedge pressure (PAWP) between three groups, RV afterload increased only in LVAD cohort (pulmonary elastance [ΔEa] LVAD: 0.4, PAH: 0.1, normal: 0.1 mmHg/ml, p = 0.0024). This afterload increase coincided with the largest rise in right atrial pressure (RAP), lowest change in RV stroke work index, and smallest CO augmentation (ΔCO LVAD: 1.5, PAH: 4.3, normal: 5.7 L/min, p = 0.0014). Peak VO2 negatively correlated with RV afterload (Ea) (r = -0.8, p = 0.0101), while VE/VCO2 slope had the inverse correlation. During exercise, pulmonary artery pulsatility index worsened while RAP:PAWP ratio was unchanged in LVAD subjects. Well-compensated LVAD patients had poor RV reserve and adaptation to load on exercise compared with PAH and normal subjects.

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.

Left Ventricular Assist Devices (LVADS): History, Clinical Application and Complications

Congestive heart failure is a major cause of morbidity and mortality as well as a major health care cost in the developed world. Despite the introduction of highly effective heart failure medical therapies and simple devices such as cardiac resynchronization therapy that reduce mortality, improve cardiac function and quality of life, there remains a large number of patients who do not respond to these therapies or whose heart failure progresses despite optimal therapy. For these patients, cardiac transplantation is an option but is limited by donor availability as well as co-morbidities which may limit survival post-transplant. For these patients, left ventricular assist devices (LVADs) offer an alternative that can improve survival as well as exercise tolerance and quality of life. These devices have continued to improve as technology has improved with substantially improved durability of the devices and fewer post-implant complications. Pump thrombosis, stroke, gastrointestinal bleeding and arrhythmias post-implant have become less common with the newest devices, making destination therapy where ventricular assist device are implanted permanently in patients with advanced heart failure, a reality and an appropriate option for many patients. This may offer an opportunity for long term survival in many patients. As the first of the totally implantable devices are introduced and go to clinical trials, LVADs may be introduced that may truly be alternatives to cardiac transplantation in selected patients. Post-implant right ventricular failure remains a significant complication and better ways to identify patients at risk as well as to manage this complication must be developed.

Role of multimodality imaging in patients with left ventricular assist device

PURPOSE OF REVIEW

The article provides an overview of recent advances in imaging patients with a left ventricular assist device (LVAD).

RECENT FINDINGS

There is a growing population of patients with LVADs. LVADs improve survival in patients with end-stage heart failure, but are also associated with significant adverse outcomes. Imaging, particularly echocardiography, plays a critical role in patient selection and in predicting and detecting complications.

SUMMARY

Recent studies have illustrated links between imaging parameters with adverse outcomes, such as pump thrombosis, right ventricular failure, and continuous aortic regurgitation. Novel parameters and imaging techniques have been developed.

HVAD Waveform Analysis as a Noninvasive Marker of Pulmonary Capillary Wedge Pressure: A First Step Toward the Development of a Smart Left Ventricular Assist Device Pump

Flow waveforms are an important feature of the HVAD left ventricular assist device (LVAD) that provides information about HVAD function and patient hemodynamics. We assessed the properties of one specific aspect of the waveform, the slope of the ventricular filling phase (VFP), and its correlation with pulmonary capillary wedge pressure (PCWP). A total of 101 screenshots from the HVAD monitor and simultaneous hemodynamic measurements were obtained simultaneously during sequential stages of invasive hemodynamic ramp studies. Each screenshot was digitized (IGOR Pro, WaveMetrics Inc., Oswego, OR) and properties of the flow waveforms including instantaneous flow and rate of change of flow were analyzed. Ventricular filling phase slope (VFPS) was calculated for each screenshot and correlated to PCWP. Ventricular filling phase slope was significantly higher in patients with PCWP ≥ 18 mm Hg than in patients with PCWP < 18 mm Hg [6.25 (5.84-7.37) L/min/s vs. 3.27 (2.00-4.69) L/min/s, p ≤ 0.0001]. A VFPS threshold of 5.8 L/min/s predicted a PCWP ≥ 18 mm Hg with a sensitivity of 87% and specificity of 95% (AUC 0.95). Ventricular filling phase slope of the HVAD flow waveform is a novel noninvasive parameter that correlates with PCWP and can discriminate elevated versus normal or low PCWP. Automated reporting of this parameter may help clinical assessment and management of patients supported by an HVAD and may serve as the basis of a smart LVAD pump that can adapt in response to changes in a patient's physiology.

Palliative Care Clinicians Caring for Patients Before and After Continuous Flow-Left Ventricular Assist Device

Left ventricular assist devices (LVADs) are an available treatment option for carefully selected patients with advanced heart failure. Initially developed as a bridge to transplantation, LVADs are now also offered to patients ineligible for transplantation as destination therapy (DT). Individuals with a DT-LVAD will live the remainder of their lives with the device in place. Although survival and quality of life improve with LVADs compared with medical therapy, complications persist including bleeding, infection, and stroke. There has been increased emphasis on involving palliative care (PC) specialists in LVAD programs, specifically the DT-LVAD population, from the pre-implantation process through the end of life. Palliative care specialists are well poised to provide education, guidance, and support to patients, families, and clinicians throughout the LVAD journey. This article addresses the complexities of the LVAD population, describes key challenges faced by PC specialists, and discusses opportunities for building collaboration between PC specialists and LVAD teams.

Driveline Infection in Ventricular Assist Devices and Its Implication in the Present Era of Destination Therapy

Advances in mechanical circulatory support devices provided the technology to develop long-term, implantable left ventricular assist devices as bridge to transplant, destination therapy, and in a lesser group of patients, as bridge to recovery. Despite the benefits from this innovative therapy, with their increased use, many complications have been encountered, one of the most common being infections. With the driveline acting as a portal to the exterior environment, an infection involving this structure is the most frequent one. Because patients with destination therapy are expected to receive circulatory support for a longer period of time, we will focus this review on the risk factors, prevention, and treatment options for driveline infections.

Left Ventricular Assist Device Therapy for Destination Therapy: Is Less Invasive Surgery a Safe Alternative?

INTRODUCTION AND OBJECTIVES

The number of older patients with congestive heart failure has dramatically increased. Because of stagnating cardiac transplantation, there is a need for an alternative therapy, which would solve the problem of insufficient donor organ supply. Left ventricular assist devices (LVADs) have recently become more commonly used as destination therapy (DT). Assuming that older patients show a higher risk-profile for LVAD surgery, it is expected that the increasing use of less invasive surgery (LIS) LVAD implantation will improve postoperative outcomes. Thus, this study aimed to assess the outcomes of LIS-LVAD implantation in DT patients.

METHODS

We performed a prospective analysis of 2-year outcomes in 46 consecutive end-stage heart failure patients older than 60 years, who underwent LVAD implantation (HVAD, HeartWare) for DT in our institution between 2011 and 2013. The patients were divided into 2 groups according to the surgical implantation technique: LIS (n = 20) vs conventional (n = 26).

RESULTS

There was no statistically significant difference in 2-year survival rates between the 2 groups, but the LIS group showed a tendency to improved patient outcome in 85.0% vs 69.2% (P = .302). Moreover, the incidence of postoperative bleeding was minor in LIS patients (0% in the LIS group vs 26.9% in the conventional surgery group, P < .05), who also showed lower rates of postoperative extended inotropic support (15.0% in the LIS group vs 46.2% in the conventional surgery group, P < .05).

CONCLUSIONS

Our data indicate that DT patients with LIS-LVAD implantation showed a lower incidence of postoperative bleeding, a reduced need for inotropic support, and a tendency to lower mortality compared with patients treated with the conventional surgical technique.

Cost-Effectiveness of Left Ventricular Assist Devices in Ambulatory Patients With Advanced Heart Failure

OBJECTIVES

This study assessed the cost-effectiveness of left ventricular assist devices (LVADs) as destination therapy in ambulatory patients with advanced heart failure.

BACKGROUND

LVADs improve survival and quality of life in inotrope-dependent heart failure, but data are limited as to their value in less severely ill patients.

METHODS

We determined costs of care among Medicare beneficiaries before and after LVAD implantation from 2009 to 2010. We used these costs and efficacy data from published studies in a Markov model to project the incremental cost-effectiveness ratio (ICER) of destination LVAD therapy compared with that of medical management. We discounted costs and benefits at 3% annually and report costs as 2016 U.S. dollars.

RESULTS

The mean cost of LVAD implantation was $175,420. The mean cost of readmission was lower before LVAD than after ($12,377 vs. $19,465, respectively; p < 0.001), while monthly outpatient costs were similar ($3,364 vs. $2,974, respectively; p = 0.54). In the lifetime simulation model, LVAD increased quality-adjusted life-years (QALYs) (4.41 vs. 2.67, respectively), readmissions (13.03 vs. 6.35, respectively), and costs ($726,200 vs. $361,800, respectively) compared with medical management, yielding an ICER of $209,400 per QALY gained and $597,400 per life-year gained. These results were sensitive to LVAD readmission rates and outpatient care costs; the ICER would be $86,900 if these parameters were 50% lower.

CONCLUSIONS

LVADs in non-inotrope-dependent heart failure patients improved quality of life but substantially increased lifetime costs because of frequent readmissions and costly follow-up care. LVADs may provide good value if outpatient costs and adverse events can be reduced.

Effect of Outflow Graft Size on Flow in the Aortic Arch and Cerebral Blood Flow in Continuous Flow Pumps: Possible Relevance to Strokes

One of the most devastating complications of continuous flow left ventricular devices (CFLVADS) is stroke, with a higher incidence in HeartWare Ventricular Assist Device (HVAD) as compared with HEARTMATE II. The reason for the observed difference in stroke rates is unclear. Because outflow graft diameters are different, we hypothesized that this could contribute to the difference in stroke rates. A computational fluid-structure interaction model was created from the computed tomography (CT) scan of a patient. Pressures were used as the boundary condition and the flow through the cerebral vessels was derived as outputs. Flow into the innominate artery was very sensitive to the anastomosis angle for a 10 mm as compared with a 14 mm graft, with the net innominate flow severely compromised with a 10 mm graft at 45° angle. Aortic insufficiency seems to affect cerebral blood flow nonlinearly with an 80% decrease at certain angles of outflow graft anastomosis. Arterial return in to the arch through a narrow graft has important jet effects and results in significant flow perturbations in the aortic arch and cerebral vessels and stasis. A 10 mm graft is more sensitive to angle of insertion than a 14 mm graft. Under some conditions, serious hypoperfusion of the innominate artery is possible. Aortic incompetence results in significant decrease of cerebral blood flow. No stasis was found in the pulsatile flow compared with LVAD flow.

High fidelity computational simulation of thrombus formation in Thoratec HeartMate II continuous flow ventricular assist device

Continuous flow ventricular assist devices (cfVADs) provide a life-saving therapy for severe heart failure. However, in recent years, the incidence of device-related thrombosis (resulting in stroke, device-exchange surgery or premature death) has been increasing dramatically, which has alarmed both the medical community and the FDA. The objective of this study was to gain improved understanding of the initiation and progression of thrombosis in one of the most commonly used cfVADs, the Thoratec HeartMate II. A computational fluid dynamics simulation (CFD) was performed using our recently updated mathematical model of thrombosis. The patterns of deposition predicted by simulation agreed well with clinical observations. Furthermore, thrombus accumulation was found to increase with decreased flow rate, and can be completely suppressed by the application of anticoagulants and/or improvement of surface chemistry. To our knowledge, this is the first simulation to explicitly model the processes of platelet deposition and thrombus growth in a continuous flow blood pump and thereby replicate patterns of deposition observed clinically. The use of this simulation tool over a range of hemodynamic, hematological, and anticoagulation conditions could assist physicians to personalize clinical management to mitigate the risk of thrombosis. It may also contribute to the design of future VADs that are less thrombogenic.

Patient Selection for Long-Term Mechanical Circulatory Support: Is It Ever too Early for the NYHA Class III Patient?

Heart failure is a common condition with significant morbidity and mortality. Pharmacologic and device therapies have resulted in substantial improvements in heart failure outcomes. Despite optimal therapy, 10 % of patients progress to advanced HF, characterized by progressive symptoms, poor quality of life, and poor prognosis. The "gold-standard" treatment of advanced heart failure remains cardiac transplantation. However, the number of patients with advanced heart failure far exceeds available donor organs. Left ventricular assist devices (LVADs) were initially developed to bridge patients with hemodynamic collapse to transplantation. Their use resulted in marked improvements in survival and quality of life in select patients giving rise to increased and expanded overall implantation. Despite these improvements, patient selection and timing for LVAD therapy is still evolving. In this article, we will review a brief history of LVADs, examine patient selection, and explore the currently debated expansion of LVADs to "less sick" patients.

Mechanical Circulatory Support: Heart Failure Therapy “in Motion”

Because the first generation of pulsatile-flow devices was primarily used to bridge the sickest patients to transplantation (bridge-to-transplant therapy), the current generation of continuous-flow ventricular assist devices qualifies for destination therapy for patients with advanced heart failure who are ineligible for transplantation. The first-generation devices were associated with frequent adverse events, limited mechanical durability, and patient discomfort due device size. In contrast, second-generation continuous-flow devices are smaller, more quiet, and durable, thus resulting in less complications and significantly improved survival rates. Heart transplantation remains an option for a limited number of patients only, and this fact has also triggered the discussion about the optimal timing for device implantation. The increasing use of continuous-flow devices has resulted in new challenges, such as adverse events during long-term support, and high hospital readmission rates. In addition, there are a number of device-related complications including mechanical problems such as device thrombosis, percutaneous driveline damage, as well as conditions such as hemolysis, infection, and cerebrovascular accidents. This review provides an overview of the evolution of mechanical circulatory support systems from bridge to transplantation to destination therapy including technological advances and clinical improvements in long-term patient survival and quality of life. In addition, recent changes in device implant strategies and current trials are reviewed and discussed. A brief glimpse into the future of mechanical circulatory support therapy will summarize the innovations that may soon enter clinical practice.

Hypertension and Stroke in Patients with Left Ventricular Assist Devices (LVADs)

Stroke is one of the most dreaded complications of left ventricular assist device therapy in patients with end-stage congestive heart failure. There is strong evidence linking anticoagulation and infection with ischemic and hemorrhagic strokes, though recent data has emerged regarding the importance of elevated blood pressure. In the recently completed Heartware Ventricular Assist Device studies, a mean arterial pressure greater than 90 mmHg was associated with greater stroke risk, particularly the hemorrhagic subtype. In this review, we discuss recent evidence regarding deleterious effects of uncontrolled hypertension in patients with left ventricular devices, and propose measurement and management strategies.

Current Status of Left Ventricular Assist Device Therapy

Congestive heart failure (HF) remains a serious burden in the Western World. Despite advances in pharmacotherapy and resynchronization, many patients have progression to end-stage HF. These patients may be candidates for heart transplant or left ventricular assist device (LVAD) therapy. Heart transplants are limited by organ shortages and in some cases by patient comorbidities; therefore, LVAD therapy is emerging as a strategy of bridge to transplant or as a destination therapy in patients ineligible for transplant. Patients initially ineligible for a transplant may, in certain cases, become eligible for transplant after physiologic improvement with LVAD therapy, and a small number of patients with an LVAD may have sufficient recovery of myocardial function to allow device explantation. This clinically oriented review will describe (1) the most frequently used pump types and aspects of the continuous-flow physiology and (2) the clinical indications for and the shift toward the use of LVADs in less sick patients with HF. Additionally, we review complications of LVAD therapy and project future directions in this field. We referred to the Interagency Registry for Mechanically Assisted Circulatory Support, landmark trials, and results from recently published studies as major sources in obtaining recent outcomes, and we searched for related published literature via PubMed. This review focuses primarily on clinical practice for primary care physicians and non-HF cardiologists in the United States.

Outcomes after stroke complicating left ventricular assist device

BACKGROUND

Stroke is one of the leading complications during continuous flow-left ventricular assist device (CF-LVAD) support. Risk factors have been well described, although less is known regarding treatment and outcomes. We present a large single-center experience on stroke outcome and transplant eligibility by stroke sub-type and severity in CF-LVAD patients.

METHODS

Between January 1, 2008, and April 1, 2015, 301 patients underwent CF-LVAD (266 HeartMate II [HM I], Thoratec Corp, Pleasanton, CA; 35 HeartWare [HVAD], HeartWare International Inc, Framingham, MA). Stroke was defined as a focal neurologic deficit with abnormal neuroimaging. Intracerebral hemorrhage (ICH) definition excluded sub-dural hematoma and hemorrhagic conversion of an ischemic stroke (IS). Treatment in IS included intra-arterial embolectomy when appropriate; treatment in ICH included reversal of coagulopathy. Stroke severity was measured using the National Institutes of Health Stroke Scale (NIHSS). Outcomes were in-hospital mortality and transplant status.

RESULTS

Stroke occurred in 40 patients: 8 ICH (4 HM II, 4 HVAD) and 32 IS (26 HM II, 6 HVAD). Among 8 ICH patients, there were 4 deaths (50%), with NIHSS of 18.8 ± 13.7 vs 1.8 ± 1.7 in survivors (p = 0.049). Among 32 IS patients, 12 had hemorrhagic conversion and 5 were treated with intra-arterial embolectomy. There were 9 deaths (28%), with NIHSS of 16.2 ± 10.8 vs 7.0 ± 7.6 in survivors (p = 0.011). Among the 32 IS patients, 12 underwent transplant, and 1 is awaiting transplant. No ICH patients received a transplant.

CONCLUSIONS

In-hospital mortality after stroke is significantly affected by the initial neurologic impairment. Patients with IS appear to benefit the most from in-hospital treatment and often make sufficient recovery to be able to progress to transplant.

Left ventricular assist device: a bridge to transplant or destination therapy?

Heart failure is a major problem worldwide; it is the leading cause of hospitalisation and is posing a huge financial burden. Advances in healthcare have contributed to increased life expectancy, with a resultant increase in the number of patients with chronic heart failure. For many patients who are still severely symptomatic despite optimal medical therapy and cardiac resynchronisation therapy, cardiac transplantation would be the preferred treatment option. However, hopes are cut short with a limited donor pool of hearts for the increasing number of patients requiring cardiac transplantation. One uprising method to fill this treatment void for patients with advanced end-stage heart failure (ESHF) is the Left Ventricular Assist Device (LVAD). Although traditionally used as a bridge to transplantation, owing to limitation of suitable donors, evidence suggests increasing potential for the use of LVAD as destination therapy (DT), that is, lifelong permanent support. Exploration of DT is a promising avenue to many patients suffering with ESHF who may never be fortunate enough to receive a heart transplant, but not without reservations of its efficacy, safety, effects on quality-adjusted life years and cost-effectiveness, especially in comparison to heart transplantation.

[Rise of the machines? Left ventricular assist devices for treatment of severe heart failure]

The use of left ventricular assist devices (LVAD) as a treatment for severe heart failure has gained momentum in recent years. Even at this stage the number of worldwide LVAD implantations far exceeds the volume of heart transplantations in view of the chronic shortage of donor organs. Third generation continuous flow assist devices have helped to improve survival, quality of life and symptom burden of heart failure patients in comparison to a regimen of optimal medication management. Alongside bridging to transplantation, destination therapy has become an established strategy of LVAD implantation. A careful patient selection process is crucial for a good clinical outcome after device implantation and risk assessment for postoperative right ventricular failure is of particular importance in this context. The rate of hospitalization during LVAD support is still high, despite the step-wise attempts to widen the indications to less severely ill heart failure patients. An effective perioperative and postoperative management will help to lower the incidence of complications (e.g. bleeding, infections, thromboembolic events and right ventricular failure) and to improve the encouraging results of mechanical circulatory support.