Low incidence of myocardial recovery after left ventricular assist device implantation in patients with chronic heart failure

Exploring Changes in Myocyte Structure, Contractility, and Energetics From Mechanical Unloading in Patients With Heart Failure Undergoing Ventricular Assist Device Implantation: A Systematic Review and Meta-Analysis

AIMS

Recent reports of myocardial recovery after mechanical unloading with left ventricular assist devices (LVADs) have challenged the prevailing notion that end-stage heart failure (HF) is irreversible. To improve our understanding of this phenomenon, we comprehensively analysed the structural, functional, and energetic changes in failing human cardiomyocytes after LVAD implantation.

METHODS

Based on a prospectively registered protocol (PROSPERO-CRD42022380214), 30 eligible studies were identified from 940 records with a pooled population of 648 patients predominantly with non-ischaemic cardiomyopathy.

RESULTS

LVAD led to a substantial regression in myocyte size similar to that of donor hearts (standardised mean difference, -1.29; p<0.001). The meta-regression analysis revealed that HF duration was a significant modifier on the changes in myocyte size. There were some suggestions of fibrosis reversal (-5.17%; p=0.009); however, this was insignificant after sensitivity analysis. Developed force did not improve in cardiac trabeculae (n=5 studies); however, non-physiological isometric contractions were tested. At the myocyte level (n=4 studies), contractile kinetics improved where the time-to-peak force reduced by 41.7%-50.7% and time to 50% relaxation fell by 47.4%-62.1% (p<0.05). Qualitatively, LVAD enhanced substrate utilisation and mitochondrial function (n=6 studies). Most studies were at a high risk of bias.

CONCLUSION

The regression of maladaptive hypertrophy, partial fibrosis reversal, and normalisation in metabolic pathways after LVAD may be a testament to the heart's remarkable plasticity, even in the advanced stages of HF. However, inconsistencies exist in force-generating capabilities. Using more physiological force-length work-loop assays, addressing the high risks of bias and clinical heterogeneity are crucial to better understand the phenomenon of reverse remodelling.

Incidence, Outcomes, and Opportunity for Left Ventricular Assist Device Weaning for Myocardial Recovery

BACKGROUND

Myocardial recovery occurs in patients with advanced heart failure on left ventricular assist device (LVAD) support, but there is the premise that it is rare with uncertain results.

OBJECTIVES

The goal of this study was to investigate the incidence and consequence of LVAD explant after myocardial recovery.

METHODS

Using the United Network for Organ Sharing registry, LVAD implants in the United States between 2005 and 2020 were tracked until death, transplantation, or explant for myocardial recovery. The cohort undergoing explant was followed up for heart failure relapse (defined as relisting followed by delisting due to death, being too ill, or transplantation; or second durable LVAD implant).

RESULTS

Of 15,728 LVAD implants, 126 patients underwent explant for recovery, which only occurred in 55 (38%) of 145 implanting centers. The crude cumulative incidence was 0.7% at 2 years, whereas the incidence reached 4.7% among designated centers in the selected young nonischemic cohort. Of 126 explanted patients, 76 (60%) were subsequently delisted for sustained recovery. Heart failure relapsing had a relatively higher hazard in the early phase, with a 30-day incidence of 6% (7 of 126) but tapered following with the freedom rate of 72.5% at 4 years.

CONCLUSIONS

In the United States, LVAD explant for myocardial recovery was underutilized, leading to a very low incidence at the national level despite a realistic rate being achieved in designated centers for selected patients. With follow-up extending up to 4 years after explant, more than one-half were successfully removed and stayed off the waitlist, and approximately 70% were free from heart failure relapse events.

Cardiological Challenges Related to Long-Term Mechanical Circulatory Support for Advanced Heart Failure in Patients with Chronic Non-Ischemic Cardiomyopathy

Long-term mechanical circulatory support by a left ventricular assist device (LVAD), with or without an additional temporary or long-term right ventricular (RV) support, is a life-saving therapy for advanced heart failure (HF) refractory to pharmacological treatment, as well as for both device and surgical optimization therapies. In patients with chronic non-ischemic cardiomyopathy (NICM), timely prediction of HF's transition into its end stage, necessitating life-saving heart transplantation or long-term VAD support (as a bridge-to-transplantation or destination therapy), remains particularly challenging, given the wide range of possible etiologies, pathophysiological features, and clinical presentations of NICM. Decision-making between the necessity of an LVAD or a biventricular assist device (BVAD) is crucial because both unnecessary use of a BVAD and irreversible right ventricular (RV) failure after LVAD implantation can seriously impair patient outcomes. The pre-operative or, at the latest, intraoperative prediction of RV function after LVAD implantation is reliably possible, but necessitates integrative evaluations of many different echocardiographic, hemodynamic, clinical, and laboratory parameters. VADs create favorable conditions for the reversal of structural and functional cardiac alterations not only in acute forms of HF, but also in chronic HF. Although full cardiac recovery is rather unusual in VAD recipients with pre-implant chronic HF, the search for myocardial reverse remodelling and functional improvement is worthwhile because, for sufficiently recovered patients, weaning from VADs has proved to be feasible and capable of providing survival benefits and better quality of life even if recovery remains incomplete. This review article aimed to provide an updated theoretical and practical background for those engaged in this highly demanding and still current topic due to the continuous technical progress in the optimization of long-term VADs, as well as due to the new challenges which have emerged in conjunction with the proof of a possible myocardial recovery during long-term ventricular support up to levels which allow successful device explantation.

The First Dedicated Comprehensive Heart Failure Program in the United States: The Division of Circulatory Physiology at Columbia Presbyterian (1992-2004)

The first dedicated multidisciplinary heart failure program in the United States was founded as the Division of Circulatory Physiology at the Columbia University College of Physicians & Surgeons in 1992. The Division was administratively and financially independent of the Division of Cardiology and grew to 24 faculty members at its peak. Its administrative innovations included (1) a comprehensive full-integrated service line, with 2 differentiated clinical teams, one devoted to drug therapy and the other to heart transplantation and ventricular assist devices; (2) a nurse specialist/physician assistant-led clinical service; and (3) a financial structure independent of (and not supported by) other cardiovascular medical or surgical services. The division had 3 overarching missions: (1) to promote a unique career development path for each faculty member to be linked to recognition in a specific area of heart failure expertise; (2) to change the trajectory and enhance the richness of intellectual discourse in the discipline of heart failure, so as to foster an understanding of fundamental mechanisms and to develop new therapeutics; and (3) to provide optimal medical care to patients and to promote the ability of other physicians to provide optimal care. The major research achievements of the division included (1) the development of beta-blockers for heart failure, from initial hemodynamic assessments to proof-of-concept studies to large-scale international trials; (2) the development and definitive assessment of flosequinan, amlodipine, and endothelin antagonists; (3) initial clinical trials and concerns with nesiritide; (4) large-scale trials evaluating dosing of angiotensin converting-enzyme inhibitors and the efficacy and safety of neprilysin inhibition; (5) identification of key mechanisms in heart failure, including neurohormonal activation, microcirculatory endothelial dysfunction, deficiencies in peripheral vasodilator pathways, noncardiac factors in driving dyspnea, and the first identification of subphenotypes of heart failure and a preserved ejection fraction; (6) the development of a volumetric approach to the assessment of myocardial shortening; (7) conceptualization and early studies of cardiac contractility modulation as a treatment for heart failure; (8) novel approaches to the identification of cardiac allograft rejection and new therapeutics to prevent allograft vasculopathy; and (9) demonstration of the effect of left ventricular assist devices to induce reverse remodeling, and the first randomized trial showing a survival benefit with ventricular assist devices. Above all, the division served as an exceptional incubator for a generation of leaders in the field of heart failure.

A Peek at LVADs Pumping to Recovery

Left ventricular assist devices (LVADs) have revolutionized the management of patients with advanced heart failure refractory to medical therapy. Current indications of LVADs include Bridge to Transplantation (BTT), Destination Therapy (DT) for long-term use, Bridge to the Decision (BTD) used as a temporary measure, and lastly Bridge to Recovery (BTR). Here, we briefly review the clinical evidence and the molecular mechanisms behind myocardial recovery following LVAD placement. We also share institutional protocols used at 2 major medical centers in the USA.

Novel Targets for a Combination of Mechanical Unloading with Pharmacotherapy in Advanced Heart Failure

LVAD therapy is an effective rescue in acute and especially chronic cardiac failure. In several scenarios, it provides a platform for regeneration and sustained myocardial recovery. While unloading seems to be a key element, pharmacotherapy may provide powerful tools to enhance effective cardiac regeneration. The synergy between LVAD support and medical agents may ensure satisfying outcomes on cardiomyocyte recovery followed by improved quality and quantity of patient life. This review summarizes the previous and contemporary strategies for combining LVAD with pharmacotherapy and proposes new therapeutic targets. Regulation of metabolic pathways, enhancing mitochondrial biogenesis and function, immunomodulating treatment, and stem-cell therapies represent therapeutic areas that require further experimental and clinical studies on their effectiveness in combination with mechanical unloading.

LVAD as a Bridge to Remission from Advanced Heart Failure: Current Data and Opportunities for Improvement

Left ventricular assist devices (LVADs) are an established treatment modality for advanced heart failure (HF). It has been shown that through volume and pressure unloading they can lead to significant functional and structural cardiac improvement, allowing LVAD support withdrawal in a subset of patients. In the first part of this review, we discuss the historical background, current evidence on the incidence and assessment of LVAD-mediated cardiac recovery, and out-comes including quality of life after LVAD support withdrawal. In the second part, we discuss current and future opportunities to promote LVAD-mediated reverse remodeling and improve our pathophysiological understanding of HF and recovery for the benefit of the greater HF population.

Protocolized screening effectively identifies myocardial recovery following destination therapy left ventricular assist device implantation

BACKGROUND

Myocardial recovery following left ventricular assist device (LVAD) implantation has been of interest in transplant candidates with non-ischemic cardiomyopathy but is rare. Evidence suggests that a combination of left ventricular unloading and pharmacologic reverse remodeling is beneficial. Recovery in non-transplant candidates (i.e., destination therapy [DT]) patients is believed to be even rarer.

METHODS

All DT LVADs between January 1, 2017 and November 23, 2020 were reviewed. All patients were subjected to an institutional protocol consisting of combined pharmacologic remodeling and mechanical unloading with proactive screening for recovery. The primary outcome of interest was the cumulative incidence of myocardial recovery. Baseline characteristics and operative outcomes were compared between recovered and non-recovered DT patients using non-parametric tests to identify predictive factors.

RESULTS

A total of 49 patients received DT LVADs. Nine patients were identified as myocardial recovery candidates using the protocol screening criteria. Overall, 11 patients underwent formal confirmatory testing for recovery, of which 10 were deemed recovered and underwent LVAD explant, defunctionalization, or transplantation. 37.5% of patients that had a concomitant coronary artery bypass during LVAD implantation achieved recovery. An equal proportion of ischemic and non-ischemic cardiomyopathy patients achieved recovery. The cumulative incidence of myocardial recovery was 25.1% at 36 months. No factors were identified as being predictive of recovery.

CONCLUSION

Myocardial recovery in DT LVAD patients can be achieved at a higher rate than previously reported. Revascularization at the time of LVAD is safe and may be beneficial. LVAD therapy may not be the final destination in these patients.

Contemporary Drug Treatment of Advanced Heart Failure with Reduced Ejection Fraction

The introduction of multiple new pharmacological agents over the past three decades in the field of heart failure with reduced ejection fraction (HFrEF) has led to reduced rates of mortality and hospitalizations, and consequently the prevalence of HFrEF has increased, and up to 10% of patients progress to more advanced stages, characterized by high rates of mortality, hospitalizations, and poor quality of life. Advanced HFrEF patients often show persistent or progressive signs of severe HF symptoms corresponding to New York Heart Association class III or IV despite being on optimal medical, surgical, and device therapies. However, a subpopulation of patients with advanced HF, those with the most advanced stages of disease, were often insufficiently represented in the major trials demonstrating efficacy and tolerability of the drugs used in HFrEF due to exclusion criteria such as low BP and kidney dysfunction. Consequently, the results of many landmark trials cannot necessarily be transferred to patients with the most advanced stages of HFrEF. Thus, the efficacy and tolerability of guideline-directed medical therapies in patients with the most advanced stages of HFrEF often remain unsettled, and this knowledge is of crucial importance in the planning and timing of consideration for referral for advanced therapies. This review discusses the evidence regarding the use of contemporary drugs in the advanced HFrEF population, covering components such as guideline HFrEF drugs, diuretics, inotropes, and the use of HFrEF drugs in LVAD recipients, and provides suggestions on how to manage guideline-directed therapy in this patient group.

A Mechanistic Lumped Parameter Model of the Berlin Heart EXCOR to Analyze Device Performance and Physiologic Interactions

PURPOSE

The Berlin Heart EXCOR (BH) is the only FDA-approved, extracorporeal pulsatile ventricular assist device (VAD) for infants and children with heart failure. Clinicians control four settings on the device-systolic and diastolic drive pressures, device pump rate, and systolic time as a percentage of the pump cycle. However, interactions between BH pneumatics and the native circulation remain poorly understood. Thus, establishing appropriate device size and settings can be challenging on a patient-to-patient basis.

METHODS

In this study we develop a novel lumped parameter network based on simplified device mechanics. We perform parametric studies to characterize device behavior, study interactions between the left ventricle (LV) and BH across different device settings, and develop patient-specific simulations. We then simulate the impact of changing device parameters for each of three patients.

RESULTS

Increasing systolic pressure and systolic time increased device output. We identified previously unobserved cycle-to-cycle variations in LV-BH interactions that may impact patient health. Patient-specific simulations demonstrated the model's ability to replicate BH performance, captured trends in LV behavior after device implantation, and emphasized the importance of device rate and volume in optimizing BH efficiency.

CONCLUSION

We present a novel, mechanistic model that can be readily adjusted to study a wide range of device settings and clinical scenarios. Physiologic interactions between the BH and the native LV produced large variability in cardiac loading. Our findings showed that operating the BH at a device rate greater than the patient's native heart decreases variability in physiological interactions between the BH and LV, increasing cardiac offloading while maintaining cardiac output. Device rates that are close to the resting heart rate may result in unfavorable cardiac loading conditions. Our work demonstrates the utility of our model to investigate BH performance for patient-specific physiologies.

Left Ventricular Recovery with Explantation of Continuous-Flow Left Ventricular Assist Device after 5 Years of Support

Mechanical circulatory support may result in sufficient myocardial recovery to allow for explantation of the left ventricular assist device (LVAD). The duration of support associated with left ventricular recovery has generally been 6–12 months. In this report, we present a patient in whom the left ventricle recovered after 5 years of support with a LVAD. Our report demonstrates that long-term monitoring for left ventricular recovery is prudent and may allow for late device explantation.

Evidence for synergy between sarcomeres and fibroblasts in an in vitro model of myocardial reverse remodeling

We have created a novel in-vitro platform to study reverse remodeling of engineered heart tissue (EHT) after mechanical unloading. EHTs were created by seeding decellularized porcine myocardial sections with a mixture of primary neonatal rat ventricular myocytes and cardiac fibroblasts. Each end of the ribbon-like constructs was fixed to a plastic clip, allowing the tissues to be statically stretched or slackened. Inelastic deformation was introduced by stretching tissues by 20% of their original length. EHTs were subsequently unloaded by returning tissues to their original, shorter length. Mechanical characterization of EHTs immediately after unloading and at subsequent time points confirmed the presence of a reverse-remodeling process, through which stress-free tissue length was increased after chronic stretch but gradually decreased back to its original value within 9 days. When a cardiac myosin inhibitor was applied to tissues after unloading, EHTs failed to completely recover their passive and active mechanical properties, suggesting a role for actomyosin contraction in reverse remodeling. Selectively inhibiting cardiomyocyte contraction or fibroblast activity after mechanical unloading showed that contractile activity of both cell types was required to achieve full remodeling. Similar tests with EHTs formed from human induced pluripotent stem cell-derived cardiomyocytes also showed reverse remodeling that was enhanced when treated with omecamtiv mecarbil, a myosin activator. These experiments suggest essential roles for active sarcomeric contraction and fibroblast activity in reverse remodeling of myocardium after mechanical unloading. Our findings provide a mechanistic rationale for designing potential therapies to encourage reverse remodeling in patient hearts.

Weaning from ventricular assist device support after recovery from left ventricular failure with or without secondary right ventricular failure

Although complete myocardial recovery after ventricular assist device (VAD) implantation is rather seldom, systematic search for recovery is worthwhile because for recovered patients weaning from VADs is feasible and can provide survival benefits with long-term freedom from heart failure (HF) recurrence, even if a chronic cardiomyopathy was the primary cause for the drug-refractory HF necessitating left ventricular (LVAD) or biventricular support (as bridge-to-transplantation or definitive therapy) and even if recovery remains incomplete. LVAD patients explanted for myoacardial recovery compared to those transplanted from LVAD support showed similar survival rates and a significant proportion of explanted patients can achieve cardiac and physical functional capacities that are within the normal range of healthy controls. In apparently sufficiently recovered patients, a major challenge remains still the pre-explant prediction of the weaning success which is meanwhile reliably possible for experienced clinicians. In weaning candidates, the combined use of certain echocardiography and right heart catheterization parameters recorded before VAD explantation can predict post-weaning cardiac stability with good accuracy. However, in the absence of standardization or binding recommendations, the protocols for assessment of native cardiac improvement and also the weaning criteria differ widely among centers. Currently there are still only few larger studies on myocardial recovery assessment after VAD implantation. Therefore, the weaning practice relies mostly on small case series, local practice patterns, and case reports, and the existing knowledge, as well as the partially differing recommendations which are based mainly on expert opinions, need to be periodically systematised. Addressing these shortcomings, our review aims to summarize the evidence and expert opinion on the evaluation of cardiac recovery during mechanical ventricular support by paying special attention to the reliability of the methods and parameters used for assessment of myocardial recovery and the challenges met in both evaluation of recovery and weaning decision making.

Characterization and timing of gastrointestinal bleeding in continuous flow left ventricular assist device recipients

BACKGROUND AND AIMS

Heart failure is one of the leading causes of morbidity and mortality in the United States. The advent of left ventricular assist devices (LVAD) has improved the survival and quality of life in patients with end stage heart failure. Gastrointestinal bleeding (GIb) remains one of the limitations of LVADs.

METHODS

A single center, retrospective review of records was performed for patients who underwent LVAD implantation between 2010 and 2015. All patients who survived more than 30 days were followed till March 2016 and are described below.

RESULTS

A total of 79 patients were included in the study. The rate of GIb was 34.1% (27 patients) with a mean time to bleed of 267 days. Older patients were more likely to bleed. Upper GI bleeding was the source of bleeding in 54% patients. Arteriovenous malformations (AVM) were the source of bleeding in 74% bleeders and 80% of these patients had de novo AVM formation. 14/27 (51%) patients had a re-bleeding event. Thrombotic events were 4.5 times more likely to occur in patients who also had a GI bleed.

CONCLUSIONS

GI bleeding in LVAD patients is common with the source of bleeding more commonly being in the upper GI tract. GI bleeding may occur as early as 10 days post procedure, despite previous negative screening endoscopies. There is an increased risk of thrombotic events in patients who have experienced a GI bleed.

The role of exercise hemodynamics in assessing patients with chronic heart failure and left ventricular assist devices

Introduction: Chronic heart failure is characterized by reduced exercise capacity. Invasive exercise hemodynamics are not routinely performed unless patients undergo transplant or left ventricular assist devices (LVAD) assessment, though now with readily available noninvasive devices, exercise hemodynamics are easily obtained. Our contention is that this is a valuable opportunity to acquire a more accurate measure of cardiac status in heart failure. Exercise hemodynamic measures such as cardiac power output can be carried out cheaply and effectively. Recent studies have highlighted the added value of exercise hemodynamics in prognostication of heart failure, and their role in assessing myocardial recovery in LVADs. Areas covered: In this review, we explore the literature available on Medline until 2019 focusing on resting and exercise hemodynamics alongside the methods of assessment (invasive and noninvasive) in heart failure with reduced ejection fraction and patients with implanted LVADs. Expert opinion: Hemodynamics measured both at rest and exercise are expected to play a significant role in the work up of transplant and LVAD patients. Furthermore, there is the potential to utilize noninvasive assessment in a complimentary fashion to support patient selection and improve the monitoring of response to treatment across the full cohort of heart failure patients.

Alteration in ventricular pressure stimulates cardiac repair and remodeling

The mammalian heart undergoes complex structural and functional remodeling to compensate for stresses such as pressure overload. While studies suggest that, at best, the adult mammalian heart is capable of very limited regeneration arising from the proliferation of existing cardiomyocytes, how myocardial stress affects endogenous cardiac regeneration or repair is unknown. To define the relationship between left ventricular afterload and cardiac repair, we induced left ventricle pressure overload in adult mice by constriction of the ascending aorta (AAC). One week following AAC, we normalized ventricular afterload in a subset of animals through removal of the aortic constriction (de-AAC). Subsequent monitoring of cardiomyocyte cell cycle activity via thymidine analog labeling revealed that an acute increase in ventricular afterload induced cardiomyocyte proliferation. Intriguingly, a release in ventricular overload (de-AAC) further increases cardiomyocyte proliferation. Following both AAC and de-AAC, thymidine analog-positive cardiomyocytes exhibited characteristics of newly generated cardiomyocytes, including single diploid nuclei and reduced cell size as compared to age-matched, sham-operated adult mouse myocytes. Notably, those smaller cardiomyocytes frequently resided alongside one another, consistent with local stimulation of cellular proliferation. Collectively, our data demonstrate that adult cardiomyocyte proliferation can be locally stimulated by an acute increase or decrease of ventricular pressure, and this mode of stimulation can be harnessed to promote cardiac repair.

Novel approaches to the management of chronic systolic heart failure: future directions and unanswered questions

Despite improvements in outcomes in the last few decades for heart failure (HF) with reduced ejection fraction (HFrEF), there still remains a need for novel therapies as many patients incompletely recover with existing therapies and progress to advanced HF. In this review, we will discuss recent advances in the management of HFrEF with a focus on upcoming therapies that hold the greatest promise for clinical use. We will discuss novel pharmacological therapies and areas of uncertainty with existing therapies. We will also discuss the potential utility and controversy surrounding novel interventions for HF such as percutaneous mitral valve repair, atrial fibrillation ablation, and other emerging interventions with positive signals for benefit in HFrEF. Finally, we will summarize the current state of stem cell and gene therapy for HFrEF and future directions.

Collapse

The heterotopic heart transplantation in mice as a small animal model to study mechanical unloading - Establishment of the procedure, perioperative management and postoperative scoring

BACKGROUND

Unloading of failing hearts by left ventricular assist devices induces an extensive cardiac remodeling which may lead to a reversal of the initial phenotype-or to its deterioration. The mechanisms underlying these processes are unclear.

HYPOTHESIS

Heterotopic heart transplantion (hHTX) is an accepted model for the study of mechanical unloading in rodents. The wide variety of genetically modified strains in mice provides an unique opportunity to examine remodeling pathways. However, the procedure is technically demanding and has not been extensively used in this area. To support investigators adopting this method, we present our experience establishing the abdominal hHTX in mice and describe refinements to the technique.

METHODS

In this model, the transplanted heart is vascularised but implanted in series, and therefore does not contribute to systemic circulation and results in a complete mechanical unloading of the donor heart. Training followed a systematic program using a combination of literature, video tutorials, cadaveric training, direct observation and training in live animals.

RESULTS

Successful transplantation was defined as a recipient surviving > 24 hours with a palpable, beating apex in the transplanted heart and was achieved after 20 transplants in live animals. A success rate of 90% was reached after 60 transplants. Operative time was shown to decrease in correlation with increasing number of procedures from 200 minutes to 45 minutes after 60 operations. Cold/warm ischemia time improved from 45/100 to 10/20 minutes. Key factors for success and trouble shootings were identified.

CONCLUSION

Abdominal hHTX in the mouse may enable future examination of specific pathways in unloading induced myocardial remodeling. Establishment of the technique, however, is challenging. Structured training programs utilising a variety of training methods can help to expedite the process. Postoperative management, including daily scoring increases animal wellbeing and helps to predict survival.

Recovery of failing hearts by mechanical unloading: Pathophysiologic insights and clinical relevance

By reduction of ventricular wall-tension and improving the blood supply to vital organs, ventricular assist devices (VADs) can eliminate the major pathophysiological stimuli for cardiac remodeling and even induce reverse remodeling occasionally accompanied by clinically relevant reversal of cardiac structural and functional alterations allowing VAD explantation, even if the underlying cause for the heart failure (HF) was dilated cardiomyopathy. Accordingly, a tempting potential indication for VADs in the future might be their elective implantation as a therapeutic strategy to promote cardiac recovery in earlier stages of HF, when the reversibility of morphological and functional alterations is higher. However, the low probability of clinically relevant cardiac improvement after VAD implantation and the lack of criteria which can predict recovery already before VAD implantation do not allow so far VAD implantations primarily designed as a bridge to cardiac recovery. The few investigations regarding myocardial reverse remodeling at cellular and sub-cellular level in recovered patients who underwent VAD explantation, the differences in HF etiology and pre-implant duration of HF in recovered patients and also the differences in medical therapy used by different institutions during VAD support make it currently impossible to understand sufficiently all the biological processes and mechanisms involved in cardiac improvement which allows even VAD explantation in some patients. This article aims to provide an overview of the existing knowledge about VAD-promoted cardiac improvement focusing on the importance of bench-to-bedside research which is mandatory for attaining the future goal to use long-term VADs also as therapy-devices for reversal of chronic HF.

Evaluation of Cardiac Recovery in Ventricular Assist Device Recipients: Particularities, Reliability, and Practical Challenges

In carefully selected patients with ventricular assist devices (VADs), good long-term results after device weaning and explantation can be achieved when reverse remodelling and improvement of native cardiac function occur. Monitoring of cardiac size, geometry, and function after initial VAD implantation is necessary to identify such patients. Formal guidelines for recovery assessment in patients with VADs do not exist, and protocols for recovery assessment and criteria for device weaning and explantation vary among centres. Barriers to evaluation of cardiac recovery include technical problems in obtaining echo images in patients with VADs, time restrictions for necessary VAD reductions/interruptions during assessment, and regurgitant flow patterns that occur with interruption of continuous flow VADs. The few larger studies addressing cardiac recovery after VAD implantation employed varied study designs, limiting interpretation. Current clinical practice is guided largely by local practice patterns, case reports, and small case series, and the available body of research-consisting mostly of expert opinions-has not been systematically addressed. This summary reviews evidence and expert opinion on VAD-promoted cardiac recovery assessment, its reliability, and associated challenges.

Treatment of chronic heart failure in the 21st century: A new era of biomedical engineering has come

Chronic heart failure (CHF) is a challenging burden on public health. Therapeutic strategies for CHF have developed rapidly in the past decades from conventional medical therapy, which mainly includes administration of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and aldosterone antagonists, to biomedical engineering methods, which include interventional engineering, such as percutaneous balloon mitral valvotomy, percutaneous coronary intervention, catheter ablation, biventricular pacing or cardiac resynchronization therapy (CRT) and CRT-defibrillator use, and implantable cardioverter defibrillator use; mechanical engineering, such as left ventricular assistant device use, internal artery balloon counterpulsation, cardiac support device use, and total artificial heart implantation; surgical engineering, such as coronary artery bypass graft, valve replacement or repair of rheumatic or congenital heart diseases, and heart transplantation (HT); regenerate engineering, which includes gene therapy, stem cell transplantation, and tissue engineering; and rehabilitating engineering, which includes exercise training, low-salt diet, nursing, psychological interventions, health education, and external counterpulsation/enhanced external counterpulsation in the outpatient department. These biomedical engineering therapies have greatly improved the symptoms of CHF and life expectancy. To date, pharmacotherapy, which is based on evidence-based medicine, large-scale, multi-center, randomized controlled clinical trials, is still a major treatment option for CHF; the current interventional and mechanical device engineering treatment for advanced CHF is not enough owing to its individual status. In place of HT or the use of a total artificial heart, stem cell technology and gene therapy in regenerate engineering for CHF are very promising. However, each therapy has its advantages and disadvantages, and it is currently possible to select better therapeutic strategies for patients with CHF according to cost-efficacy analyses of these therapies. Taken together, we think that a new era of biomedical engineering for CHF has begun.

Structural and functional cardiac profile after prolonged duration of mechanical unloading: potential implications for myocardial recovery

Clinical and experimental studies have suggested that the duration of left ventricular assist device (LVAD) support may affect remodeling of the failing heart. We aimed to 1) characterize the changes in Ca2+/calmodulin-dependent protein kinase type-IIδ (CaMKIIδ), growth signaling, structural proteins, fibrosis, apoptosis, and gene expression before and after LVAD support and 2) assess whether the duration of support correlated with improvement or worsening of reverse remodeling. Left ventricular apex tissue and serum pairs were collected in patients with dilated cardiomyopathy ( n = 25, 23 men and 2 women) at LVAD implantation and after LVAD support at cardiac transplantation/LVAD explantation. Normal cardiac tissue was obtained from healthy hearts ( n = 4) and normal serum from age-matched control hearts ( n = 4). The duration of LVAD support ranged from 48 to 1,170 days (median duration: 270 days). LVAD support was associated with CaMKIIδ activation, increased nuclear myocyte enhancer factor 2, sustained histone deacetylase-4 phosphorylation, increased circulating and cardiac myostatin (MSTN) and MSTN signaling mediated by SMAD2, ongoing structural protein dysregulation and sustained fibrosis and apoptosis (all P < 0.05). Increased CaMKIIδ phosphorylation, nuclear myocyte enhancer factor 2, and cardiac MSTN significantly correlated with the duration of support. Phosphorylation of SMAD2 and apoptosis decreased with a shorter duration of LVAD support but increased with a longer duration of LVAD support. Further study is needed to define the optimal duration of LVAD support in patients with dilated cardiomyopathy. NEW & NOTEWORTHY A long duration of left ventricular assist device support may be detrimental for myocardial recovery, based on myocardial tissue experiments in patients with prolonged support showing significantly worsened activation of Ca2+/calmodulin-dependent protein kinase-IIδ, increased nuclear myocyte enhancer factor 2, increased myostatin and its signaling by SMAD2, and apoptosis as well as sustained histone deacetylase-4 phosphorylation, structural protein dysregulation, and fibrosis.

First Successful use of the New ab5000 Portable Circulatory Support Console as Bridge to Recovery in a Case of Dilated Cardiomyopathy

Introduction

Growing clinical experience and improved technology have led to more widespread use of ventricular assist devices in patients with end-stage heart failure.

Methods

We report the case of a patient with preexisting cardiomyopathy who arrived at our center in cardiogenic shock and received a biventricular assist device.

Results

The new compact Abiomed Portable Circulatory Support Console facilitated mobilization of the patient which was particularly advantageous in the face of transient hemiparesis. After recovery from cardiogenic shock, device removal was performed following a bridge-to-recovery concept. He was discharged in a state of full cardiac recompensation and is back to everyday life with stable cardiac function up to 24 months after the incident.

Conclusions

This is the first report describing successful clinical use of the AB5000 assist device in combination with the portable console. Furthermore, it underlines the potential of temporary circulatory support to induce permanent myocardial recovery even in cases of preexisting cardiomyopathy.

Prevalence of Myocardial Fibrosis by Left Ventricular Assist Device Apical Core Biopsy and Correlation with Other Markers of Myocardial Recovery

Myocardial fibrosis identified by apical core pathology at the time of left ventricular assist device (LVAD) implantation may add information regarding myocardial recovery potential. In this analysis, we report the prevalence of myocardial fibrosis by cardiomyopathy type and its association with other known markers of left ventricular recovery. Left ventricular assist device core pathology was reviewed on 332 patients who underwent LVAD implantation at a single institution between 2005 and 2016. Baseline clinical and echocardiographic characteristics were compared among patients with and without myocardial fibrosis by cardiomyopathy type. Among the 332 LVAD core specimens, myocardial fibrosis was present in 79%. Myocardial fibrosis was more common in ischemic than in nonischemic patients (90% vs. 66%; p < 0.001). Patients with fibrosis were older than those without (58 ± 12 vs. 55 ± 19; p < 0.05). Among the nonischemic cardiomyopathy cases, those with fibrosis were more likely to have an implantable cardioverter defibrillator (ICD) 81% and to be diabetic 81%. Fibrosis was not associated with left ventricular end-diastolic diameter (LVEDD), creatinine, or N-terminal prohormone of brain natriuretic peptide (NT-pro BNP). Myocardial fibrosis by apical core biopsy correlated with several known markers of left ventricular recovery including cardiomyopathy type, age, and presence of an ICD. In nonischemic cardiomyopathy patients, the degree of myocardial fibrosis may add information regarding recovery potential.

Chronic Heart Failure Model Induced by Coronary Embolization in Sheep

Objective

To create a model of chronic heart failure in a large animal.

Methods

Heart failure was induced in sheep by single intracoronary injection of polymer macrobeads, which were administered into left main coronary artery (n=3) or selectively into left anterior descending (n=4) or left circumflex (n=5) coronary artery. The animals were followed by echocardigraphy for 20 weeks. Measurements comprised fractional area change (FAC), and diastolic ventricular area (EDVA) and regional wall-thickening fraction (WT%).

Results

EDVA increased from 14.2±2.1 cm2 prior to embolization to 16.9±3.1 cm2 on day 1 (p<0.05), and remained significantly increased until completion of the follow-up period. FAC dropped from 47.9±4.6% at baseline to 29.3±4.4% on day 1 (p<0.001) and remained significantly depressed until 20 weeks later. In 9 selectively embolized animals WT% of the embolized area decreased from 33.8±8.0% at baseline to 5.3±2.6% on day 1 and remained significantly decreased.

Conclusions

A simple model of chronic heart failure was developed. It shows relatively high stability over time and may prove beneficial in experimental work on ventricular assist devices.

Role of Echocardiography in the Evaluation of Left Ventricular Assist Devices: the Importance of Emerging Technologies

The role of left ventricular assist devices (LVAD) in patients with end-stage heart failure is well known, both as a temporary treatment before transplantation and as destination therapy, in a scenario of a relative shortage of donors to satisfy the increasing requests for transplantation. The increased population of LVAD patients needs careful imaging assessment before, during, and after LVAD implantation; echocardiography is the best tool for their evaluation and is considered the diagnostic technique of choice for the assessment before, during, and after device implantation. Although the conventional echocardiographic assessment is quite effective in evaluating the main critical issues, the role of new technologies like three-dimensional echocardiography and myocardial deformation measurements is still not properly clarified. In this review, we aim to provide an overview of the main elements that should be considered in the assessment of these patients, underlining the role that could be played by new techniques to improve the diagnostic and prognostic effectiveness of echocardiography in this setting.

A dual therapy of off-pump temporary left ventricular extracorporeal device and amniotic stem cell for cardiogenic shock

Background

Temporary mechanical circulatory support device without sternotomy has been highly advocated for severe cardiogenic shock patient but little is known when coupled with amniotic stem cell therapy.

Case presentation

This case reports the first dual therapy of temporary left ventricular extracorporeal device CentriMag with distal banding technique and human amniotic stem cell injection for treating a severe refractory cardiogenic shock of an 68-year-old female patient. A minimally-invasive off-pump LVAD was established by draining from the left ventricle and returning to the right axillary artery with distal arterial banding to prevent right upper extremity hyperperfusion. Amniotic stem cells were injected intramyocardially at the left ventricular apex, lateral wall, inferior wall, and right subclavian vein.

Conclusion

The concomitant use of the temporary minimally-invasive off-pump CentriMag placement and stem cell therapy not only provided an alternative to cardiopulmonary bypass and full-median sternotomy procedures but may have also synergistically enhanced myocardial reperfusion and regeneration.

Cell-Specific Pathways Supporting Persistent Fibrosis in Heart Failure

BACKGROUND

Only limited data exist describing the histologic and noncardiomyocyte function of human myocardium in end-stage heart failure (HF).

OBJECTIVES

The authors sought to determine changes in noncardiomyocyte cellular activity in patients with end-stage HF after left ventricular assist device (LVAD)-induced remodeling to identify mechanisms impeding recovery.

METHODS

Myocardium was obtained from subjects undergoing LVAD placement and/or heart transplantation. Detailed histological analyses were performed, and, when feasible, mononuclear cells were isolated from fresh, dissociated myocardium for quantitative reverse transcription polymerase chain reaction studies. Echocardiographic and catheterization data were obtained during routine care.

RESULTS

Sixty-six subjects were enrolled; 54 underwent 8.0 ± 1.2 months of LVAD unloading. Despite effective hemodynamic unloading and remodeling, there were no differences after LVAD use in capillary density (0.78 ± 0.1% vs. 0.9 ± 0.1% capillary area; n = 42 and 28, respectively; p = 0.40), cardiac fibrosis (25.7 ± 2.4% vs. 27.9 ± 2.4% fibrosis area; n = 44 and 31, respectively; p = 0.50), or macrophage density (80.7 ± 10.4 macrophages/mm² vs. 108.6 ± 15 macrophages/mm²; n = 33 and 28, respectively; p = 0.1). Despite no change in fibrosis or myofibroblast density (p = 0.40), there was a 16.7-fold decrease (p < 0.01) in fibroblast-specific collagen expression. Furthermore, there was a shift away from pro-fibrotic/alternative pro-fibrotic macrophage signaling after LVAD use.

CONCLUSIONS

Despite robust cardiac unloading, capillary density and fibrosis are unchanged compared with loaded hearts. Fibroblast-specific collagen expression was decreased and might be due to decreased stretch and/or altered macrophage polarization. Dysfunctional myocardium may persist, in part, from ongoing inflammation and poor extracellular matrix remodeling. Understanding these changes could lead to improved therapies for HF.

Impact of Ischemic Heart Failure Etiology on Cardiac Recovery During Mechanical Unloading

BACKGROUND

Small-scale studies focused mainly on nonischemic cardiomyopathy (NICM) have shown that a subset of left ventricular assist device (LVAD) patients can achieve significant improvement of their native heart function, but the impact of ischemic cardiomyopathy (ICM) has not been specifically investigated. Many patients with acute myocardial infarction are discharged from their index hospitalization without heart failure (HF), only to return much later with overt HF syndrome, mainly caused by chronic remodeling of the noninfarcted region of the myocardium.

OBJECTIVES

This study sought to prospectively investigate the effect of ICM HF etiology on LVAD-associated improvement of cardiac structure and function using NICM as control.

METHODS

Consecutive patients (n = 154) with documented chronic and dilated cardiomyopathy (ICM, n = 61; NICM, n = 93) requiring durable support with continuous-flow LVAD were prospectively evaluated with serial echocardiograms and right heart catheterizations.

RESULTS

In patients supported with LVAD for at least 6 months, we found that 5% of subjects with ICM and 21% of subjects with NICM achieved left ventricular ejection fraction ≥40% (p = 0.034). LV end-diastolic and end-systolic volumes and diastolic function were significantly and similarly improved in patients with ICM and NICM.

CONCLUSIONS

LVAD-associated unloading for 6 months resulted in a substantial improvement in myocardial structure, and systolic and diastolic function in 1 in 20 ICM and 1 in 5 NICM patients. These specific incidence and timeline findings may provide guidance in clinical practice and research design for sequencing and prioritizing advanced HF and heart transplantation therapeutic options in patients with ICM and NICM.

Left ventricular assist device-induced reverse remodeling: it's not just about myocardial recovery

INTRODUCTION

The abnormal structure, function and molecular makeup of dilated cardiomyopathic hearts can be partially normalized in patients supported by a left ventricular assist device (LVAD), a process called reverse remodeling. This leads to recovery of function in many patients, though the rate of full recovery is low and in many cases is temporary, leading to the concept of heart failure remission, rather than recovery. Areas covered: We summarize data indicative of ventricular reverse remodeling, recovery and remission during LVAD support. These terms were used in searches performed in Pubmed. Duplication of topics covered in depth in prior review articles were avoided. Expert commentary: Although most patients undergoing mechanical circulatory support (MCS) show a significant degree of reverse remodeling, very few exhibit sufficiently improved function to justify device explantation, and many from whom LVADs have been explanted have relapsed back to the original heart failure phenotype. Future research has the potential to clarify the ideal combination of pharmacological, cell, gene, and mechanical therapies that would maximize recovery of function which has the potential to improve exercise tolerance of patients while on support, and to achieve a higher degree of myocardial recovery that is more likely to persist after device removal.

Targeted myocardial gene expression in failing hearts by RNA sequencing

Background

Myocardial recovery with left ventricular assist device (LVAD) therapy is highly variable and difficult to predict. Next generation ribonucleic acid (RNA) sequencing is an innovative, rapid, and quantitative approach to gene expression profiling in small amounts of tissue. Our primary goal was to identify baseline transcriptional profiles in non-ischemic cardiomyopathies that predict myocardial recovery in response to LVAD therapy. We also sought to verify transcriptional differences between failing and non-failing human hearts.

Methods

RNA was isolated from failing (n = 16) and non-failing (n = 8) human hearts. RNA from each patient was reverse transcribed and quantitatively sequenced on the personal genome machine (PGM) sequencer (Ion torrent) for 95 heart failure candidate genes. Coverage analysis as well as mapping the reads and alignment was done using the Ion Torrent Browser Suite™. Differential expression analyses were conducted by empirical analysis of digital gene expression data in R (edgeR) to identify differential expressed genes between failing and non-failing groups, and between responder and non-responder groups respectively. Targeted cardiac gene messenger RNA (mRNA) expression was analyzed in proportion to the total number of reads. Gene expression profiles from the PGM sequencer were validated by performing RNA sequencing (RNAseq) with the Illumina Hiseq2500 sequencing system.

Results

The failing sample population was 75% male with an average age of 50 and a left ventricular ejection fraction (LVEF) of 16%. Myosin light chain kinase (MYLK) and interleukin (IL)-6 genes expression were significantly higher in LVAD responders compared to non-responders. Thirty-six cardiac genes were expressed differentially between failing and non-failing hearts (23 decreased, 13 elevated). MYLK, Beta-1 adrenergic receptor (ADRB1) and myosin heavy chain (MYH)-6 expression were among those significantly decreased in failing hearts compared to non-failing hearts. Natriuretic peptide B (NPPB) and IL-6 were significantly elevated. Targeted gene expression profiles obtained from the Ion torrent PGM sequencer were consistent with those obtained from Illumina HiSeq2500 sequencing system.

Conclusions

Heart failure is associated with a network of transcriptional changes involving contractile proteins, metabolism, adrenergic receptors, protein phosphorylation, and signaling factors. Myocardial MYLK and IL-6 expression are positively correlated with ejection fraction (EF) response to LVAD placement. Targeted RNA sequencing of myocardial gene expression can be utilized to predict responders to LVAD therapy and to better characterize transcriptional changes in human heart failure.

DURABLE MECHANICAL CIRCULATION SUPPORT AS AN ALTERNATIVE TO HEART TRANSPLANTATION

In the review a comparative analysis of the treatment of end-stage chronic heart failure using heart transplantation and durable mechanical circulatory is conducted. It shows the main advantages and limitations of heart transplantation and the prospects of application of durable mechanical circulatory support technology. The main directions of this technology, including two-stage heart transplant (bridge to transplant – BTT), assisted circulation for myocardial recovery (bridge to recovery – BTR) and implantation of an auxiliary pump on a regular basis (destination therapy, DT). 

Transcriptional patterns of reverse remodeling with left ventricular assist devices: a consistent signature

INTRODUCTION

Left ventricular assist device (LVAD) therapy has revolutionized the treatment of patients with advanced heart failure. Although originally intended for bridge-to-transplantation and destination therapy indications, a small subset of patients supported with LVADs exhibit complete myocardial recovery leading to device explanation. However, genetic and molecular determinants of partial and/or complete myocardial recovery remain largely unknown. Areas covered: We summarize current knowledge on alterations in heart failure transcriptome in response to LVAD support, as well as discuss common gene signatures potentially responsible for the reverse remodeling phenotype in the failing human heart. Expert commentary: Reverse remodeling after LVAD is likely a continuum between fully and partially recovered myocardium. Multicenter cardiac tissue repositories linked with detailed phenotype information may facilitate identification of genetic signals responsible for myocardial recovery in LVAD supported patients in the foreseeable future.

Partial LVAD restores ventricular outputs and normalizes LV but not RV stress distributions in the acutely failing heart in silico

PURPOSE

Heart failure is a worldwide epidemic that is unlikely to change as the population ages and life expectancy increases. We sought to detail significant recent improvements to the Dassault Systèmes Living Heart Model (LHM) and use the LHM to compute left ventricular (LV) and right ventricular (RV) myofiber stress distributions under the following 4 conditions: (1) normal cardiac function; (2) acute left heart failure (ALHF); (3) ALHF treated using an LV assist device (LVAD) flow rate of 2 L/min; and (4) ALHF treated using an LVAD flow rate of 4.5 L/min.

METHODS AND RESULTS

Incorporating improved systolic myocardial material properties in the LHM resulted in its ability to simulate the Frank-Starling law of the heart. We decreased myocardial contractility in the LV myocardium so that LV ejection fraction decreased from 56% to 28%. This caused mean LV end diastolic (ED) stress to increase to 508% of normal, mean LV end systolic (ES) stress to increase to 113% of normal, mean RV ED stress to decrease to 94% of normal and RV ES to increase to 570% of normal. When ALHF in the model was treated with an LVAD flow rate of 4.5 L/min, most stress results normalized. Mean LV ED stress became 85% of normal, mean LV ES stress became 109% of normal and mean RV ED stress became 95% of normal. However, mean RV ES stress improved less dramatically (to 342% of normal values).

CONCLUSIONS

These simulations strongly suggest that an LVAD is effective in normalizing LV stresses but not RV stresses that become elevated as a result of ALHF.

Endogenous Mechanisms of Cardiac Regeneration

Zebrafish possess a remarkable capacity for cardiac regeneration throughout their lifetime, providing a model for investigating endogenous cellular and molecular mechanisms regulating myocardial regeneration. By contrast, adult mammals have an extremely limited capacity for cardiac regeneration, contributing to mortality and morbidity from cardiac diseases such as myocardial infarction and heart failure. However, the viewpoint of the mammalian heart as a postmitotic organ was recently revised based on findings that the mammalian heart contains multiple undifferentiated cell types with cardiogenic potential as well as a robust regenerative capacity during a short period early in life. Although it occurs at an extremely low level, continuous cardiomyocyte turnover has been detected in adult mouse and human hearts, which could potentially be enhanced to restore lost myocardium in damaged human hearts. This review summarizes and discusses recent advances in the understanding of endogenous mechanisms of cardiac regeneration.

Differential impact of mechanical unloading on structural and nonstructural components of the extracellular matrix in advanced human heart failure

Adverse remodeling of the extracellular matrix (ECM) is a significant characteristic of heart failure. Reverse remodeling of the fibrillar ECM secondary to mechanical unloading of the left ventricle (LV) by left ventricular assist device (LVAD) has been subject of intense investigation; however, little is known about the impacts on nonfibrillar ECM and matricellular proteins that also contribute to disease progression. Explanted failing hearts were procured from patients with nonischemic dilated cardiomyopathy (DCM) with or without LVAD support, and compared to nonfailing control hearts. LV free wall specimens were formalin-fixed, flash-frozen or optimum cutting temperature-mount frozen. Histologic and biochemical assessment of fibrillar ECM showed that LVAD support was associated with lower levels of insoluble collagen, collagen type I mRNA, and collagen I/III ratio compared with no-LVAD hearts. A disintegrin and Metalloproteinase with Thrombospondin Motifs-2 (ADAM-TS2), a procollagen endopeptidase, was reduced in no-LVAD but not in LVAD hearts. The rise in ECM proteolytic activities was significantly lower in LVAD hearts. Matrix metalloproteinases (MMP1, MMP2, MMP8, MMP13, and MT1-MMP/MMP14) were comparable between DCM hearts. Tissue inhibitor of metalloproteinase (TIMP)3 and TIMP4 messenger RNA and protein showed the greatest reduction in no-LVAD hearts. Basement membrane proteins exhibited less severe disarray of laminin and fibronectin-1 in LVAD-supported hearts. The rise in matricellular protein, osteopontin, was suppressed in LVAD hearts, whereas secreted protein, acidic, cysteine-rich (SPARC) levels was unaffected by LVAD. Mechanical unloading of the failing DCM hearts can restore the fibrillar ECM and the basement membrane, contributing toward improved clinical outcomes. However, persistent elevation of matricellular proteins such as SPARC could contribute to the relapse of failing hearts on removal of LVAD support.

Acquired von Willebrand syndrome associated with left ventricular assist device

Left ventricular assist devices (LVAD) provide cardiac support for patients with end-stage heart disease as either bridge or destination therapy, and have significantly improved the survival of these patients. Whereas earlier models were designed to mimic the human heart by producing a pulsatile flow in parallel with the patient's heart, newer devices, which are smaller and more durable, provide continuous blood flow along an axial path using an internal rotor in the blood. However, device-related hemostatic complications remain common and have negatively affected patients' recovery and quality of life. In most patients, the von Willebrand factor (VWF) rapidly loses large multimers and binds poorly to platelets and subendothelial collagen upon LVAD implantation, leading to the term acquired von Willebrand syndrome (AVWS). These changes in VWF structure and adhesive activity recover quickly upon LVAD explantation and are not observed in patients with heart transplant. The VWF defects are believed to be caused by excessive cleavage of large VWF multimers by the metalloprotease ADAMTS-13 in an LVAD-driven circulation. However, evidence that this mechanism could be the primary cause for the loss of large VWF multimers and LVAD-associated bleeding remains circumstantial. This review discusses changes in VWF reactivity found in patients on LVAD support. It specifically focuses on impacts of LVAD-related mechanical stress on VWF structural stability and adhesive reactivity in exploring multiple causes of AVWS and LVAD-associated hemostatic complications.

Functional significance of the discordance between transcriptional profile and left ventricular structure/function during reverse remodeling

To elucidate the mechanisms for reverse LV remodeling, we generated a conditional (doxycycline [dox] off) transgenic mouse tetracycline transactivating factor-TRAF2 (tTA-TRAF2) that develops a dilated heart failure (HF) phenotype upon expression of a proinflammatory transgene, TNF receptor-associated factor 2 (TRAF2), and complete normalization of LV structure and function when the transgene is suppressed. tTA-TRAF2 mice developed a significant increase in LV dimension with decreased contractile function, which was completely normalized in the tTA-TRAF2 mice fed dox for 4 weeks (tTA-TRAF2^dox4W). Normalization of LV structure and function was accompanied by partial normalization (~60%) of gene expression associated with incident HF. Similar findings were observed in patients with dilated cardiomyopathy who underwent reverse LV remodeling following mechanical circulatory support. Persistence of the HF gene program was associated with an exaggerated hypertrophic response and increased mortality in tTA-TRAF2^dox4W mice following transaortic constriction (TAC). These effects were no longer observed following TAC in tTA-TRAF2^dox8W, wherein there was a more complete (88%) reversal of the incident HF genes. These results demonstrate that reverse LV remodeling is associated with improvements in cardiac myocyte biology; however, the persistence of the abnormal HF gene program may be maladaptive following perturbations in hemodynamic loading conditions.

Management of Patients With Recovered Systolic Function

Advancements in the treatment of heart failure (HF) with systolic dysfunction have given rise to a new population of patients with improved ejection fraction (EF). The management of this distinct population is not well described due to a lack of consensus on the definition of myocardial recovery, a scarcity of data on the natural history of these patients, and the absence of focused clinical trials. Moreover, an improvement in EF may have different prognostic and management implications depending on the underlying etiology of cardiomyopathy. This can be challenging for the clinician who is approached by a patient inquiring about a reduction of medical therapy after apparent EF recovery. This review explores management strategies for HF patients with recovered EF in a disease-specific format.