Reversal of impaired myocardial beta-adrenergic receptor signaling by continuous-flow left ventricular assist device support

Predictors of long-term success after successful explantation of continuous flow left ventricular assist device support

OBJECTIVES

Predictors and evaluations of continuous flow left ventricular assist device (cf-LVAD) explantation in recovered patients remain under discussion due to lack of evidence on long-term safety and efficacy. This study summarized our experiences regarding cf-LVAD explantation in non-ischaemic dilated cardiomyopathy patients and estimated a predictor for sufficient myocardial recovery allowing left ventricular assist device explant.

METHODS

We retrospectively identified 135 adult patients with cf-LVAD therapy as bridge to heart transplant due to non-ischaemic dilated cardiomyopathy. Of those, 13 patients underwent device explantation (recovery group) after myocardial recovery. Twelve (92%) of the explanted patients were evaluated using our weaning protocol and underwent surgical explantation. Meanwhile, the remaining 122 continued with cf-LVAD therapy (non-recovery group).

RESULTS

Multivariate logistic regression analysis revealed time interval between the first heart failure event and cf-LVAD implantation as an independent predictor for successful explantation. The optimal time interval cutoff value to predict cf-LVAD explantation was 7 months, with a sensitivity of 91.0% and specificity of 84.6%. Echocardiography in patients with successful cf-LVAD explantation showed significant improvement of left ventricular function and dimensions at 6 months postoperatively. The 13 explanted patients are currently alive at a median of 30 (interquartile range; 18-58) months after explantation. The survival rate free from rehospitalization due to heart failure following explantation was 100%. Left ventricular function and remodelling after explantation were also preserved.

CONCLUSIONS

In non-ischaemic dilated cardiomyopathy patients with a short interval between the first heart failure event and cf-LVAD therapy, left ventricular myocardium may recover in an early phase after device implantation.

Myocardial Recovery

In this paper, the feasibility of myocardial recovery is analyzed through a literature review. First, the phenomena of remodeling and reverse remodeling are analyzed, approached through the physics of elastic bodies, and the terms myocardial depression and myocardial recovery are defined. Continuing, potential biochemical, molecular, and imaging markers of myocardial recovery are reviewed. Then, the work focuses on therapeutic techniques that can facilitate the reverse remodeling of the myocardium. Left ventricular assist device (LVAD) systems are one of the main ways to promote cardiac recovery. The changes that take place in cardiac hypertrophy, extracellular matrix, cell populations and their structural elements, β-receptors, energetics, and several biological processes, are reviewed. The attempt to wean the patients who experienced cardiac recovery from cardiac assist device systems is also discussed. The characteristics of the patients who will benefit from LVAD are presented and the heterogeneity of the studies performed in terms of patient populations included, diagnostic tests performed, and their results are addressed. The experience with cardiac resynchronization therapy (CRT) as another way to promote reverse remodeling is also reviewed. Myocardial recovery is a phenomenon that presents with a continuous spectrum of phenotypes. There is a need for algorithms to screen suitable patients who may benefit and identify specific ways to enhance this phenomenon in order to help combat the heart failure epidemic.

Biology of myocardial recovery in advanced heart failure with long-term mechanical support

Cardiac remodeling is an adaptive, compensatory biological process following an initial insult to the myocardium that gradually becomes maladaptive and causes clinical deterioration and chronic heart failure (HF). This biological process involves several pathophysiological adaptations at the genetic, molecular, cellular, and tissue levels. A growing body of clinical and translational investigations demonstrated that cardiac remodeling and chronic HF does not invariably result in a static, end-stage phenotype but can be at least partially reversed. One of the paradigms which shed some additional light on the breadth and limits of myocardial elasticity and plasticity is long term mechanical circulatory support (MCS) in advanced HF pediatric and adult patients. MCS by providing (a) ventricular mechanical unloading and (b) effective hemodynamic support to the periphery results in functional, structural, cellular and molecular changes, known as cardiac reverse remodeling. Herein, we analyze and synthesize the advances in our understanding of the biology of MCS-mediated reverse remodeling and myocardial recovery. The MCS investigational setting offers access to human tissue, providing an unparalleled opportunity in cardiovascular medicine to perform in-depth characterizations of myocardial biology and the associated molecular, cellular, and structural recovery signatures. These human tissue findings have triggered and effectively fueled a "bedside to bench and back" approach through a variety of knockout, inhibition or overexpression mechanistic investigations in vitro and in vivo using small animal models. These follow-up translational and basic science studies leveraging human tissue findings have unveiled mechanistic myocardial recovery pathways which are currently undergoing further testing for potential therapeutic drug development. Essentially, the field is advancing by extending the lessons learned from the MCS cardiac recovery investigational setting to develop therapies applicable to the greater, not end-stage, HF population. This review article focuses on the biological aspects of the MCS-mediated myocardial recovery and together with its companion review article, focused on the clinical aspects, they aim to provide a useful framework for clinicians and investigators.

Myocardial recovery evaluation from ventricular assist device in patients with dilated cardiomyopathy

AIMS

The removal of left ventricular assist device (LVAD) after myocardial recovery can provide survival benefits with freedom from LVAD-associated complications. However, in the absence of standardization, the weaning evaluation and surgical strategy differ widely among centres. Therefore, we analysed the experiences of LVAD explantation with our protocol in dilated cardiomyopathy (DCM) patients and investigated the validity of our weaning evaluation and surgical strategy from the perspective of optimal long-term survival.

METHODS AND RESULTS

All LVAD explantation patients in our institution between May 2012 and May 2020 were enrolled. All patients were evaluated by our three-phase weaning assessment: (i) clinical stability with improved cardiac function under LVAD support; (ii) haemodynamic stability shown by ramp-loading and saline-loading test; (iii) intraoperative pump-off test. Explant surgery involved removal of the whole system including driveline, pump, sewing ring and outflow-graft, and closure of an apical hole. Intra-operative, peri-operative, and post-operative outcomes, including all-cause mortality and LVAD associated major complications, were retrospectively analysed. A total of 12 DCM patients (DuraHeart, n = 2; EVAHEART, n = 2; HeartMate II, n = 6; HeartMate 3, n = 2) had myocardial recovery after a median 10 months [interquartile range (IQR); 6.3-15 months] support and qualified for our LVAD explantation study protocol [median age: 37 y, IQR; 34-41 years; 83% men]. The median left ventricular ejection fraction was 20% (IQR; 12-23%) at LVAD-implantation and 54% (IQR: 45-55%) before LVAD explantation (P < 0.001). There were no perioperative complications and median ICU stay was 4 days (IQR; 2-4 days). All patients were discharged after a median of 24 days (IQR: 17-28 days) postoperatively. No patient suffered from any cardiac event (heart failure hospitalization, re-implantation of LVAD, or heart transplantation) at a median of 40 months (IQR: 17-58 months) follow up. All patients are alive with NYHA functional class 1 with preserved left ventricular function.

CONCLUSIONS

The evaluation of LVAD explant candidates by our weaning protocol was safe and effective. In the patients completing our protocol successfully, LVAD explantation is feasible and an excellent long-term cardiac event free-survival seems to be achieved.

Left ventricular reverse remodelling and its predictors in non-ischaemic cardiomyopathy

Adverse remodelling following an initial insult is the hallmark of heart failure (HF) development and progression. It is manifested as changes in size, shape, and function of the myocardium. While cardiac remodelling may be compensatory in the short term, further neurohumoral activation and haemodynamic overload drive this deleterious process that is associated with impaired prognosis. However, in some patients, the changes may be reversed. Left ventricular reverse remodelling (LVRR) is characterized as a decrease in chamber volume and normalization of shape associated with improvement in both systolic and diastolic function. LVRR might occur spontaneously or more often in response to therapeutic interventions that either remove the initial stressor or alleviate some of the mechanisms that contribute to further deterioration of the failing heart. Although the process of LVRR in patients with new‐onset HF may take up to 2 years after initiating treatment, there is a significant portion of patients who do not improve despite optimal therapy, which has serious clinical implications when considering treatment escalation towards more aggressive options. On the contrary, in patients that achieve delayed improvement in cardiac function and architecture, waiting might avoid untimely implantable cardioverter‐defibrillator implantation. Therefore, prognostication of successful LVRR based on clinical, imaging, and biomarker predictors is of utmost importance. LVRR has a positive impact on prognosis. However, reverse remodelled hearts continue to have abnormal features. In fact, most of the molecular, cellular, interstitial, and genome expression abnormalities remain and a susceptibility to dysfunction redevelopment under biomechanical stress persists in most patients. Hence, a distinction should be made between reverse remodelling and true myocardial recovery. In this comprehensive review, current evidence on LVRR, its predictors, and implications on prognostication, with a specific focus on HF patients with non‐ischaemic cardiomyopathy, as well as on novel drugs, is presented.

Cardiac recovery following left ventricular assist device therapy: experience of complete device explantation including ventricular patch plasty

OBJECTIVES

Myocardial recovery is a rare phenomenon in left ventricular assist device (LVAD) therapy. Surgical LVAD removal is associated with the risk of cardiac failure, and the individual evaluation of sufficient myocardial recovery is crucial. Thus, complete device explantation is not consistently performed to minimize perioperative risk. However, the remaining ventricular assist device components bear significant risks of infection or thrombosis. Therefore, we developed this study to evaluate a complete LVAD explantation protocol.

METHODS

All patients in our institution who had an LVAD explanted were enrolled in the study. Explant surgery involved removal of the driveline, pump housing, sewing ring and outflow graft. The ventricular wall was reconstructed by double patch plasty. Our analysis focused on surgical and postoperative outcome parameters, including all-cause mortality and major adverse cardiac and cerebrovascular events.

RESULTS

A total of 12 patients (HVAD, n = 5; HeartMate II, n = 3; HeartMate 3, n = 4) had myocardial recovery and qualified for our LVAD explantation study protocol [median age: 40 years, interquartile range (IQR) 33-52 years; 50% men]. Primary heart failure aetiology: myocarditis (n = 5), dilated cardiomyopathy (n = 4), toxic cardiomyopathy (n = 2) and valvular heart failure (n = 1). The median average duration on LVAD was 10 months (25-75%: IQR 8.5-30 months). The median left ventricular ejection fraction was 15% (IQR 13-18%) at LVAD implantation and 50% (IQR 45-50%) before LVAD explantation (P = 0.0025).The 30-day survival was 100%. The 1-year survival was 91.7%. All patients were discharged after a median 13 days (IQR 10-18 days) postoperatively. No patient had major adverse cardiac and cerebrovascular events. The New York Heart Association functional class remained consistent during the follow-up period (median New York Heart Association functional class: II, IQR II-II class) including preservation of ventricular function.

CONCLUSIONS

Complete LVAD explantation with ventricular patch plasty is feasible and has consistent long-term results.

Reverse Remodeling With Left Ventricular Assist Devices

This review provides a comprehensive overview of the past 25+ years of research into the development of left ventricular assist device (LVAD) to improve clinical outcomes in patients with severe end-stage heart failure and basic insights gained into the biology of heart failure gleaned from studies of hearts and myocardium of patients undergoing LVAD support. Clinical aspects of contemporary LVAD therapy, including evolving device technology, overall mortality, and complications, are reviewed. We explain the hemodynamic effects of LVAD support and how these lead to ventricular unloading. This includes a detailed review of the structural, cellular, and molecular aspects of LVAD-associated reverse remodeling. Synergisms between LVAD support and medical therapies for heart failure related to reverse remodeling, remission, and recovery are discussed within the context of both clinical outcomes and fundamental effects on myocardial biology. The incidence, clinical implications and factors most likely to be associated with improved ventricular function and remission of the heart failure are reviewed. Finally, we discuss recognized impediments to achieving myocardial recovery in the vast majority of LVAD-supported hearts and their implications for future research aimed at improving the overall rates of recovery.

Hurdles to Cardioprotection in the Critically Ill

Cardiovascular disease is the largest contributor to worldwide mortality, and the deleterious impact of heart failure (HF) is projected to grow exponentially in the future. As heart transplantation (HTx) is the only effective treatment for end-stage HF, development of mechanical circulatory support (MCS) technology has unveiled additional therapeutic options for refractory cardiac disease. Unfortunately, despite both MCS and HTx being quintessential treatments for significant cardiac impairment, associated morbidity and mortality remain high. MCS technology continues to evolve, but is associated with numerous disturbances to cardiac function (e.g., oxidative damage, arrhythmias). Following MCS intervention, HTx is frequently the destination option for survival of critically ill cardiac patients. While effective, donor hearts are scarce, thus limiting HTx to few qualifying patients, and HTx remains correlated with substantial post-HTx complications. While MCS and HTx are vital to survival of critically ill cardiac patients, cardioprotective strategies to improve outcomes from these treatments are highly desirable. Accordingly, this review summarizes the current status of MCS and HTx in the clinic, and the associated cardiac complications inherent to these treatments. Furthermore, we detail current research being undertaken to improve cardiac outcomes following MCS/HTx, and important considerations for reducing the significant morbidity and mortality associated with these necessary treatment strategies.

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.

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.

Novel Molecular Approaches in Heart Failure: Seven Trans-Membrane Receptors Signaling in the Heart and Circulating Blood Leukocytes

Heart failure (HF) is the result of molecular, cellular, and structural changes induced by cardiac load or injury. A complex network of signaling pathways have been involved in the development and progression of cardiac dysfunction. In this review, we summarize the pivotal role of seven trans-membrane receptors (7TMRs), also called G-protein-coupled receptors (GPCRs), in HF. Moreover, we will discuss the current knowledge on the potential mirroring of 7TMR signaling between circulating blood leukocytes and the heart, and the related future possibilities in the management of HF patients.

Myocardial recovery during mechanical circulatory support: cellular, molecular, genomic and organ levels

Mechanical circulatory support is a life-saving therapy that will become either a bridge-to-transplantation or definitive therapy if heart transplantation is not possible. Failing hearts supported by a ventricular assist device  were often found to recover at molecular and cellular level but translation of these changes into functionally-stable cardiac recovery allowing long-term heart transplantation/ventricular assist device-free outcomes after weaning from ventricular assist device is relatively rare and related to the etiology, severity and duration of myocardial damage. The reason for the discrepancy between high recovery rates on the cellular and molecular levels and the low rate of cardiac recovery allowing ventricular assist device explantation is unknown.

G protein-coupled receptor kinase 2: a link between myocardial contractile function and cardiac metabolism

Heart failure (HF) causes a tremendous burden on the worldwide healthcare system, affecting >23 million people. There are many cardiovascular disorders that contribute to the development of HF and multiple risk factors that accelerate its occurrence, but regardless of its underlying cause, HF is characterized by a marked decrease in myocardial contractility and loss of pump function. One biomarker molecule consistently shown to be upregulated in human HF and several animal models is G protein-coupled receptor kinase-2 (GRK2), a kinase originally discovered to be involved in G protein-coupled receptor desensitization, especially β-adrenergic receptors. Higher levels of GRK2 can impair β-adrenergic receptor-mediated inotropic reserve and its inhibition, or molecular reduction has shown to improve pump function in several animal models including a preclinical pig model of HF. Recently, nonclassical roles for GRK2 in cardiovascular disease have been described, including negative regulation of insulin signaling, a role in myocyte cell survival and apoptotic signaling, and it has been shown to be localized in/on mitochondria. These new roles of GRK2 suggest that GRK2 may be a nodal link in the myocyte, influencing both cardiac contractile function and cell metabolism and survival and contributing to HF independent of its canonical role in G protein-coupled receptor desensitization. In this review, classical and nonclassical roles for GRK2 will be discussed, focusing on recently discovered roles for GRK2 in cardiomyocyte metabolism and the effects that these roles may have on myocardial contractile function and HF development.

Assessment of myocardial viability and left ventricular function in patients supported by a left ventricular assist device

BACKGROUND

Chronically supported left ventricular assist device (LVAD) patients may be candidates for novel therapies aimed at promoting reverse remodeling and myocardial recovery. However, the effect of hemodynamic unloading with a LVAD on myocardial viability and LV function in chronically supported LVAD patients has not been fully characterized. We aimed to develop a non-invasive imaging protocol to serially quantify native cardiac structure, function, and myocardial viability while at reduced LVAD support.

METHODS

Clinically stable (n = 18) ambulatory patients (83% men, median age, 61 years) supported by a HeartMate II (Thoratec, Pleasanton, CA) LVAD (median durations of heart failure 4.6 years and LVAD support 7 months) were evaluated by echocardiography and technetium-99m ((99m)Tc)-sestamibi single photon emission computed tomography (SPECT) imaging at baseline and after an interval of 2 to 3 months. Echocardiographic measures of LV size and function, including speckle tracking-derived circumferential strain, were compared between ambulatory and reduced LVAD support at baseline and between baseline and follow-up at reduced LVAD support. The extent of myocardial viability by SPECT was compared between baseline and follow-up at reduced LVAD support.

RESULTS

With reduction in LVAD speeds (6,600 rpm; interquartile range: 6,200, 7,400 rpm), LV size increased, LV systolic function remained stable, and filling pressures nominally worsened. After a median 2.1 months, cardiac structure, function, and the extent of viable myocardium, globally and regionally, was unchanged on repeat imaging while at reduced LVAD speed.

CONCLUSIONS

In clinically stable chronically supported LVAD patients, intrinsic cardiac structure, function, and myocardial viability did not significantly change over the pre-specified time frame. Echocardiographic circumferential strain and (99m)Tc-sestamibi SPECT myocardial viability imaging may provide useful non-invasive end points for the assessment of cardiac structure and function, particularly for phase II studies of novel therapies aimed at promoting reverse remodeling and myocardial recovery in LVAD patients.

Targeting GRK2 by gene therapy for heart failure: benefits above β-blockade

Heart failure (HF) is a common pathological end point for several cardiac diseases. Despite reasonable achievements in pharmacological, electrophysiological and surgical treatments, prognosis for chronic HF remains poor. Modern therapies are generally symptom oriented and do not currently address specific intracellular molecular signaling abnormalities. Therefore, new and innovative therapeutic approaches are warranted and, ideally, these could at least complement established therapeutic options if not replace them. Gene therapy has potential to serve in this regard in HF as vectors can be directed toward diseased myocytes and directly target intracellular signaling abnormalities. Within this review, we will dissect the adrenergic system contributing to HF development and progression with special emphasis on G-protein-coupled receptor kinase 2 (GRK2). The levels and activity of GRK2 are increased in HF and we and others have demonstrated that this kinase is a major molecular culprit in HF. We will cover the evidence supporting gene therapy directed against myocardial as well as adrenal GRK2 to improve the function and structure of the failing heart and how these strategies may offer complementary and synergistic effects with the existing HF mainstay therapy of β-adrenergic receptor antagonism.

Myocardial G protein receptor-coupled kinase expression correlates with functional parameters and clinical severity in advanced heart failure

BACKGROUND

In heart failure (HF), sympathetic hyperactivation induces deleterious effects in myocardial β-adrenergic signaling, with receptor down-regulation and desensitization mediated by G protein receptor-coupled kinases (GRKs). We hypothesised that changes in GRK isoforms may be associated with clinical status in advanced HF, using the Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) scale.

METHODS

We included 31 patients with advanced HF undergoing transplantation. According to INTERMACS profiles, mRNA and protein levels of GRK isoforms in left ventricular (LV) myocardium were analyzed and compared with nonfailing LV samples.

RESULTS

In failing LV myocardium, GRK2 and GRK5 (but not GRK3) protein was up-regulated compared with control samples. Among HF patients, an increase in GRK2 and GRK5 mRNA and protein abundance was observed in β-agonist-treated patients (vs β-blockers: P < .05) and in higher-risk INTERMACS status (profiles 2 and 3 vs 4 and 5: P < .05). A significant negative correlation of GRK2 expression with LV stroke volume supported these findings.

CONCLUSIONS

Increased GRK2 correlates with clinical severity using the INTERMACS scale and LV stroke volume, supporting it as a potential target in advanced HF. These changes are paralleled by GRK5 expression in the failing myocardium, suggesting a relevant role in human HF.

G protein coupled receptor kinases as therapeutic targets in cardiovascular disease

G protein-coupled receptors (GPCRs) represent the largest family of membrane receptors and are responsible for regulating a wide variety of physiological processes. This is accomplished via ligand binding to GPCRs, activating associated heterotrimeric G proteins and intracellular signaling pathways. G protein-coupled receptor kinases (GRKs), in concert with β-arrestins, classically desensitize receptor signal transduction, thus preventing hyperactivation of GPCR second-messenger cascades. As changes in GRK expression have featured prominently in many cardiovascular pathologies, including heart failure, myocardial infarction, hypertension, and cardiac hypertrophy, GRKs have been intensively studied as potential diagnostic or therapeutic targets. Herein, we review our evolving understanding of the role of GRKs in cardiovascular pathophysiology.

betaARKct: a therapeutic approach for improved adrenergic signaling and function in heart disease

One of the most powerful regulators of cardiovascular function is catecholamine-stimulated adrenergic receptor (AR) signaling. The failing heart is characterized by desensitization and impaired beta-AR responsiveness as a result of upregulated G protein-coupled receptor kinase-2 (GRK2) present in injured myocardium. Deterioration of cardiac function is progressively enhanced by chronic adrenergic over-stimulation due to increased levels of circulating catecholamines. Increased GRK2 activity contributes to this pathological cycle of over-stimulation but lowered responsiveness. Over the past two decades the GRK2 inhibitory peptide betaARKct has been identified as a potential therapy that is able to break this vicious cycle of self-perpetuating deregulation of the beta-AR system and subsequent myocardial malfunction, thus halting development of cardiac failure. The betaARKct has been shown to interfere with GRK2 binding to the betagamma subunits of the heterotrimeric G protein, therefore inhibiting its recruitment to the plasma membrane that normally leads to phosphorylation and internalization of the receptor. In this article we summarize the current data on the therapeutic effects of betaARKct in cardiovascular disease and report on recent and ongoing studies that may pave the way for this peptide towards therapeutic application in heart failure and other states of cardiovascular disease.