The time course of natriuretic hormones as plasma markers of myocardial recovery in heart transplant candidates during ventricular assist device support reveals differences among device types

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.

Prognostic Implications of Ambulatory N-Terminal Pro-B-Type Natriuretic Peptide Changes in Patients with Continuous-Flow Left Ventricular Assist Devices

Data regarding the role of N-terminal Pro-B-type natriuretic peptide (NT-pro BNP) in patients with a continuous-flow left ventricular assist device (CFLVAD) is scarce. To evaluate the prognostic implications of measuring both absolute values and changes in NT-pro BNP concentrations in ambulatory patients with a CFLVAD, we performed a retrospective study of 168 consecutive patients who had an LVAD implantation at our institution and survived beyond their index hospitalization. Of these, 127 patients (56.2 ± 12.5 years, 21.2% female) had NT-pro BNP measured at 1 and 3 months postdischarge in ambulatory settings. Compared to the NT-pro BNP concentration at 1 month, 94 patients (74%) had a decline, and 33 patients (26%) had an increase in concentrations, from their 1 month baseline. After a median follow-up of 17 months, a total of 53 (41.7%) adverse events occurred. Of these, 37 (69.8%) were heart failure (HF) hospitalizations, and 16 (30.2%) were deaths. For each 1,000 unit increase in NT-pro BNP concentration at 3 months, there was a 17% increase in the risk of HF hospitalization or death (hazard ratio [HR] = 1.17, 95% confidence interval [CI] = 1.04-1.32, p = 0.007). Conversely, each 1000 unit decline during the same time, was associated with an 11% decrease in the risk of HF hospitalization or death (HR = 0.89, 95% CI = 0.77-0.98, p = 0.04). In conclusion, in patients with a CFLAD, an increase in NT-pro BNP concentration from 1 to 3 months is associated with an increased risk of HF hospitalization and death. In contrast, a decline is associated with a reduction in the risk of HF hospitalization and death.

Biomarkers in Patients with Left Ventricular Assist Device: An Insight on Current Evidence

Left ventricular assist devices (LVADs) have been representing a cornerstone therapy for patients with end-stage heart failure during the last decades. However, their use induces several pathophysiological modifications which are partially responsible for the complications that typically characterize these patients, such as right ventricular failure, thromboembolic events, as well as bleedings. During the last years, biomarkers involved in the pathways of neurohormonal activation, myocardial injury, adverse remodeling, oxidative stress and systemic inflammation have raised attention. The search and analysis of potential biomarkers in LVAD patients could lead to the identification of a subset of patients with an increased risk of developing these adverse events. This could then promote a closer follow-up as well as therapeutic modifications. Furthermore, it might highlight some new therapeutic pharmacological targets that could lead to improved long-term survival. The aim of this review is to provide current evidence on the role of different biomarkers in patients with LVAD, in particular highlighting their possible implications in clinical practice.

The contribution of cardiac and extracardiac factors to NT-proBNP concentrations in patients with advanced heart failure before and after left ventricular assist device implantation

The clinical significance of N-terminal pro-brain natriuretic peptide (NT-proBNP) in patients undergoing left ventricular assist device (LVAD) implantation is not fully explored. NT-proBNP concentrations are influenced by body composition, renal function and intracardiac pressures; dynamic measures pre- and post-LVAD implantation. We sought to identify the individual contribution of cardiac and extracardiac factors to NT-proBNP concentrations in advanced heart failure patients before and after LVAD implantation. We retrospectively collected data from 63 patients implanted with a LVAD with NT -proBNP measurements (2006-2019). Hemodynamic measurements were obtained through right heart catheterization (RHC). Univariable linear regression and multivariable stepwise regression models were used to analyze variables associated with NT-proBNP concentrations in the pre- and post-LVAD setting. Paired t-test was performed on a subpopulation of 13 patients with complete data. We found significant differences in all extracardiac (BMI, creatinine, eGFR) and all invasive hemodynamic measurements pre-LVAD compared to post-LVAD. NT-proBNP decreased by 83 %, in the subpopulation of 13 patients: 736 pmol/L [IQR 498-1330] to 126 pmol/L [IQR 74.8-241.7]. In multivariable analysis, only creatinine remained significantly associated with NT-proBNP before LVAD implant (p = 0.016), whereas pulmonary capillary wedge pressure (PCWP) was the only independent variable associated with NT-proBNP after LVAD implant (p < 0.0001). Creatinine and PCWP were the only independent factors associated with NT-proBNP concentrations before and after LVAD implantation, respectively. Invasive hemodynamic measurements were more closely associated with NT-proBNP concentration after LVAD than extracardiac factors and reversely pre-LVAD, suggesting that NT-proBNP serves as a useful biomarker of cardiac conditions post-LVAD implantation.

Biomarkers in Advanced Heart Failure: Implications for Managing Patients With Mechanical Circulatory Support and Cardiac Transplantation

Biomarkers have a well-defined role in the diagnosis and management of chronic heart failure, but their role in patients with left ventricular assist devices and cardiac transplant is uncertain. In this review, we summarize the available literature in this patient population, with a focus on clinical application. Some ubiquitous biomarkers, for example, natriuretic peptides and cardiac troponin, may assist in the diagnosis of left ventricular assist device complications and transplant rejection. Novel biomarkers focused on specific pathological processes, such as left ventricular assist device thrombosis and profiling of leukocyte activation, continue to be developed and show promise in altering the management of the advanced heart failure patient. Few biomarkers at this time have been assessed with sufficient scrutiny to warrant broad, universal application, but encouraging limited data and large potential for impact should prompt ongoing investigation.

Dynamics and prognostic value of B-type natriuretic peptide in left ventricular assist device recipients

Background

The prognostic utility of B-type natriuretic peptide (BNP) in heart failure is well recognized. Previous studies demonstrated that BNP levels decrease after left ventricular assist device (LVAD) implantation. We sought to investigate the predictive value of baseline and changes in BNP levels in LVAD recipients.

Methods

BNP was measured in baseline and follow-up plasma samples from consecutive patients receiving a continuous-flow LVAD from 2010 through 2016. Absolute values and changes from baseline were related to clinical outcomes.

Results

Median BNP at baseline was 885 [interquartile range (IQR): 450-1,624] pg/mL, decreasing to 289 (IQR: 154-534) pg/mL at 90 days after LVAD implantation. Cox regression analysis revealed that higher baseline and follow-up BNP levels were not associated with increased risk of death at 180 days (P=0.12 and P=0.32, respectively). In the univariate analysis 90-day BNP, but not baseline BNP, was significantly associated with the combined death/hospitalization outcome 180 days after LVAD implantation [hazard ratio (HR) 1.03, 95% CI: 1.01-1.06; P=0.006]. This significance was not preserved after adjusting for multiple covariates (HR 1.01, 95% CI: 0.98-1.04; P=0.62). At 90 days, there was no BNP lowering in 20.6% of subjects. This was not associated with higher risk for death or the composite of death/hospitalization (P=0.11 and P=0.06 respectively).

Conclusions

BNP absolute levels and changes from baseline are not independently associated with clinical outcomes after LVAD-implantation. These findings suggest an impaired prognostic performance of BNP after LVAD implantation.

Initial Results of Clinical Trial with a New Left Ventricular Assist Device (LVAD) Providing Synchronous Pulsatile Flow

Objectives

A multicentric European Clinical Study is ongoing to evaluate safety and efficacy of a new pulsatile implantable LVAD (BestBeat), smaller and lighter than similar devices, capable of providing synchronous and counterpulsating flow with respect to the LV of end-stage heart failure patients. Preliminary clinical results are reported.

Methods

The new BestBeat LVAD was used, consisting of an implantable pulsatile blood pump, electromechanically driven by a ball screw mechanism, and a wearable electronic controller and power sources. The clinical trial was conducted at 5 European centers. Adult patients affected by CHF in NYHA Class IV despite optimized medical treatment were enrolled. The primary study endpoint was survival at 90 days. Further study endpoints were maintenance of adequate LVAD pump flow and a minimum rate of adverse events during support.

Results

As of June 2008, 6 patients received the implant. Cumulative support time was 3.7 years, median support time 176 days. All patients who completed the study survived except for one, who died after 48 days, due to combined infection and cerebrovascular accident. Another two patients died: one from intracranial bleeding 113 days after implant, and one from septic shock after 123 days. Hemodynamic improvement with Cl>2.0 l/min/m2 and recovery of end-organ function expressed by consistent improvement of BUN, creatinine and bilirubin were reached in all patients. No device failure was observed. There was no bleeding requiring re-exploration, no hemolysis and only two device-related infections (both in one patient). Neurologic events were reported, the most serious ones occurring in patients with pre-implant respiratory and kidney failure. Three patients were discharged home. Two patients were successfully transplanted, one after 6 months and one after 13 months on device.

Conclusions

Good performance and efficacy of the device were observed; the endpoints of the study were achieved, and its safety was consistent with expectations. The ongoing study will allow further conclusions to be drawn.

Serum Brain Natriuretic Peptide Concentration 60 Days After Surgery as a Predictor of Long-Term Prognosis in Patients Implanted With a Left Ventricular Assist Device

Mechanical circulatory support by a left ventricular assist device (LVAD) is used to bridge patients with advanced heart failure to transplant or as a definitive treatment. We retrospectively sought predictors of long-term outcome in a cohort of 83 patients who had undergone LVAD treatment. We subjected perioperative clinical data of patients to statistical analysis to establish parameters associated with all-cause mortality, and the cutoff values, sensitivity, and specificity of those that had a statistically significant relation with survival. Mean follow-up was 717 days (standard deviation, 334 days; range, 17-1,592 days). Fourteen patients (16.8%) died, but nine (10.8%) were weaned from support. Serum brain natriuretic peptide (BNP) concentration measured 60 days after implantation was significantly associated with all-cause mortality. The optimal BNP cutoff value to predict death during LVAD support was 322 pg/ml, with a sensitivity of 71.4% and specificity of 79.8%. Two-year survival was 92.0% in those with 60 days serum BNP concentration <322 pg/ml compared with 70.5% in those in whom it was ≥322 pg/ml (p = 0.003). The relation between BNP and survival likely reflects recovery of native myocardial function and improvements in global health and should assist clinicians in the on-going management of long-term LVAD therapy.

Effects of left ventricular assist device support on biomarkers of cardiovascular stress, fibrosis, fluid homeostasis, inflammation, and renal injury

OBJECTIVES

The purpose of this study was to examine changes in a broad panel of biomarkers following left ventricular assist device (LVAD) support in advanced heart failure (HF).

BACKGROUND

LVAD therapy mechanically unloads the failing heart and may result in reversal of certain aspects of the end-stage HF phenotype. Changes in markers of myocardial stress, fibrosis, inflammation, fluid homeostasis, and renal injury in this setting are unknown.

METHODS

Amino-terminal pro-B-type natriuretic peptide (NT-proBNP), galectin-3, ST2, copeptin, growth differentiation factor (GDF)-15, C-reactive protein (CRP), and neutrophil gelatinase associated lipocalin (NGAL) levels were measured in frozen plasma collected from 37 individuals prior to continuous flow LVAD implantation and a median of 136 (interquartile range: 94 to 180) days after implantation.

RESULTS

The median age of patients was 68 years old. LVAD therapy was associated with significant decreases in NT-proBNP (3,093 to 2,090 pg/ml; p = 0.02), ST2 (67.5 to 45.2 ng/ml, p <0.01), galectin-3 (24.7 to 22.0 ng/ml; p = 0.04), GDF-15 (3,232 to 2,613 ng/l;p <0.001), hs-CRP (22.4 to 11.9 mg/l; p = 0.01), and copeptin (103 to 94 pmol/l; p = 0.003) but not NGAL (132 to 135 ng/ml; p = 0.06). Despite improvement over time, absolute values of each biomarker remained extremely abnormal. Greater reductions in biomarkers were noted in individuals with >25% decrease in NT-proBNP concentrations but reached statistical significance only in the case of galectin-3 (p = 0.01).

CONCLUSIONS

The biomarker profile in patients after LVAD placement improves but nonetheless remains significantly abnormal. Our results suggest the need for targeted therapeutic interventions to mitigate such abnormalities and potentially increase rates of myocardial recovery.

Biomarkers in mechanical circulatory support

Heart failure is a complex multifaceted syndrome occurring as a result of impaired cardiac function. Understanding the neurohormonal, inflammatory and molecular pathways involved in the pathophysiology of this syndrome has led to the development of effective and widely used pharmacological treatments. Despite this, mortality and hospitalization rates associated with this condition remain high. The natural course of this illness is usually progressive, often leading inexorably to end stage heart failure, for which orthotopic heart transplant is a treatment option but one with limited resource. In the past decade, mechanical circulatory support has emerged as a potential therapy for certain patients with advanced heart failure. This article reviews the published data regarding biomarkers in the setting of mechanical circulatory support, and highlights areas of ongoing work and potential future areas of interest.

Adipose tissue biology and cardiomyopathy: translational implications

It is epidemiologically established that obesity is frequently associated with the metabolic syndrome and poses an increased risk for the development of type 2 diabetes mellitus and cardiovascular disease. The molecular links that connect the phenomenon of obesity, per se, with insulin resistance and cardiovascular disease are still not fully elucidated. It is increasingly apparent that fully functional adipose tissue can be cardioprotective by reducing lipotoxic effects in other peripheral tissues and by maintaining a healthy balance of critical adipokines, thereby allowing the heart to maintain its full metabolic flexibility. The present review highlights both basic and clinical findings that emphasize the complex interplay of adipose tissue physiology and adipokine-mediated effects on the heart exerted by either direct effects on cardiac myocytes or indirect actions via central mechanisms through sympathetic outflow to the heart.

Myocardial recovery with left ventricular assist devices

OPINION STATEMENT

Advanced heart failure (HF) is a condition that is rarely thought of in terms of cure. Left ventricular assist devices (LVADs), like no therapy before them, provide complete decongestion of the left ventricle, with resulting favorable changes at all levels, from reversal of hypertrophy of cardiomyocytes to recovery of normal geometry and function of the ventricles. Although not a frequent phenomenon at most institutions, LV recovery is achieved in 20-25 % of LVAD recipients in some programs. Patients with good chances for recovery are usually young, with nonischemic cardiomyopathy and short duration of HF symptoms. After LVAD removal, patients with recovered function remain asymptomatic for years. To reach this level of sustainable restoration of cardiac function, several steps need to be taken: 1) myocardial recovery has to be recognized as a therapeutic goal, especially in patients with nonischemic cardiomyopathy; 2) HF medications have to be restarted and aggressively uptitrated after LVAD implantation; 3) regular monitoring for signs of myocardial recovery (eg, echocardiography or hemodynamics) should become a standard practice in LVAD centers; and 4) weaning protocols should be discussed and accepted at each LVAD program. While some protocols involve extensive several-day testing both at rest and with exercise, others are mostly guided by echocardiographic evaluation.

The natriuretic peptide time-course in end-stage heart failure patients supported by left ventricular assist device implant: focus on NT-proCNP

This study aimed to evaluate left ventricular assist device (LVAD) effects on natriuretic peptide (NP) prohormone plasma levels in end-stage heart failure (HF) patients, especially NT-proCNP, in order to better characterize the NP system during hemodynamic recovery by LVAD. HF patients (n=17, NYHA III-IV) undergoing LVAD were studied: 6 died of multi-organ failure syndrome (NS) and 11 survived (S). Total sequential organ failure assessment (t-SOFA) score and blood samples were obtained at admission (T1) and at 24, 72h and 1, 2, 4 weeks (T2-T6) after LVAD. In S, NT-proANP and NT-proCNP significantly increased at 24h after implantation, reaching a reduction to basal levels at 4 weeks following LVAD [NT-proANP: T1 vs. T2 p=0.017, NT-proCNP: T1 vs. T2 p=0.028, T1 vs. T3 p=0.043]. Elevated NT-proBNP plasma levels were observed at all times. In NS, NP plasma levels sustained higher with respect to S. No statistical variation was observed for NT-proCNP and NT-proANP in S and NS while NT-proBNP reached significant differences at T4 in NS. Considering S+NS, only NT-proCNP strongly correlated with t-SOFA score at T1 (rho=0.554, p=0.04) while subdividing patients NT-proCNP positively correlated in NS with t-SOFA score (rho=0.988, p=0.002) only at T4. In NS a correlation between NT-proCNP and NT-proBNP at T1 was observed (rho=-0.900, p=0.037). Both IL-6 and TNF-alpha sustained higher in NS patients than in S; in particular, statistical significance was observed for IL-6. The study of new peptides, such as NT-proCNP, would provide additional information for identifying patients who are more likely to recover.

Novel biomarkers in human terminal heart failure and under mechanical circulatory support

This review summarizes recent findings on novel biochemical plasma biomarkers in terminal heart failure patients, which might predict an advanced mortality risk or even recovery. Moreover, we discussed the regulation of these heart failure-related biomarkers under mechanical circulatory support.

The influence of operational protocol on the fluid dynamics in the 12 cc Penn state pulsatile pediatric ventricular assist device: the effect of end-diastolic delay

The success of adult ventricular assist devices (VADs), coupled with the high transplant waiting list mortality of infants (40%) has prompted Penn State to develop a pediatric version of the clinically successful adult device. Although the primary use of this device will be bridge-to-transplant, there has been sufficient clinical data to demonstrate the efficacy of VADs in a bridge-to-recovery setting. However, removing the patient from the device, a process known as weaning, demands operation of the device at a lower beat rate and concomitant increased risk for thromboembolism. Previous studies have shown that the interrelated flow characteristics necessary for the prevention of thrombosis in a pulsatile VAD are a strong inlet jet, a late diastolic recirculating flow, and a wall shear rate greater than 500/s. In an effort to develop a strong inlet jet and rotational flow pattern at a lower beat and flow rate, we have compressed diastole by altering the end-diastolic delay time (EDD). Particle image velocimetry was used to compare the flow fields and wall shear rates in the chamber of the 12 cc Penn State pulsatile pediatric VAD operated at 50 beats per minute using EDDs of 10, 50, and 100 ms. Although we expected the 100 ms EDD to have the best wall shear profiles, we found that the 50 ms EDD condition was superior to both the 10 and 100 EDD conditions, due to a longer sustained inlet jet.

Left ventricular remodeling and myocardial recovery on mechanical circulatory support

BACKGROUND

Myocardial recovery after ventricular assist devices (VAD) is rare but appears more common in nonischemic cardiomyopathies (NICM). We sought to evaluate left ventricular (LV) end diastolic diameter (LVEDD) for predicting recovery after VAD.

METHODS AND RESULTS

NICM patients receiving long-term mechanical support between 1996 and 2008 were reviewed. Subjects were divided into 3 groups: mild, moderate, and severe dilation (Group A: LVEDD <6.0 cm [n = 22]; Group B: 6.0-7.0 cm [n = 32]; Group C: >7.0 cm [n = 48], respectively). Overall, recovery (successful explant without transplantation) occurred in 14 of 102 subjects (14%). Of these, 2 died and 2 required transplantation within 1 year. Recovery was more common in patients without LV dilation (Groups A/B/C = 32%/22%/0%, P < .001), as was sustained recovery (alive and transplant free 1 year after explant; A/B/C = 27%/10%/0%, P = .001). Of the recovery patients in Group A, 6/7 (86%) had sustained recovery versus 3/6 (50%) in Group B.

CONCLUSIONS

Recovery occurred in 32% of NICM patients without significant LV dilation at time of VAD, the majority of whom experienced significant sustained recovery. Recovery was not evident in those with severe LV dilation. Routine echocardiography at the time of implant may assist in targeting patients for recovery after VAD.

Increased number of circulating progenitor cells after implantation of ventricular assist devices

BACKGROUND

Bone marrow-derived circulating progenitor cells possess tissue repair potential, improving perfusion, left ventricular remodeling, and contractility in experimental models. We quantified and investigated the kinetics of 4 circulating progenitor cell sub-populations on the basis of CD34, CD133, and vascular endothelial growth factor receptor-2 (VEGFR-2) antigen expression.

METHODS

CD34+, CD34+/CD133+/VEGFR-2-, CD34+/CD133+/VEGFR-2+, and CD34+/CD133-/VEGFR-2+ cells were counted in 10 male patients with end-stage congestive heart failure. Five underwent left ventricular/biventricular assist device (LVAD/BiVAD) implantation (VAD group), and 5 were ineligible for VAD implantation (no-VAD group). Peripheral blood was collected at 3 time points for each patient: before, 15, and 60 days after VAD placement in the VAD group and at the same time points in the no-VAD group. Purified CD34+ cells were stained with anti-CD34, anti-CD133, and anti-VEGFR-2 monoclonal antibodies and analyzed by flow cytometry. Serum levels of granulocyte-colony stimulating factor (G-CSF), interleukin-8, vascular endothelial growth factor-alpha (VEGF-alpha), and B-type natriuretic peptide (BNP) were also measured.

RESULTS

In the VAD group the number of CD34+ cells/ml of blood tended to increase, from 159.6 +/- 137.0 at baseline to 428.9 +/- 224.3 at 15 days, and decreased to 343.8 +/- 165.7 at 60 days (p = 0.05 vs no-VAD group). In the other 3 cell populations, no significant differences occurred over time or between groups. A significant interaction between BNP levels and VAD status was observed (p = 0.005): BNP levels decreased over time in VAD patients vs no-VAD patients. G-CSF levels tended to decrease over time in both groups, but without a significant difference (p = 0.3). Serum levels of interleukin-8 and VEGF-alpha over time or between VAD and no-VAD patients were not significantly different.

CONCLUSIONS

After VAD implantation, a transient increase occurs in the number of circulating CD34+ cells, in parallel to a reduction in BNP levels. Release of these cells from the bone marrow may contribute to the improvement of tissue perfusion and cardiac recovery occasionally seen after VAD placement.

Elevated afterload, neuroendocrine stimulation, and human heart failure increase BNP levels and inhibit preload-dependent SERCA upregulation

BACKGROUND

In heart failure, brain-type natriuretic peptide (BNP) is elevated and the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) downregulated. We previously showed that preload-induced SERCA-upregulation is suppressed by exogenous BNP.

METHODS AND RESULTS

Here we tested the hypothesis that afterload and neurohumoral activation would counterregulate preload-dependent SERCA upregulation through BNP, which finally results in decreased SERCA levels. We studied the effects of 6 hours preload, afterload, and isoproterenol stimulation on BNP and SERCA mRNA expression in rabbit and human failing muscles strips. Preload resulted in a pronounced upregulation of SERCA by 149% (isotonic versus slack, P<0.01). This upregulation was largely suppressed in afterloaded muscles (isometric versus slack: +32%; P<0.05). Similarly, presence of isoproterenol prevented SERCA upregulation in isotonic muscles. Afterload and isoproterenol resulted in a pronounced increase in BNP expression compared with slack by 225% (P<0.05) and 198% (P<0.01), respectively. Isoproterenol also increased expression of phospholamban by 84% (P<0.01). SERCA upregulation in preloaded muscles is associated with frequency-dependent potentiation of contractile force, which is absent in afterloaded muscles. In failing human myocardium, BNP expression was upregulated compared with nonfailing (+631%; P<0.05). Neither unloading nor preload or afterload induced a change in SERCA or BNP expression after 6 hours.

CONCLUSIONS

Afterload and neuroendocrine stimulation increase BNP expression thereby causing inhibition of preload-dependent SERCA upregulation. In failing human myocardium, high BNP expression may underlie the loss of preload-dependent upregulation of SERCA. BNP may thus contribute to adverse myocardial remodelling in heart failure.

Left ventricular assist device-induced molecular changes in the failing myocardium

PURPOSE OF REVIEW

There is considerable increase in the use of left ventricular assist devices for the treatment of severe heart failure. Traditionally viewed as a bridge to transplantation and more recently as a destination therapy, left ventricular assist device support is now recognized to offer potential for myocardial recovery through reverse remodeling, a potential that is further enhanced by combination with pharmacologic therapy. In this study, we examine the molecular changes associated with left ventricular assist device support and how these may contribute to the recovery process.

RECENT FINDINGS

Studies in both patients and experimental models have demonstrated that improved function is associated with alterations in several key pathways including cell survival, cytokine signaling, calcium handling, adrenergic receptor signaling, cytoskeletal and contractile proteins, energy metabolism, extracellular matrix, and endothelial and microvascular functions. Moreover, the unique research opportunities offered by left ventricular assist device analysis are beginning to distinguish changes associated with recovery from those of mechanical unloading alone and identify potential predictors and novel therapeutic targets capable of enhancing myocardial repair.

SUMMARY

Significant progress has been made toward revealing molecular changes associated with myocardial recovery from heart failure. These studies also offer new insight into the pathogenesis of heart failure and point to novel therapeutic strategies.

Plasma biomarkers of myocardial fibrosis and remodeling in terminal heart failure patients supported by mechanical circulatory support devices

BACKGROUND

In this study we analyzed putative biomarkers for myocardial remodeling in plasma from 55 endstage heart failure patients with the need for mechanical circulatory support (MCS). We compared our data to 40 healthy controls and examined if MCS by either ventricular assist devices or total artificial hearts has an impact on plasma concentrations of remodeling biomarkers.

METHODS & RESULTS

Plasma biomarkers were analysed pre and 30 days post implantation of a MCS device using commercially available enzyme linked immunosorbent assays (ELISA). We observed that the plasma concentrations of remodeling biomarkers: tissue inhibitor of metalloproteinase 1 (TIMP1), tenascin C (TNC), galectin 3 (LGALS3), osteopontin (OPN) and of neurohumoral biomarker brain natriuretic peptide (BNP), are significantly elevated in patients with terminal heart failure compared to healthy controls. We did not find elevated plasma concentrations for matrix metalloproteinase 2 (MMP2) and procollagen I C-terminal peptide (PCIP). However, only BNP plasma levels were reduced by MCS, whereas the concentrations of remodeling biomarkers remained elevated or even increased further 30 days after MCS. LGALS3 plasma concentrations at device implantation were significantly higher in patients who did not survive MCS due to multi organ failure (MOF).

CONCLUSIONS

Our findings indicate that mechanical unloading in endstage heart failure is not reflected by a rapid reduction of remodeling plasma biomarkers.

Decreased myocardial chromogranin a expression and colocalization with brain natriuretic peptide during reverse cardiac remodeling after ventricular unloading

AIMS

In chronic heart failure, atrial and brain natriuretic peptide expression is increased and serves as a clinical marker of cardiac hypertrophy. Chromogranin A is also up-regulated during chronic heart failure and associated with disease severity and prognosis. Significant decrease of both natriuretic peptide and hypertrophy after left ventricular assist device (LVAD) treatment was reported. This study investigated whether chromogranin A and neural cell adhesion molecule (NCAM)/CD56 are associated with cardiac hypertrophy and regulated by LVAD.

METHODS

Expression of atrial and brain natriuretic peptide, chromogranin A, and NCAM/CD56 were investigated by immunohistochemistry and morphometrically quantified in 33 paired myocardial samples before and after LVAD. In a different set of patients, chromogranin A was evaluated in the plasma. Cardiomyocyte colocalization of brain natriuretic peptide and chromogranin A was visualized by immunofluorescence doublestaining.

RESULTS

Natriuretic peptide and chromogranin A protein expression is significantly decreased after LVAD (p < 0.05). NCAM/CD56 expression remains unaltered by unloading. In contrast with natriuretic peptide, chromogranin A and NCAM/CD56 expression is not correlated with cardiomyocyte diameters. Although increased compared with controls, no significant differences for chromogranin A plasma levels were found before and after LVAD. Sarcoplasmic colocalization of chromogranin A and brain natriuretic peptide is considerably decreased after LVAD.

CONCLUSIONS

Neither chromogranin A nor CD56 is associated with cardiac hypertrophy. Chromogranin A is significantly decreased by ventricular support. Sarcoplasmic colocalization of brain natriuretic peptide and chromogranin A is diminished after unloading. However, owing to its low expression, the negative regulation of chromogranin A is not reflected by plasma levels and thus does not appear to be an appropriate biomarker of reverse cardiac remodeling after unloading.

Effects of pulsatile- and continuous-flow left ventricular assist devices on left ventricular unloading

BACKGROUND

In patients with end-stage heart failure, the use of left ventricular assist devices (LVADs) has improved clinical outcomes. Although newer continuous-flow devices have significant advantages, the effect of continuous flow on left ventricular unloading and hemodynamics is less well established. The aim of this investigation was to compare the effects of pulsatile- vs continuous-flow LVADs on left ventricular reverse remodeling and hemodynamic indices.

METHODS

Thirty-five patients undergoing implantation with a pulsatile volume displacement pump operating at fixed speed (n = 15; HeartMate XVE; Thoratec Corp., Pleasanton, CA) or a continuous-flow rotary pump with an axial design operating at a fixed rotor speed (n = 20; HeartMate II; Thoratec) were evaluated. Right heart catheterization and echocardiography were performed pre-operatively, and at 1- and 6-month follow-up intervals.

RESULTS

Thirty-five of 40 eligible patients with end-stage heart failure were included in this study. When used at fixed speed, use of both devices led to a substantial reduction in left ventricular volumes and dimensions at 1 month (p < 0.01). A marked and sustained reduction in filling pressures was also noted with both devices at 1 and 6 months (p < 0.01). The volume and pressure unloading effects of the HeartMate XVE were not superior to those with the HeartMate II (all p-values not statistically significant).

CONCLUSIONS

Substantial left ventricular unloading and hemodynamic improvement is achieved with the HeartMate XVE and the HeartMate II. We conclude that continuous-flow LVADs are as effective as pulsatile-flow LVADs with regard to degree of left ventricular unloading and cardiac hemodynamics.

Selective upregulation of β1-adrenergic receptors and dephosphorylation of troponin I in end-stage heart failure patients supported by ventricular assist devices

In terminal failing hearts, adrenergic receptors are downregulated and intracellular adrenergic signal transduction is inhibited. Mechanical circulatory support by ventricular assist devices (VAD) is used to bridge patients to heart transplantation. Mechanical unloading by VAD may induce reverse remodeling in heart transplantation (HTx) candidates. However, little is known on beta-adrenergic receptor subtype regulation and adrenergic signal transduction under VAD-support. We investigated paired myocardial samples from 16 VAD-supported patients and 9 non-failing donor hearts. We analyzed beta-adrenergic receptor subtype regulation by real-time PCR and radioligand binding and cardiac troponin I phosphorylation (by phospho-cTnI-specific antibodies). We found that the beta1-adrenergic receptor (beta1AR) is downregulated at VAD-implantation on mRNA and protein levels whereas the beta2-adrenergic receptor (beta2AR) was not. After VAD-support, beta1AR protein but not its mRNA was upregulated, whereas the degree of cTnI-phosphorylation was reduced. Upregulation of beta1AR was enhanced by beta blocking medication during VAD-support. However, in 9 out of 15 patients, beta1AR-density remained below the 0.25 percentile of donor hearts. VAD-support is associated with partial normalization of the betaAR-signal transduction pathways. This beneficial effect is related to a posttranscriptional increase in beta1AR-density.

Relevance of brain natriuretic peptide in preload-dependent regulation of cardiac sarcoplasmic reticulum Ca2+ ATPase expression

BACKGROUND

In heart failure (HF), ventricular myocardium expresses brain natriuretic peptide (BNP). Despite the association of elevated serum levels with poor prognosis, BNP release is considered beneficial because of its antihypertrophic, vasodilating, and diuretic properties. However, there is evidence that BNP-mediated signaling may adversely influence cardiac remodeling, with further impairment of calcium homeostasis.

METHODS AND RESULTS

We studied the effects of BNP on preload-dependent myocardial sarcoplasmic reticulum Ca2+ ATPase (SERCA2a) expression. In rabbit isolated muscle strips stretched to high preload and shortening isotonically over 6 hours, the SERCA/glyceraldehyde phosphate dehydrogenase mRNA ratio was enhanced by 168% (n=8) compared with unloaded preparations (n=8; P<0.001). Recombinant human BNP at a concentration typically found in end-stage HF patients (350 pg/mL) abolished SERCA upregulation by stretch (n=9; P<0.0001 versus BNP free). Inhibition of cyclic guanosine 3',5' monophosphate (cGMP)-phosphodiesterase-5 mimicked this effect, whereas inhibition of cGMP-dependent protein kinase restored preload-dependent SERCA upregulation in the presence of recombinant human BNP. Furthermore, in myocardium from human end-stage HF patients undergoing cardiac transplantation (n=15), BNP expression was inversely correlated with SERCA levels. Moreover, among 23 patients treated with left ventricular assist devices, significant SERCA2a recovery occurred in those downregulating BNP.

CONCLUSIONS

Our data indicate that preload stimulates SERCA expression. BNP antagonizes this mechanism via guanylyl cyclase-A, cGMP, and cGMP-dependent protein kinase. This novel action of BNP to uncouple preload-dependent SERCA expression may adversely affect contractility in patients with HF.

Left Ventricular Assist Device Weaning: Hemodynamic Response and Relationship to Stroke Volume and Rate Reduction Protocols

Clinical evidence of myocardial recovery in a small cohort of patients supported with a left ventricular assist device (LVAD) has been reported. Development of an optimal LVAD weaning protocol is needed for these patients to sustain recovery after device explant. In this study, we tested the hypothesis that LVAD stroke volume reduction produces a steady-state mechanical reloading of left ventricular (LV) pressures and volumes compared with LVAD rate reduction that results in transient mechanical reloading of the heart due to beat-to-beat variation in LV pressures and volumes. The relationship of LVAD flow to LVAD stroke volume and systolic interval over a range of LVAD rates (60, 80, 100, 120, and 140 bpm) was validated in a mock circulatory flow loop. In six acute experiments, calves were implanted with a pneumatic paracorporeal LVAD (PVAD, Thoratec, Pleasanton, CA). The PVAD was operated asynchronously in the auto volume mode (full decompression) for 30 minutes to establish a baseline control condition. The calf hearts were then mechanically reloaded by LVAD rate reduction (80, 60, and 40 bpm) or LVAD stroke volume reduction (100, 120, and 140 bpm) protocols consisting of 30 minutes of support at each LVAD beat rate. The order of weaning protocols was randomized with a 30-minute recovery period (LVAD volume mode to fully decompress heart allowing it to rest) between protocols to enable return to baseline control state. Aortic pressure and flow, LV pressure and volume, pulmonary artery flow, and LVAD flow waveforms were recorded for each test condition. The LVAD stroke volume reduction protocol produced steady-state mechanical reloading compared with VAD rate reduction that resulted in transient LV mechanical reloading. This distinction is due to differences in their temporal relationships between LVAD and LV filling and emptying cycles. The acute hemodynamic benefit of LVAD stroke volume reduction was greater reduction in LV end-diastolic pressure and increase in LV segmental shortening than LVAD rate reduction. The long-term effects of steady-state and transient LV mechanical reloading on myocardial structure and function toward achieving sustained myocardial recovery warrant further investigation.

LVAD-Induced Reverse Remodeling: Basic and Clinical Implications for Myocardial Recovery

BACKGROUND

With improved technology, increasing clinical experience, and expanding indications for use, left ventricular assist devices (LVADs) are assuming a greater role in the care of patients with end-stage heart failure. Early in the course of LVAD use as a bridge to transplant, it became evident that some patients exhibit substantial recovery of ventricular function, which led to the concept of reverse remodeling.

METHODS AND RESULTS

Herein we summarize and integrate insights derived from a multitude of studies that have investigated how LVAD support influences ventricular structural, cellular, extracellular matrix, molecular, biochemical, and metabolic characteristics of the end-stage failing heart. The focus includes a review of the extent and sustainability of reverse remodeling, the important advances in understanding of the pathophysiology of heart failure derived from these studies and the implications of these findings for development of new therapeutic strategies.

CONCLUSION

In brief, studies of LVAD-heart interactions have led to the understanding that although we once considered the end-stage failing heart of patients near death to be irreversibly diseased, when given sufficient mechanical unloading and restoration of more normal neurohormonal milieu, a relatively large degree of myocardial recovery is possible. Comparison of effects on right and left ventricles have provided mechanistic insights by implicating hemodynamic unloading as primarily regulating certain aspects of reverse remodeling, neurohormonal factors as regulating other aspects, and joint regulation of still other aspects. As such these observations have driven a shift of thinking of chronic heart failure as a progressive irreversible disease process to a potentially treatable entity.

Myocardial recovery using ventricular assist devices: prevalence, clinical characteristics, and outcomes

BACKGROUND

Ventricular assist devices (VADs) are important bridges to cardiac transplantation. VAD support may also function as a bridge to ventricular recovery (BTR); however, clinical predictors of recovery and long-term outcomes remain uncertain. We examined the prevalence, characteristics, and outcomes of BTR subjects in a large single center series.

METHODS AND RESULTS

We implanted VADs in 154 adults at the University of Pittsburgh from 1996 through 2003. Of these implants, 10 were BTR. This included 2/80 (2.5%) ischemic patients (supported 42 and 61 days, respectively). Both subjects had surgical revascularization, required perioperative left VAD support, and were alive and transplant-free at follow up (232 and 1319 days, respectively). A larger percentage of nonischemic patients underwent BTR (8/74, 11%; age 30+/-14; 88% female; left ventricular ejection fraction 18+/-6%; supported 112+/-76 days). Three had myocarditis, 4 had post-partum cardiomyopathy (PPCM), and 1 had idiopathic cardiomyopathy. Five received biventricular support. After explantation, ventricular function declined in 2 PPCM patients who then required transplantation. Ventricular recovery in the 6 nonischemic patients surviving transplant-free was maintained (left ventricular ejection fraction 54+/-5%; follow-up 1.5+/-0.9 years). Overall, 8 of 10 BTR patients are alive and free of transplant (follow-up 1.6+/-1.1 years).

CONCLUSIONS

In a large single center series, BTR was evident in 11% of nonischemic patients, and the need for biventricular support did not preclude recovery. For most BTR subjects presenting with acute inflammatory cardiomyopathy, ventricular recovery was maintained long-term. VAD support as BTR should be considered in the care of acute myocarditis and PPCM.

Brain Natriuretic Peptide is Produced Both by Cardiomyocytes and Cells Infiltrating the Heart in Patients with Severe Heart Failure Supported by a Left Ventricular Assist Device

BACKGROUND

Brain natriuretic peptide (BNP) is a cardiac neurohormone synthesized in cardiac ventricles as a result of increased wall stress. Left ventricular assist device (LVAD) support in patients with end-stage heart failure results in reduced wall stress and therefore may change BNP levels in the heart.

METHODS

BNP plasma levels were measured in 17 patients with end-stage HF before LVAD implantation and at 1 week, 1 month, and 3 months after LVAD support. BNP-messenger RNA (mRNA) expression in cardiac biopsy specimens of 27 patients before and after LVAD support was determined by quantitative polymerase chain reaction. Immunohistochemistry (IHC) and IHC-double staining was used in biopsy specimens from 32 patients before and after LVAD support to localize the BNP protein expression in the heart.

RESULTS

BNP plasma levels significantly decreased from 1,872 +/- 1,098 pg/ml before implantation to 117 +/- 91 pg/ml at 3 months after LVAD implantation. This decrease in plasma levels was accompanied by a significant decrease in mRNA expression (relative quantity) in the heart. IHC and IHC-double staining showed BNP immunoreactivity in the cardiomyocytes, endothelial cells, infiltrating T cells, and macrophages.

CONCLUSIONS

The significant decrease in serum BNP concentration after LVAD support coincides with a decrease in BNP mRNA and protein expression in the heart. BNP is produced in the left ventricle not only by cardiomyocytes but also by endothelial cells, T cells, and macrophages. Unloading of the left ventricle by a LVAD results in decreased BNP expression in the heart and plasma and may play an important role in the reverse remodeling process of the heart.

Differential Exercise Performance on Ventricular Assist Device Support

BACKGROUND

Ventricular assist devices (VADs) are approved for destination therapy because they improve survival in end-stage heart failure (HF). VADs are powered pneumatically or electrically. Pneumatic and electric left ventricular assist devices (LVADs) and biventricular assist devices (BiVADs) provide excellent hemodynamic support at rest, but differences in their effects on exercise tolerance are unclear. We sought to evaluate the effect of devices with varying operating parameters on exercise capacity.

METHODS

Exercise physiology data obtained during maximal exercise with on-line gas-exchange analysis were collected for 38 consecutive VAD-implanted HF patients referred for exercise testing.

RESULTS

Electric LVADs were implanted in 18 patients, and pneumatic LVADs in 10 patients. Percent of predicted peak exercise oxygen consumption (VO2%) was significantly greater in pneumatic LVAD patients (52.1 +/- 11.1% vs 38.2 +/- 11.3%, p < 0.05). The 10 patients implanted with a pneumatically powered LVAD were compared to 10 patients implanted with a pneumatically powered BiVAD. LVAD-supported patients had a higher VO2% (52.1 +/- 11.1% vs 36.5 +/- 17.7%, p < 0.05).

CONCLUSIONS

HF patients supported with a pneumatic LVAD appear to have better exercise tolerance than those receiving an electric LVAD. Patients on LVAD support have better exercise tolerance than BiVAD-supported patients. This highlights the importance of right ventricular function to exercise tolerance in HF patients, and may have implications for future VAD design.

Reloading the heart: A new animal model of left ventricular assist device removal

OBJECTIVES

Left ventricular assist devices are proposed as a bridge to recovery, but recurrent ventricular deterioration has limited this approach. We describe a new animal model that simulates the effects of left ventricular assist device unloading and then reloading after device removal. The model might facilitate the evaluation of interventions intended to prevent recurrent ventricular dysfunction.

METHODS

The hearts and lungs of Lewis rats were removed and transplanted into the abdomen of recipient rats by anastomosing the donor's ascending aorta to the recipient's abdominal aorta. The transplanted hearts were maintained unloaded for 2 weeks in 49 animals. Eighteen transplanted hearts were removed after 2 weeks of unloading. In 17 animals the donor's right pulmonary artery was anastomosed to the recipient's abdominal aorta to reload the heart for an additional 2 weeks. In 14 animals the hearts were maintained unloaded for 4 weeks (an additional 2 weeks). The unloaded and reloaded hearts were compared with normal rat hearts (n = 18).

RESULTS

In the unloaded hearts the left ventricular end-diastolic pressures remained low. The left ventricular systolic pressures were lower than the aortic pressures. The left ventricular weights (n = 8) and volumes (n = 4) remained significantly lower ( P < .01) than in the normal hearts. Two weeks after reloading, the left ventricular end-diastolic pressure (n = 8) increased ( P < .01), and the ventricle ejected. The left ventricular systolic pressures exceeded the aortic pressures. The left ventricular weights and volumes increased ( P < .01) and approached those of normal hearts. Matrix metalloproteinase 9 (n = 6/group) levels decreased in the unloaded state ( P = .02) and increased back to normal values after reloading.

CONCLUSIONS

This surgical model simulated left ventricular assist device unloading of the left ventricle. The second operation reloaded the left ventricle, which then enlarged. This model will permit the evaluation of adjunctive interventions, such as cell transplantation, intended to facilitate successful left ventricular assist device removal and prevent recurrent dilatation.

Plasma neurohormone levels correlate with left ventricular functional and morphological improvement in LVAD patients1

OBJECTIVE

Brain natriuretic peptide (BNP) and endothelin-1 (ET-1) have been shown to be markers of left ventricular (LV) function. To determine the feasibility of using serial assays of these neurohormones in the assessment of cardiac status in the left ventricular assist device (LVAD) setting, we examined the relationship between LV function, myocardial morphology, and plasma levels of these hormones in LVAD recipients.

METHODS

Plasma BNP and ET-1 levels were serially assayed in 19 end-stage congestive heart failure (CHF) patients before and after LVAD implantation with various devices (i.e., MicroMed DeBakeyVAD/DVAD, Novacor/NVAD, TCI Heartmate/TCI, Thoratec/TVAD). Echocardiography performed correspondingly at the time points of the hormonal assays and immunohistochemical collagen staining of left ventricular tissue samples, derived from six non-failing hearts as well as from LVAD patients at the time of device insertion and removal, were then contrasted. Patients were grouped according to device used and etiology of heart disease (ischemic or dilated cardiomyopathy, ICM/DCM).

RESULTS

LVAD therapy significantly improved LV ejection fraction (EF%: 21 +/- 3.8% to 28.11 +/- 3.57%), cardiac output (CO: 3.49 +/- 1.3 to 7.3 +/- 0.2 l/m), and left ventricular end-diastolic diameter (LVEDD: 6.68 +/- 0.92 versus 4.79 +/- 1.54 cm, P < 0.0001) in all patients. Absolute BNP and ET-1 plasma levels remained significantly lower in all patients after LVAD implantation (both P < 0.001). The NVAD group exhibited the most BNP reduction and EF% increase (P < 0.0004 and P < 0.038, respectively). Average collagen levels were reduced in all patients (P < 0.0005). Among the devices, the NVAD group demonstrated the most evident change (P < 0.0036), while there was comparable reduction in the DCM and ICM groups (both P < 0.03). In general, postoperative BNP and ET-1 trends exhibited a notable parallelism with both manifesting bi-phasic tendencies and an inverse proportionality to corresponding EF% measurements.

CONCLUSIONS

Device selection appears to influence the cardiac morphological and neurohormonal expressive tendencies exhibited by recipients. Plasma BNP and ET-1 levels correlate with both LV function and myocardial morphological improvement. Alterations in the levels of these hormones during LVAD support may be real-time indicators of prevailing myocardial autocrine/paracrine activity and as such may be of potential use in future algorithms of cardiac assessment and therapeutic decision-making with regard to transplant urgency and/or possible device explantation.

Weaning of rotary blood pump recipients after myocardial recovery: a computer study of changes in cardiac energetics

BACKGROUND

Weaning of patients from mechanical cardiac support after myocardial recovery has always involved multiple, interacting factors, particularly the training of the myocardium during reduction of pump flow. Rotary pumps offer training advantages when support flow is reduced, even to nearly zero. We report a computer analysis that evaluates the work required of the heart during partial unloading and removal of rotary pumps.

METHODS AND RESULTS

A computer model of the assisted circulation, previously implemented in MATLAB (The MathWorks Inc, Natick, Mass), has been augmented with a model of the MicroMed DeBakey ventricular assist device (MicroMed Technology, Inc, Houston, Tex). Flow, pressure patterns, and external work (pressure-volume area, calculated as the area of the ventricular pressure-volume loop [external work] plus potential energy) were calculated for nonassisted and various continuously assisted patients. Under low-flow conditions, the heart imposes an oscillating forward-backward flow through the non-occlusive rotary pump, causing an increase in ventricular work. Thus, an assist flow of 1 to 1.5 L/min requires work equivalent to that of the unsupported heart. At 60% contractility, the nonassisted pressure-volume area is 1.10 Ws/beat, and the potential energy is 0.38 Ws/beat. At a Qpump of 1 L/min, the pressure-volume area is 1.21 Ws/beat, and the potential energy is 0.37 Ws/beat. At a Qpump of 3 L/min, the pressure-volume area is 0.93 Ws/beat, and the potential energy is 0.29 Ws/beat. These conditions cannot be achieved with pulsatile systems.

CONCLUSION

During weaning and retraining, an implanted rotary pump can provide a workload to the heart like that in the nonassisted situation, thus increasing the predictability of weaning and reducing the risk of reiterating heart failure.

The structural examination of myocardial samples from patients with end-stage heart failure supported by ventricular assist devices using electron microscopy and amino acid analysis reveals low degree of reverse remodeling

BACKGROUND

Chronic heart failure is a multifactorial, progressive disease of many causes and is associated with complex ventricular remodeling. Deposition of extracellular matrix proteins and sarcomeric disarray of the myocytes occur in end-stage heart failure. Ventricular assist devices (VAD), implanted as bridge to transplantation, may reverse ventricular remodeling. Although successfully weaning patients from VAD support has been reported, it is not clear to what degree reversal of remodeling occurs in unloaded failing hearts. Because collagen deposition and ultrastructural disarray are hallmarks of myocardial remodeling, we analyzed the myocardial ultrastructure and collagen content of VAD-supported hearts before and after mechanical unloading.

METHODS

We used amino acid analysis to measure collagen content (4-hydroxyproline content) in 24 transplant candidates receiving VAD support. We used transmission electron microscopy to examine the ultrastructure in 6 patients receiving VAD support.

RESULTS

The 4-hydroxyproline content increased significantly at VAD implantation and was not altered by mechanical unloading. The ultrastructure showed signs of persisting cardiomyopathy.

CONCLUSION

Mechanical unloading does not alter the total collagen content of the supported, failing heart. Thus, structural reversal of the remodeling process associated with heart failure is not a general phenomenon in mechanically unloaded hearts.

Differential regulation of Ca2+-dependent ATPase-activity in left ventricular myocardium during mechanical circulatory support

BACKGROUND

Myocardial recovery is observed in some end-stage heart failure patients after mechanical circulatory support. The sarcoplasmic reticulum Ca(2+)-adenosine triphosphatase (Ca2+-ATPase) activity is down-regulated in failing myocardium and contributes to heart failure-associated contraction/relaxation abnormalities. Regulation of Ca(2+)-ATPase after mechanical support was shown to be heterogeneous. Thus, we analyzed Ca(2+)-ATPase activity and protein expression in the paired myocardial samples of 21 patients supported by ventricular assist devices to identify factors that influence restoration of the Ca(2+)-transient after ventricular assist device support.

METHODS

We measured Ca(2+)-ATPase activity using a reduced nicotinamide-adenine dinucleotide-coupled reaction, determined sarcoplasmic reticulum Ca(2+)-dependent ATPase protein using Western blotting, and determined 4-hydroxyproline using amino-acid analysis.

RESULTS

The mean Ca(2+)-ATPase activity decreased at assist-device implantation and slightly increased at transplantation, but remained significantly lower than in non-failing donor hearts. However, individual responses were heterogeneous. Patients with older age, increased left ventricular diameter, and increased 4-hydroxyproline content showed down-regulation of Ca(2+)-ATPase activity, whereas we found up-regulation in patients with low values for these parameters after assist-device support.

CONCLUSIONS

Sarcoplasmic reticulum Ca(2+)-ATPase activity, which influences the myocardial Ca(2+)-transient, generally is not restored to normal values in assist-device-supported hearts, but depends on a combined score of the left ventricular end-diastolic diameter, degree of ventricular fibrosis, and age of the patient at the time of assist-device implantation.

Ventricular assist devices

PURPOSE OF REVIEW

Recent advances in technology as well as new indications for implantation have appeared in the field of ventricular assist devices. Progress has also been made in the understanding of the underlying mechanisms of myocardial recovery after ventricular assist device support.

RECENT FINDINGS

Technological progress includes the development of fully implantable pulsatile and continuous flow pumps, either axial flow or centrifugal, for left ventricular and total heart assistance. Among the new indications for ventricular assist device support, the most important is the use of the device as permanent treatment for end-stage cardiac failure patients. Increased knowledge has been acquired regarding the effects of mechanical assistance and of unloading of the heart on haemodynamics, as well as on the cellular, molecular and electrophysiological characteristics of the failing heart. All these findings suggest that depressed myocardial function can sometimes recover with ventricular assist device therapy. Ventricular assist device support, however, still carries a high rate of complications: the device itself can fail, bleeding and thromboembolism are common, immunity is disturbed and the incidence of infection remains high.

SUMMARY

In patients with end-stage heart failure, ventricular assist devices can be used as a bridge to transplantation or to recovery, but they are now also considered as a long-term myocardial replacement therapy. Which device is the most appropriate for each indication, however, remains to be defined. Even if the underlying mechanisms of myocardial recovery are progressively clarified, the use of ventricular assist devices as a bridge to recovery still has limited clinical success. Clinical trials with the fully implantable devices are in their early stages, but these pumps appear promising in terms of efficacy, reliability and complication rate, as well as being easy to implant. Because more patients will benefit from ventricular assist device placement in the future, anaesthesiologists must be prepared to manage patients undergoing ventricular assist device placement or presenting for noncardiac surgery while under ventricular assist device support.