The impact of angiotensin-converting enzyme inhibitor therapy on the extracellular collagen matrix during left ventricular assist device support in patients with end-stage heart failure

Morphological and molecular changes of the myocardium after left ventricular mechanical support

Left ventricular assist devices (LVAD) are currently used to either “bridge” patients with terminal congestive heart failure (CHF) until cardiac transplantation is possible or optionally for patients with contraindications for transplantation (“destination therapy”). Mechanical support is associated with a marked decrease of cardiac dilation and hypertrophy as well as numerous cellular and molecular changes (“reverse cardiac remodeling”), which can be accompanied by improved cardiac function (“bridge to recovery”) in a relatively small subset of patients with heart transplantation no longer necessary even after removal of the device (“weaning”). In the recent past, novel pharmacological strategies have been developed and are combined with mechanical support, which has increased the percentage of patients with improved clinical status and cardiac performance. Gene expression profiles have demonstrated that individuals who recover after LVAD show different gene expression compared to individuals who do not respond to unloading. This methodology holds promise for the future to develop read out frames to identify individuals who can recover after support. Aside from describing the morphological changes associated with “reverse cardiac remodeling”, this review will focus on signal transduction, transcriptional regulation, apoptosis, cell stress proteins, matrix remodeling, inflammatory mediators and aspects of neurohormonal activation in the failing human heart before and after ventricular unloading.

Pharmacotherapy for Mechanical Circulatory Support: A Comprehensive Review

Objective

To provide a comprehensive review of the pharmacotherapy associated with the provision of mechanical circulatory support (MCS) to patients with end-stage heart failure and guidance regarding the selection, assessment, and optimization of drug therapy for this population.

Data Sources:

The MEDLINE/PubMed, EMBASE, and Cochrane databases were searched from 1960 to July 2010 for articles published in English using the search terms mechanical circulatory support, ventricular assist system, ventricular assist device, left ventricular assist device, right ventricular assist device, biventricular assist device, total artificial heart, pulsatile, positive displacement, axial, centrifugal, hemostasis, bleeding, hemodynamic, blood pressure, thrombosis, antithrombotic therapy, anticoagulant, antiplatelet, right ventricular failure, ventricular arrhythmia, anemia, arteriovenous malformation, stroke, infection, and clinical pharmacist.

Study Selection And Data Extraction:

All relevant original studies, metaanalyses, systematic reviews, guidelines, and reviews were assessed for inclusion. References from pertinent articles were examined for content not found during the initial search.

Data Synthesis:

MCS has advanced significantly since the first left ventricular assist device was implanted in 1966. Further advancements in MCS technology that occurred in the tatter decade are changing the overall management of end-stage heart failure care and cardiac transplantation. These pumps allow for improved bridge-to-transplant rates, enhanced survival, and quality of life. Pharmacotherapy associated with MCS devices may optimize the performance of the pumps and improve patient outcomes, as well as minimize morbidity related to their adverse effects. This review highlights the knowledge needed to provide appropriate clinical pharmacy services for patients supported by MCS devices.

Conclusions:

The HeartMate II clinical investigators called for the involvement of pharmacists in MCS patient assessment and optimization. Pharmacotherapeutic management of patients supported with MCS devices requires individualized care, with pharmacists as part of the team, based on the characteristics of each pump and recipient.

Contemporary use of ventricular assist devices

The introduction of the heart lung machine more than 50 years ago proved in principle that heart function can be replaced, albeit for short periods. This was followed by attempts to produce total or partial artificial hearts that could function for prolonged periods of time. Progress in this field has been intermittent but has accelerated considerably in the past 10 years, with ventricular assist devices (VADs) reaching an impressive degree of sophistication and complexity owing to the contributions from clinicians, engineers, scientists, industrialists, and others. This review describes the currently available types of VADs, their current clinical use, the patient selection process, the trend toward use of VADs in patients with less severe heart failure, and the use of VADs for myocardial recovery in combination with novel pharmacological strategies, gene therapy, and cell therapy.

The impact of left ventricular assist device-induced left ventricular unloading on the myocardial renin-angiotensin-aldosterone system: therapeutic consequences?

AIMS

Angiotensin-converting enzyme inhibitors (ACE-Is) prevent the rise in myocardial angiotensin II that occurs after left ventricular assist device (LVAD) implantation, but do not fully normalize cardiac function. Here, we determined the effect of LVAD implantation, with or without ACE-Is, on cardiac renin, aldosterone, and norepinephrine, since these hormones, like angiotensin II, are likely determinants of myocardial recovery during LVAD support.

METHODS AND RESULTS

Biochemical measurements were made in paired LV myocardial samples obtained from 20 patients before and after LVAD support in patients with and without ACE-I therapy. Pre-LVAD renin levels were 100x normal and resulted in almost complete cardiac angiotensinogen depletion. In non-ACE-I users, LVAD support, by normalizing blood pressure, reversed this situation. Cardiac aldosterone decreased in parallel with cardiac renin, in agreement with the concept that cardiac aldosterone is blood-derived. Cardiac norepinephrine increased seven-fold, possibly due to the rise in angiotensin II. Angiotensin-converting enzyme inhibitor therapy prevented these changes: renin and aldosterone remained high, and no increase in norepinephrine occurred.

CONCLUSION

Although LV unloading lowers renin and aldosterone, it allows cardiac angiotensin generation to increase and thus to activate the sympathetic nervous system. Angiotensin-converting enzyme inhibitors prevent the latter, but do not affect aldosterone. Thus, mineralocorticoid receptor antagonist therapy during LVAD support may play a role in further promoting recovery.

Tricuspid annular motion as a predictor of severe right ventricular failure after left ventricular assist device implantation

BACKGROUND

Right ventricular (RV) failure after left ventricular assist device (LVAD) implantation is associated with a high rate of morbidity and mortality. We sought to determine pre-operative right heart echocardiographic predictors of post-LVAD severe RV failure.

METHODS

RV failure, defined as the need for inotropic support or pulmonary vasodilators for >or=14 days post-operatively, was evaluated in 33 patients (age 54 +/- 13 years) with LVADs. Preoperative RV systolic and diastolic echocardiographic parameters, including RV fractional area change, tricuspid annular motion, right atrial volume index, RV index of myocardial performance, hepatic vein Doppler velocities, tricuspid regurgitation severity, and RV systolic pressures (RVSPs) in patients with and without RV failure were compared.

RESULTS

Of the 33 patients evaluated, 11 (33%) had post-LVAD RV failure (2 needed RVAD support). Patients with post-LVAD RV failure had significantly lower pre-operative tricuspid annular motion (8 +/- 4 vs 15 +/- 6 mm, p < 0.01) and higher RVSPs (60 +/- 14 vs 46 +/- 11 mm Hg, p = 0.02). In 13 patients (39%) with moderate tricuspid regurgitation, pre-operative tricuspid annular motion remained significantly reduced (6.0 +/- 0.5 vs 13.5 +/- 5.0 mm, p = 0.045). Other echocardiographic parameters were not significantly different between patients. Tricuspid annular motion of <7.5 mm provides 91% specificity and 46% sensitivity in predicting post-LVAD RV failure.

CONCLUSION

Tricuspid annular motion is a predictor of post-LVAD RV failure. Using tricuspid annular motion in addition to conventional criteria may aid in early identification of patients with prolonged inotropic support or severe RV failure and allow for better pre-operative planning.

Imaging left ventricular remodeling: targeting the neurohumoral axis

Left ventricular remodeling is a key determinant of the clinical course and outcome of systolic heart failure. The myocardial renin-angiotensin system (RAS) has been closely linked to the major maladaptive cellular and molecular changes that accompany left ventricular remodeling. Direct inhibition of various components of the RAS, such as the angiotensin-converting enzyme, angiotensin II type 1 receptor, and aldosterone, has resulted in favorable clinical responses in heart failure. Many questions, however, remain unanswered regarding the timing of initiation, optimum doses, need for simultaneous use of RAS inhibitors, and proper monitoring of RAS blockade. Additionally, significant variation has been noted in individual responses to RAS blockade as a result of genetic differences. Answering these questions requires direct access to the myocardial component of RAS, which is largely independent of its systemic component. Molecular imaging using radiotracers with high affinities for myocardial angiotensin-converting enzyme and angiotensin II type 1 receptors can provide direct access to tissue RAS and thus provide a better understanding of the pathophysiology of left ventricular remodeling in individual patients. This Article briefly reviews the potential for evaluating the tissue expression of angiotensin in heart failure by targeted RAS imaging.

Urinary levels of matrix metalloproteinases and their tissue inhibitors in nephrotic children

The aim of this study was to determine the effects of cyclosporine A (CyA) on urinary levels of matrix metalloproteinase 2 and 9 (MMP2, MMP9) and their tissue inhibitors 1 and 2 (TIMP1, TIMP2) in steroid-dependent nephrotic syndrome (SDNS). The study group (1) consisted of 18 children SDNS aged 3.5-17.0 years treated with CyA. All NS children were examined three times: (A) at proteinuria relapse, before CyA treatment, (B) after 6 months, and (C) after 12 months of CyA administration. The control group (2) consisted of 18 healthy children. Serum CyA level was assessed by immunofluorescence. Enzyme-linked immunosorbent assay kits for total human MMP2 and 9 and TIMP1 and 2 were obtained from R&D Systems. Compared with healthy controls, urinary MMP9/Cr in NS children before CyA was on the same level and increased during CyA treatment, and urinary TIMP1/Cr was twice as high and increased significantly during CyA treatment. MMP9/TIMP1 in NS children treated with CyA increased, but the difference was not statistically significant. Urinary MMP2/Cr was similar, and urinary TIMP2/Cr was significantly higher in children treated with CyA (p < 0.01). The MMP2/TIMP2 ratio in NS children treated with CyA was significantly lower in comparison with healthy controls (p < 0.01). A negative correlation was noted between urinary MMP2/TIMP2 ratio and serum CyA in NS children (r = -0.541, p < 0.01). An imbalance within the MMP2 and TIMP2 and MMP9 and TIMP1 system may play a role in the pathogenesis CyA nephropathy.

Reverse cardiac remodeling enabled by mechanical unloading of the left ventricle

Cardiac remodeling is a characteristic and basic component of heart failure progression and is associated with a poor prognosis. Attenuating or reversing remodeling is an accepted goal of heart failure therapy. Cardiac mechanical support with left ventricular assist devices, in addition to its established role as "bridge to transplantation" or "destination therapy" in patients not eligible for cardiac transplantation, offers the potential for significant and sustained myocardial recovery through reverse remodeling. This review discusses the emerging role of left ventricular assist devices as a "bridge to recovery". Clinical and basic aspects of cardiac remodeling and cardiac reverse remodeling enabled by mechanical unloading, potential candidates for this modality of treatment as well as unresolved issues regarding the use of mechanical circulatory support as a bridge to recovery are discussed.

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.

Impact of left ventricular assist device (LVAD) support on the cardiac reverse remodeling process

With improved technology 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. Following LVAD implantation with the intention of bridge to transplant, it became evident that some patients exhibit substantial recovery of ventricular function. This prompted explantation of some devices in lieu of transplantation, the so-called bridge-to-recovery (BTR) therapy. However, clinical outcomes following these experiences are not always successful. Patients treated in this fashion have often progressed rapidly back to heart failure. Special knowledge has emerged from studies of hearts supported by LVADs that provides insights into the basic mechanisms of ventricular remodeling and possible limits of ventricular recovery. In general, it was these studies that spawned the concept of reverse remodeling now recognized as an important goal of many heart failure treatments. Important examples of myocardial and/or ventricular properties that do not regress towards normal during LVAD support include abnormal extracellular matrix metabolism, increased tissue angiotensin levels, myocardial stiffening and partial recovery of gene expression involved with metabolism. Nevertheless, 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, an unprecedented degree of myocardial recovery is possible, when given sufficient mechanical unloading and restoration of more normal neurohormonal milieu. Evidence supporting and unsupporting the notion of reverse remodeling and clinical implications of this process will be reviewed.

Pathogenesis of chronic heart failure: change of dominating paradigm

The review considers literature data reflecting the evolution of views on pathogenesis of chronic heart failure. Connection of revision of a dominating paradigm of pathogenesis at every stage of development of cardiology with changes in approaches to therapy of chronic heart failure is analyzed.