Advanced Heart Failure Management and Transplantation

In vivo rescue of genetic dilated cardiomyopathy by systemic delivery of nexilin

BACKGROUND

Dilated cardiomyopathy (DCM) is one of the most common causes of heart failure. Multiple identified mutations in nexilin (NEXN) have been suggested to be linked with severe DCM. However, the exact association between multiple mutations of Nexn and DCM remains unclear. Moreover, it is critical for the development of precise and effective therapeutics in treatments of DCM.

RESULTS

In our study, Nexn global knockout mice and mice carrying human equivalent G645del mutation are studied using functional gene rescue assays. AAV-mediated gene delivery is conducted through systemic intravenous injections at the neonatal stage. Heart tissues are analyzed by immunoblots, and functions are assessed by echocardiography. Here, we identify functional components of Nexilin and demonstrate that exogenous introduction could rescue the cardiac function and extend the lifespan of Nexn knockout mouse models. Similar therapeutic effects are also obtained in G645del mice, providing a promising intervention for future clinical therapeutics.

CONCLUSIONS

In summary, we demonstrated that a single injection of AAV-Nexn was capable to restore the functions of cardiomyocytes and extended the lifespan of Nexn knockout and G645del mice. Our study represented a long-term gene replacement therapy for DCM that potentially covers all forms of loss-of-function mutations in NEXN.

Left Ventricular Assist Device Implantation in Hypertrophic and Restrictive Cardiomyopathy: A Systematic Review

Left ventricular assist device (LVAD) implantation in patients with advanced heart failure due to hypertrophic or restrictive cardiomyopathy (HCM/RCM) presents technical and physiologic challenges. We conducted a systematic review of observational studies to evaluate the utilization and clinical outcomes associated with LVAD implantation in patients with HCM/RCM and compared these to patients with dilated or ischemic cardiomyopathy (DCM/ICM). We searched MEDLINE, EMBASE, and Scopus from inception through May 2019 and included appropriate studies describing the use of an LVAD in patients with HCM/RCM. We identified six studies with a total of 2,766 patients with HCM/RCM and advanced heart failure, among whom 338 patients (12.2%) underwent LVAD implantation. In patients listed for transplant, the rate of LVAD implantation was significantly lower in patients with HCM/RCM compared to that in patients with DCM/ICM (4.4% vs. 18.2%, p < 0.001). Adverse clinical outcomes were significantly higher in HCM/RCM than in DCM/ICM, including operative/short-term mortality (14.0% vs. 9.0%), right ventricular failure (50.0% vs. 21.0%), infection (15.5% vs. 11.2%), bleeding (40.2% vs. 12.5%), renal failure (15.0% vs. 5.1%), stroke (5.0% vs. 2.4%), and arrhythmias (18.0% vs. 7.7%) (all p values <0.001).

Platelet Dysfunction During Mechanical Circulatory Support: Elevated Shear Stress Promotes Downregulation of αIIbβ3 and GPIb via Microparticle Shedding Decreasing Platelet Aggregability

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Intracellular calcium leak in heart failure and atrial fibrillation: a unifying mechanism and therapeutic target

Ca²⁺ is a fundamental second messenger in all cell types and is required for numerous essential cellular functions, including cardiac and skeletal muscle contraction. The intracellular concentration of free Ca²⁺ ([Ca²⁺]) is regulated primarily by ion channels, pumps (ATPases), exchangers and Ca²⁺-binding proteins. Defective regulation of [Ca²⁺] is found in a diverse spectrum of pathological states that affect all the major organs. In the heart, abnormalities in the regulation of cytosolic and mitochondrial [Ca²⁺] occur in heart failure (HF) and atrial fibrillation (AF), two common forms of heart disease and leading contributors to morbidity and mortality. In this Review, we focus on the mechanisms that regulate ryanodine receptor 2 (RYR2), the major sarcoplasmic reticulum (SR) Ca²⁺-release channel in the heart, how RYR2 becomes dysfunctional in HF and AF, and its potential as a therapeutic target. Inherited RYR2 mutations and/or stress-induced phosphorylation and oxidation of the protein destabilize the closed state of the channel, resulting in a pathological diastolic Ca²⁺ leak from the SR that both triggers arrhythmias and impairs contractility. On the basis of our increased understanding of SR Ca²⁺ leak as a shared Ca²⁺-dependent pathological mechanism in HF and AF, a new class of drugs developed in our laboratory, known as rycals, which stabilize RYR2 channels and prevent Ca²⁺ leak from the SR, are undergoing investigation in clinical trials.

Spleen size improvement in advanced heart failure patients using a left ventricular assist device

The spleen has been recognized as an important organ that holds a reserve of 20% to 30% of the total blood volume. Spleen contraction and splenic volume reduction occur in patients with hypovolemic shock. However, the change in the spleen volume and the association between spleen size and hemodynamic parameters remain unclear in patients with advanced heart failure (HF) who need left ventricular assist device (LVAD) support. This study was performed to investigate the change in spleen size and the relationship between spleen size and hemodynamic parameters before and after LVAD implantation in patients with advanced HF. We enrolled 20 patients with advanced HF on LVAD support. All patients underwent right heart catheterization and computed tomography before and after LVAD implantation. The spleen size was measured by computed tomography volumetry. We excluded patients with a mean right atrial pressure (RAP) of <5 mm Hg because of the possibility of hypovolemia and those with a cardiac index of >2.2 L/min/m² before LVAD implantation. The splenic volume significantly increased from 160.6 ± 46.9 mL before LVAD implantation to 224.6 ± 73.5 mL after LVAD implantation (P < .001). Before LVAD implantation, there was a significant negative correlation between spleen volume and systemic vascular resistance (SVR). After LVAD implantation, however, there were significant correlations between spleen volume and the cardiac index, RAP, and pulmonary capillary wedge pressure despite the absence of a significant correlation between spleen volume and SVR. Furthermore, one patient developed reworsening HF because of LVAD failure due to pump thrombosis. In this case, the splenic volume was 212 mL before LVAD implantation and increased to 418 mL after LVAD implantation, although it decreased to 227 mL after LVAD failure. The spleen size may change depending on hemodynamics in patients with advanced HF with LVAD support, reflecting sympathetic nerve activity and the systemic volume status.

Effect of miR-744 on Ameliorating Heart Allograft Rejection in BALB/c Mice Via Regulation of TNFRSF4 Expression in Regulatory T Cells

CD134 (TNFRSF4) is a member of the TNFR superfamily, which is specifically expressed on T cells. Previous studies have shown that blocking of CD134L-CD134 interaction reduces the percentage of activated T cells and prevents effector T cell-mediated graft rejection in heart transplantation. However, the role of microRNA-regulated inhibition of the CD134 signal in cardiac transplantation of T-regulatory (Treg) cells is not clear. In this study, we found microRNA 744 (miR-744) agomir administration enhanced the expression levels of miR-744 in CD4⁺CD25⁺ Treg cells from heart transplantation mice. Moreover, miR-744 agomir administration significantly enhanced the expression levels of CD62L and Ki67 in CD4⁺CD25⁺ Treg cells from heart transplantation mice and further enhanced immunosuppressive function of Treg cells following coculture with CD4⁺CD25^- T cells for different ratios. In addition, miR-744 agomir treatment significantly prolonged survival time and reduced rejection response of heart allografts in vivo, which are involved in downregulation of TNFRSF4 expression. These results provided a novel molecular mechanism of ameliorating heart allograft rejection in Treg cells, which could be used in the treatment of heart allograft rejection clinically.

Advanced Heart Failure and End-Stage Heart Failure: Does a Difference Exist

Advanced heart failure (AdHF) represents a challenging aspect of heart failure patients. Because of worsening clinical symptoms, high rates of re-hospitalization and mortality, AdHF represents an unstable condition where standard treatments are inadequate and additional interventions must be applied. A heart transplant is considered the optimal therapy for AdHF, but the great problem linked to the scarcity of organs and long waiting lists have led to the use of mechanical circulatory support with ventricular-assist device (VAD) as a destination therapy. VAD placement improves the prognosis, functional status, and quality of life of AdHF patients, with high rates of survival at 1 year, similar to transplant. However, the key element is to select the right patient at the right moment. The complete assessment must include a careful clinical evaluation, but also take into account psychosocial factors that are of crucial importance in the out-of-hospital management. It is important to distinguish between AdHF and end-stage HF, for which advanced therapy interventions would be unreasonable due to severe and irreversible organ damage and, instead, palliative care should be preferred to improve quality of life and relief of suffering. The correct selection of patients represents a great issue to solve, both ethically and economically.