Effect of renal function under left ventricular assist device support on the cardiac function and clinical events after heart transplantation

AIM

We investigated the effects of pre-transplantation renal dysfunction under left ventricular assisted device (LVAD) support on post-transplantation cardiac function, and patient prognosis after heart transplantation (HTx).

METHOD

All patients who were bridged by LVAD and underwent HTx at our hospital between 2007 and 2022 were included in this study. Patients were classified into two groups based on estimated glomerular filtration rate (eGFR) before HTx: renal dysfunction (RD) group (eGFR < 60 mL/min/1.73 m2 ) and non-renal dysfunction (NRD) group.

RESULT

A total of 132 patients were analyzed, of whom 48 were classified into the RD group and 84 into the NRD group (RD group, 47.9 ± 10.1 years; NRD group, 38.4 ± 11.9 years, p < .0001). Under LVAD support before HTx, the RD group tended to have a history of right ventricular failure (RD group, nine (19%); NRD group, seven (8%); p = .098). After HTx, the echocardiographic parameters did not differ between the two groups in the long term. Furthermore, more concise hemodynamic parameters, exemplified by right heart catheterization, were not significantly different between the two groups. Regarding graft rejection, no significant differences were found in acute cellular rejection and cardiac allograft vasculopathy following HTx. In contrast, patients with RD before HTx had significantly increased mortality in the chronic phase after HTx and initiation of maintenance dialysis, without any overt changes in cardiac function.

CONCLUSION

Pre-transplantation renal dysfunction under LVAD support significantly affected clinical course after HTx without any overt changes in graft cardiac function.

PGC-1α-mediated angiogenesis prevents pulmonary hypertension in mice

Pulmonary hypertension (PH) is a life-threatening disease characterized by a progressive narrowing of pulmonary arterioles. Although VEGF is highly expressed in lung of patients with PH and in animal PH models, the involvement of angiogenesis remains elusive. To clarify the pathophysiological function of angiogenesis in PH, we compared the angiogenic response in hypoxia (Hx) and SU5416 (a VEGFR2 inhibitor) plus Hx (SuHx) mouse PH models using 3D imaging. The 3D imaging analysis revealed an angiogenic response in the lung of the Hx-PH, but not of the severer SuHx-PH model. Selective VEGFR2 inhibition with cabozantinib plus Hx in mice also suppressed angiogenic response and exacerbated Hx-PH to the same extent as SuHx. Expression of endothelial proliferator-activated receptor γ coactivator 1α (PGC-1α) increased along with angiogenesis in lung of Hx-PH but not SuHx mice. In pulmonary endothelial cell-specific Ppargc1a-KO mice, the Hx-induced angiogenesis was suppressed, and PH was exacerbated along with increased oxidative stress, cellular senescence, and DNA damage. By contrast, treatment with baicalin, a flavonoid enhancing PGC-1α activity in endothelial cells, ameliorated Hx-PH with increased Vegfa expression and angiogenesis. Pulmonary endothelial PGC-1α-mediated angiogenesis is essential for adaptive responses to Hx and might represent a potential therapeutic target for PH.

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Heart failure with preserved ejection fraction (HFpEF) is a condition characterized by diastolic dysfunction and exercise intolerance. While exercise-stressed hemodynamic tests or MRI can be used to detect diastolic dysfunction and diagnose HFpEF in humans, such modalities are limited in basic research using mouse models. A treadmill exercise test is commonly used for this purpose in mice, but its results can be influenced by body weight, skeletal muscle strength, and mental state. Here, we describe an atrial-pacing protocol to detect heart rate (HR)-dependent changes in diastolic performance and validate its usefulness in a mouse model of HFpEF. The method involves anesthetizing, intubating, and performing pressure-volume (PV) loop analysis concomitant with atrial pacing. In this work, a conductance catheter was inserted via a left ventricular apical approach, and an atrial pacing catheter was placed in the esophagus. Baseline PV loops were collected before the HR was slowed with ivabradine. PV loops were collected and analyzed at HR increments ranging from 400 bpm to 700 bpm via atrial pacing. Using this protocol, we clearly demonstrated HR-dependent diastolic impairment in a metabolically induced HFpEF model. Both the relaxation time constant (Tau) and the end-diastolic pressure-volume relationship (EDPVR) worsened as the HR increased compared to control mice. In conclusion, this atrial pacing-controlled protocol is useful for detecting HR-dependent cardiac dysfunctions. It provides a new way to study the underlying mechanisms of diastolic dysfunction in HFpEF mouse models and may help develop new treatments for this condition.

A new assessment method for right ventricular diastolic function using right heart catheterization by pressure-volume loop

Diastolic stiffness coefficient (β) and end-diastolic elastance (Eed) are ventricular-specific diastolic parameters. However, the diastolic function of right ventricle had not been investigated sufficiently due to the lack of established evaluation method. We evaluated the validity of these parameters calculated using only data of right heart catheterization (RHC) and assessed it in patients with restrictive cardiomyopathy (RCM) and cardiac amyloidosis. We retrospectively analyzed 46 patients with heart failure who underwent RHC within 10 days of cardiac magnetic resonance (CMR). Right ventricular end-diastolic volume and end-systolic volume were calculated using only RHC data, which were found to be finely correlated with those obtained from CMR. β and Eed calculated by this method were also significantly correlated with those derived from conventional method using CMR. By this method, β and Eed were significantly higher in RCM with amyloidosis group than dilated cardiomyopathy group. In addition, the β and Eed calculated by our method were finely correlated with E/A ratio on echocardiography. We established an easy method to estimate β and Eed of right ventricle from only RHC. The method finely demonstrated right ventricular diastolic dysfunction in patients with RCM and amyloidosis.

NLRP3 Inflammasome Activation Through Heart-Brain Interaction Initiates Cardiac Inflammation and Hypertrophy During Pressure Overload

BACKGROUND

Mechanical stress on the heart, such as high blood pressure, initiates inflammation and causes hypertrophic heart disease. However, the regulatory mechanism of inflammation and its role in the stressed heart remain unclear. IL-1β (interleukin-1β) is a proinflammatory cytokine that causes cardiac hypertrophy and heart failure. Here, we show that neural signals activate the NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing 3) inflammasome for IL-1β production to induce adaptive hypertrophy in the stressed heart.

METHODS

C57BL/6 mice, knockout mouse strains for NLRP3 and P2RX7 (P2X purinoceptor 7), and adrenergic neuron-specific knockout mice for SLC17A9, a secretory vesicle protein responsible for the storage and release of ATP, were used for analysis. Pressure overload was induced by transverse aortic constriction. Various animal models were used, including pharmacological treatment with apyrase, lipopolysaccharide, 2'(3')-O-(4-benzoylbenzoyl)-ATP, MCC950, anti-IL-1β antibodies, clonidine, pseudoephedrine, isoproterenol, and bisoprolol, left stellate ganglionectomy, and ablation of cardiac afferent nerves with capsaicin. Cardiac function and morphology, gene expression, myocardial IL-1β and caspase-1 activity, and extracellular ATP level were assessed. In vitro experiments were performed using primary cardiomyocytes and fibroblasts from rat neonates and human microvascular endothelial cell line. Cell surface area and proliferation were assessed.

RESULTS

Genetic disruption of NLRP3 resulted in significant loss of IL-1β production, cardiac hypertrophy, and contractile function during pressure overload. A bone marrow transplantation experiment revealed an essential role of NLRP3 in cardiac nonimmune cells in myocardial IL-1β production and cardiac phenotype. Pharmacological depletion of extracellular ATP or genetic disruption of the P2X7 receptor suppressed myocardial NLRP3 inflammasome activity during pressure overload, indicating an important role of ATP/P2X7 axis in cardiac inflammation and hypertrophy. Extracellular ATP induced hypertrophic changes of cardiac cells in an NLRP3- and IL-1β-dependent manner in vitro. Manipulation of the sympathetic nervous system suggested sympathetic efferent nerves as the main source of extracellular ATP. Depletion of ATP release from sympathetic efferent nerves, ablation of cardiac afferent nerves, or a lipophilic β-blocker reduced cardiac extracellular ATP level, and inhibited NLRP3 inflammasome activation, IL-1β production, and adaptive cardiac hypertrophy during pressure overload.

CONCLUSIONS

Cardiac inflammation and hypertrophy are regulated by heart-brain interaction. Controlling neural signals might be important for the treatment of hypertensive heart disease.

Prognostic value of follow-up vasoreactivity test in pulmonary arterial hypertension

BACKGROUND

Acute vasoreactivity test with inhaled nitric oxide (NO) is performed during diagnostic right heart catheterization (RHC) to identify patients with pulmonary arterial hypertension (PAH) who respond to calcium channel blockers. Our purpose was to investigate the prognostic importance of follow-up vasoreactivity test after treatment.

METHODS

We retrospectively analyzed 36 PAH patients (mean age, 47 years; 61 % treatment-naïve), who underwent diagnostic and follow-up RHC and vasoreactivity tests at our center. The primary outcome was all-cause mortality.

RESULTS

The median time between baseline and follow-up RHC was 9.7 months. Absolute change in mean pulmonary arterial pressure (ΔmPAP) during NO challenge was less pronounced after treatment, but there was great variability among patients. Overall cohort was dichotomized into two groups: preserved vasoreactivity (ΔmPAP ≤ -1 mmHg) and less vasoreactivity (ΔmPAP ≥0 mmHg) at follow-up RHC. Less vasoreactivity group had higher usage rate of endothelin receptor antagonists and parenteral prostacyclin analogues. During a median observation period of 6.3 years after follow-up RHC, 7 patients died, of which 6 showed less vasoreactivity at follow-up. Absolute ΔmPAP ≥0 at follow-up RHC was associated with all-cause mortality in univariable Cox regression analysis (hazard ratio, 8.728; 95 % confidence interval, 1.045-72.887; p = 0.045), whereas other hemodynamic parameters were not. Absolute ΔmPAP ≥0 at follow-up RHC was associated with all-cause mortality in multivariable Cox analysis adjusted for age and known PAH prognostic factors (HR, 12.814; 95 % CI, 1.088-150.891; p = 0.043). Kaplan-Meier survival analysis revealed a significantly worse survival of less vasoreactivity group compared to preserved vasoreactivity group (log-rank test, p = 0.016).

CONCLUSIONS

Follow-up vasoreactivity test after treatment could contribute to the detection of high-risk subgroups who might need careful monitoring and referral for lung transplantation.

Tie2-Cre-Induced Inactivation of Non-Nuclear Estrogen Receptor-α Signaling Abrogates Estrogen Protection Against Vascular Injury

Using the Cre-loxP system, we generated the first mouse model in which estrogen receptor-α non-nuclear signaling was inactivated in endothelial cells. Estrogen protection against mechanical vascular injury was impaired in this model. This result indicates the pivotal role of endothelial estrogen receptor-α non-nuclear signaling in the vasculoprotective effects of estrogen.

A Pacing-Controlled Protocol for Frequency-Diastolic Relations Distinguishes Diastolic Dysfunction Specific to A Mouse HFpEF Model

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is characterized as an insufficient exercise capacity and is a growing health problem worldwide. One major difficulty with experimental research of HFpEF is the lack of methods to consistently detect diastolic dysfunction in mouse models. We focus on the exercise intolerance and developed a pacing-controlled PV loop protocol for the assessment of diastolic function at different heart rates in mouse cardiac disease models, including a HFpEF model and a pressure-overload hypertrophy model (PO).

METHODS

A HFpEF model was generated by high-fat diet (HFD)-feeding with concomitant L-NAME administration, and a PO model was produced by surgical constriction of transverse aorta (TAC). HR was slowed (lower than 400 bpm) by i.p. injection of ivabradine. PV loop data were acquired at HR incrementing by 100 bpm from 400 to 700 bpm via atrial pacing.

RESULTS

At baseline without pacing, no significant difference was detected between groups. Frequency-diastolic pacing, however, distinguished HFpEF from other two groups in diastolic parameters like tau or stiffness-coefficient of end-diastolic pressure volume relationship. No remarkable difference was observed with systolic parameters.

CONCLUSIONS

Frequency-dependent pressure-volume analysis could detect and characterize diastolic dysfunction specific to the HFpEF, though no significant difference between HFpEF and pressure overload models could be detected at baseline analysis. One of characteristic of HFpEF is exercise intolerance, but no physiological analysis or modality associated with exercise capacity was available in analyzing cardiac functions of murine models. This protocol would significantly contribute to the basic research for HFpEF.

Cyclic GMP and PKG Signaling in Heart Failure

Cyclic guanosine monophosphate (cGMP), produced by guanylate cyclase (GC), activates protein kinase G (PKG) and regulates cardiac remodeling. cGMP/PKG signal is activated by two intrinsic pathways: nitric oxide (NO)-soluble GC and natriuretic peptide (NP)-particulate GC (pGC) pathways. Activation of these pathways has emerged as a potent therapeutic strategy to treat patients with heart failure, given cGMP-PKG signaling is impaired in heart failure with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF). Large scale clinical trials in patients with HFrEF have shown positive results with agents that activate cGMP-PKG pathways. In patients with HFpEF, however, benefits were observed only in a subgroup of patients. Further investigation for cGMP-PKG pathway is needed to develop better targeting strategies for HFpEF. This review outlines cGMP-PKG pathway and its modulation in heart failure.

Sex Differences and Regulatory Actions of Estrogen in Cardiovascular System

Great progress has been made in the understanding of the pathophysiology of cardiovascular diseases (CVDs), and this has improved the prevention and prognosis of CVDs. However, while sex differences in CVDs have been well documented and studied for decades, their full extent remains unclear. Results of the latest clinical studies provide strong evidence of sex differences in the efficacy of drug treatment for heart failure, thereby possibly providing new mechanistic insights into sex differences in CVDs. In this review, we discuss the significance of sex differences, as rediscovered by recent studies, in the pathogenesis of CVDs. First, we provide an overview of the results of clinical trials to date regarding sex differences and hormone replacement therapy. Then, we discuss the role of sex differences in the maintenance and disruption of cardiovascular tissue homeostasis.

Preexisting heart failure with reduced ejection fraction attenuates renal fibrosis after ischemia reperfusion via sympathetic activation

Although chronic heart failure is clinically associated with acute kidney injury (AKI), the precise mechanism that connects kidney and heart remains unknown. Here, we elucidate the effect of pre-existing heart failure with reduced ejection fraction (HFrEF) on kidney via sympathetic activity, using the combining models of transverse aortic constriction (TAC) and unilateral renal ischemia reperfusion (IR). The evaluation of acute (24 h) and chronic (2 weeks) phases of renal injury following IR 8 weeks after TAC in C57BL/6 mice revealed that the development of renal fibrosis in chronic phase was significantly attenuated in TAC mice, but not in non-TAC mice, whereas no impact of pre-existing heart failure was observed in acute phase of renal IR. Expression of transforming growth factor-β, monocyte chemoattractant protein-1, and macrophage infiltration were significantly reduced in TAC mice. Lastly, to investigate the effect of sympathetic nerve activity, we performed renal sympathetic denervation two days prior to renal IR, which abrogated attenuation of renal fibrosis in TAC mice. Collectively, we demonstrate the protective effect of pre-existing HFrEF on long-term renal ischemic injury. Renal sympathetic nerve may contribute to this protection; however, further studies are needed to fully clarify the comprehensive mechanisms associated with attenuated renal fibrosis and pre-existing HFrEF.

Endothelial-specific Ablation of Non-nuclear Estrogen Receptor alpha Signaling Deteriorates Vascular Remodelling Response

Background and introduction

The difference in cardiovascular disease risk between age-matched women and men narrows as transition through menopause in observational studies. Estrogen exerts complex physiological effects via its non-nuclear and nuclear actions. Experimental studies have shown that endothelial estrogen receptors mediate vasoprotection via endothelial nitric oxide production, reendothelialization, and atherosclerosis. Prior studies in vitro addressed estrogen's effects on endothelial cells and vascular smooth muscle cells, leading to vasoprotection. However, the in vivo evidences are lacking for beneficial effects of endothelium non-nuclear ERα signaling on vascular remodelling in response to injury.

Purpose

This study aims to clarify the impact of endothelial ERα non-nuclear signaling in the vasoprotection, using a novel mouse model lacking tissue-specific ERα non-nuclear signaling.

Methods

We identified the amino acids of ERα which were responsible for its binding to p85α subunit of phosphatidylinositol 3-kinase in vitro. We generated a novel mouse model in which non-nuclear signaling of ERα was ablated in endothelial cells by crossing Tie2-Cre transgenic mice with floxed ERα mutants (RR259/260AA) in which p85α and ERα interaction was disrupted.

Results

In endothelial cells isolated from ERαKI/KITie2 cre/+ animals, E2 failed to induce phosphorylation of Akt, confirming the absence of ERα non-nuclear signaling. Baseline characteristics at 8 to 12 weeks of age were undistinguishable between the genotypes, including body weight, systolic blood pressure, uterine weight and echocardiographic fractional shortening. We then assessed how vascular remodelling process was impacted in a carotid artery wire injury model. Histological analyses with Elastica van Gieson staining two weeks after injury revealed that estrogen dependent suppression of remodelling response (intima to medial ratio) was abolished in ERαki/kiTie2cre/+mice (P=0.0004). Masson's Trichrome staining showed that in the presence of E2 fibrosis was significantly higher in ERαki/kiTie2cre/+ mice than ERαki/kiTie2cre/− mice (P=0.0015).

Conclusions

We generated a novel mouse model for tissue-specific ablation of ERα non-nuclear signaling by interfering ERα-PI3K interaction. Our results demonstrate that the pivotal role for ERα non-nuclear signaling of endothelial cells in carotid arterial protection following injury with its minimal impact on baseline cardiovascular phenotype.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Japan Heart Foundation Research Grant, SENSHIN Medical Research Foundation

Usefulness of central venous saturation as a predictor of thiamine deficiency in critically ill patients: a case report

Background

Central venous oxygen saturation (ScvO₂) reflects the balance of oxygen delivery and consumption. Low ScvO₂ indicates the presence of inadequate oxygen delivery, while high ScvO₂ indicates reduced oxygen consumption and is sometimes associated with a high mortality rate in critically ill patients from dysoxia. Thiamine is an essential cofactor in cellular aerobic metabolism. Thiamine deficiency is more prevalent than was previously thought, and underlies severe conditions in critically ill patients. However, currently, there is no rapid diagnostic test for thiamine deficiency. Considering oxygen flux, high ScvO₂ might be associated with thiamine deficiency.

Case presentation

A 70-year-old man admitted to the hospital with chief complaint of malaise and edema. He was diagnosed with heart failure with preserved ejection function and was treated with loop diuretics, which resulted in shock. Venoarterial extracorporeal membrane oxygenation and intra-aortic balloon pumping was indicated. The right heart catheter showed high ScvO₂, normal cardiac output, and low systemic vascular resistance. Thiamine deficiency was suspected and we started the thiamine infusion. His hemodynamic status improved after thiamine replacement. After his recovery, it was discovered that he had a 1-month history of anorexia and thiamine deficiency. His final diagnosis was beriberi.

Conclusions

The current case showed the relation between thiamine deficiency and high ScvO₂. A literature review also suggested that thiamine deficiency is associated with high ScvO₂. Thiamine deficiency causes impaired tissue oxygen extraction, which could lead to high ScvO₂. In this context, high ScvO₂ might serve as a predictor of thiamine deficiency in critically ill patients.