Stretch-induced compliance mechanism in pregnancy-induced cardiac hypertrophy and the impact of cardiovascular risk factors

Pressure overload-induced hypertrophy compromises cardiac stretch-induced compliance (SIC) after acute volume overload (AVO). We hypothesized that SIC could be enhanced by physiological hypertrophy induced by pregnancy's chronic volume overload. This study evaluated SIC-cardiac adaptation in pregnant women with or without cardiovascular risk (CVR) factors. Thirty-seven women (1st trimester, 1stT) and a separate group of 31 (3rd trimester, 3rdT) women [healthy or with CVR factors (obesity and/or hypertension and/or with gestational diabetes)] underwent echocardiography determination of left ventricular end-diastolic volume (LVEDV) and E/e' before (T0), immediately after (T1), and 15 min after (T2; SIC) AVO induced by passive leg elevation. Blood samples for NT-proBNP quantification were collected before and after the AVO. Acute leg elevation significantly increased inferior vena cava diameter and stroke volume from T0 to T1 in both 1stT and 3rdT, confirming AVO. LVEDV and E/e' also increased immediately after AVO (T1) in both 1stT and 3rdT. SIC adaptation (T2, 15 min after AVO) significantly decreased E/e' in both trimesters, with additional expansion of LVEDV only in the 1stT. NT-pro-BNP increased slightly after AVO but only in the 1stT. CVR factors, but not parity or age, significantly impacted SIC cardiac adaptation. A distinct functional response to SIC was observed between 1stT and 3rdT, which was influenced by CVR factors. The LV of 3rdT pregnant women was hypertrophied, showing a structural limitation to dilate with AVO, whereas the lower LV filling pressure values suggest increased diastolic compliance.NEW & NOTEWORTHY The sudden increase of volume overload triggers an acute myocardial stretch characterized by an immediate rise in contractility by the Frank-Starling mechanism, followed by a progressive increase known as the slow force response. The present study is the first to characterize echocardiographically the stretch-induced compliance (SIC) mechanism in the context of physiological hypertrophy induced by pregnancy. A distinct functional adaptation to SIC was observed between first and third trimesters, which was influenced by cardiovascular risk factors.

Acute and chronic effects of levosimendan in the ZSF1 obese rat model of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is a syndrome characterized by impaired cardiovascular reserve in which therapeutic options are scarce. Our aim was to evaluate the inodilator levosimendan in the ZSF1 obese rat model of HFpEF. Twenty-week-old male Wistar-Kyoto (WKY), ZSF1 lean (ZSF1 Ln) and ZSF1 obese rats chronically treated for 6-weeks with either levosimendan (1 mg/kg/day, ZSF1 Ob + Levo) or vehicle (ZSF1 Ob + Veh) underwent peak-effort testing, pressure-volume (PV) haemodynamic evaluation and echocardiography (n = 7 each). Samples were collected for histology and western blotting. In obese rats, skinned and intact left ventricular (LV) cardiomyocytes underwent in vitro functional evaluation. Seven additional ZSF1 obese rats underwent PV evaluation to assess acute levosimendan effects (10 μg/kg + 0.1 μg/kg/min). ZSF1 Ob + Veh presented all hallmarks of HFpEF, namely effort intolerance, elevated end-diastolic pressures and reduced diastolic compliance as well as increased LV mass and left atrial area, cardiomyocyte hypertrophy and increased interstitial fibrosis. Levosimendan decreased systemic arterial pressures, raised cardiac index, and enhanced LV relaxation and diastolic compliance in both acute and chronic experiments. ZSF1 Ob + Levo showed pronounced attenuation of hypertrophy and interstitial fibrosis alongside increased effort tolerance (endured workload raised 38 %) and maximum O2 consumption. Skinned cardiomyocytes from ZSF 1 Ob + Levo showed a downward shift in sarcomere length-passive tension relationship and intact cardiomyocytes showed decreased diastolic Ca2+ levels and enhanced Ca2+ sensitivity. On molecular grounds, levosimendan enhanced phosphorylation of phospholamban and mammalian target of rapamycin. The observed effects encourage future clinical trials with levosimendan in a broad population of HFpEF patients.

Myocardial stretch-induced compliance is abrogated under ischemic conditions and restored by cGMP/PKG-related pathways

Introduction: Management of acute myocardial infarction (MI) mandates careful optimization of volemia, which can be challenging due to the inherent risk of congestion. Increased myocardial compliance in response to stretching, known as stretch-induced compliance (SIC), has been recently characterized and partly ascribed to cGMP/cGMP-dependent protein kinase (PKG)-related pathways. We hypothesized that SIC would be impaired in MI but restored by activation of PKG, thereby enabling a better response to volume loading in MI. Methods: We conducted experiments in ex vivo rabbit right ventricular papillary muscles under ischemic and non-ischemic conditions as well as pressure-volume hemodynamic evaluations in experimental in vivo MI induced by left anterior descending artery ligation in rats. Results: Acutely stretching muscles ex vivo yielded increased compliance over the next 15 min, but not under ischemic conditions. PKG agonists, but not PKC agonists, were able to partially restore SIC in ischemic muscles. A similar effect was observed with phosphodiesterase-5 inhibitor (PDE5i) sildenafil, which was amplified by joint B-type natriuretic peptide or nitric oxide donor administration. In vivo translation revealed that volume loading after MI only increased cardiac output in rats infused with PDE5i. Contrarily to vehicle, sildenafil-treated rats showed a clear increase in myocardial compliance upon volume loading. Discussion: Our results suggest that ischemia impairs the adaptive myocardial response to acute stretching and that this may be partly prevented by pharmacological manipulation of the cGMP/PKG pathway, namely, with PDE5i. Further studies are warranted to further elucidate the potential of this intervention in the clinical setting of acute myocardial ischemia.

Clinical and Pathophysiologic Insights of Free triiodothyronine/Free thyroxine Ratio in Patients with Heart Failure with Preserved Ejection Fraction: Data from the NETDiamond Cohort

BACKGROUND

Thyroid dysfunction is common in patients with heart failure (HF). Impaired conversion of free T4 (FT4) into free T3 (FT3) is thought to occur in these patients, decreasing the availability of FT3 and contributing to HF progression. In HF with preserved ejection fraction (HFpEF), it is not known whether changes in conversion of thyroid hormones (THs) are associated with clinical status and outcomes.

OBJECTIVES

The objective of this study was to evaluate the association of FT3/FT4 ratio and TH with clinical, analytical, and echocardiographic parameters, as well as their prognostic impact in individuals with stable HFpEF.

METHODS

We evaluated 74 HFpEF participants of the NETDiamond cohort without known thyroid disease. We performed regression modeling to study the associations of TH and FT3/FT4 ratio with clinical, anthropometric, analytical, and echocardiographic parameters, and survival analysis to evaluate associations with the composite of diuretic intensification, urgent HF visit, HF hospitalization, or cardiovascular death over a median follow-up of 2.8 years.

RESULTS

The mean age was 73.7 years and 62% were men. The mean FT3/FT4 ratio was 2.63 (standard deviation: 0.43). Subjects with lower FT3/FT4 ratio were more likely to be obese and have atrial fibrillation. Lower FT3/FT4 ratio was associated with higher body fat (β = -5.60 kg per FT3/FT4 unit, p = 0.034), higher pulmonary arterial systolic pressure (PASP) (β = -10.26 mm Hg per FT3/FT4 unit, p = 0.002), and lower left ventricular ejection fraction (LVEF) (β = 3.60% per FT3/FT4 unit, p = 0.008). Lower FT3/FT4 ratio was associated with higher risk for the composite HF outcome (HR = 2.50, 95% CI: 1.04-5.88, per 1-unit decrease in FT3/FT4, p = 0.041).

CONCLUSIONS

In patients with HFpEF, lower FT3/FT4 ratio was associated with higher body fat, higher PASP, and lower LVEF. Lower FT3/FT4 predicted a higher risk of diuretic intensification, urgent HF visits, HF hospitalization, or cardiovascular death. These findings suggest that decreased FT4 to FT3 conversion might be a mechanism associated with HFpEF progression.

Human-umbilical cord matrix mesenchymal cells improved left ventricular contractility independently of infarct size in swine myocardial infarction with reperfusion

Background

Human umbilical cord matrix-mesenchymal stromal cells (hUCM-MSC) have demonstrated beneficial effects in experimental acute myocardial infarction (AMI). Reperfusion injury hampers myocardial recovery in a clinical setting and its management is an unmet need. We investigated the efficacy of intracoronary (IC) delivery of xenogeneic hUCM-MSC as reperfusion-adjuvant therapy in a translational model of AMI in swine.

Methods

In a placebo-controlled trial, pot-belied pigs were randomly assigned to a sham-control group (vehicle-injection; n = 8), AMI + vehicle (n = 12) or AMI + IC-injection (n = 11) of 5 × 10⁵ hUCM-MSC/Kg, within 30 min of reperfusion. AMI was created percutaneously by balloon occlusion of the mid-LAD. Left-ventricular function was blindly evaluated at 8-weeks by invasive pressure-volume loop analysis (primary endpoint). Mechanistic readouts included histology, strength-length relationship in skinned cardiomyocytes and gene expression analysis by RNA-sequencing.

Results

As compared to vehicle, hUCM-MSC enhanced systolic function as shown by higher ejection fraction (65 ± 6% vs. 43 ± 4%; p = 0.0048), cardiac index (4.1 ± 0.4 vs. 3.1 ± 0.2 L/min/m²; p = 0.0378), preload recruitable stroke work (75 ± 13 vs. 36 ± 4 mmHg; p = 0.0256) and end-systolic elastance (2.8 ± 0.7 vs. 2.1 ± 0.4 mmHg*m²/ml; p = 0.0663). Infarct size was non-significantly lower in cell-treated animals (13.7 ± 2.2% vs. 15.9 ± 2.7%; Δ = -2.2%; p = 0.23), as was interstitial fibrosis and cardiomyocyte hypertrophy in the remote myocardium. Sarcomere active tension improved, and genes related to extracellular matrix remodelling (including MMP9, TIMP1 and PAI1), collagen fibril organization and glycosaminoglycan biosynthesis were downregulated in animals treated with hUCM-MSC.

Conclusion

Intracoronary transfer of xenogeneic hUCM-MSC shortly after reperfusion improved left-ventricular systolic function, which could not be explained by the observed extent of infarct size reduction alone. Combined contributions of favourable modification of myocardial interstitial fibrosis, matrix remodelling and enhanced cardiomyocyte contractility in the remote myocardium may provide mechanistic insight for the biological effect.

Relaxin-2, pathophysiological insights and outcomes in heart failure with preserved ejection fraction: Findings from the NETDiamond cohort

AIMS

The role of relaxin-2 as a circulating marker in heart failure (HF) with preserved ejection fraction (HFpEF) is poorly understood. We aimed to characterize relaxin-2 circulating levels in a population of chronic HFpEF patients and their association with long-term prognosis.

METHODS

Relaxin-2 serum levels were measured in 85 chronic HFpEF patients from a prospective cohort study (NETDiamond). Clinical, imaging, and analytical data were compared across relaxin-2 tertiles. The primary outcome was a composite of cardiovascular death, HF hospitalisation, acute HF episode or diuretic intensification and the secondary outcome a composite of cardiovascular death and total HF hospitalisations. Cox regression and negative binomial models were used to assess the relation between relaxin-2 and the outcomes.

RESULTS

Relaxin-2 levels were positively associated with left atrial volume, left ventricular mass and peripheral oedema, and negatively associated with ischemic heart disease and statin use. Higher relaxin-2 levels were associated with an increased risk of primary outcome, even after adjustment for age, B-type natriuretic peptide (BNP) and glomerular filtration rate (eGFR) (adjusted HR = 2.80, 95%CI 1.4-7.3, p = 0.034 for tertile 3). They were also associated with the occurrence of the secondary outcome (Incidence Rate Ratio = 5.28, 95%CI 1.2-23.2, p = 0.027), but this significance was lost when simultaneously adjusted for BNP and eGFR.

CONCLUSION

In chronic HFpEF patients, higher relaxin-2 circulating levels were associated with left chambers remodelling, congestion, and adverse prognosis. These findings support a potential role for relaxin-2 as a pathophysiological agent and as a circulating biomarker in HFpEF.

Assessing Rodent Cardiac Function in vivo Using Hemodynamic Pressure-Volume Loops

Heart failure (HF) triggered by cardiovascular and non-cardiovascular diseases is a leading cause of death worldwide and translational research is urgently needed to better understand the mechanisms of the failing heart. For this purpose, rodent models of heart disease combined with in vivo cardiac functional assessment have provided valuable insights into the physiological significance of a given genetic or pharmacological modification. In small animals, cardiac function and structure can be evaluated by methods such as echocardiography, telemetry or hemodynamics using conductance catheters. Indeed, hemodynamic analysis of pressure-volume loops (PV-loops) has become the gold standard methodology to study in vivo cardiac function in detail. This method provides simultaneous measurement of both pressure and volume signals from rodents intact beating hearts. On the one hand, PV-loop analysis has deeply expanded the knowledge on molecular cardiac physiology by allowing establishing important functional correlations. On the other hand, these measurements allow dissecting the cardiovascular functional impact of certain therapeutic interventions or specific signaling pathways using transgenic models of disease. However, a detailed assessment of cardiac function and structure in vivo still warrants proper standardization and optimization to boost the progress of HF research. With increasing concerns over data accuracy and reproducibility, guidelines and best practices for cardiac physiology measurements in experimental settings are needed. This article aims to review the best practices for carrying out cardiac hemodynamic assessment using PV-loops in vivo in rodents intact beating hearts, also providing an overview of its advantages, disadvantages and applications in cardiovascular research.

A systematic review and meta-analysis of randomized controlled studies comparing off-pump versus on-pump coronary artery bypass grafting in the elderly

AIM

Comparison of short and mid-term outcomes between off-pump CABG (OPCAB) and on-pump CABG (ONCAB) in patients older than 65 throughout a meta-analysis of randomized clinical trials (RCTs).

EVIDENCE ACQUISITION

A literature search was conducted using 3 databases. RCTs reporting mortality outcomes of OPCAB versus ONCAB among the elderly were included. Data on myocardial infarction, stroke, re-revascularization, renal failure and composite endpoints after CABG were also collected. Random effects models were used to compute statistical combined measures and 95% confidence intervals (CI).

EVIDENCE SYNTHESIS

Five RCTs encompassing 6221 patients were included (3105 OPCAB and 3116 ONCAB). There were no significant differences on mid-term mortality (pooled HR: 1.02, 95%CI: 0.89-1.17, p=0.80) and composite endpoint incidence (pooled HR: 0.98, 95%CI: 0.88-1.09, p=0.72) between OPCAB and ONCAB. At 30-day, there were no differences in mortality, myocardial infarction, stroke and renal complications. The need for early re-revascularization was significantly higher in OPCAB (pooled OR: 3.22, 95%CI: 1.28-8.09, p=0.01), with a higher percentage of incomplete revascularization being reported for OPCAB in trials included in this pooled result (34% in OPCAB vs 29% in ONCAB, p<0.01).

CONCLUSIONS

Data from RCTs in elderly patients showed that OPCAB and ONCAB provide similar mid-term results. OPCAB was associated with a higher risk of early rerevascularization. As CABG on the elderly is still insufficiently explored, further RCTs, specifically designed targeting this population, are needed to establish a better CABG strategy for these patients.

Histological and haemodynamic characterization of right ventricle in sedentary and trained rats with heart failure with preserved ejection fraction

NEW FINDINGS

What is the central question of this study? Right ventricle (RV) dysfunction is highly prevalent in heart failure with preserved ejection fraction (HFpEF), nearly doubling the risk of death: what are the RV functional and structural changes in HFpEF and how does aerobic exercise impact them? What is the main finding and its importance? The HFpEF ZSF1 rat model presents RV structural and functional changes mimicking the human condition. Aerobic exercise prevented the decline in V ̇ O 2 max , lowered surrogate markers of RV overload (e.g., higher mean and maximum systolic pressure) and improved diastolic dysfunction (e.g., end-diastolic pressure and relaxation time constant). This emphasizes the importance of using exercise to manage HFpEF.

ABSTRACT

Right ventricle (RV) dysfunction is highly prevalent in heart failure with preserved ejection fraction (HFpEF) and is a marker of poor prognosis. We assessed the obese ZSF1 rat model of HFpEF to ascertain if these animals also develop RV dysfunction and evaluated whether aerobic exercise could prevent this. Obese ZSF1 rats were randomly allocated to an aerobic exercise training group (n = 7; treadmill running, 5 days/week, 60 min/day, 15 m/min for 5 weeks) or to a sedentary group (n = 7). We used lean ZSF1 rats (n = 7) as the control group. After 5 weeks, rats were submitted to an exercise tolerance test and invasive haemodynamic evaluation, killed and samples from the RV collected for histological analysis. Obese sedentary ZSF1 rats showed lower V ̇ O 2 max , RV pressure overload (e.g., higher mean and maximum systolic pressure) and diastolic dysfunction (e.g., higher minimum and end-diastolic pressure and relaxation time constant), paralleled by RV cardiomyocyte hypertrophy. Except for cardiomyocyte hypertrophy, aerobic exercise prevented these functional changes. Our data support that this model of HFpEF shows functional and structural changes in the RV that resemble the human HFpEF phenotype, reinforcing its utility to understand this pathophysiology and to adress novel therapeutic targets to manage HFpEF. In addition, we showed that aerobic exercise is cardioprotective for the RV. A deeper knowledge of the mechanisms underlying the benefits of aerobic exercise could also lead to the identification of therapeutic targets to be further explored.

Chronic Sildenafil Therapy in the ZSF1 Obese Rat Model of Metabolic Syndrome and Heart Failure With Preserved Ejection Fraction

Although decreased protein kinase G (PKG) activity was proposed as potential therapeutic target in heart failure with preserved ejection fraction (HFpEF), randomized clinical trials (RCTs) with type-5 phosphodiesterase inhibitors (PDE5i) showed neutral results. Whether specific subgroups of HFpEF patients may benefit from PDE5i remains to be defined. Our aim was to test chronic sildenafil therapy in the young male ZSF1 obese rat model of HFpEF with severe hypertension and metabolic syndrome. Sixteen-week-old ZSF1 obese rats were randomly assigned to receive sildenafil 100 mg·Kg^-1·d^-1 dissolved in drinking water (ZSF1 Ob SIL, n = 8), or placebo (ZSF1 Ob PL, n = 8). A group of Wistar-Kyoto rats served as control (WKY, n = 8). Four weeks later animals underwent effort tests, glucose metabolism studies, hemodynamic evaluation, and samples were collected for aortic ring preparation, left ventricular (LV) myocardial adenosine triphosphate (ATP) quantification, immunoblotting and histology. ZSF1 Ob PL rats showed systemic hypertension, aortic stiffening, impaired LV relaxation and increased LV stiffness, with preserved ejection fraction and cardiac index. Their endurance capacity was decreased as assessed by maximum workload and peak oxygen consumption (V˙O₂) and respiratory quotient were increased, denoting more reliance on anaerobic metabolism. Additionally, ATP levels were decreased. Chronic sildenafil treatment attenuated hypertension and decreased LV stiffness, modestly enhancing effort tolerance with a concomitant increase in peak, ATP levels and VASP phosphorylation. Chronic sildenafil therapy in this model of HFpEF of the young male with extensive and poorly controlled comorbidities has beneficial cardiovascular effects which support RCTs in HFpEF patient subgroups with similar features.

Nicotinamide for the treatment of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is a highly prevalent and intractable form of cardiac decompensation commonly associated with diastolic dysfunction. Here, we show that diastolic dysfunction in patients with HFpEF is associated with a cardiac deficit in nicotinamide adenine dinucleotide (NAD⁺). Elevating NAD⁺ by oral supplementation of its precursor, nicotinamide, improved diastolic dysfunction induced by aging (in 2-year-old C57BL/6J mice), hypertension (in Dahl salt-sensitive rats), or cardiometabolic syndrome (in ZSF1 obese rats). This effect was mediated partly through alleviated systemic comorbidities and enhanced myocardial bioenergetics. Simultaneously, nicotinamide directly improved cardiomyocyte passive stiffness and calcium-dependent active relaxation through increased deacetylation of titin and the sarcoplasmic reticulum calcium adenosine triphosphatase 2a, respectively. In a long-term human cohort study, high dietary intake of naturally occurring NAD⁺ precursors was associated with lower blood pressure and reduced risk of cardiac mortality. Collectively, these results suggest NAD⁺ precursors, and especially nicotinamide, as potential therapeutic agents to treat diastolic dysfunction and HFpEF in humans.

Multiple versus single arterial grafting in the elderly: a meta-analysis of randomized controlled trials and propensity score studies

INTRODUCTION

The benefit of adding a second arterial conduit is still controversial, mainly in specific subgroups. We conducted a meta-analysis of randomized controlled trials (RCTs) and propensity score (PS) studies comparing survival and early results in elderly patients who underwent coronary artery bypass grafting (CABG) with multiple (MAG) versus single arterial grafting (SAG).

EVIDENCE ACQUISITION

MEDLINE, Web of Science and Cochrane Library were used to find relevant literature (1960-April 2020). Survival at a ≥ 1-year follow-up and early outcomes were evaluated. Outcomes were collected from matched samples or PS adjusted analysis: hazard ratio (HR) along with their variance, frequencies or odds ratios. Random effect models were used to compute combined statistical measures and 95% confidence intervals (CI) through generic inverse variance method (time-to-event) or Mantel-Haenszel method (binary events).

EVIDENCE SYNTHESIS

Eleven PS cohorts and 1 RCT comprising > 18,800 patients older than 70 (>6200 MAG and >12,500 SAG) were included in this meta-analysis. MAG was associated with lower long-term mortality (pooled HR: 0.81, 95%CI: 0.72-0.91, p<0.01, I2=64%) in the absence of higher risk of early mortality (pooled OR: 0.74, 95%CI: 0.44 to 1.25, p=0.27, I2=0%). In a meta-regression, MAG survival advantage was more pronounced in studies with a higher MAG usage rate (β = -0.0052, p=0.021).

CONCLUSIONS

Current evidence suggests that advanced age should not limit MAG's use considering its benefits in long-term survival. Of note, an individualized patient selection for this approach is warranted.

Human umbilical cord tissue-derived mesenchymal stromal cells as adjuvant therapy for myocardial infarction: a review of current evidence focusing on pre-clinical large animal models and early human trials

Although biologically appealing, the concept of tissue regeneration underlying first- and second-generation cell therapies has failed to translate into consistent results in clinical trials. Several types of cells from different origins have been tested in pre-clinical models and in patients with acute myocardial infarction (AMI). Mesenchymal stromal cells (MSCs) have gained attention because of their potential for immune modulation and ability to promote endogenous tissue repair, mainly through their secretome. MSCs can be easily obtained from several human tissues, the umbilical cord being the most abundant source, and further expanded in culture, making them attractive as an allogeneic "of-the-shelf" cell product, suitable for the AMI setting. The available evidence concerning umbilical cord-derived MSCs in AMI is reviewed, focusing on large animal pre-clinical studies and early human trials. Molecular and cellular mechanisms as well as current limitations and possible translational solutions are also discussed.

Arterial Stiffness Changes in Severe Aortic Stenosis Patients Submitted to Valve Replacement Surgery

BACKGROUND

Little is known about the impact of severe aortic stenosis (AS) in aortic stiffness and if there is any change after removing AS barrier with aortic valve replacement (AVR) surgery.

OBJECTIVE

To estimate carotid-femoral pulse wave velocity (PWV) changes after AVR surgery and to define PWV predictors in severe AS patients.

METHODS

Single-center retrospective cohort, including patients with severe AS who underwent AVR surgery with bioprostheses, between February 2017 and January 2019 and performed PWV measurements (Complior®) before and after the procedure (2±1 months). Before and after AVR, PWV values were compared through paired tests. The associations of PWV with clinical data were studied and linear regression models were applied to estimate pre and postoperative PWV independent predictors. The significance level was set at 5%.

RESULTS

We included 150 patients in the sample, with mean age of 72±8 years, and 51% being males. We found a statistically significant increase in PWV values after surgery (9.0±2.1 m/s vs. 9.9±2.2, p<0.001, before and after AVR, respectively) and an inverse association with AS severity variables. In the linear regression model, age and systolic blood pressure (SBP) were established as independent predictors of higher pre- and postoperative PWV, while higher mean valvular gradient emerged as a determinant of lower pre-AVR PWV.

CONCLUSION

We documented an inverse correlation of arterial stiffness with the severity of AS in patients with AS, and a significant increase in PWV values after AVR surgery. Advanced age and higher SBP were associated with higher PWV values, although arterial function measurements were within the normal range. (Arq Bras Cardiol. 2021; 116(3):475-482).

Comparison of levosimendan, NO, and inhaled iloprost for pulmonary hypertension reversibility assessment in heart transplant candidates

Aims

Assessing reversibility of pulmonary vascular changes through vasoreactivity testing (VRT) optimizes end‐stage heart failure patient selection for heart transplant. All efforts should be made to unload the left ventricle and reduce pulmonary vascular resistance to effectively exclude irreversible pulmonary hypertension.

Methods and results

We reviewed our centre's cardiac transplant registry database (2009–2017) for VRT and compared haemodynamic responses with 40 ppm inhaled NO (n = 14), 14–17 μg inhaled iloprost (n = 7), and 24 h 0.1 μg/kg/min intravenous levosimendan (n = 14). Response to levosimendan was assessed by repeat right heart catheterization within 72 h. Baseline clinical and haemodynamic features were similar between groups. VRT was well tolerated in all patients. All drugs effectively reduced pulmonary artery pressures and transpulmonary gradient while increasing cardiac index, although levosimendan had a greater impact on cardiac index increase (P = 0.036). Levosimendan was the only drug that reduced pulmonary artery wedge pressure (P = 0.004) and central venous pressures (P < 0.001) and increased both left and right ventricular stroke work indexes (P = 0.020 and P = 0.042, respectively) and cardiac power index (P < 0.001) compared with NO and iloprost. Right ventricular end‐diastolic pressures and central venous pressure were only decreased by levosimendan. The rate of positive responses (≥10 mmHg decrease or final mean pulmonary artery pressure ≤40 mmHg with increased/unaltered cardiac index) was lower with inhaled iloprost (14%) than with either levosimendan or NO (71% and 64%, respectively; P < 0.05).

Conclusions

Levosimendan may be a safe and effective alternative for pulmonary hypertension reversibility assessment or a valuable pre‐test medical optimization tool in end‐stage heart failure patient assessment for heart transplantation offering extended haemodynamic benefits. Whether it increases the rate of positive responses or allows a better selection of candidates to heart transplantation remains to be established.

Exosome-Derived Mediators as Potential Biomarkers for Cardiovascular Diseases: A Network Approach

Cardiovascular diseases (CVDs) are widely recognized as the leading cause of mortality worldwide. Despite the advances in clinical management over the past decades, the underlying pathological mechanisms remain largely unknown. Exosomes have drawn the attention of researchers for their relevance in intercellular communication under both physiological and pathological conditions. These vesicles are suggested as complementary prospective biomarkers of CVDs; however, the role of exosomes in CVDs is still not fully elucidated. Here, we performed a literature search on exosomal biogenesis, characteristics, and functions, as well as the different available exosomal isolation techniques. Moreover, aiming to give new insights into the interaction between exosomes and CVDs, network analysis on the role of exosome-derived mediators in coronary artery disease (CAD) and heart failure (HF) was also performed to incorporate the different sources of information. The upregulated exosomal miRNAs miR-133a, miR-208a, miR-1, miR-499-5p, and miR-30a were described for the early diagnosis of acute myocardial infarction, while the exosome-derived miR-192, miR-194, miR-146a, and miR-92b-5p were considered as potential biomarkers for HF development. In CAD patients, upregulated exosomal proteins, including fibrinogen beta/gamma chain, inter-alpha-trypsin inhibitor heavy chain, and alpha-1 antichymotrypsin, were assessed as putative protein biomarkers. From downregulated proteins in CAD patients, albumin, clusterin, and vitamin D-binding protein were considered relevant to assess prognosis. The Vesiclepedia database included miR-133a of exosomal origin upregulated in patients with CAD and the exosomal miR-192, miR-194, and miR-146a upregulated in patients with HF. Additionally, Vesiclepedia included 5 upregulated and 13 downregulated exosomal proteins in patients in CAD. The non-included miRNAs and proteins have not yet been identified in exosomes and can be proposed for further research. This report highlights the need for further studies focusing on the identification and validation of miRNAs and proteins of exosomal origin as biomarkers of CAD and HF, which will enable, using exosomal biomarkers, the guiding of diagnosis/prognosis in CVDs.

Early And Midterm Outcomes Following Aortic Valve Replacement With Mechanical Versus Bioprosthetic Valves In Patients Aged 50 To 70 Years

OBJECTIVES

To compare 7-year survival and freedom from reoperation, as well as early clinical and hemodynamic outcomes, after surgical aortic valve replacement (SAVR) with mechanical or bioprosthetic valves in patients aged 50-70 years.

METHODS

single-center retrospective cohort study including adults aged 50-70 years who underwent SAVR in 2012 with a mechanical or bioprosthetic valve. Median follow-up was 7 years. Univariable analyses were performed using Kaplan-Meier curves and Log-Rank tests for survival and freedom from reoperation analyses. Multivariable time-to-event analyses were conducted using Cox Regression.

RESULTS

Of a total of 193 patients, 76 (39.4%) received mechanical valves and 117 (60.6%) received bioprosthetic valves. A trend for better survival was found for mechanical prostheses when adjusting for EuroSCORE II (HR: 0.35; 95%CI: 0.12-1.02, p=0.054), but using a backward stepwise Cox regression prosthesis type was not retained by the model as an independent predictor of survival. Moreover, mechanical prostheses showed trends for higher freedom from reoperation (100% vs. 95.5%, Log-Rank, p=0.076), higher median EuroSCORE II (2.52% vs. 1.95%, p=0.06) and early mortality (7.9% vs. 2.6%, p=0.086). However, after adjusting for EuroSCORE II, there was no significant difference in early mortality (OR: 2.3, 95%CI: 0.5-10.5, p=0.272). Regarding hemodynamic performance at follow-up echocardiogram, there were no differences other than left ventricular mass regression, which was not as pronounced in the mechanical group (-12% vs. -21%, p=0.002).

CONCLUSION

Mechanical and bioprosthetic aortic valves prostheses showed similar mid-term survival in the 50-70 age group. Further prospective and larger studies are needed to provide evidence-based recommendations on this topic.

Towards standardization of echocardiography for the evaluation of left ventricular function in adult rodents: a position paper of the ESC Working Group on Myocardial Function

Echocardiography is a reliable and reproducible method to assess non-invasively cardiac function in clinical and experimental research. Significant progress in the development of echocardiographic equipment and transducers has led to the successful translation of this methodology from humans to rodents, allowing for the scoring of disease severity and progression, testing of new drugs, and monitoring cardiac function in genetically modified or pharmacologically treated animals. However, as yet, there is no standardization in the procedure to acquire echocardiographic measurements in small animals. This position paper focuses on the appropriate acquisition and analysis of echocardiographic parameters in adult mice and rats, and provides reference values, representative images, and videos for the accurate and reproducible quantification of left ventricular function in healthy and pathological conditions.

Stretch-induced compliance: a novel adaptive biological mechanism following acute cardiac load

Aims

The heart is constantly challenged with acute bouts of stretching or overload. Systolic adaptations to these challenges are known but adaptations in diastolic stiffness remain unknown. We evaluated adaptations in myocardial stiffness due to acute stretching and characterized the underlying mechanisms.

Methods and results

Left ventricles (LVs) of intact rat hearts, rabbit papillary muscles and myocardial strips from cardiac surgery patients were stretched. After stretching, there was a sustained >40% decrease in end-diastolic pressure (EDP) or passive tension (PT) for 15 min in all species and experimental preparations. Stretching by volume loading in volunteers and cardiac surgery patients resulted in E/E' and EDP decreases, respectively, after sustained stretching. Stretched samples had increased myocardial cGMP levels, increased phosphorylated vasodilator-stimulated phosphoprotein phosphorylation, as well as, increased titin phosphorylation, which was reduced by prior protein kinase G (PKG) inhibition (PKGi). Skinned cardiomyocytes from stretched and non-stretched myocardia were studied. Skinned cardiomyocytes from stretched hearts showed decreased PT, which was abrogated by protein phosphatase incubation; whereas those from non-stretched hearts decreased PT after PKG incubation. Pharmacological studies assessed the role of nitric oxide (NO) and natriuretic peptides (NPs). PT decay after stretching was significantly reduced by combined NP antagonism, NO synthase inhibition and NO scavenging, or by PKGi. Response to stretching was remarkably reduced in a rat model of LV hypertrophy, which also failed to increase titin phosphorylation.

Conclusions

We describe and translate to human physiology a novel adaptive mechanism, partly mediated by titin phosphorylation through cGMP-PKG signalling, whereby myocardial compliance increases in response to acute stretching. This mechanism may not function in the hypertrophic heart.

Arterial Remodeling and Dysfunction in the ZSF1 Rat Model of Heart Failure With Preserved Ejection Fraction

BACKGROUND

The interplay between the stiffened heart and vessels has long been viewed as a core mechanism in heart failure with preserved ejection fraction, but the incremental vascular molecular remodeling mechanisms from systemic arterial hypertension to heart failure with preserved ejection fraction remain poorly investigated. Our aim was to characterize central arterial remodeling and dysfunction in ZSF1 obese rats and to compare it with hypertensive ZSF1 lean and healthy Wistar-Kyoto controls.

METHODS AND RESULTS

Twenty-week-old male ZSF1 obese (n=9), lean (n=9), and Wistar-Kyoto rats (n=9) underwent left ventricular pressure-volume loop evaluation and synchronous acquisition of ascending aortic flow and pressure. Aortic rings underwent functional evaluation, histology, and molecular biology studies. Although mean arterial pressure, characteristic aortic impedance, and reactivity to phenylephrine were similarly increased in hypertensive ZSF1 lean and obese, only ZSF1 obese showed impaired relaxation and upward-shifted end-diastolic pressure-volume relationships despite preserved systolic function indexes, denoting heart failure with preserved ejection fraction. ZSF1 obese phenotype further showed decreased aortic compliance, increased wave reflection, and impaired direct NO donor and endothelial-mediated vasodilation which were accompanied on structural and molecular grounds by aortic media thickening, higher collagen content and collagen/elastin ratio, increased fibronectin and α-5 integrin protein expression and upregulated TGF (transforming growth factor)-β and CTGF (connective tissue growth factor) levels.

CONCLUSIONS

Functional, molecular, and structural disturbances of central vessels and their potentially underlying pathways were newly characterized in experimental heart failure with preserved ejection fraction rendering the ZSF1 obese rat model suitable for preclinical testing.

Hemodynamic and clinical performance of Solo stentless bioprosthetic aortic valves

OBJECTIVE

To report the hemodynamic profile and short- and medium-term outcomes of Freedom Solo and Solo Smart stentless aortic valves implanted at our center.

METHODS

Between 2009 and 2015, all patients undergoing aortic valve replacement using Solo stentless valves at our center were enrolled. Clinical and echocardiographic follow-up was carried out six months postoperatively. Survival and major events, including structural valve deterioration and non-structural valve dysfunction, endocarditis, reoperation and stroke, were assessed through medical records or telephone interview with the referring cardiologist up to November 2015 (mean and maximum follow-up 39±22 and 78 months, respectively).

RESULTS

Patients' (n=345) mean age was 72±8 years, 52% were female and median euroSCORE II was 2.7 (1.5-4.7). There was no intraoperative mortality and in-hospital mortality was 2.6%. Postoperatively, mean transvalvular gradient was 11.9±4.5 mmHg and effective orifice area was 1.9±0.5 cm². Patient-prosthesis mismatch occurred in 14% but was severe in only one patient. Cumulative survival at six years was 72%. Six patients were reoperated: three due to endocarditis, two for structural prosthesis deterioration and one because of periprosthetic fistula. Five patients suffered stroke, three had medically-treated endocarditis and one had structural valve deterioration but was not considered suitable for reoperation. None of the remainder had structural valve deterioration or non-structural valve dysfunction.

CONCLUSIONS

Solo stentless aortic valves are safe to implant, with promising clinical outcomes in short- and medium-term assessment. Moreover, they show an excellent hemodynamic performance: low transvalvular gradients, large effective orifice areas and low incidence of patient-prosthesis mismatch.

Silencing of Apis mellifera dorsal genes reveals their role in expression of the antimicrobial peptide defensin-1

Like all other insects, two key signalling pathways [Toll and immune deficiency (Imd)] regulate the induction of honey bee immune effectors that target microbial pathogens. Amongst these effectors are antimicrobial peptides (AMPs) that are presumed to be produced by the nuclear factors kappa B (NF-κB) Dorsal and Relish from the Toll and Imd pathways, respectively. Using in silico analysis, we previously proposed that the honey bee AMP defensin-1 was regulated by the Toll pathway, whereas hymenoptaecin was regulated by Imd and abaecin by both the Toll and Imd pathways. Here we use an RNA interference (RNAi) assay to determine the role of Dorsal in regulating abaecin and defensin-1. Honey bees have two dorsal genes (dorsal-1 and dorsal-2) and two splicing isoforms of dorsal-1 (dorsal-1A and dorsal-1B). Accordingly, we used both single and multiple (double or triple) isoform knockdown strategies to clarify the roles of dorsal proteins and their isoforms. Down-regulation of defensin-1 was observed for dorsal-1A and dorsal-2 knockdowns, but abaecin expression was not affected by dorsal RNAi. We conclude that defensin-1 is regulated by Dorsal (Toll pathway).

Randomized controlled trial of remote ischaemic conditioning in ST-elevation myocardial infarction as adjuvant to primary angioplasty (RIC-STEMI)

To test whether remote ischaemic conditioning (RIC) as adjuvant to standard of care (SOC) would prevent progression towards heart failure (HF) after ST-elevation myocardial infarction (STEMI). Single-centre parallel 1:1 randomized trial (computerized block-randomization, concealed allocation) to assess superiority of RIC (3 cycles of intermittent 5 min lower limb ischaemia) over SOC in consecutive STEMI patients (NCT02313961, clinical trials.gov). From 258 patients randomized to RIC or SOC, 9 and 4% were excluded because of unconfirmed diagnosis and previously unrecognized exclusion criteria, respectively. Combined primary outcome of cardiac mortality and hospitalization for HF was reduced in RIC compared with SOC (n = 231 and 217, respectively; HR = 0.35, 95% CI 0.15-0.78) as well as each outcome in isolation. No difference was found in serum troponin I levels between groups. Median and maximum follow-up time were 2.1 and 3.7 years, respectively. In-hospital HF (RR = 0.68, 95% CI 0.47-0.98), need for diuretics (RR = 0.68, 95% CI 0.48-0.97) and inotropes and/or intra-aortic balloon pump (RR = 0.17, 95% CI 0.04-0.76) were decreased in RIC. On planned 12 months follow-up echocardiography (n = 193 and 173 in RIC and SOC, respectively) ejection fraction (EF) recovery was enhanced in patients presenting with impaired left ventricular (LV) function (10% absolute difference in median EF compared with SOC; P < 0.001). In addition to previously reported improved myocardial salvage index and reduced infarct size RIC was shown beneficial in a combined hard clinical endpoint of cardiac mortality and hospitalization for HF. Improved EF recovery was also documented in patients with impaired LV function.

Cardiac Catheterization After CABG With BIMA Grafting: Independent Predictors and Mid-term Bypass Viability

INTRODUCTION

Coronary artery bypass graft (CABG) patency is an important variable, but rarely studied as the main outcome. The best use of bilateral internal mammary artery (BIMA) grafting regarding configuration type or combination with saphenous vein graft (SVG) is still debated.

PURPOSE

To find independent predictors for need of cardiac catheterization and for significant lesions in CABG follow-up.

METHODS

Retrospective cohort including all patients who underwent isolated CABG with BIMA grafts between 2004 and 2013 in a tertiary center. Preoperative, surgical and postoperative data were collected through clinical files and informatics databases. Kaplan-Meier curves, Cox regression and logistic regression were used to find predictors for the need of catheterization and for significant angiographic lesions after CABG. Secondary end-points studied were mid- term survival and need of re-revascularization either surgically or percutaneously.

RESULTS

We included 1030 patients in this analysis. Median follow-up time was 5.5 years and 150 (15%) patients were re-catheterized in that period. Most of these procedures was due to ischemia suspicion (74%) and 61 (41%) were positive for significant angiographic lesions of conduits (IMA: 3.2% and SVG: 3.8%, p=0.488). In multivariate analysis, SVG use was found as an independent predictor of cardiac catheterization on follow-up (HR: 1.610, CI 95%: 1.038-2.499, p=0.034). On the other side, independent predictors of graft lesions were younger age (OR: 0.951, CI 95%: 0.921-0.982, p=0.002), female gender (OR: 2.231, CI 95%: 1.038-4.794, p=0.040), arterial hypertension (OR: 1.968, CI 95%: 1.022-3.791, p=0.043) and 3-vessel disease (OR: 2.820, CI 95%: 1.155-6.885, p=0.023). Among the patients with significant angiographic lesions, 48 underwent repeat revascularization (44 PCI e 4 CABG). Arterial hypertension and younger age were independent predictors of re-revascularization.

CONCLUSION

In BIMA patients the addition of SVG predicts the need of catheterization; however prevalence of significant angiographic lesions was similar in IMA and SVG. Our results suggest that arterial hypertension is an independent predictor of graft patency and re-revascularization rate.

Postoperative Atrial Fibrillation After Coronary Artery Bypass Grafting Surgery

INTRODUCTION

Postoperative atrial fibrillation (PoAF) is the most common arrhythmia following cardiac surgery, which increase the patient's morbidity and mortality.

PURPOSE

The aim of this study was to evaluate new onset of atrial fibrillation (AF) after isolated coronary artery bypass grafting (CABG) surgery, its clinical and surgical predictors, and its impact in immediate and long-term outcomes.

METHODS

Retrospective study including all CABG surgeries performed in a tertiary centre, between 2004 and 2011. Patients with documented episodes of AF or pacing rhythm before cardiac surgery were excluded. Preoperative, surgical and postoperative data were collected through clinical files and informatics databases. Qui-square tests and independent t-tests were used to compare categorical and continuous data, respectively, between patients with and without PoAF. A multivariate logistic regression model was used to identify independent risk factors of PoAF. To determine the effect of PoAF in long-term survival, we used Kaplan-Meier curves, Log Rank test and multivariate Cox regression (maximum follow-up time: 13 years).

RESULTS

We included 2511 patients, mean age of 63±10 years, 78.7% being male. PoAF occurred in 450 patients (18.0%), 3±3 days after surgery, the majority pharmacologically cardioverted with amiodarone (96.2%). These patients were older (67±9 vs. 62±10 years, p<0.001), more frequently obese (27.8% vs. 22.9%, p=0.026), hypertensive (76.7% vs. 69.7%, p=0.003) and had lower preoperative creatinine clearance (CC) values (73.2±27.4 vs. 81.4±28.3 ml/min, p<0.001), longer cardiopulmonary bypass time (60.0% vs. 54.8%, p=0.043) compared with patients without PoAF. In multivariate analysis, older age (OR: 1.035, 95% CI: 1.015-1.056, p=0.001), lower preoperative CC values (OR: 0.992, 95% CI: 0.985-0.999, p=0.032) and larger left atrial diameter (OR: 1.058, 95% CI: 1.024-1.093, p=0.001) were determined as independent predictors of PoAF. These patients also revealed longer hospitalization time (8 [4 to 193] vs. 6 [4 to 114] days, p<0.001) and higher hospital mortality (2.9% vs. 0.8%, p<0.001). Regarding long-term survival, patients with PoAF showed lower cumulative survival than patients without AF events (52% vs. 66%, p<0.001). PoAF was also found as an independent predictor of mortality in multivariate Cox regression (HR: 1.394, 95% CI: 1.147- 1.695, p=0.001).

CONCLUSION

PoAF incidence after CABG surgery was 18%. Older age, lower CC values and larger left atrial diameter were settled as PoAF independent predictors. Additionally, the occurrence of this arrhythmia was independently associated with lower long-term survival, after CABG surgery.

Endothelial Function and Vascular Properties in Severe Aortic Stenosis Before and After Aortic Valve Replacement Surgery

INTRODUCTION

The degenerative process that results in aortic valve stenosis (AS) has pathophysiological features similar to the atherosclerotic process. We therefore hypothesized that, as in atherosclerosis, endothelial and vascular dysfunction could be a pathophysiologic feature of AS.

AIM

To evaluate endothelial function before and after aortic valve replacement (AVR) surgery in patients with severe AS. To correlate endothelial function with severity of AS and clinical profile.

METHODS

Two noninvasive methods were used to evaluate endothelial function (Reactive Hyperemia Index (RHI) measure with EndoPATTM2000 system) and vascular properties (carotid-femoral Pulse Wave Velocity (PWV) measured by Complior® Analyse) in 13 patients with severe AS undergoing AVR. Sample was collected by convenience in a single-center between February and July of 2017. Pre- -operative, surgical and post-operative data were collected through clinical files and informatics databases. PWV, RHI, Augmentation Index (AI) were assessed at the day of surgery and 2.4±1.2 months post-operatively. Mean transvalvular gradients (MTG), aortic valve area (AVA) and left ventricular function were evaluated by transthoracic echocardiography at 3.4±1.6 months of follow-up. Wilcoxon or paired t-tests were used to compare pre- and post-operative values of continuous variables. Spearman correlations (rho) were done to find associations between endothelial/ vascular function parameters and clinical data.

RESULTS

In our sample, mean age was 70±8 years and 69% were females. Arterial hypertension was present in 11 (85%) patients, diabetes in 3 (23%) and pre-operative NYHA functional class ≥III in 4 (31%). No patient was currently smoker and only 2 had previous history of smoking. No significant changes were observed between pre- and post-operative endothelial/vascular function values. PWV (m/s), AI (%) and RHI before and after AVR surgery were: 10.5 (6.1 to 16) vs. 9.4 (4.7 to 21.6), p=0.701; 33% [-24 to 54] vs. 23% [0 to 47], p=0.116 and 1.83 (1.08 to 3.13) vs. 1.71 (1.06 to 3.12), p=0.638, respectively. We found a significant inverse correlation between pre- operative AVA and AI (rho= -0.652, p=0.016) and a positive correlation between age and post-operative PWV (rho= 0.639, p=0.019). Pre- and post-operative MTG and AVA were 54±5 mmHg and 0.7± 0.1 cm2 vs.12±4 mmHg and 2.0±0.5 cm2, respectively (p<0.001).

CONCLUSION

Considering small sample size, no differences were found in indices of endothelial/vascular function before and after AVR surgery due to AS. However, it seems that endothelial dysfunction is associated with severity of AS assessed by AVA.

Dose–Response Head-to-Head Comparison of Inodilators Dobutamine, Milrinone, and Levosimendan in Chronic Experimental Pulmonary Hypertension

The choice of inodilator drug in the acute management of patients with pulmonary hypertension (PH) having right ventricular (RV) failure remains unsettled and challenging. Comprehensive experimental evaluations may provide further insight and fundamental translational research clues to support inodilator selection and clinical trial design. Our aim was to compare acute dose–response hemodynamic effects of inodilators dobutamine (DOB), milrinone (MIL), and levosimendan (LEV) in chronic experimental PH. Seven-week-old male Wistar rats were randomly injected with 60 mg·kg−1 monocrotaline (MCT) or vehicle (Ctrl, n = 7) and underwent systemic and pulmonary artery (PA) pressure and RV pressure–volume (PV) hemodynamic evaluation under halogenate anesthesia 24 to 30 days after injection. The MCT-injected animals (n = 7 each) randomly received dose–response infusions of DOB (1, 3, 6 and 12 μg·kg−1·min−1), MIL (MIL: 1, 3, 6 and 12 μg·kg−1·min−1), or LEV (0.3, 0.6, 1.2 and 2.4 μg·kg−1·min−1). Load-independent indexes were obtained by inferior vena cava occlusion at baseline and after the last dose. All inodilators increased RV ejection fraction, preload recruitable stroke work, and ventricular–vascular coupling without jeopardizing perfusion pressure. Dobutamine raised heart rate and PA pressure. Only LEV increased cardiac index and decreased PA elastance and pulmonary vascular resistance (PVR). Moreover, only LEV downward-shifted the end-diastolic PV relationship, thereby improving RV compliance. Adding sildenafil to LEV further decreased PVR. Levosimendan had beneficial acute systolic and diastolic functional effects in experimental chronic PH and RV afterload compared to DOB and MIL. It should be further tested in clinical trials enrolling patients with PH in the perioperative and critical care settings.

Right ventricular end-diastolic stiffness heralds right ventricular failure in monocrotaline-induced pulmonary hypertension

Recent studies suggest right ventricular (RV) stiffness is important in pulmonary hypertension (PH) prognosis. Smaller stroke volume (SV) variation after a certain RV end-diastolic pressure (EDP) respiratory variation as assessed by spectral transfer function (STF) may identify RV stiffness. Our aim was to evaluate RV stiffness in monocrotaline (MCT)-induced PH progression and to validate STF gain between EDP and SV as marker of stiffness. Seven-week-old male Wistar rats randomly injected with 60 mg/kg MCT or vehicle were divided into three groups ( n = 12 each) according to cardiac index (CI): controls (Ctrl), preserved CI (MCT pCI), and reduced CI (MCT rCI). All underwent RV pressure-volume (PV) evaluation 24–34 days after MCT, under halogenate anesthesia and constant positive-pressure ventilation. End-diastolic stiffness (βi), end-systolic elastance (Eesi), arterial elastance for indexed volumes (Eai), and preload recruitable stroke work (PRSW) were obtained and beat-to-beat fluctuations during ventilation assessed by STF. Eai was the strongest determinant of CI, alongside βi but not PRSW. MCT rCI showed impaired ventricular-vascular coupling (VVC) and higher βi, along with low end-diastolic pressure (EDP) and stroke volume index (SVi) STF gain, denoting impaired preload reserve. On multivariate analysis βi and not Eesi correlated with EDP-SVi STF gain ( P < 0.001). Receiver-operating characteristics (ROC) curve analysis of EDP-SVi STF gain showed an area under curve of 0.84 for βi prediction ( P = 0.002). Afterload, impaired VVC and RV stiffness are major players in RV failure. RV stiffness can be assessed by STF gain analysis of respiratory fluctuations between EDP and SVi, which may constitute a prognostic tool in PH.

Trap-Nesting Bees in Montane Grassland (Campo Rupestre) and Cerrado in Brazil: Collecting Generalist or Specialist Nesters

Species richness and seasonal abundance of solitary bees were investigated in rocky, montane grassland (campo rupestre) (1180 m asl) and cerrado sensu stricto (680 m asl) in the Biribiri State Park, Diamantina, state of Minas Gerais, Brazil. Three hundred nineteen nest traps of bamboo canes and black cardboard tubes were monthly inspected at each site during 15 months. A total of eight species of bees built 97 nests. Four species were common to both sites. Tetrapedia aff. curvitarsis Friese and Tetrapedia aff. peckoltii Friese were the most abundant at campo rupestre and cerrado s.s., respectively, followed by Centris analis (Fabricius) in campo rupestre and Centris tarsata Smith in cerrado s.s. The nesting peaks occurred in May in campo rupestre and in February in cerrado s.s. Three cuckoo bees and one bee-fly were collected as natural enemies. The findings suggest that differences between the sites were related more to ecological factors (floral resources, natural nest sites) than to the altitudinal difference. The species richness was similar to that in other habitats with open vegetation. We demonstrate the need to use several types of trap-nest to increase the range of species sampled; some species used only one of the two types traps provided. We also comment on the limitations of trap-nests in cerrado vegetation. Most cerrado species of bees are very selective in their choice for a nesting site, but bees that use trap-nests are more generalists.

Distinct Endothelial Cell Responses in the Heart and Kidney Microvasculature Characterize the Progression of Heart Failure With Preserved Ejection Fraction in the Obese ZSF1 Rat With Cardiorenal Metabolic Syndrome

BACKGROUND

The combination of cardiac and renal disease driven by metabolic risk factors, referred to as cardiorenal metabolic syndrome (CRMS), is increasingly recognized as a critical pathological entity. The contribution of (micro)vascular injury to CRMS is considered to be substantial. However, mechanistic studies are hampered by lack of in vivo models that mimic the natural onset of the disease. Here, we evaluated the coronary and renal microvasculature during CRMS development in obese diabetic Zucker fatty/Spontaneously hypertensive heart failure F1 hybrid (ZSF1) rats.

METHODS AND RESULTS

Echocardiographic, urine, and blood evaluations were conducted in 3 groups (Wistar-Kyoto, lean ZSF1, and obese ZSF1) at 20 and 25 weeks of age. Immunohistological evaluation of renal and cardiac tissues was conducted at both time points. At 20 and 25 weeks, obese ZSF1 rats showed higher body weight, significant left ventricular hypertrophy, and impaired diastolic function compared with all other groups. Indices of systolic function did not differ between groups. Obese ZSF1 rats developed hyperproliferative vascular foci in the subendocardium, which lacked microvascular organization and were predilection sites of inflammation and fibrosis. In the kidney, obese ZSF1 animals showed regression of the peritubular and glomerular microvasculature, accompanied by tubulointerstitial damage, glomerulosclerosis, and proteinuria.

CONCLUSIONS

The obese ZSF1 rat strain is a suitable in vivo model for CRMS, sharing characteristics with the human syndrome during the earliest onset of disease. In these rats, CRMS induces microvascular fibrotic responses in heart and kidneys, associated with functional impairment of both organs.

Animal models of heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) constitutes a clinical syndrome in which the diagnostic criteria of heart failure are not accompanied by gross disturbances of systolic function, as assessed by ejection fraction. In turn, under most circumstances, diastolic function is impaired. Although it now represents over 50 % of all patients with heart failure, the mechanisms of HFpEF remain understood, precluding effective therapy. Understanding the pathophysiology of HFpEF has been restricted by both limited access to human myocardial biopsies and by the lack of animal models that fully mimic human pathology. Animal models are valuable research tools to clarify subcellular and molecular mechanisms under conditions where the comorbidities and other confounding factors can be precisely controlled. Although most of the heart failure animal models currently available represent heart failure with reduced ejection fraction, several HFpEF animal models have been proposed. However, few of these fulfil all the features present in human disease. In this review we will provide an overview of the currently available models to study HFpEF from rodents to large animals as well as present advantages and disadvantages of these models.

[De novo atrial fibrillation following aortic valve replacement surgery]

Objetives: The present study aimed to explore the risk factors associated with de novo atrial fibrillation following isolated aortic valve replacement surgery and its prevalence in a high volume cardiothoracic surgery center.

METHODS

This is a cross-sectional retrospective observational study including all patients submitted to isolated aortic valve replacement surgery during 2014 and the corresponding data. Patients with previous history of atrial fibrillation, endocarditis or aortic valve prosthesis were excluded. The statistical analysis was conducted according to the type of variables concerned.

RESULTS

One hundred and seventy-three patients were included and 45.1% had de novo atrial fibrillation, with a median occurrence on 2.4 ±1.5 days of the postoperative period. Age was significantly associated with the arrhythmia (p=0.028). Atrial fibrillation patients had a significantly lower minimum of postoperative creatinine clearance (p=0.026) and a higher postoperative plasmatic C-reactive protein peak (p=0.025). Arrhythmic patients had a median time of hospital stay significantly superior to those who did not develop atrial fibrillation (p=0.008). Hospital mortality was low and similar between groups (3%, p=0.796).

DISCUSSION/CONCLUSION

This study confirms the high prevalence of atrial fibrillation following aortic valve replacement surgery. The increased C-reactive protein and decreased creatinine clearance reinforce the importance of inflammation in its pathophysiology. The longer hospital stay in these patients also contributes to the importance of atrial fibrillation prevention and risk stratification.

Afterload-induced diastolic dysfunction contributes to high filling pressures in experimental heart failure with preserved ejection fraction

Myocardial stiffness and upward-shifted end-diastolic pressure-volume (P-V) relationship (EDPVR) are the key to high filling pressures in heart failure with preserved ejection fraction (HFpEF). Nevertheless, many patients may remain asymptomatic unless hemodynamic stress is imposed on the myocardium. Whether delayed relaxation induced by pressure challenge may contribute to high end-diastolic pressure (EDP) remains unsettled. Our aim was to assess the effect of suddenly imposed isovolumic afterload on relaxation and EDP, exploiting a highly controlled P-V experimental evaluation setup in the ZSF1 obese rat (ZSF1 Ob) model of HFpEF. Twenty-week-old ZSF1 Ob ( n = 12), healthy Wistar-Kyoto rats (WKY, n = 11), and hypertensive ZSF1 lean control rats (ZSF1 Ln, n = 10) underwent open-thorax left ventricular (LV) P-V hemodynamic evaluation under anesthesia with sevoflurane. EDPVR was obtained by inferior vena cava occlusions to assess LV ED chamber stiffness constant β, and single-beat isovolumic afterload acquisitions were obtained by swift occlusions of the ascending aorta. ZSF1 Ob showed increased ED stiffness, delayed relaxation, as assessed by time constant of isovolumic relaxation (τ), and elevated EDP with normal ejection fraction. Isovolumic afterload increased EDP without concomitant changes in ED volume or heart rate. In isovolumic beats, relaxation was delayed to the extent that time for complete relaxation as predicted by 3.5 × monoexponentially derived τ (τexp) exceeded effective filling time. EDP elevation correlated with reduced time available to relax, which was the only independent predictor of EDP rise in multiple linear regression. Our results suggest that delayed relaxation during pressure challenge is an important contributor to lung congestion and effort intolerance in HFpEF.

Spectral transfer function analysis of respiratory hemodynamic fluctuations predicts end-diastolic stiffness in preserved ejection fraction heart failure

Preserved ejection fraction heart failure (HFpEF) diagnosis remains controversial, and invasive left ventricular (LV) hemodynamic evaluation and/or exercise testing is advocated by many. The stiffer HFpEF myocardium may show impaired stroke volume (SV) variation induced by fluctuating LV filling pressure during ventilation. Our aim was to investigate spectral transfer function (STF) gain from end-diastolic pressure (EDP) to indexed SV (SVi) in experimental HFpEF. Eighteen-week-old Wistar-Kyoto (WKY) and ZSF1 lean (ZSF1 Ln) and obese rats (ZSF1 Ob) randomly underwent LV open-chest (OC, n = 8 each group) or closed-chest hemodynamic evaluation (CC, n = 6 each group) under halogenate anesthesia and positive-pressure ventilation at constant inspiratory pressure. Beat-to-beat fluctuations in hemodynamic parameters during ventilation were assessed by STF. End-diastolic stiffness (βi) and end-systolic elastance (Eesi) for indexed volumes were obtained by inferior vena cava occlusion in OC (multibeat) or single-beat method estimates in CC. ZSF1 Ob showed higher EDP spectrum (P < 0.001), higher STF gain between end-diastolic volume and EDP, and impaired STF gain between EDP and SVi compared with both hypertensive ZSF1 Ln and normotensive WKY controls (P < 0.001). Likewise βi was only higher in ZSF1 Ob while Eesi was raised in both ZSF1 groups. On multivariate analysis βi and not Eesi correlated with impaired STF gain from EDP to SVi (P < 0.001), and receiver-operating characteristics analysis showed an area under curve of 0.89 for higher βi prediction (P < 0.001). Results support further clinical testing of STF analysis from right heart catheterization-derived EDP surrogates to noninvasively determined SV as screening/diagnostic tool to assess myocardial stiffness in HFpEF.

[Do diabetic patients benefit from bilateral internal mammary artery?]

INTRODUCTION

Bilateral internal mammary artery (BIMA) grafting has been associated with increased long term survival when compared to single IMA, but its benefit on diabetic patients remains controversial.

AIMS

To compare long-term survival following BIMA versus single internal mammary artery (SIMA) grafting between diabetic and non-diabetic patients.

METHODS

We retrospectively reviewed all the patients who underwent isolated CABG and received two or more grafts with at least one IMA graft between 2004 and 2013. Mean follow-up was 4 years and maximum 10. Kaplan-Meier analysis was used to compare long-term survival between BIMA and SIMA in both groups (diabetic vs. non-diabetic). Propensity score matching was used to adjust for treatment selection bias.

RESULTS

1259 out of 3045 eligible patients were diabetic. BIMA was associated with better long-term survival than SIMA on unadjusted analysis in both groups (cumulative survival of 87% vs. 70% in diabetic patients and 89% vs. 79% in non-diabetic patients, respectively). After propensity score matching, BIMA was associated with increased long-term survival in the non-diabetic cohort (n=1042, HR: 0.570 CI95%: 0.342-0.950), but there was no statistically significant difference in the diabetic cohort (n=850, HR: 0.774 CI95% 0.447-1.339). In-hospital mortality and sternal wound infection were low in matching cohorts irrespectively of the number of IMA grafts or diabetes status.

CONCLUSIONS

BIMA grafting appears to be safe for diabetic patients, despite the apparent lack of significant survival advantage.

Abstract 210: Titin Phosphorylation by Protein Kinase G as a Novel Mechanism of Diastolic Adaptation to Acute Hemodynamic Overload

Titin is the main determinant of myocardial passive tension and its distensibility is increased via phosphorylation by protein kinase G (PKG), activated by nitric oxide (NO) and natriuretic peptides (NP) upon acute overload. We hypothesized whether myocardial stretch led to decreased stiffness, optimizing diastolic filling along with the usual increase in contractility.

Intact rat Langendorff hearts, strips dissected from the LV or right atrium of cardiac surgery patients and rabbit papillary muscles were acutely stretched for 15min. Passive tension (PT) was measured in skinned cardiomyocytes extracted from the LV of control and stretched rat hearts for sarcomere lengths (SL) 1.8-2.3μm before and after incubation with PKG. Rabbit muscles were incubated with a PKG inhibitor or, simultaneously, a NO synthase inhibitor, a NO scavenger, a NP receptor A antagonist. All-total titin phosphorylation was stained with Pro-Q Diamond and indexed to total-protein signals using SYPRO Ruby. Values are given as mean±SEM and statistical significance was set to p<0.05.

After acute stretch there was a progressive decrease in passive tension/diastolic pressure over 15min: 27±8% and 27±6% in human atrium and ventricular muscles, respectively, and 43±2% in rabbit papillary muscles and isolated hearts. This decrease in myocardial stiffness was significantly blunted by PKG inhibition (40%) and NO/NP pathway inhibition (29%). PT of cardiomyocytes was significantly lower (≈60%) in the previously stretched group for all SL. A similar effect, only significant in the control group, was observed after incubation with PKG. Titin phosphorylation increased markedly 15 minutes after acute myocardial stretch in human (atrial: 11±1% vs 41±8%; LV: 27±8% vs 71±21%) and rabbit (13±2% vs 23±3%) myocardium.

The progressive decrease in myocardial stiffness after acute hemodynamic overload is preserved at the myofilamental level and seems to depend on PKG activity, representing a potential therapeutic target in patients with pathologically rigid myocardium. Moreover, blocking PKG activation seems to attenuate this adaptive diastolic response. Therefore, titin phosphorylation by this kinase is probably involved in this new myocardial response to stretch in both animals and humans.

Echocardiography and invasive hemodynamics during stress testing for diagnosis of heart failure with preserved ejection fraction: an experimental study

Inclusion of exercise testing in diagnostic guidelines for heart failure with preserved ejection fraction (HFpEF) has been advocated, but the target population, technical challenges, and underlying pathophysiological complexity raise difficulties to implementation. Hemodynamic stress tests may be feasible alternatives. Our aim was to test Trendelenburg positioning, phenylephrine, and dobutamine in the ZSF1 obese rat model to find echocardiographic surrogates for end-diastolic pressure (EDP) elevation and HFpEF. Seventeen-week-old Wistar-Kyoto, ZSF1 lean, and obese rats (n = 7 each) randomly and sequentially underwent (crossover) Trendelenburg (30°), 5 μg·Kg(-1)·min(-1) dobutamine, and 7.5 μg·Kg(-1)·min(-1) phenylephrine with simultaneous left ventricular (LV) pressure-volume loop and echocardiography evaluation under halogenate anesthesia. Effort testing with maximum O2 consumption (V̇o 2 max) determination was performed 1 wk later. Obese ZSF1 showed lower effort tolerance and V̇o 2 max along with higher resting EDP. Both Trendelenburg and phenylephrine increased EDP, whereas dobutamine decreased it. Significant correlations were found between EDP and 1) peak early filling Doppler velocity of transmitral flow (E) to corresponding myocardial tissue Doppler velocity (E') ratio, 2) E to E-wave deceleration time (E/DT) ratio, and 3) left atrial area (LAA). Diagnostic efficiency of E/DT*LAA by receiver-operating characteristic curve analysis for elevation of EDP above a cut-off of 13 mmHg during hemodynamic stress was high (area under curve, AUC = 0.95) but not higher than that of E/E' (AUC = 0.77, P = 0.15). Results in ZSF1 obese rats suggest that noninvasive echocardiography after hemodynamic stress induced by phenylephrine or Trendelenburg can enhance diagnosis of stable HFpEF and constitute an alternative to effort testing.

[Bilateral Internal Mammary Artery Versus Single Internal Mammary Artery in Myocardial Revascularization Surgery. Propensity Score - Adjusted Survival Analysis]

BACKGROUND

Although arterial grafts are superior to venous grafts in terms of long-term patency, single internal mammary artery (SIMA) is still the preferred strategy in most cardiac surgical centres. Our main aim was to compare long- -term survival between BIMA and SIMA at our own tertiary care centre.

METHODS

Retrospective cohort including patients referred to Centro Hospitalar São João (CHSJ), from 2004 to 2011, who underwent isolated CABG and received two or more bypass with at least 1 IMA graft. Kaplan-Meier, Cox regression and propensity score matching 2:1 were used to compare long-term survival between BIMA and SIMA.

RESULTS

BIMA was performed in 696 (29.3%) out of 2329 eligible procedures. Mean follow-up time was 5.1 years (2-9.9 years). All-cause mortality was superior in patients with only one internal mammary artery - cumulative survival of 75% for SIMA vs 88% for BIMA. Because of discrepancy between groups regarding preoperative and surgical characteristics, we ran a propensity score matching which revealed BIMA as an independent predictor of survival (n=1510, 40.3% BIMA, HR: 0.648, 95% CI: 0.452-0.927).

CONCLUSION

BIMA is associated with significantly better long-term survival than SIMA in CABG. A higher sample size might clarify BIMA advantages, discriminating specific groups that might profit the most with this approach.

Levosimendan: The current situation and new prospects

Levosimendan is a pyridazinone-dinitrile derivative with positive inotropic and vasodilatory effects that has beneficial effects on myocardial performance. In previous randomized studies levosimendan improved hemodynamics and clinical course, but its effect on prognosis is still unclear. This important issue has limited its use. Although primarily used in the management of acute heart failure syndromes, this new inotropic agent may play a role in other clinical conditions. This review aims to summarize current knowledge on levosimendan and to present future prospects for the use of this drug.