Retrofitting the Heart: Explaining the Enigmatic Septal Thickening in Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is the most common genetic cardiac disease and is characterized by left ventricular hypertrophy. Although this hypertrophy often associates with sarcomeric gene mutations, nongenetic factors also contribute to the disease, leading to diastolic dysfunction. Notably, this dysfunction manifests before hypertrophy and is linked to hypercontractility, as well as nonuniform contraction and relaxation (myofibril asynchrony) of the myocardium. Although the distribution of hypertrophy in hypertrophic cardiomyopathy can vary both between and within individuals, in most cases, it is primarily confined to the interventricular septum. The reasons for septal thickening remain largely unknown. In this article, we propose that alterations in muscle fiber geometry, present from birth, dictate the septal shape. When combined with hypercontractility and exacerbated by left ventricular outflow tract obstruction, these factors predispose the septum to an isometric type of contraction during systole, consequently constraining its mobility. This contraction, or more accurately, this focal increase in biomechanical stress, prompts the septum to adapt and undergo remodeling. Drawing a parallel, this is reminiscent of how earthquake-resistant buildings are retrofitted with vibration dampers to absorb the majority of the shock motion and load. Similarly, the heart adapts by synthesizing viscoelastic elements such as microtubules, titin, desmin, collagen, and intercalated disc components. This pronounced remodeling in the cytoskeletal structure leads to noticeable septal hypertrophy. This structural adaptation acts as a protective measure against damage by attenuating myofibril shortening while reducing cavity tension according to Laplace Law. By examining these events, we provide a coherent explanation for the septum's predisposition toward hypertrophy.

Exploring the Connection Between Relaxed Myosin States and the Anrep Effect

The Anrep effect is an adaptive response that increases left ventricular contractility following an acute rise in afterload. Although the mechanistic origin remains undefined, recent findings suggest a two-phase activation of resting myosin for contraction, involving strain-sensitive and posttranslational phases. We propose that this mobilization represents a transition among the relaxed states of myosin-specifically, from the super-relaxed (SRX) to the disordered-relaxed (DRX)-with DRX myosin ready to participate in force generation. This hypothesis offers a unified explanation that connects myosin's SRX-DRX equilibrium and the Anrep effect as parts of a singular phenomenon. We underscore the significance of this equilibrium in modulating contractility, primarily studied in the context of hypertrophic cardiomyopathy, the most common inherited cardiomyopathy associated with diastolic dysfunction, hypercontractility, and left ventricular hypertrophy. As we posit that the cellular basis of the Anrep effect relies on a two-phased transition of myosin from the SRX to the contraction-ready DRX configuration, any dysregulation in this equilibrium may result in the pathological manifestation of the Anrep phenomenon. For instance, in hypertrophic cardiomyopathy, hypercontractility is linked to a considerable shift of myosin to the DRX state, implying a persistent activation of the Anrep effect. These valuable insights call for additional research to uncover a clinical Anrep fingerprint in pathological states. Here, we demonstrate through noninvasive echocardiographic pressure-volume measurements that this fingerprint is evident in 12 patients with hypertrophic obstructive cardiomyopathy before septal myocardial ablation. This unique signature is characterized by enhanced contractility, indicated by a leftward shift and steepening of the end-systolic pressure-volume relationship, and a prolonged systolic ejection time adjusted for heart rate, which reverses post-procedure. The clinical application of this concept has potential implications beyond hypertrophic cardiomyopathy, extending to other genetic cardiomyopathies and even noncongenital heart diseases with complex etiologies across a broad spectrum of left ventricular ejection fractions.

The individual relationship between atrial fibrillation sources from CARTOFINDER mapping and atrial cardiomyopathy: The catch me if you can trial

BACKGROUND

Targeting individual sources identified during atrial fibrillation (AF) has been used as an ablation strategy with varying results.

OBJECTIVE

Aim of this study was to evaluate the relationship between regions of interest (ROIs) from CARTOFINDER (CF) mapping and atrial cardiomyopathy from late gadolinium enhancement (LGE) cardiovascular magnetic resonance imaging (CMR).

METHODS

Twenty consecutive patients underwent index catheter ablation for persistent AF (PERS AF). Pre-processed LGE CMR images were merged with the results from CF mapping to visualize harboring regions for focal and rotational activities. Atrial cardiomyopathy was classified based on the four Utah stages.

RESULTS

Procedural success was achieved in all patients (n = 20, 100%). LGE CMR revealed an intermediate amount of 21.41% ± 6.32% for LA fibrosis. ROIs were identified in all patients (mean no ROIs per patient n = 416.45 ± 204.57). A tendency towards a positive correlation between the total amount of atrial cardiomyopathy and the total number of ROIs per patient (regression coefficient, β = 10.86, p = .15) was observed. The degree of fibrosis and the presence of ROIs per segment showed no consistent spatial correlation (posterior: β = 0.36, p-value (p) = .24; anterior: β = -0.08, p = .54; lateral: β = 0.31, p = 39; septal: β = -0.12; p = .66; right PVs: β = 0.34, p = .27; left PVs: β = 0.07, p = .79; LAA: β = -0.91, p = .12). 12 months AF-free survival was 70% (n = 14) after ablation.

CONCLUSION

The presence of ROIs from CF mapping was not directly associated with the extent and location of fibrosis. Further studies evaluating the relationship between focal and rotational activity and atrial cardiomyopathy are mandatory.

Alcohol Septal Ablation or Mavacamten for Obstructive Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterized by an increased left ventricular wall thickness in the absence of increased afterload conditions. In addition to diastolic dysfunction, obstruction of the left ventricular outflow tract is common in HCM and has an important influence on symptoms and outcome. Over the last five decades or two decades, respectively, surgical myectomy and alcohol septal ablation were the only therapeutic options if standard medical care was not sufficient. Recently, a new option has become available that has the potential to revolutionize the therapeutic strategies for patients with HCM. Mavacamten is a myosin inhibitor that belongs to a completely new drug class and targets the excessive actin-myosin cross-bridging that is the underlying pathology of HCM. By reducing the actin-myosin interactions, mavacamten not only reduces the left ventricular outflow tract (LVOT) obstruction but also seems to have positive effects on the diastolic function, microcirculation, and cardiac structure. This article summarizes the current evidence on alcohol septal ablation and reviews the preclinical and clinical data on mavacamten for the treatment of patients with obstructive HCM.

New insights into the hemodynamics of pulmonary homograft patients under stress echocardiography: The contribution of pressure recovery

BACKGROUND

The importance of pulmonary artery pressure recovery (PR) in patients with Ross procedures in whom a homograft substitutes the resected pulmonary valve, is unknown. The aim of the study was to evaluate the occurrence and extent of PR in the pulmonary artery in 65 asymptomatic patients with pulmonary homograft after Ross surgery during rest and exercise.

METHODS

Stress echocardiography was performed in 65 pulmonary homograft patients and 31 controls with native pulmonary valves up to 75 W. Right ventricular systolic pressure (RVSP), transvalvular flow, mean pressure gradient (Pmean ), valve resistance, and RV stroke work were determined in the exercise (max. 75 W) and recovery phases in increments of 25 W each.

RESULTS

Pulmonary homografts demonstrated significantly elevated Pmean compared to controls at all stages. When considering pressure recovery (absolute and relative PR at rest 3.8 ± 1.8 mm Hg, 42.6 ± 7.2%, respectively) and transvalvular energy loss (EL; at rest 4.5 ± 4.3 mm Hg) the homograft hemodynamics reached the level of controls. In a subgroup of patients with tricuspid regurgitation, resting RVSP was the same in homograft patients and controls (21.3 ± 6.1 vs. 20.4 ± 6.3, p = .62), despite significant different Pmax values.

CONCLUSIONS

Ross patients with pulmonary homograft showed systematically increased hemodynamic parameters compared to normal pulmonary valves. These differences were abolished when PR was considered for homograft patients. The equality of RVSP values at rest in both groups shows non-invasive evidence for PR in the pulmonary system after homograft implantation. Therefore, PR appears to be an important measure in calculating the actual hemodynamics in pulmonary homografts.

Functional interaction of aortic valve and ascending aorta in patients after valve-sparing procedures

Pressure recovery (PR) is essential part of the post stenotic fluid mechanics and depends on the ratio of EOA/AA, the effective aortic valve orifice area (EOA) and aortic cross-sectional area (AA). In patients with advanced ascending aortic aneurysm and mildly diseased aortic valves, the effect of AA on pressure recovery and corresponding functional aortic valve opening area (ELCO) was evaluated before and after valve-sparing surgery (Dacron graft implantation). 66 Patients with ascending aortic aneurysm (mean aortic diameter 57 +/- 10 mm) and aortic valve-sparing surgery (32 reimplantation technique (David), 34 remodeling technique (Yacoub)) were routinely investigated by Doppler echocardiography. Dacron graft with a diameter between 26 and 34 mm were implanted. EOA was significantly declined after surgery (3.4 +/- 0.8 vs. 2.6 +/- 0.9cm2; p < 0.001). Insertion of Dacron prosthesis resulted in a significant reduction of AA (26.7 +/- 10.2 vs. 6.8 +/- 1.1cm2; p < 0.001) with increased ratio of EOA/AA (0.14 +/- 0.05 vs. 0.40 +/- 0.1; p < 0.001) and pressure recovery index (PRI; 0.24 +/- 0.08 vs. 0.44 +/- 0.06; p < 0.0001). Despite reduction of EOA, ELCO (= EOA corrected for PR) increased from 4.0 +/- 1.1 to 5.0 +/- 3.1cm2 (p < 0.01) with reduction in transvalvular LV stroke work (1005 +/- 814 to 351 +/- 407 mmHg × ml, p < 0.001) after surgery. These effects were significantly better in patients with Yacoub technique than with the David operation. The hemodynamic findings demonstrate a valve-vessel interaction almost entirely caused by a marked reduction in the ascending AA with significant PR gain. The greater hemodynamic benefit of the Yacoub technique due to higher EOA values compared to the David technique was evident and may be of clinical relevance.

Hemodynamic Assessment in Takotsubo Syndrome

BACKGROUND

Takotsubo syndrome (TTS) is a reversible form of heart failure with incompletely understood pathophysiology.

OBJECTIVES

This study analyzed altered cardiac hemodynamics during TTS to elucidate underlying disease mechanisms.

METHODS

Left ventricular (LV) pressure-volume loops were recorded in 24 consecutive patients with TTS and a control population of 20 participants without cardiovascular diseases.

RESULTS

TTS was associated with impaired LV contractility (end-systolic elastance 1.74 mm Hg/mL vs 2.35 mm Hg/mL [P = 0.024]; maximal rate of change in systolic pressure over time 1,533 mm Hg/s vs 1,763 mm Hg/s [P = 0.031]; end-systolic volume at a pressure of 150 mm Hg, 77.3 mL vs 46.4 mL [P = 0.002]); and a shortened systolic period (286 ms vs 343 ms [P < 0.001]). In response, the pressure-volume diagram was shifted rightward with significantly increased LV end-diastolic (P = 0.031) and end-systolic (P < 0.001) volumes, which preserved LV stroke volume (P = 0.370) despite a lower LV ejection fraction (P < 0.001). Diastolic function was characterized by prolonged active relaxation (relaxation constant 69.5 ms vs 45.9 ms [P < 0.001]; minimal rate of change in diastolic pressure -1,457 mm Hg/s vs -2,192 mm Hg/s [P < 0.001]), whereas diastolic stiffness (1/compliance) was not affected during TTS (end-diastolic volume at a pressure of 15 mm Hg, 96.7 mL vs 109.0 mL [P = 0.942]). Mechanical efficiency was significantly reduced in TTS (P < 0.001) considering reduced stroke work (P = 0.001), increased potential energy (P = 0.036), and a similar total pressure-volume area compared with that of control subjects (P = 0.357).

CONCLUSIONS

TTS is characterized by reduced cardiac contractility, a shortened systolic period, inefficient energetics, and prolonged active relaxation but unaltered diastolic passive stiffness. These findings may suggest decreased phosphorylation of myofilament proteins, which represents a potential therapeutic target in TTS. (Optimized Characterization of Takotsubo Syndrome by Obtaining Pressure Volume Loops [OCTOPUS]; NCT03726528).

Left atrial appendage closure in end-stage renal disease and hemodialysis: Data from a German multicenter registry

BACKGROUND

Left atrial appendage closure (LAAC) has emerged as an alternative to oral anticoagulation (OAC) for stroke prevention in patients with atrial fibrillation (AF). OAC treatment has been proven feasible in mild-to-moderate chronic kidney disease (CKD). In contrast, the optimal antithrombotic management of AF patients with end-stage renal disease (ESRD) is unknown and LAAC has not been proven in these patients in prospective randomized clinical trials.

OBJECTIVES

The objective of this study is to evaluate safety and efficacy of LAAC in patients with ESRD.

METHODS

Patients undergoing LAAC were collected in a German multicenter real-world observational registry. A composite endpoint consisting of the occurrence of ischemic stroke/transient ischemic attack, systemic embolism, and/or major clinical bleeding was assessed. Patients with ESRD were compared with propensity score-matched patients without severe CKD. ESRD was defined as a glomerular filtration rate < 15 ml/min/1.73 m² or chronic hemodialysis treatment.

RESULTS

A total of 604 patients were analyzed, including 57 with ESRD and 57 propensity-matched patients. Overall, 596 endocardial and 8 epicardial LAAC procedures were performed. Frequency of major complications was 7.0% (42/604 patients) in the overall cohort, 8.8% (5/57 patients) in patients with ESRD, and 10.5% (6/57 patients) in matched controls (p = 0.75). The estimated event-free survival of the combined endpoint after 500 days was 90.7 ± 4.5% in patients with ESRD and 90.2 ± 5.5% in matched controls (p = 0.33).

CONCLUSIONS

LAAC had comparable procedural safety and clinical efficacy in patients with ESRD and patients without severe CKD.

Inhibition of TRIF-Dependent Inflammation Decelerates Afterload-Induced Myocardial Remodeling

Pressure-overload-induced cardiac hypertrophy represents one cause of the development of heart failure. The aim of this study is to characterize the influence of the TIR-domain-containing adapter-inducing interferon-β (TRIF) during afterload-induced myocardial remodeling. After trans-aortic constriction (TAC), cardiac pressure overload leads to an early increase in MyD88- (Myeloid differentiation primary response gene 88) and TRIF-dependent cytokines. The maximum cytokine expression appeared within the first week and decreased to its control level within five weeks. While cardiomyocyte hypertrophy was comparable, the myocardial accumulation of the inflammatory cells was lower in TRIF^−/−mice. At d7, TRIF deficiency reduced transcription factors and TRIF-dependent cytokines. Through the modulation of the TGF-β-signaling pathway and anti-fibrotic microRNAs, TRIF was involved in the development of interstitial fibrosis. The absence of TRIF was associated with a decreased expression of proapoptotic proteins. In echocardiography and working heart analyses, TRIF deficiency slowed left-ventricular wall thickening, myocardial hypertrophy, and reduces the ejection fraction. In summary, TRIF is an important adapter protein for the release of inflammatory cytokines and the accumulation of inflammatory cells in the early stage of maladaptive cardiac remodeling. TRIF is involved in the development of cardiac fibrosis by modulating inflammatory and fibrotic signal transduction pathways.

Repeat catheter ablation in patients with atrial arrhythmia recurrence despite durable pulmonary vein isolation

INTRODUCTION

Arrhythmia recurrence after pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF) is common and often linked to pulmonary vein reconnection. In patients with arrhythmia recurrences despite durable PVI the optimal ablation approach is unclear. The purpose of the present study was to analyze efficacy of extended ablation maneuvers in these patients and predictors of procedural success.

METHODS

Consecutive patients with durable PVI undergoing repeat ablation procedures were prospectively enrolled. Patients underwent substrate modification with creation of linear lesions and/or mechanism-specific atrial tachycardia (AT) ablation. 3D-mapping images were analyzed for the presence of left atrial (LA) low-voltage areas according to published scoring systems.

RESULTS

Seventy-four patients were analyzed. Mode of recurrence after durable PVI was AF in 27 patients (36.5%) and AT in 47 patients (63.5%). Linear lesion ablation was performed in 60 patients (81.1%). Twenty-four patients (32.4%) were treated for focal AT mechanisms. Mean follow-up was 565±342 days. Estimated arrhythmia-free survival after 24 months was significantly higher in patients with AT than in patients with AF as mode of recurrence after durable PVI (42.9±8.2% vs. 24.7±8.5%, p=0.023) and in patients without compared to patients with marked LA low-voltage areas (40.5±9.2% vs. 22.8±8.5%, p=0.041). The mode of recurrence after durable PVI was the only independent predictor of further arrhythmia recurrence after repeat ablation.

CONCLUSION

Arrhythmia-free survival following repeat ablation procedures in patients with durable PVI highly depends on mode of arrhythmia recurrence and the presence of LA low-voltage areas. This article is protected by copyright. All rights reserved.

Zyxin protects from hypertension-induced cardiac dysfunction

Arterial hypertension causes left ventricular hypertrophy leading to dilated cardiomyopathy. Following compensatory cardiomyocyte hypertrophy, cardiac dysfunction develops due to loss of cardiomyocytes preceded or paralleled by cardiac fibrosis. Zyxin acts as a mechanotransducer in vascular cells that may promote cardiomyocyte survival. Here, we analyzed cardiac function during experimental hypertension in zyxin knockout (KO) mice. In zyxin KO mice, made hypertensive by way of deoxycorticosterone acetate (DOCA)-salt treatment telemetry recording showed an attenuated rise in systolic blood pressure. Echocardiography indicated a systolic dysfunction, and isolated working heart measurements showed a decrease in systolic elastance. Hearts from hypertensive zyxin KO mice revealed increased apoptosis, fibrosis and an upregulation of active focal adhesion kinase as well as of integrins α5 and β1. Both interstitial and perivascular fibrosis were even more pronounced in zyxin KO mice exposed to angiotensin II instead of DOCA-salt. Stretched microvascular endothelial cells may release collagen 1α2 and TGF-β, which is characteristic for the transition to an intermediate mesenchymal phenotype, and thus spur the transformation of cardiac fibroblasts to myofibroblasts resulting in excessive scar tissue formation in the heart of hypertensive zyxin KO mice. While zyxin KO mice per se do not reveal a cardiac phenotype, this is unmasked upon induction of hypertension and owing to enhanced cardiomyocyte apoptosis and excessive fibrosis causes cardiac dysfunction. Zyxin may thus be important for the maintenance of cardiac function in spite of hypertension.

[Atrial fibrillation-Syndromic phenotype in HFpEF or primary disease?]

Atrial fibrillation and heart failure with preserved left ventricular (LV) ejection fraction (HFpEF) are of high importance in cardiology due to the increasing number of cases. Both diseases can mutually affect each other and important cardiovascular risk factors, e.g. arterial hypertension, diabetes mellitus, obesity and chronic renal insufficiency can be observed with increasing frequency. Currently proven treatment concepts for patients with heart failure and reduced ejection fraction (HFrEF) do not appear to have a comparable prognostic or symptomatic benefit for patients with HFpEF. In addition, there are indications that de novo manifestation of atrial fibrillation in HFpEF patients has been linked to reduced survival. Also, heart and kidney function are negatively affected by atrial fibrillation. Retrospective analyses of patients with HFpEF and atrial fibrillation who had been treated by pulmonary vein isolation could show that interventional treatment of the atrial fibrillation led to an improvement in the New York Heart Association (NYHA) stage and diastolic function. Currently running prospective randomized clinical trials, such as the AMPERE study including patients with HFpEF and atrial fibrillation undergoing pulmonary vein isolation, will hopefully provide reliable prospective randomized data and possibly show an improved symptom control and perhaps also prognostically relevant treatment for HFpEF patients with atrial fibrillation.

Reduced left ventricular contractility, increased diastolic operant stiffness and high energetic expenditure in patients with severe aortic regurgitation without indication for surgery

OBJECTIVES

Recent mortality studies showed worse prognosis in patients (ARNS) with severe aortic regurgitation and preserved ejection fraction (EF) not fulfilling the criteria of current guidelines for surgery. The aim of our study was to analyse left ventricular (LV) systolic and diastolic function and mechanical energetics to find haemodynamic explanations for the reduced prognosis of these patients and to seek a new concept for surgery.

METHODS

Global longitudinal strain (GLS) and echo-based single-beat pressure-volume analyses were performed in patients with ARNS (LV end-diastolic diameter <70 mm, EF >50%, GLS > -19% n = 41), with indication for surgery (ARS; n = 19) and in mild hypertensive controls (C; n = 20). Additionally, end-systolic elastance (LV contractility), stroke work and total energy (pressure-volume area) were calculated.

RESULTS

ARNS demonstrated significantly depressed LV contractility versus C: end-systolic elastance (1.58 ± 0.7 vs 2.54 ± 0.8 mmHg/ml; P < 0.001), despite identical EF (EF: 59 ± 6% vs 59 ± 7%). Accordingly, GLS was decreased [-15.7 ± 2.7% (n = 31) vs -21.2 ± 2.4%; P < 0.001], end-diastolic volume (236 ± 90 vs 136 ± 30 ml; P < 0.001) and diastolic operant stiffness were markedly enlarged, as were pressure-volume area and stroke work, indicating waste of energy. The correlation of GLS versus end-systolic elastance was good (r = -0.66; P < 0.001). ARNS and ARS patients demonstrated similar haemodynamic disorders, whereas only GLS was worse in ARS.

CONCLUSIONS

ARNS patients almost matched the ARS patients in their haemodynamic and energetic deterioration, thereby explaining poor prognosis reported in literature. GLS has been shown to be a reliable surrogate for LV contractility, possibly overestimating contractility due to exhausted preload reserve in aortic regurgitation patients. GLS may outperform conventional echo parameters to predict more precisely the timing of surgery.

Effects of selective heart rate reduction with ivabradine on LV function and central hemodynamics in patients with chronic coronary syndrome

Objectives

We assessed left ventricular (LV) function and central hemodynamic effects in patients with a heart rate (HR) at rest of ≥70 beats per minute (bpm) and chronic coronary syndrome (CCS) after long-term treatment with ivabradine compared to placebo by cardiac magnetic resonance (CMR) imaging.

Methods and results

In a randomized, double-blinded, prospective cross-over design, 23 patients (18 male, 5 female) were treated with ivabradine (7.5 mg bid) or placebo for 6 months. CMR imaging was performed at baseline and after 6 and 12 months to determine LV functional parameters.Mean resting HR on treatment with ivabradine was 58 ± 8.2 bpm and 70.2 ± 8.3 bpm during placebo (p < 0.0001).There was no difference in systolic LV ejection fraction (ivabradine 57.4 ± 11.2% vs placebo 53.0 ± 10.9%, p = 0.18), indexed end-diastolic (EDVi) or end-systolic volumes (ESVi). Indexed stroke volume (SVi) (ml/m²) remained unchanged after treatment with ivabradine. Volume time curve parameters reflecting systolic LV function (peak ejection rate and time) were unaffected by ivabradine, while both peak filling rate (PFR) and PFR/EDV were significantly increased. Mean aortic velocity (cm/s) was significantly reduced during treatment with ivabradine (ivabradine 6.7 ± 2.7 vs placebo 9.0 ± 3.4, p = 0.01). Aortic flow parameters were correlated to parameters of vascular stiffness. The strongest correlation was revealed for mean aortic velocity with aortic distensibility (AD) (r = -0.86 [-0.90 to -0.85], p < 0.0001).

Conclusion

Long-term reduction of HR with ivabradine in patients with CCS improved diastolic function and reduced mean aortic flow velocity.

GPA-Induced Granulomatous Endocarditis Mimicking a Thrombotic Mitral Valve Stenosis

We present the case of a patient with granulomatous endocarditis of the mitral valve leading to severe valve stenosis caused by granulomatosis with polyangiitis. Endocarditis is a rare complication of granulomatosis with polyangiitis that may be misdiagnosed as infectious endocarditis or, as in our case, thrombotic lesions. (Level of Difficulty: Intermediate.)

Cathepsin A contributes to left ventricular remodeling by degrading extracellular superoxide dismutase in mice

In the heart, the serine carboxypeptidase cathepsin A (CatA) is distributed between lysosomes and the extracellular matrix (ECM). CatA-mediated degradation of extracellular peptides may contribute to ECM remodeling and left ventricular (LV) dysfunction. Here, we aimed to evaluate the effects of CatA overexpression on LV remodeling. A proteomic analysis of the secretome of adult mouse cardiac fibroblasts upon digestion by CatA identified the extracellular antioxidant enzyme superoxide dismutase (EC-SOD) as a novel substrate of CatA, which decreased EC-SOD abundance 5-fold. In vitro, both cardiomyocytes and cardiac fibroblasts expressed and secreted CatA protein, and only cardiac fibroblasts expressed and secreted EC-SOD protein. Cardiomyocyte-specific CatA overexpression and increased CatA activity in the LV of transgenic mice (CatA-TG) reduced EC-SOD protein levels by 43%. Loss of EC-SOD-mediated antioxidative activity resulted in significant accumulation of superoxide radicals (WT, 4.54 μmol/mg tissue/min; CatA-TG, 8.62 μmol/mg tissue/min), increased inflammation, myocyte hypertrophy (WT, 19.8 μm; CatA-TG, 21.9 μm), cellular apoptosis, and elevated mRNA expression of hypertrophy-related and profibrotic marker genes, without affecting intracellular detoxifying proteins. In CatA-TG mice, LV interstitial fibrosis formation was enhanced by 19%, and the type I/type III collagen ratio was shifted toward higher abundance of collagen I fibers. Cardiac remodeling in CatA-TG was accompanied by an increased LV weight/body weight ratio and LV end diastolic volume (WT, 50.8 μl; CatA-TG, 61.9 μl). In conclusion, CatA-mediated EC-SOD reduction in the heart contributes to increased oxidative stress, myocyte hypertrophy, ECM remodeling, and inflammation, implicating CatA as a potential therapeutic target to prevent ventricular remodeling.

CaMKII activity contributes to homeometric autoregulation of the heart: A novel mechanism for the Anrep effect

KEY POINTS

The Anrep effect represents the alteration of left ventricular (LV) contractility to acutely enhanced afterload in a few seconds, thereby preserving stroke volume (SV) at constant preload. As a result of the missing preload stretch in our model, the Anrep effect differs from the slow force response and has a different mechanism. The Anrep effect demonstrated two different phases. First, the sudden increased afterload was momentary equilibrated by the enhanced LV contractility as a result of higher power strokes of strongly-bound myosin cross-bridges. Second, the slightly delayed recovery of SV is perhaps dependent on Ca²⁺ /calmodulin-dependent protein kinase II activation caused by oxidation and myofilament phosphorylation (cardiac myosin-binding protein-C, myosin light chain 2), maximizing the recruitment of available strongly-bound myosin cross-bridges. Short-lived oxidative stress might present a new facet of subcellular signalling with respect to cardiovascular regulation. Relevance for human physiology was demonstrated by echocardiography disclosing the Anrep effect in humans during handgrip exercise.

ABSTRACT

The present study investigated whether oxidative stress and Ca²⁺ /calmodulin-dependent protein kinase II (CaMKII) activity are involved in triggering the Anrep effect. LV pressure-volume (PV) analyses of isolated, preload controlled working hearts were performed at two afterload levels (60 and 100 mmHg) in C57BL/6N wild-type (WT) and CaMKII-double knockout mice (DKO^CaMKII ). In snap-frozen WT hearts, force-pCa relationship, H₂ O₂ generation, CaMKII oxidation and phosphorylation of myofilament and Ca²⁺ handling proteins were assessed. Acutely raised afterload showed significantly increased wall stress, H₂ O₂ generation and LV contractility in the PV diagram with an initial decrease and recovery of stroke volume, whereas end-diastolic pressure and volume, as well as heart rate, remained constant. Afterload induced increase in LV contractility was blunted in DKO^CaMKII -hearts. Force development of single WT cardiomyocytes was greater with elevated afterload at submaximal Ca²⁺ concentration and associated with increases in CaMKII oxidation and phosphorylation of cardiac-myosin binding protein-C, myosin light chain and Ca²⁺ handling proteins. CaMKII activity is involved in the regulation of the Anrep effect and associates with stimulation of oxidative stress, presumably starting a cascade of CaMKII oxidation with downstream phosphorylation of myofilament and Ca²⁺ handling proteins. These mechanisms improve LV inotropy and preserve stroke volume within few seconds.

Disturbed ventricular-arterial coupling and increased left atrial stiffness in a patient with heart failure with preserved ejection fraction and hyperaldosteronism: a case report

Background

Aldosterone is involved in almost all parts of the cardiovascular system. Hyperaldosteronism causes arterial hypertension and might predispose to stroke, atrial fibrillation, and heart failure.

Case summary

A 60-year-old obese woman with long-standing hypertension, hypokalaemia, and shortness of breath was admitted to our hospital. Hypertension was caused by primary hyperaldosteronism due to an adenoma of the adrenal gland. Detailed transthoracic echocardiography revealed diastolic dysfunction, disturbed ventricular–arterial interaction, and atrial compliance resulting in heart failure with preserved ejection fraction (HFPEF). Three months of aldosterone antagonist treatment improved ventricular–arterial coupling, while left ventricular diastolic and atrial dysfunction remained unchanged.

Discussion

Presumably, hyperaldosteronism is the reason for HFPEF in this case. Standard criteria to diagnose HFPEF include clinical symptoms of heart failure and an ejection fraction (EF) >50% as well as echocardiographically or invasively assessed elevated filling pressures. Single beat pressure-volume analysis gives insights on the pathophysiology of increased filling pressures, showing in our case diastolic dysfunction as well as disturbed ventricular–arterial interaction. Three months of aldosterone antagonist treatment reduced blood pressure with concomitant improvement of ventricular–arterial interaction, thereby reducing stroke work while stroke volume remained nearly unchanged. Diastolic dysfunction and increased atrial stiffness were unaltered.

P1421 Patients with severe aortic regurgitation showed systolic dysfunction and increased stroke work despite preserved EF; clues for reconsidering optimal time point of surgery

Background

Current guidelines recommend surgery in patients with severe aortic regurgitation (AR) with clinical symptoms or subnormal ejection fraction (EF). Furthermore, surgery should be considered in patients with severe AR, preserved EF and increased left ventricular diameters (LVEDD &gt;70mm, LVESD &gt;50mm). The aim of the study was to investigate LV systolic function as well as mechanical energetics using non-invasive pressure-volume- and strain analysis in patients with severe AR and preserved EF as well as moderately dilated ventricles (LVEDD &lt;70mm).

Methods and Results

Echocardiographic strain and single beat pressure-volume analyses were performed in patients with severe AR and moderately increased ventricular size (LVEDD &lt; 70mm, EF &gt;50% n = 39) as well as healthy, age-matched controls (n = 20) using echo-derived volume and arm-cuff blood pressure measurements. Load independent parameters of systolic contractile function like end-systolic elastance (Ees) and end-systolic volume at 100mmHg (ESV100) were calculated as well as stroke work ((SW) and total pressure volume area (PVA = SW + potential energy). Patients with AR demonstrated significant depression of systolic function beyond ejection fraction: global longitudinal strain was reduced compared to controls (-16 ±2.5% vs. -21.5 ±2%; p &lt; 0.001). Accordingly load independent parameters of LV contractility like Ees (1.5mmHg/ml ±0.7 vs. 2.25mmHg/ml ±0.7; p &lt; 0.001), ESV100 (65.7ml ±19.4 vs. 42.4ml ±19.8; p &lt; 0.05) were reduced despite comparable ejection fractions (EF: 0.56% ±0.05 vs. 0.60% ±0.07 p = 0,10). End-diastolic volume of AR patients was markedly elevated (236ml ±90 vs. 136ml ±30; p &lt; 0.001), while PVA (20470mmHg x ml ±10400 vs. 11907mmHg x ml ±2877; p &lt; 0.01) and stroke work (13200mmHg x ml ±5700 vs. 7606 mmHG x ml ±2048; p&lt; 0.01) were markedly elevated indicating waste of energy.

Conclusion

Patients with severe AR and moderately enhanced LV showed depressed values of contractility and waste of energy using more advanced parameters of LV systolic function although EF was preserved. The data may demonstrate that surgery is performed too late in many of those patients and may give clues for reconsidering guidelines to meet the optimal time point of surgery.

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Long-Term Hemodynamic Improvement after Transcatheter Mitral Valve Repair

BACKGROUND

Correction of mitral regurgitation (MR) alters the load on the left ventricle. There are few data on the long-term hemodynamic adaptations of the cardiovascular system after transcatheter mitral valve repair (TMVR). The aim of this study was to determine a comprehensive hemodynamic status using noninvasive pressure-volume analysis.

METHODS

Pressure-volume parameters were calculated from echocardiography with simultaneous arm-cuff blood pressure measurements at baseline before TMVR and 12 months after TMVR. Eighty-eight consecutive patients undergoing edge-to-edge mitral clip implantation because of grade 3+ or 4+, symptomatic (79.5% in New York Heart Association functional class ≥III) MR were prospectively enrolled. The mean left ventricular (LV) ejection fraction was 42 ± 14%. Sixty-seven percent of the patients had secondary MR.

RESULTS

Twelve months after TMVR, 17.7% of patients had died, and 19.0% were rehospitalized because of decompensated heart failure. MR grade was ≤2+ in 90% of surviving patients, and 77% were in New York Heart Association functional class ≤II. LV end-diastolic volume index decreased from 87 ± 38 to 77 ± 40 mL/m² (P < .0001), end-systolic volume index changed from 54 ± 34 to 50 ± 36 mL/m² (P = .018), hence total stroke volume index was reduced (from 34 ± 11 to 28 ± 7 ml/m², P < .0001). Ejection fraction and global longitudinal peak systolic strain remained unchanged. Increased forward ejection fraction (30 ± 14% vs 41 ± 20%, P < .0001), cardiac index (from 1.7 ± 0.4 to 1.9 ± 0.5 mL/min/m², P = .003), and peak power index (214 ± 114 vs 280 ± 149 mm Hg/sec, P = .0001) as well as similar end-systolic elastance at reduced LV volumes indicated improved LV performance. Cardiac efficiency, measured as cardiac index relative to myocardial energy, was improved (0.012 ± 0.008 vs 0.019 ± 0.010 mm Hg^-1, P = .002). Logistic regression analysis revealed baseline values of total ejection fraction and diastolic pulmonary pressure gradient as predictors of clinical improvement (odds ratios, 1.076 [P = .009] and 0.812 [P = .015], respectively) after TMVR.

CONCLUSIONS

One year after TMVR, patients showed reverse remodeling and improved LV performance that was associated with improved symptom status. This hemodynamic improvement supports TMVR as long-term effective therapy for patients with symptomatic MR.

Conventional echocardiographic parameters or three-dimensional echocardiography to evaluate right ventricular function in percutaneous edge-to-edge mitral valve repair (PMVR)

Introduction

In this study, we evaluated right ventricular (RV) function before and after percutaneous mitral valve repair (PMVR) using conventional echocardiographic parameters and novel 3DE data sets acquired prior to and directly after the procedure.

Patients and methods

Observational study on 45 patients undergoing PMVR at an university hospital.

Results

In the overall collective, the 3D RV-EF before and after PMVR showed no significant change (p = 0.16). While there was a significant increase of the fractional area change (FAC, from 23 [19–29] % to 28 [24–33] %, p = 0.001), no significant change of the tricuspid annular plane systolic excursion (TAPSE, from 17 ± 6 mm to 18 ± 5 mm (standard deviation), p = 0.33) was observed. Regarding patients with a reduced RV-EF (< 35%), a significant RV-EF improvement was observed (from 27 [23–34] % to 32.5 [30–39] % (p = 0.001). 71.4% of patients had an improved clinical outcome (improvement in 6-minute walk test and/or improvement in NYHA class of more than one grade), whereas clinical outcome did not improve in 28.6% of patients. Using univariate logistic regression analysis, the post-PMVR RV-EF (OR 1.15: 95% CI 1.02–1.29; p = 0.02) and the change in RV-EF (OR 1.13: 95% CI 1.02–1.25; p = 0.02) were significant predictors for improved clinical outcome at 6 months follow up.

Conclusion

Thus, RV function may be an important non-invasive parameter to add to the predictive parameters indicating a potential clinical benefit from treatment of severe mitral regurgitation using PMVR.

Defibrillator-Heart Pump: An Implantable Ventricular Assist Device With Integrated Defibrillator Component-The First In Vitro Testing

Left ventricular assist devices (LVADs) are an important therapeutic option for patients with end-stage heart failure waiting for heart transplantation or in older patients as definite therapy for heart failure. Interestingly, about 62% of patients receiving LVADs do not have an automatic implantable cardioverter-defibrillator (AICD) at the time of implantation, although these patients have increased risk of being confronted with dangerous arrhythmia. Therefore, an LVAD system including AICD function is a reasonable alternative for such heart failure patients thereby avoiding a second surgical intervention for AICD implantation. In this article, a newly developed system including LVAD and AICD function is introduced, and we also report its first in vitro testing.

Prognostic Significance of Remote Myocardium Alterations Assessed by Quantitative Noncontrast T1 Mapping in ST-Segment Elevation Myocardial Infarction

OBJECTIVES

This study assessed the prognostic significance of remote zone native T1 alterations for the prediction of clinical events in a population with ST-segment elevation myocardial infarction (STEMI) who were treated by primary percutaneous coronary intervention (PPCI) and compared it with conventional markers of infarct severity.

BACKGROUND

The exact role and incremental prognostic relevance of remote myocardium native T1 mapping alterations assessed by cardiac magnetic resonance (CMR) after STEMI remains unclear.

METHODS

We included 255 consecutive patients with STEMI who were reperfused within 12 h after symptom onset. CMR core laboratory analysis was performed to assess left ventricular (LV) function, standard infarct characteristics, and native T1 values of the remote, noninfarcted myocardium. The primary endpoint was a composite of death, reinfarction, and new congestive heart failure within 6 months (major adverse cardiac events [MACE]).

RESULTS

Patients with increased remote zone native T1 values (>1,129 ms) had significantly larger infarcts (p = 0.012), less myocardial salvage (p = 0.002), and more pronounced LV dysfunction (p = 0.011). In multivariable analysis, remote zone native T1 was independently associated with MACE after adjusting for clinical risk factors (p = 0.001) or other CMR variables (p = 0.007). In C-statistics, native T1 of remote myocardium provided incremental prognostic information beyond clinical risk factors, LV ejection fraction, and other markers of infarct severity (all p < 0.05). The addition of remote zone native T1 to a model of prognostic CMR parameters (ejection fraction, infarct size, and myocardial salvage index) led to net reclassification improvement of 0.82 (95% confidence interval: 0.46 to 1.17; p < 0.001) and to an integrated discrimination improvement of 0.07 (95% confidence interval: 0.02 to 0.13; p = 0.01).

CONCLUSIONS

In STEMI patients treated by PPCI, evaluation of remote zone alterations by quantitative noncontrast T1 mapping provided independent and incremental prognostic information in addition to clinical risk factors and traditional CMR outcome markers. Remote zone alterations may thus represent a novel therapeutic target and a useful parameter for optimized risk stratification. (Effect of Conditioning on Myocardial Damage in STEMI [LIPSIA-COND]; NCT02158468).

Hyperaldosteronism induces left atrial systolic and diastolic dysfunction

Patients with hypertension and hyperaldosteronism show an increased risk of stroke compared with patients with essential hypertension. Aim of the study was to assess the effects of aldosterone on left atrial function in rats as a potential contributor to thromboembolism. Osmotic mini-pumps delivering 1.5 μg aldosterone/h were implanted in rats subcutaneously (Aldo, n = 39; controls, n = 38). After 8 wk, left ventricular pressure-volume analysis of isolated working hearts was performed, and left atrial systolic and diastolic function was also assessed by atrial pressure-diameter loops. Moreover, left atrial myocytes were isolated to investigate their global and local Ca2+ handling and contractility. At similar heart rates, pressure-volume analysis of isolated hearts and in vivo hemodynamic measurements revealed neither systolic nor diastolic left ventricular dysfunction in Aldo. In particular, atrial filling pressures and atrial size were not increased in Aldo. Aldo rats showed a significant reduction of atrial late diastolic A wave, atrial active work index, and increased V waves. Consistently, in Aldo rats, sarcomere shortening and the amplitude of electrically evoked global Ca2+ transients were substantially reduced. Sarcoplasmic reticulum-Ca2+ content and fractional Ca2+ release were decreased, substantiated by a reduced sarcoplasmic reticulum calcium ATPase activity, resulting from a reduced CAMKII-evoked phosphorylation of phospholamban. Hyperaldosteronism induced atrial systolic and diastolic dysfunction, while atrial size and left ventricular hemodynamics, including filling pressures, were unaffected in rats. The described model suggests a direct causal link between hyperaldosteronism and decreased atrial contractility and diastolic compliance.

Early Hemodynamic Improvement after Percutaneous Mitral Valve Repair Evaluated by Noninvasive Pressure-Volume Analysis

BACKGROUND

Mitral regurgitation represents a volume load on the left ventricle leading to congestion and symptoms of heart failure. The aim of this study was to characterize early hemodynamic adaptions after percutaneous mitral valve (MV) repair.

METHODS

Forty-six consecutive patients with symptomatic high-grade MV insufficiency (mean age, 72 years; 54% men) were prospectively included in the study and examined before and after successful catheter-based clip implantation. Seventy percent of patients had secondary mitral regurgitation. Noninvasive pressure-volume loops were reconstructed from echocardiography with simultaneous blood pressure measurements.

RESULTS

MV repair reduced left ventricular end-diastolic volume index from 87 ± 41 to 80 ± 40 mL/m(2) (P < .0001). End-systolic volume index was 55 ± 37 mL/m(2) before versus 54 ± 37 mL/m(2) after repair (P = .52). Hence, total stroke volume decreased from 60 ± 23 to 49 ± 16 mL (P < .0001), as did total ejection fraction (from 41 ± 14% to 37 ± 13%, P = .002) and global longitudinal strain (from -11 ± 4.9% to -9.1 ± 4.4%, P = .0001). Forward stroke volume, forward ejection fraction, and forward cardiac output remained constant (43 ± 12 mL vs 42 ± 11 mL, 33 ± 17% vs 35 ± 18%, and 3.2 ± 0.9 L/min vs 3.4 ± 0.8 L/min, respectively). Parameters of left ventricular contractility (end-systolic elastance and peak power index) and measurements of afterload (arterial elastance, end-systolic wall stress, and total peripheral resistance) were similar before and after MV repair. Forward ejection fraction correlated more strongly with end-systolic elastance (r = 0.61, P < .0001) than did total ejection fraction (r = 0.35, P = .0007) or global longitudinal strain (r = -0.38, P = .0002). Total mechanical energy (pressure-volume area) decreased from 10,903 ± 4,410 to 9,124 ± 2,968 mm Hg × mL (P = .0007) because of reduced stroke work (5,546 ± 2,241 mm Hg × mL vs 4,414 ± 1,412 mm Hg × mL, P < .0001). At 3 months, symptom status had improved (76% of patients in New York Heart Association classes I and II), and 97% of patients had mitral regurgitation grade ≤2+.

CONCLUSIONS

Left ventricular contractility and forward cardiac output remained unchanged after percutaneous MV repair despite decreases in total ejection fraction and global longitudinal strain. The left ventricle was unloaded through reduced end-diastolic volume. Thus, MV repair is associated with an improved hemodynamic state in noninvasive pressure-volume analysis.

Cardiac remodeling in Gαq and Gα11 knockout mice

BACKGROUND

Although both Gαq- and Gα11-protein signaling are believed to be involved in the regulation of cardiac hypertrophy, their detailed contribution to myocardial function remains elusive.

METHODS AND RESULTS

We studied remodeling processes in healthy transgenic mice with genetically altered Gαq/Gα11-expression, in particular a global Gα11-knockout and a novel inducible cardiac specific Gαq-knockout, as well as a combined double knockout (dKO) mouse line. Echocardiography and telemetric ECG recordings revealed that compared with wild type mice, hearts of dKO mice showed an increased ejection fraction and a decreased heart rate, irrespective of age resulting in a maintained cardiac output. We attributed these findings to the lack of Gα11, which the absence was associated with a decreased afterload. Histological analysis of the extracellular matrix in the heart depicted a diminished presence of collagen in aging hearts of dKO mice compared to wild-type mice. The results of a transcriptome analysis on isolated ventricular cardiac myocytes revealed alterations of the activity of genes involved in the Gαq/Gα11-dependent regulation of the extracellular matrix, such as the matricellular protein Cyr61.

CONCLUSIONS

From our data we conclude that Gαq/Gα11 signaling pathways play a pivotal role in maintaining gene activity patterns. For the heart we revealed their importance in modulating the properties of the extracellular matrix, a mechanism that might be an important contributor and mechanistic basis for the development of pressure-overload induced cardiac hypertrophy.

Reversal of Mitochondrial Transhydrogenase Causes Oxidative Stress in Heart Failure

Mitochondrial reactive oxygen species (ROS) play a central role in most aging-related diseases. ROS are produced at the respiratory chain that demands NADH for electron transport and are eliminated by enzymes that require NADPH. The nicotinamide nucleotide transhydrogenase (Nnt) is considered a key antioxidative enzyme based on its ability to regenerate NADPH from NADH. Here, we show that pathological metabolic demand reverses the direction of the Nnt, consuming NADPH to support NADH and ATP production, but at the cost of NADPH-linked antioxidative capacity. In heart, reverse-mode Nnt is the dominant source for ROS during pressure overload. Due to a mutation of the Nnt gene, the inbred mouse strain C57BL/6J is protected from oxidative stress, heart failure, and death, making its use in cardiovascular research problematic. Targeting Nnt-mediated ROS with the tetrapeptide SS-31 rescued mortality in pressure overload-induced heart failure and could therefore have therapeutic potential in patients with this syndrome.

Atrial Remodeling Following Catheter-Based Renal Denervation Occurs in a Blood Pressure- and Heart Rate-Independent Manner

OBJECTIVES

This study sought to investigate left atrial (LA) remodeling in relation to blood pressure (BP) and heart rate (HR) after renal sympathetic denervation (RDN).

BACKGROUND

In addition to reducing BP and HR in certain patients with hypertension, RDN can decrease left ventricular (LV) mass and ameliorate LV diastolic dysfunction.

METHODS

Before and 6 months after RDN, BP, HR, LV mass, left atrial volume index (LAVI), diastolic function (echocardiography), and premature atrial contractions (PAC) (Holter electrocardiogram) were assessed in 66 patients with resistant hypertension.

RESULTS

RDN reduced office BP by 21.6 ± 3.0/10.1 ± 2.0 mm Hg (p < 0.001), and HR by 8.0 ± 1.3 beats/min (p < 0.001). At baseline, LA size correlated with LV mass, diastolic function, and pro-brain natriuretic peptide, but not with BP or HR. Six months after RDN, LAVI was reduced by 4.0 ± 0.7 ml/kg/m(2) (p < 0.001). LA size decrease was stronger when LAVI at baseline was higher. In contrast, the decrease in LAVI was not dependent on LV mass or diastolic function (E/E' or E/A) at baseline. Furthermore, LAVI decreased without relation to decrease in systolic BP or HR. Additionally, occurrence of PAC (median of >153 PAC/24 h) was reduced (to 68 PAC/24 h) by RDN, independently of changes in LA size.

CONCLUSIONS

In patients with resistant hypertension, LA volume and occurrence of PAC decreased 6 months after RDN. This decrease was independent of BP and HR at baseline or the reduction in BP and HR reached by renal denervation. These data suggest that there is a direct, partly BP-independent effect of RDN on cardiac remodeling and occurrence of premature atrial contractions.

Resting heart rate: risk indicator and emerging risk factor in cardiovascular disease

Resting heart rate is central to cardiac output and is influenced by changes occurring in numerous diseases. It predicts longevity and cardiovascular diseases, and current evidence suggests that it is also an important marker of outcome in cardiovascular disease, including heart failure. Beta-blockers improve outcomes in heart failure; however, they have effects outside reducing heart rate. Ivabradine has demonstrated efficacy in reducing rehospitalizations and mortality in heart failure and in improving exercise tolerance and reducing angina attacks in patients with coronary artery disease, whereas selective heart rate reduction may also prove to be beneficial in therapeutic areas outside those in which ivabradine has already demonstrated clinical efficacy. This review provides an update on the associations between heart rate and cardiovascular outcomes in various conditions, the experimental effects of heart rate reduction with ivabradine, and the potential new indications in cardiovascular disease.

Cardiac CaM Kinase II genes δ and γ contribute to adverse remodeling but redundantly inhibit calcineurin-induced myocardial hypertrophy

BACKGROUND

Ca(2+)-dependent signaling through CaM Kinase II (CaMKII) and calcineurin was suggested to contribute to adverse cardiac remodeling. However, the relative importance of CaMKII versus calcineurin for adverse cardiac remodeling remained unclear.

METHODS AND RESULTS

We generated double-knockout mice (DKO) lacking the 2 cardiac CaMKII genes δ and γ specifically in cardiomyocytes. We show that both CaMKII isoforms contribute redundantly to phosphorylation not only of phospholamban, ryanodine receptor 2, and histone deacetylase 4, but also calcineurin. Under baseline conditions, DKO mice are viable and display neither abnormal Ca(2+) handling nor functional and structural changes. On pathological pressure overload and β-adrenergic stimulation, DKO mice are protected against cardiac dysfunction and interstitial fibrosis. But surprisingly and paradoxically, DKO mice develop cardiac hypertrophy driven by excessive activation of endogenous calcineurin, which is associated with a lack of phosphorylation at the auto-inhibitory calcineurin A site Ser411. Likewise, calcineurin inhibition prevents cardiac hypertrophy in DKO. On exercise performance, DKO mice show an exaggeration of cardiac hypertrophy with increased expression of the calcineurin target gene RCAN1-4 but no signs of adverse cardiac remodeling.

CONCLUSIONS

We established a mouse model in which CaMKII's activity is specifically and completely abolished. By the use of this model we show that CaMKII induces maladaptive cardiac remodeling while it inhibits calcineurin-dependent hypertrophy. These data suggest inhibition of CaMKII but not calcineurin as a promising approach to attenuate the progression of heart failure.

HDAC4 controls histone methylation in response to elevated cardiac load

In patients with heart failure, reactivation of a fetal gene program, including atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), is a hallmark for maladaptive remodeling of the LV. The mechanisms that regulate this reactivation are incompletely understood. Histone acetylation and methylation affect the conformation of chromatin, which in turn governs the accessibility of DNA for transcription factors. Using human LV myocardium, we found that, despite nuclear export of histone deacetylase 4 (HDAC4), upregulation of ANP and BNP in failing hearts did not require increased histone acetylation in the promoter regions of these genes. In contrast, di- and trimethylation of lysine 9 of histone 3 (H3K9) and binding of heterochromatin protein 1 (HP1) in the promoter regions of these genes were substantially reduced. In isolated working murine hearts, an acute increase of cardiac preload induced HDAC4 nuclear export, H3K9 demethylation, HP1 dissociation from the promoter region, and activation of the ANP gene. These processes were reversed in hearts with myocyte-specific deletion of Hdac4. We conclude that HDAC4 plays a central role for rapid modifications of histone methylation in response to variations in cardiac load and may represent a target for pharmacological interventions to prevent maladaptive remodeling in patients with heart failure.

Cardiac remodeling and myocardial dysfunction in obese spontaneously hypertensive rats

Background

The additive effects of obesity and metabolic syndrome on left ventricular (LV) maladaptive remodeling and function in hypertension are not characterized.

Methods

We compared an obese spontaneously hypertensive rat model (SHR-ob) with lean spontaneously hypertensive rats (SHR-lean) and normotensive controls (Ctr). LV-function was investigated by cardiac magnetic resonance imaging and invasive LV-pressure measurements. LV-interstitial fibrosis was quantified and protein levels of phospholamban (PLB), Serca2a and glucose transporters (GLUT1 and GLUT4) were determined by immunohistochemistry.

Results

Systolic blood pressure was similar in SHR-lean and SHR-ob (252 ± 7 vs. 242 ± 7 mmHg, p = 0.398) but was higher when compared to Ctr (155 ± 2 mmHg, p < 0.01 for both). Compared to SHR-lean and Ctr, SHR-ob showed impaired glucose tolerance and increased body-weight. In SHR-ob, LV-ejection fraction was impaired vs. Ctr (46.2 ± 1.1 vs. 59.6 ± 1.9%, p = 0.007). LV-enddiastolic pressure was more increased in SHR-ob than in SHR-lean (21.5 ± 4.1 vs. 5.9 ± 0.81 mmHg, p = 0.0002) when compared to Ctr (4.3 ± 1.1 mmHg, p < 0.0001 for both), respectively. Increased LV-fibrosis together with increased myocyte diameters and ANF gene expression in SHR-ob were associated with increased GLUT1-protein levels in SHR-ob suggestive for an upregulation of the GLUT1/ANF-axis. Serca2a-protein levels were decreased in SHR-lean but not altered in SHR-ob compared to Ctr. PLB-phosphorylation was not altered.

Conclusion

In addition to hypertension alone, metabolic syndrome and obesity adds to the myocardial phenotype by aggravating diastolic dysfunction and a progression towards systolic dysfunction. SHR-ob may be a useful model to develop new interventional and pharmacological treatment strategies for hypertensive heart disease and metabolic disorders.

Is heart rate a treatment target in heart failure?

Clinical and experimental studies confirmed an association between elevated resting heart rate and the risk of mortality in heart failure patients. Importantly, elevated heart rate at rest has been identified as a key finding in heart failure addressing a major treatment target. This review shows that heart rate level at rest and its extent of reduction is a sensitive indicator for successful therapy in heart failure patients demonstrating the specific influence of heart rate reduction on clinical outcome in the analyzed patients. Currently, experimental data provide convincing evidence of a pathophysiological concept of heart rate reduction; nevertheless, transition from experimental results to clinical evidence needs further clarification, especially in patients with diastolic heart failure. Since heart rate can be easily determined during physical examination, decrease in heart rate of patients allows a simple hint on prognosis and efficiency of heart failure therapy.

Heart rate reduction by If-inhibition improves vascular stiffness and left ventricular systolic and diastolic function in a mouse model of heart failure with preserved ejection fraction

AIMS

In diabetes mellitus, heart failure with preserved ejection fraction (HFPEF) is a significant comorbidity. No therapy is available that improves cardiovascular outcomes. The aim of this study was to characterize myocardial function and ventricular-arterial coupling in a mouse model of diabetes and to analyse the effect of selective heart rate (HR) reduction by If-inhibition in this HFPEF-model.

METHODS AND RESULTS

Control mice, diabetic mice (db/db), and db/db mice treated for 4 weeks with the If-inhibitor ivabradine (db/db-Iva) were compared. Aortic distensibility was measured by magnetic resonance imaging. Left ventricular (LV) pressure-volume analysis was performed in isolated working hearts, with biochemical and histological characterization of the cardiac and aortic phenotype. In db/db aortic stiffness and fibrosis were significantly enhanced compared with controls and were prevented by HR reduction in db/db-Iva. Left ventricular end-systolic elastance (Ees) was increased in db/db compared with controls (6.0 ± 1.3 vs. 3.4 ± 1.2 mmHg/µL, P < 0.01), whereas other contractility markers were reduced. Heart rate reduction in db/db-Iva lowered Ees (4.0 ± 1.1 mmHg/µL, P < 0.01), and improved the other contractility parameters. In db/db active relaxation was prolonged and end-diastolic capacitance was lower compared with controls (28 ± 3 vs. 48 ± 8 μL, P < 0.01). These parameters were ameliorated by HR reduction. Neither myocardial fibrosis nor hypertrophy were detected in db/db, whereas titin N2B expression was increased and phosphorylation of phospholamban was reduced both being prevented by HR reduction in db/db-Iva.

CONCLUSION

In db/db, a model of HFPEF, selective HR reduction by If-inhibition improved vascular stiffness, LV contractility, and diastolic function. Therefore, If-inhibition might be a therapeutic concept for HFPEF, if confirmed in humans.

Procollagen propeptides: serum markers for atrial fibrosis?

BACKGROUND

Atrial fibrosis and its spatial heterogeneity are regarded as a substrate for the perpetuation of atrial arrhythmias. During collagen synthesis and degradation, collagen propeptides and telopeptides are released into the blood. This study tested the hypothesis that serum markers of collagen turnover correlate with atrial fibrosis.

METHODS

We prospectively included 28 patients in sinus rhythm undergoing cardiac surgery. Plasma concentrations of the carboxy- and amino-terminal propeptide of procollagen type-I (PICP and PINP) and type-III (PIIINP), and the C-terminal telopeptide of type-I collagen (ICTP) were determined. Interstitial fibrosis of left (n = 10) and right atrial appendages (n = 28) was analyzed histologically.

RESULTS

We found a correlation between left and right atrial fibrosis (r (s) = 0.79, p < 0.01). Interestingly, the higher the interstitial collagen content, the higher was the spatial heterogeneity of fibrosis (r (s) = 0.90, p < 0.001). However, PICP, PIIINP, and ICTP were not correlated to left or right atrial collagen content, or to the spatial heterogeneity of atrial fibrosis. There was a weak and even negative correlation between the serum PINP concentration and the degree of fibrosis in both the left and the right atrium (r (s) = -0.65 (p = 0.04) and r (s) = -0.42 (p = 0.03), respectively).

CONCLUSIONS

A high degree of interstitial atrial fibrosis indicates a high degree of spatial heterogeneity of interstitial collagen. Although serum PICP is known to be correlated with ventricular fibrosis, this and other serum markers of collagen turnover (PINP, PIIINP, and ICTP) do not directly reflect atrial fibrosis in patients with severe cardiac disease.