Effects of Atrial Fibrillation on the Human Ventricle.

RATIONALE: Atrial fibrillation (AF) and heart failure often coexist, but their interaction is poorly understood. Clinical data indicate that the arrhythmic component of AF may contribute to left ventricular (LV) dysfunction. OBJECTIVE: This study investigates the effects and molecular mechanisms of AF on the human LV. METHODS AND RESULTS: Ventricular myocardium from patients with aortic stenosis and preserved LV function with sinus rhythm or rate-controlled AF was studied. LV myocardium from patients with sinus rhythm and patients with AF showed no differences in fibrosis. In functional studies, systolic Ca2+ transient amplitude of LV cardiomyocytes was reduced in patients with AF, while diastolic Ca2+ levels and Ca2+ transient kinetics were not statistically different. These results were confirmed in LV cardiomyocytes from nonfailing donors with sinus rhythm or AF. Moreover, normofrequent AF was simulated in vitro using arrhythmic or rhythmic pacing (both at 60 bpm). After 24 hours of AF-simulation, human LV cardiomyocytes from nonfailing donors showed an impaired Ca2+ transient amplitude. For a standardized investigation of AF-simulation, human iPSC-cardiomyocytes were tested. Seven days of AF-simulation caused reduced systolic Ca2+ transient amplitude and sarcoplasmic reticulum Ca2+ load likely because of an increased diastolic sarcoplasmic reticulum Ca2+ leak. Moreover, cytosolic Na+ concentration was elevated and action potential duration was prolonged after AF-simulation. We detected an increased late Na+ current as a potential trigger for the detrimentally altered Ca2+/Na+-interplay. Mechanistically, reactive oxygen species were higher in the LV of patients with AF. CaMKII (Ca2+/calmodulin-dependent protein kinase IIδc) was found to be more oxidized at Met281/282 in the LV of patients with AF leading to an increased CaMKII activity and consequent increased RyR2 phosphorylation. CaMKII inhibition and ROS scavenging ameliorated impaired systolic Ca2+ handling after AF-simulation. CONCLUSIONS: AF causes distinct functional and molecular remodeling of the human LV. This translational study provides the first mechanistic characterization and the potential negative impact of AF in the absence of tachycardia on the human ventricle.

A context-specific cardiac ß-catenin and GATA4 interaction influences TCF7L2 occupancy and remodels chromatin driving disease progression in the adult heart.

Chromatin remodelling precedes transcriptional and structural changes in heart failure. A body of work suggests roles for the developmental Wnt signalling pathway in cardiac remodelling. Hitherto, there is no evidence supporting a direct role of Wnt nuclear components in regulating chromatin landscapes in this process. We show that transcriptionally active, nuclear, phosphorylated(p)Ser675-ß-catenin and TCF7L2 are upregulated in diseased murine and human cardiac ventricles. We report that inducible cardiomyocytes (CM)-specific pSer675-ß-catenin accumulation mimics the disease situation by triggering TCF7L2 expression. This enhances active chromatin, characterized by increased H3K27ac and TCF7L2 occupancies to cardiac developmental and remodelling genes in vivo. Accordingly, transcriptomic analysis of ß-catenin stabilized hearts shows a strong recapitulation of cardiac developmental processes like cell cycling and cytoskeletal remodelling. Mechanistically, TCF7L2 co-occupies distal genomic regions with cardiac transcription factors NKX2-5 and GATA4 in stabilized-ß-catenin hearts. Validation assays revealed a previously unrecognized function of GATA4 as a cardiac repressor of the TCF7L2/ß-catenin complex in vivo, thereby defining a transcriptional switch controlling disease progression. Conversely, preventing ß-catenin activation post-pressure-overload results in a downregulation of these novel TCF7L2-targets and rescues cardiac function. Thus, we present a novel role for TCF7L2/ß-catenin in CMs-specific chromatin modulation, which could be exploited for manipulating the ubiquitous Wnt pathway.

Protein kinase/phosphatase balance mediates the effects of increased late sodium current on ventricular calcium cycling.

Increased late sodium current (late INa) is an important arrhythmogenic trigger in cardiac disease. It prolongs cardiac action potential and leads to an increased SR Ca2+ leak. This study investigates the contribution of Ca2+/Calmodulin-dependent kinase II (CaMKII), protein kinase A (PKA) and conversely acting protein phosphatases 1 and 2A (PP1, PP2A) to this subcellular crosstalk. Augmentation of late INa (ATX-II) in murine cardiomyocytes led to an increase of diastolic Ca2+ spark frequency and amplitudes of Ca2+ transients but did not affect SR Ca2+ load. Interestingly, inhibition of both, CaMKII and PKA, attenuated the late INa-dependent induction of the SR Ca2+ leak. PKA inhibition additionally reduced the amplitudes of systolic Ca2+ transients. FRET-measurements revealed increased levels of cAMP upon late INa augmentation, which could be prevented by simultaneous inhibition of Na+/Ca2+-exchanger (NCX) suggesting that PKA is activated by Ca2+-dependent cAMP-production. Whereas inhibition of PP2A showed no effect on late INa-dependent alterations of Ca2+ cycling, additional inhibition of PP1 further increased the SR Ca2+ leak. In line with this, selective activation of PP1 yielded a strong reduction of the late INa-induced SR Ca2+ leak and did not affect systolic Ca2+ release. This study indicates that phosphatase/kinase-balance is perturbed upon increased Na+ influx leading to disruption of ventricular Ca2+ cycling via CaMKII- and PKA-dependent pathways. Importantly, an activation of PP1 at RyR2 may represent a promising new toehold to counteract pathologically increased kinase activity.

Endothelial alterations in a canine model of immune thrombocytopenia.

Bleeding heterogeneity amongst patients with immune thrombocytopenia (ITP) is poorly understood. Platelets play a role in maintaining endothelial integrity, and variable thrombocytopenia-induced endothelial changes may influence bleeding severity. Platelet-derived endothelial stabilizers and markers of endothelial integrity in ITP are largely underexplored. We hypothesized that, in a canine ITP model, thrombocytopenia would lead to alterations in the endothelial ultrastructure and that the Von Willebrand factor (vWF) would serve as a marker of endothelial injury associated with thrombocytopenia. Thrombocytopenia was induced in healthy dogs with an antiplatelet antibody infusion; control dogs received an isotype control antibody. Cutaneous biopsies were obtained prior to thrombocytopenia induction, at platelet nadir, 24 hours after nadir, and on platelet recovery. Cutaneous capillaries were assessed by electron microscopy for vessel thickness, the number of pinocytotic vesicles, the number of large vacuoles, and the number of gaps between cells. Pinocytotic vesicles are thought to represent an endothelial membrane reserve that can be used for repair of damaged endothelial cells. Plasma samples were assessed for vWF. ITP dogs had significantly decreased pinocytotic vesicle numbers compared to control dogs (P = 0.0357) and the increase in plasma vWF from baseline to 24 hours correlated directly with the endothelial large vacuole score (R = 0.99103; P < 0.0001). This direct correlation between plasma vWF and the number of large vacuoles, representing the vesiculo-vacuolar organelle (VVO), a permeability structure, suggests that circulating vWF could serve as a biomarker for endothelial alterations and potentially a predictor of thrombocytopenic bleeding. Overall, our results indicate that endothelial damage occurs in the canine ITP model and variability in the degree of endothelial damage may account for differences in the bleeding phenotype among patients with ITP.

The combined effects of ranolazine and dronedarone on human atrial and ventricular electrophysiology.

INTRODUCTION: Pharmacological rhythm control of atrial fibrillation (AF) in patients with structural heart disease is limited. Ranolazine in combination with low dose dronedarone remarkably reduced AF-burden in the phase II HARMONY trial. We thus aimed to investigate the possible mechanisms underlying these results. METHODS AND RESULTS: Patch clamp experiments revealed that ranolazine (5µM), low-dose dronedarone (0.3µM), and the combination significantly prolonged action potential duration (APD90) in atrial myocytes from patients in sinus rhythm (prolongation by 23.5±0.1%, 31.7±0.1% and 25.6±0.1% respectively). Most importantly, in atrial myocytes from patients with AF ranolazine alone, but more the combination with dronedarone, also prolonged the typically abbreviated APD90 (prolongation by 21.6±0.1% and 31.9±0.1% respectively). It was clearly observed that neither ranolazine, dronedarone nor the combination significantly changed the APD or contractility and twitch force in ventricular myocytes or trabeculae from patients with heart failure (HF). Interestingly ranolazine, and more so the combination, but not dronedarone alone, caused hyperpolarization of the resting membrane potential in cardiomyocytes from AF. As measured by confocal microscopy (Fluo-3), ranolazine, dronedarone and the combination significantly suppressed diastolic sarcoplasmic reticulum (SR) Ca(2+) leak in myocytes from sinus rhythm (reduction by ranolazine: 89.0±30.7%, dronedarone: 75.6±27.4% and combination: 78.0±27.2%), in myocytes from AF (reduction by ranolazine: 67.6±33.7%, dronedarone: 86.5±31.7% and combination: 81.0±33.3%), as well as in myocytes from HF (reduction by ranolazine: 64.8±26.5% and dronedarone: 65.9±29.3%). CONCLUSIONS: Electrophysiological measurements during exposure to ranolazine alone or in combination with low-dose dronedarone showed APD prolongation, cellular hyperpolarization and reduced SR Ca(2+) leak in human atrial myocytes. The combined inhibitory effects on various currents, in particular Na(+) and K(+) currents, may explain the anti-AF effects observed in the HARMONY trial. Therefore, the combination of ranolazine and dronedarone, but also ranolazine alone, may be promising new treatment options for AF, especially in patients with HF, and merit further clinical investigation.

Sex difference in appropriate shocks but not mortality during long-term follow-up in patients with implantable cardioverter-defibrillators.

AIMS: Implantable cardioverter-defibrillators (ICDs) have been shown to improve survival, although a considerable number of patients never receive therapy. Implantable cardioverter-defibrillators are routinely implanted regardless of sex. There is continuing controversy whether major outcomes differ between men and women. METHODS AND RESULTS: In this retrospective single-centre study, 1151 consecutive patients (19% women) undergoing ICD implantation between 1998 and 2010 were followed for mortality and first appropriate ICD shock over 4.9 ± 2.7 years. Sex-related differences were investigated using multivariable Cox models adjusting for potential confounders. During follow-up, 318 patients died, a rate of 5.9% per year among men and 4.6% among women (uncorrected P = 0.08); 266 patients received a first appropriate ICD shock (6.3% per year among men vs. 3.6% among women, P = 0.002). After multivariate correction, independent predictors of all-cause mortality were age (hazard ratio, HR = 1.04 per year of age, 95% confidence interval (CI) [1.03-1.06], P < 0.001), left ventricular ejection fraction (HR = 0.98 per %, 95% CI [0.97-1.00], P = 0.025), renal function (HR = 0.99 per mL/min/1.73 m(2), 95% CI [0.99-1.00], P = 0.009), use of diuretics (HR = 1.81, 95% CI [1.29-2.54], P = 0.0023), peripheral arterial disease (HR = 2.21, 95% CI [1.62-3.00], P < 0.001), and chronic obstructive pulmonary disease (HR = 1.48, 95% CI [1.13-1.94], P = 0.029), but not sex. Female sex (HR = 0.51, 95% CI [0.33-0.81], P = 0.013), older age (HR = 0.98, 95% CI [0.97-0.99], P < 0.001), and primary prophylactic ICD indication (HR = 0.69, 95% CI [0.52-0.93], P = 0.043) were independent predictors for less appropriate shocks. CONCLUSION: Women receive 50% less appropriate shocks than men having similar mortality in this large single-centre population. These data may pertain to individually improved selection of defibrillator candidates using risk factors, e.g. sex as demonstrated in this study.

Sex-dependent alterations of Ca2+ cycling in human cardiac hypertrophy and heart failure.

AIMS: Clinical studies have shown differences in the propensity for malignant ventricular arrhythmias between women and men suffering from cardiomyopathies and heart failure (HF). This is clinically relevant as it impacts therapies like prophylactic implantable cardioverter-defibrillator implantation but the pathomechanisms are unknown. As an increased sarcoplasmic reticulum (SR) Ca(2+) leak is arrhythmogenic, it could represent a cellular basis for this paradox. METHODS/RESULTS: We evaluated the SR Ca(2+) leak with respect to sex differences in (i) afterload-induced cardiac hypertrophy (Hy) with preserved left ventricular (LV) function and (ii) end-stage HF. Cardiac function did not differ between sexes in both cardiac pathologies. Human cardiomyocytes isolated from female patients with Hy showed a significantly lower Ca(2+) spark frequency (CaSpF, confocal microscopy, Fluo3-AM) compared with men (P < 0.05). As Ca(2+) spark width and duration were similar in women and men, this difference in CaSpF did not yet translate into a significant difference of the calculated SR Ca(2+) leak between both sexes at this stage of disease (P = 0.14). Epifluorescence measurements (Fura2-AM) revealed comparable Ca(2+) cycling properties (diastolic Ca(2+) levels, amplitude of systolic Ca(2+) transients, SR Ca(2+) load) in patients of both sexes suffering from Hy. Additionally, the increased diastolic CaSpF in male patients with Hy did not yet translate into an elevated ratio of cells showing arrhythmic events (Ca(2+) waves, spontaneous Ca(2+) transients) (P = 0.77). In the transition to HF, both sexes showed an increase of the CaSpF (P < 0.05) and the sex dependence was even more pronounced. Female patients had a 69 ± 10% lower SR Ca(2+) leak (P < 0.05), which now even translated into a lower ratio of arrhythmic cells in female HF patients compared with men (P < 0.001). CONCLUSION: These data show that the SR Ca(2+) leak is lower in women than in men with comparable cardiac impairment. Since the SR Ca(2+) leak triggers delayed afterdepolarizations, our findings may explain why women are less prone to ventricular arrhythmias and confirm the rationale of therapeutic measures reducing the SR Ca(2+) leak.

Inhibition of CaMKII Attenuates Progressing Disruption of Ca(2+) Homeostasis Upon Left Ventricular Assist Device Implantation in Human Heart Failure.

In heart failure, left ventricular assist device (LVAD) implantation is performed to ensure sufficient cardiac output. Whereas some patients are subsequently weaned from LVAD support, other patients still need heart transplantation. To elucidate underlying mechanisms, we assessed the arrhythmogenic SR-Ca(2+) leak at the time of LVAD implantation (HF-Im) and heart transplantation (HF-Tx) and evaluated the effects of CaMKII-inhibition. Human left-ventricular cardiomyocytes were isolated, paced at 1 Hz for 10 beats to ensure SR-Ca(2+) loading and scanned for diastolic Ca(2+) sparks (confocal microscopy). In HF-Im, the high diastolic spark frequency (CaSpF) of 0.76 ± 0.12 × 100 µm(-1) × s(-1) could be reduced to 0.48 ± 0.10 × 100 µm(-1) × s(-1) by CaMKII inhibition (AIP, 1 µM). The amplitude of Ca(2+) sparks, width, and length was not significantly altered. In sum, CaMKII inhibition yielded a clear tendency toward a reduction of the SR-Ca(2+) leak (n cells/patients = 76/6 vs. 108/6, P = 0.08). In HF-Tx, we detected an even higher CaSpF of 1.00 ± 0.10 100 µm(-1) × s(-1) and a higher SR-Ca(2+) leak compared with HF-Im (increase by 81 ± 33%, n cells/patients = 156/7 vs. 130/7, P < 0.05), which fits to the further decreased LV function. Here, CaMKII inhibition likewise reduced CaSpF (0.35 ± 0.09 100 µm(-1) × s(-1,) P = 0.06) and significantly reduced spark duration (n sparks/patients = 58/3 vs. 159/3, P < 0.05). Conclusively, the SR-Ca(2+) leak was reduced by 69 ± 12% in HF-Tx upon CaMKII inhibition (n cells/patients = 53/3 vs. 91/3, P < 0.05). These data show that the SR-Ca(2+) leak correlates with the development of LV function after LVAD implantation and may represent an important pathomechanism. The fact that CaMKII inhibition reduces the SR-Ca(2+) leak in HF-Tx suggests that CaMKII inhibition may be a promising option to beneficially influence clinical course after LVAD implantation.

Selective targeting of bioengineered platelets to prostate cancer vasculature: new paradigm for therapeutic modalities.

Androgen deprivation therapy (ADT) provides palliation for most patients with advanced prostate cancer (CaP); however, greater than 80% subsequently fail ADT. ADT has been indicated to induce an acute but transient destabilization of the prostate vasculature in animal models and humans. Human re-hydrated lyophilized platelets (hRL-P) were investigated as a prototype for therapeutic agents designed to target selectively the tumour-associated vasculature in CaP. The ability of hRL-P to bind the perturbed endothelial cells was tested using thrombin- and ADP-activated human umbilical vein endothelial cells (HUVEC), as well as primary xenografts of human prostate tissue undergoing acute vascular involution in response to ADT. hRL-P adhered to activated HUVEC in a dose-responsive manner. Systemically administered hRL-P, and hRL-P loaded with super-paramagnetic iron oxide (SPIO) nanoparticles, selectively targeted the ADT-damaged human microvasculature in primary xenografts of human prostate tissue. This study demonstrated that hRL-P pre-loaded with chemo-therapeutics or nanoparticles could provide a new paradigm for therapeutic modalities to prevent the rebound/increase in prostate vasculature after ADT, inhibiting the transition to castration-recurrent growth.

Enhanced late INa induces proarrhythmogenic SR Ca leak in a CaMKII-dependent manner.

OBJECTIVE: Enhanced late Na current (late INa) induces Na-dependent Ca overload as well as proarrhythmogenic events on the cellular level that include spatio-temporally uncoordinated diastolic Ca release from the sarcoplasmic reticulum (SR) and delayed afterdepolarizations (DADs). The Ca/calmodulin-dependent protein kinase II (CaMKII) gets activated upon increases in [Ca]i and mediates diastolic SR Ca leak as well as DADs. RATIONALE: We hypothesized that increased late INa (in disease-comparable ranges) exerts proarrhythmogenic events in isolated ventricular mouse myocytes in a manner depending on CaMKII-dependent SR Ca leak. We further tested whether inhibition of disease-related late INa may reduce proarrhythmogenic SR Ca leak in myocytes from failing human hearts. METHODS: Ventricular myocytes were isolated from healthy wildtype (WT), failing CaMKIIδC transgenic (TG) mouse, and failing human hearts. ATX-II (0.25-10 nmol/L) was used to enhance late INa. Spontaneous Ca loss from the SR during diastole (Ca sparks), DADs, non-triggered diastolic Ca transients in myocytes and premature beats of isometrically twitching papillary muscles were used as readouts for proarrhythmogenic events. CaMKII autophosphorylation was assessed by immunoblots. Late INa was inhibited using ranolazine (Ran, 10 µmol/L) or TTX (2 µmol/L), and CaMKII by KN-93 (1 µmol/L) or AIP (1 µmol/L). RESULTS: In WT myocytes, sub-nanomolar ATX-II exposure (0.5 nmol/L) enhanced late INa by ~60%, which resulted in increased diastolic SR Ca loss despite unaltered SR Ca content. In parallel, DADs and non-triggered diastolic Ca transients arose. Inhibition of enhanced late INa by RAN or TTX significantly attenuated diastolic SR Ca loss and suppressed DADs as well as mechanical alternans in mouse and diastolic SR Ca loss in failing human myocytes. ATX-II caused Ca-dependent CaMKII-activation without changes in protein expression, which was reversible by Ran or AIP. Conversely, CaMKII-inhibition decreased diastolic SR Ca loss, DADs and non-triggered diastolic Ca transients despite ATX-II-exposure. Finally, failing mouse myocytes with increased CaMKII activity (TG CaMKIIδC) showed an even aggravated diastolic SR Ca loss that was associated with an increased frequency of non-triggered diastolic Ca transients upon enhanced late INa. CONCLUSIONS: Increased late INa (in disease-comparable ranges) induces proarrhythmogenic events during diastole in healthy and failing mouse myocytes, which are mediated via CaMKII-dependent SR Ca loss. Inhibition of late INa not only attenuated these cellular arrhythmias in mouse myocytes but also in failing human myocytes indicating some antiarrhythmic potential for an inhibition of the elevated late INa/CaMKII signaling pathway in this setting.

Ca2+/calmodulin-dependent protein kinase II and protein kinase A differentially regulate sarcoplasmic reticulum Ca2+ leak in human cardiac pathology.

BACKGROUND: Sarcoplasmic reticulum (SR) Ca(2+) leak through ryanodine receptor type 2 (RyR2) dysfunction is of major pathophysiological relevance in human heart failure (HF); however, mechanisms underlying progressive RyR2 dysregulation from cardiac hypertrophy to HF are still controversial. METHODS AND RESULTS: We investigated healthy control myocardium (n=5) and myocardium from patients with compensated hypertrophy (n=25) and HF (n=32). In hypertrophy, Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and protein kinase A (PKA) both phosphorylated RyR2 at levels that were not different from healthy myocardium. Accordingly, inhibitors of these kinases reduced the SR Ca(2+) leak. In HF, however, the SR Ca(2+) leak was nearly doubled compared with hypertrophy, which led to reduced systolic Ca(2+) transients, a depletion of SR Ca(2+) storage and elevated diastolic Ca(2+) levels. This was accompanied by a significantly increased CaMKII-dependent phosphorylation of RyR2. In contrast, PKA-dependent RyR2 phosphorylation was not increased in HF and was independent of previous ß-blocker treatment. In HF, CaMKII inhibition but not inhibition of PKA yielded a reduction of the SR Ca(2+) leak. Moreover, PKA inhibition further reduced SR Ca(2+) load and systolic Ca(2+) transients. CONCLUSIONS: In human hypertrophy, both CaMKII and PKA functionally regulate RyR2 and may induce SR Ca(2+) leak. In the transition from hypertrophy to HF, the diastolic Ca(2+) leak increases and disturbed Ca(2+) cycling occurs. This is associated with an increase in CaMKII- but not PKA-dependent RyR2 phosphorylation. CaMKII inhibition may thus reflect a promising therapeutic target for the treatment of arrhythmias and contractile dysfunction.

A novel canine model of immune thrombocytopenia: has immune thrombocytopenia (ITP) gone to the dogs?

Canine immune thrombocytopenia (ITP) is analogous to human ITP, with similar platelet counts and heterogeneity in bleeding phenotype among affected individuals. With a goal of ultimately investigating this bleeding heterogeneity, a canine model of antibody-mediated ITP was developed. Infusion of healthy dogs with 2F9, a murine IgG2a monoclonal antibody to the canine platelet glycoprotein GPIIb (a common target of autoantibodies in ITP) resulted in profound, dose-dependent thrombocytopenia. Model dogs developed variable bleeding phenotypes, e.g. petechiae and haematuria, despite similar degrees of thrombocytopenia. 2F9 infusion was not associated with systemic inflammation, consumptive coagulopathy, or impairment of platelet function. Unexpectedly however, evaluation of cytokine profiles led to the identification of platelets as a potential source of serum interleukin-8 (IL8) in dogs. This finding was confirmed in humans with ITP, suggesting that platelet IL8 may be a previously unrecognized modulator of platelet-neutrophil crosstalk. The utility of this model will allow future study of bleeding phenotypic heterogeneity including the role of neutrophils and endothelial cells in ITP.

[Cardiac channelopathies in the context of hereditary arrhythmia syndromes]. / Kardiale Kanalopathien im Kontext hereditärer Arrhythmiesyndrome.

Genetic arrhythmia disorders are rare diseases; however, they are a common cause of sudden cardiac death in children, adolescents, and young adults. In principle, a distinction can be made between channelopathies and cardiomyopathies in the context of genetic diseases. This paper focuses on the channelopathies long and short QT syndrome, Brugada syndrome, and catecholaminergic polymorphic ventricular tachycardia (CPVT). Early diagnosis of these diseases is essential, as drug therapy, behavioral measures, and if necessary, implantation of a cardioverter defibrillator can significantly improve the prognosis and quality of life of patients. This paper highlights the pathophysiological and genetic basis of these channelopathies, describes their clinical manifestations, and comments on the principles of diagnosis, risk stratification and therapy.

Activated rate-response is associated with increased mortality risk in cardiac device carriers with acute heart failure.

AIMS: This study investigated whether an activated R-mode in patients carrying a cardiac implantable electronic device (CIED) is associated with worse prognosis during and after an episode of acutely decompensated heart failure (AHF). METHODS: Six hundred and twenty-three patients participating in an ongoing prospective cohort study that phenotypes and follows patients admitted for AHF were studied. We compared CIED carriers with activated R-mode stimulation (CIED-R) to CIED carriers not in R-mode (CIED-0) and patients without CIEDs (no-CIED). The independent impact of R-mode activation on 12-month all-cause death was examined using uni- and multivariable Cox proportional hazards regression taking into account potential confounders, and hazard ratios (HR) with their 95% confidence intervals (CI) were reported. RESULTS: Mean heart rate on admission was lower in CIED-R (n = 37, 16% women) vs. CIED-0 (n = 64, 23% women) or no-CIED (n = 511, 43% women): 70 bpm vs. 80 bpm or 82 bpm; both p<0.001. In-hospital mortality was similar across groups, but age- and sex-adjusted all-cause 12-month mortality risk was differentially affected by R-mode activation; CIED-R vs. CIED-0: HR 2.44, 95%CI 1.25-4.74; CIED-R vs. no-CIED: HR 2.61, 95%CI 1.59-4.29. These effects persisted after multivariable adjustment for potential confounders. Within CIED-R, mortality risk was similar in patients with pacemakers vs. ICDs and in subgroups with left ventricular ejection fraction (LVEF) <50% vs. ≥50%. CONCLUSION: In patients admitted with AHF, R-mode stimulation was associated with a significantly increased 12-month mortality risk. Our findings shed new light on "admission heart rate" as a potentially treatable target in AHF. Our data are compatible with the concept that chronotropic incompetence contributes to an adverse outcome in these patients and may not be adequately treated through accelerometer-based R-mode stimulation.

The Ca-calmodulin dependent kinase II: a promising target for future antiarrhythmic therapies?

Treating arrhythmias is a challenge for clinicians because pharmacological therapies are often ineffective or have severe side effects. Patients with heart failure frequently present with supreventricular and ventricular arrhythmias. New antiarrhythmic therapies are needed that modulate the specific pathomechanisms underlying the development of cardiac arrhythmias and may have a better safety-profile. The Ca-calmodulin dependent kinase II (CaMKII) seems to be involved in the development of heart failure and arrhythmias and may therefore be a promising target for the development of antiarrhythmic therapies. The current review aims at discussing some novel as well as known cytosolic and sarcolemmal mechanisms involved in CaMKII-dependent arrhythmias without being able to cover all aspects known in the field.

Role of late sodium current as a potential arrhythmogenic mechanism in the progression of pressure-induced heart disease.

The aim of the study was to determine the characteristics of the late Na current (INaL) and its arrhythmogenic potential in the progression of pressure-induced heart disease. Transverse aortic constriction (TAC) was used to induce pressure overload in mice. After one week the hearts developed isolated hypertrophy with preserved systolic contractility. In patch-clamp experiments both, INaL and the action potential duration (APD90) were unchanged. In contrast, after five weeks animals developed heart failure with prolonged APDs and slowed INaL decay time which could be normalized by addition of the INaL inhibitor ranolazine (Ran) or by the Ca/calmodulin-dependent protein kinase II (CaMKII) inhibitor AIP. Accordingly the APD90 could be significantly abbreviated by Ran, tetrodotoxin and the CaMKII inhibitor AIP. Isoproterenol increased the number of delayed afterdepolarizations (DAD) in myocytes from failing but not sham hearts. Application of either Ran or AIP prevented the occurrence of DADs. Moreover, the incidence of triggered activity was significantly increased in TAC myocytes and was largely prevented by Ran and AIP. Western blot analyses indicate that increased CaMKII activity and a hyperphosphorylation of the Nav1.5 at the CaMKII phosphorylation site (Ser571) paralleled our functional observations five weeks after TAC surgery. In pressure overload-induced heart failure a CaMKII-dependent augmentation of INaL plays a crucial role in the AP prolongation and generation of cellular arrhythmogenic triggers, which cannot be found in early and still compensated hypertrophy. Inhibition of INaL and CaMKII exerts potent antiarrhythmic effects and might therefore be of potential therapeutic interest. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".

The ryanodine receptor leak: how a tattered receptor plunges the failing heart into crisis.

It has been persuasively shown in the last two decades that the development of heart failure is closely linked to distinct alterations in Ca(2+) cycling. A crucial point in this respect is an increased spontaneous release of Ca(2+) out of the sarcoplasmic reticulum during diastole via ryanodine receptors type 2 (RyR2). The consequence is a compromised sarcoplasmic reticulum Ca(2+) storage capacity, which impairs systolic contractility and possibly diastolic cardiac function due to Ca(2+) overload. Additionally, leaky RyR2 are more and more regarded to potently induce proarrhythmic triggers. Elimination of spontaneously released Ca(2+) via RyR2 in diastole can cause a transient sarcolemmal inward current and hence delayed after depolarisations as substrate for cardiac arrhythmias. In this article, the pathological role and consequences of the SR Ca(2+)-leak and its regulation are reviewed with a main focus on protein kinase A and Ca(2+)-calmodulin-dependent kinase II. We summarise clinical consequences of "leaky RyR2" as well as possible therapeutic strategies in order to correct RyR2 dysfunction and discuss the significance of the available data.

Focal atrial tachycardia mimicking catecholaminergic polymorphic ventricular tachycardia: a case report.

Background: In childhood and adolescence, cardiac arrhythmias are often benign in the absence of congenital heart defects. Nevertheless, life-threatening inherited arrhythmogenic syndromes can become clinically manifest in early childhood. As early symptoms may be similar in both conditions, thorough workup is fundamental to avoid delayed diagnosis and misdiagnosis. Case summary: We present the case of a 26-year-old Caucasian female patient who presented with recurrent non-sustained polymorphic wide complex tachycardia. Structural heart disease was excluded by echocardiography as well as cardiac magnetic resonance imaging. Due to wide complex extrasystoles and couplets with alternating QRS axis occurring at low levels of physical exertion, catecholaminergic polymorphic ventricular tachycardia (CPVT) was suspected and further investigated. Epinephrine testing in combination with an electrophysiological (EP) study with placement of a coronary sinus catheter and subsequent programmed stimulation ruled out CPVT and unmasked wide complex tachycardia as varying aberrant conduction of focal atrial tachycardia (FAT). 3D-navigated mapping of FAT revealed a direct parahisian origin. Due to significantly increased risk of atrio-ventricular (AV) block during ablation, the patient refused ablation and preferred medical antiarrhythmic therapy. Discussion: Given the consequences of both, delayed diagnosis and misdiagnosis of CPVT, thorough workup is fundamental. In case of doubt regarding potential aberrant AV conduction in the context of wide complex tachycardia, an invasive EP study may easily and safely prove or rule out aberrancy.

Impact of coronavirus disease (COVID-19) pandemic on physical activity of patients with cardiac implantable electronic devices-A remote monitoring study.

OBJECTIVES: The study aims to investigate the impact of COVID-19 pandemic on physical activity and frequency of implantable cardioverter-defibrillator (ICD) therapies of patients with cardiac implantable electronic devices. METHODS AND RESULTS: Physical activity, heart rate and ICD-therapies were assessed via routine remote monitoring over two years. We focussed on a 338-day period during COVID-19 pandemic that was divided in 6 time-intervals defined by public health interventions and compared to the previous regular year. Paired nonparametric longitudinal analysis was performed to detect differences between time-intervals. To model effects of age, sex and time we applied a nonparametric ANOVA-type-statistic. 147 patients with cardiac implantable electronic devices were analysed. Longitudinal analysis of physical activity in 2019 and 2020 showed a specific weekly and seasonal pattern. Physical activity was reduced during the pandemic (mean daily physical activity 2019: 12.4% vs. 2020: 11.5%; p<0.0001) with the strongest reductions (fold changes 0.885/0.889, p<0.0001/p<0.0001) during the two lockdown-periods. In older patients (>70 years), physical activity was decreased in every time-interval of the year 2020. In time-intervals of eased restrictions, physical activity of younger patients (≤70 years) was not different compared to 2019. No variation in mean heart rate, arrhythmia-burden and count of ICD-therapies was found. CONCLUSION: Physical activity shows fluctuations dependent on days of the week and time of the year. During the pandemic, physical activity was reduced in patients with cardiac implantable electronic devices with the strongest reductions during lockdown-periods. Younger patients resumed former levels of physical activity in times of eased restrictions while older patients remained less active. Thus, activation of the elderly population is important to prevent long-term health impairments due to the pandemic.

Imaging and Elastometry of Blood Clots Using Magnetomotive Optical Coherence Tomography and Labeled Platelets.

Improved methods for imaging and assessment of vascular defects are needed for directing treatment of cardiovascular pathologies. In this paper, we employ magnetomotive optical coherence tomography (MMOCT) as a platform both to detect and to measure the elasticity of blood clots. Detection is enabled through the use of rehydrated, lyophilized platelets loaded with superparamagnetic iron oxides (SPIO-RL platelets) that are functional infusion agents that adhere to sites of vascular endothelial damage. Evidence suggests that the sensitivity for detection is improved over threefold by magnetic interactions between SPIOs inside RL platelets. Using the same MMOCT system, we show how elastometry of simulated clots, using resonant acoustic spectroscopy, is correlated with the fibrin content of the clot. Both methods are based upon magnetic actuation and phase-sensitive optical monitoring of nanoscale displacements using MMOCT, underscoring its utility as a broad-based platform to detect and measure the molecular structure and composition of blood clots.