Differential effects of heart rate reduction with ivabradine in two models of endothelial dysfunction and oxidative stress

Relationship of resting heart rate and blood pressure with all-cause and cardiovascular disease mortality

OBJECTIVES

This study aimed to investigate associations of resting heart rate (RHR) and blood pressure (BP) with all-cause and cardiovascular disease (CVD) mortality.

STUDY DESIGN

A retrospective cohort study.

METHODS

A total of 67,028 Chinese participants aged ≥60 years were included in the analysis. RHR, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were evaluated according to quartiles ([41-69, 70-74, 75-79, 80-127 beats/min], [80-119, 120-129, 130-139, 140-238 mm Hg], and [40-70, 71-79, 80-84, 85-133 mm Hg]). Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of all-cause and CVD mortality with RHR, SBP, and DBP. Restricted cubic splines were used to evaluate the dose-response association.

RESULTS

During the 361,975 person-year follow-up, 9326 deaths were recorded, of which 5039 deaths were due to CVD. The risk of all-cause mortality was increased by 25% with the quartiles four vs quartile one of RHR (HR [95% CI]:1.25 [1.17-1.33]), and CVD mortality was increased by 32% (HR [95% CI]: 1.32 [1.22-1.44]). Similar results were observed when comparing the quartiles four vs quartile one of SBP with the risk of all-cause and CVD mortality (HRs [95% CIs]: 1.14 [1.07, 1.22] and 1.23 [1.12. 1.34]) and DBP with the risk of all-cause and CVD mortality (HRs [95% CIs]: 1.17 [1.11. 1.24] and 1.36 [1.26. 1.47]). We found linear associations of RHR, SBP, and DBP with all-cause and CVD mortality (P_{non-linearity} >0.05), except for the approximately J-shaped association between DBP and all-cause mortality (P_{non-linearity} = 0.008). There was a significant interaction of RHR and SBP with all-cause and CVD mortality (P_interaction <0.05).

CONCLUSIONS

RHR and BP increased the risk of all-cause and CVD mortality, especially fast RHR combined with high SBP.

Ivabradine in the management of COVID-19-related cardiovascular complications: A perspective

Abstract:

Besides acute respiratory distress syndrome, acute cardiac injury is a major complication in severe coronavirus disease 2019 (COVID-19) and associates with a poor clinical outcome. Acute cardiac injury with COVID-19 can be of various etiologies, including myocardial ischemia or infarction and myocarditis, and may compromise cardiac function, resulting in acute heart failure or cardiogenic shock. Systemic inflammatory response increases heart rate (HR), which disrupts the myocardial oxygen supply/demand balance and worsens cardiac energy efficiency, thus further deteriorating the cardiac performance of the injured myocardium. In fact, the combination of elevated resting HR and markers of inflammation synergistically predicts adverse cardiovascular prognosis. Thus, targeted HR reduction may potentially be of benefit in cardiovascular pathologies associated with COVID-19. Ivabradine is a drug that selectively reduces HR via If current inhibition in the sinoatrial node without a negative effect on inotropy. Besides selective HR reduction, ivabradine was found to exert various beneficial pleiotropic effects, either HR-dependent or HR-independent, including anti-inflammatory, anti-atherosclerotic, anti-oxidant and antiproliferative actions and the attenuation of endothelial dysfunction and neurohumoral activation. Cardioprotection by ivabradine has already been indicated in cardiovascular pathologies that are prevalent with COVID-19, including myocarditis, acute coronary syndrome, cardiogenic shock or cardiac dysautonomia. Here, we suggest that ivabradine may be beneficial in the management of COVID-19-related cardiovascular complications.

Pleiotropic vascular effects of ivabradine in streptozotocin-induced diabetes

AIMS

Ivabradine (IVA) reduces heart rate (HR) by inhibiting hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in sinoatrial node. Studies suggest that IVA has other beneficial effects on cardiovascular system that are not related to its effect on HR such as prevention of endothelial injury and the antioxidant effects. In addition to sinoatrial node, HCN channels exist in other tissues and their expression pattern differs in certain pathologies such as hypertension and hypertrophy. We investigated the mechanism of IVA effect in the setting of streptozotocin (STZ)-induced cardiovascular damage. Direct effects of IVA and their mechanism on thoracic aorta as well as possible prevention of vascular dysfunction in diabetes were investigated in this study.

METHODS AND RESULTS

The effects of IVA on vascular function were investigated in control and STZ-diabetic rats. Some control and diabetic rats were treated with IVA. IVA treatment prevented diabetes-induced increase in plasma p-selectin and vascular cell adhesion molecule-1 levels and the decrease in nitric oxide content in the aortas of diabetic animals. When added to isolated organ bath, IVA induced concentration-dependent relaxations in thoracic aorta. Pre-incubation with Nω-Nitro- L -arginine methyl ester reduced IVA-induced relaxations. Expression patterns of all isoforms of HCN proteins were affected by both diabetes and IVA treatment.

CONCLUSION

IVA improves vascular function in diabetes and HCN channels support vascular activity against damaging effects of diabetes. IVA may be added to prevent diabetic cardiovascular dysfunction with these beneficial effects that are unrelated to its primary mechanism of action.

Potential Influential Factors of In-Hospital Myocardial Reinfarction in ST-Segment Elevation Myocardial Infarction (STEMI) Patients: Finding from the Improving Care for Cardiovascular Disease in China- (CCC-) Acute Coronary Syndrome (ACS) Project

In this study, 39915 inpatients with a discharge diagnosis of STEMI from the CCC-ACS project phase I and II were included. The prevalence of the medical history, clinical complications on admission and treatment during hospitalization in the STEMI inpatients with and without in-hospital reinfarction was presented. The factors that were differentially distributed and of critical clinical significance (e.g., age, sex, heart rate, smoking, MI history, HF history, COPD history, stroke, hypertension, diabetes, PCI treatment, administration of DAPT, and statins) were entered into standard Cox regression model and competing risk model for potential influential factors of in-hospital reinfarction. Patients with a higher heart rate (OR 1.018; 95% CI 1.003 to 1.033) were more susceptible to in-hospital reinfarction. Myocardial infarction history (OR 2.840; 95% CI 1.160 to 6.955) was a risk factor of in-hospital reinfarction independent of hypertension, diabetes, and dyslipidaemia.

Real-time heart rate monitoring system for cardiotoxicity assessment of Daphnia magna using high-speed digital holographic microscopy

Machine vision techniques for monitoring heart rates in aquatic bioassays have been applied to cardiotoxicity assessment. However, the requisite large data sizes and long calculation times make long-term observations of heart rates difficult. In this study, we developed a real-time heart rate monitoring system for individual Daphnia magna in a water chamber mounter that immobilizes their movement in 100 mL media. Heart rates are calculated from real-time, time-resolved relative phase information from digital holograms acquired with a 200 fps camera and parallel computation using a graphics processing unit. With this system, we monitored the real-time changes in the heart rates of individual D. magna specimens exposed to H₂O₂ as a positive control for reactive oxygen species (ROS) levels in an aquatic environment for 10 h, a period long enough to observe dynamic heart rate responses to the mounting process and exposure and to establish heart rate trends. An additional group analysis was conducted to compare to conventional cardiotoxicity assessment, with results of both assessments showing that the heart rates reduced according to ROS level by H₂O₂ exposure concentration. Notably, the results of our real-time dynamic heart rate monitoring in aquatic conditions indicated that establishing a relaxation heart rate before measurements could improve the accuracy of toxicity assessment. It is believed that the system developed in this study, achieving the simultaneous measurement, analysis, and display of reconstructed results, will find wide application in other aquatic bioassays.

Ivabradine Ameliorates Kidney Fibrosis in L-NAME-Induced Hypertension

Hypertension-induced renal injury is characterized by structural kidney alterations and function deterioration. Therapeutics for kidney protection are limited, thus novel renoprotectives in hypertension are being continuously sought out. Ivabradine, an inhibitor of the I_f current in the sinoatrial node reducing heart rate (HR), was shown to be of benefit in various cardiovascular pathologies. Yet, data regarding potential renoprotection by ivabradine in hypertension are sparse. Thirty-six adult male Wistar rats were divided into non-diseased controls and rats with N^G-nitro-L-arginine methyl ester (L-NAME)-induced hypertension to assess ivabradine's site-specific effect on kidney fibrosis. After 4 weeks of treatment, L-NAME increased the average systolic blood pressure (SBP) (by 27%), decreased glomerular density (by 28%) and increased glomerular tuft area (by 44%). Moreover, L-NAME induced glomerular, tubulointerstitial, and vascular/perivascular fibrosis by enhancing type I collagen volume (16-, 19- and 25-fold, respectively). L-NAME also increased the glomerular type IV collagen volume and the tubular injury score (3- and 8-fold, respectively). Ivabradine decreased average SBP and HR (by 8 and 12%, respectively), increased glomerular density (by 57%) and reduced glomerular tuft area (by 30%). Importantly, ivabradine decreased type I collagen volume at all three of the investigated sites (by 33, 38, and 72%, respectively) and enhanced vascular/perivascular type III collagen volume (by 67%). Furthermore, ivabradine decreased the glomerular type IV collagen volume and the tubular injury score (by 63 and 34%, respectively). We conclude that ivabradine attenuated the alterations of glomerular density and tuft area and modified renal fibrosis in a site-specific manner in L-NAME-hypertension. It is suggested that ivabradine may be renoprotective in hypertensive kidney disease.

Ivabradine and endothelium: an update

Ivabradine is a pure heart-rate lowering drug that is nowadays used, accordingly to the last ESC Guidelines, to reduce mortality and heart failure (HF) hospitalization in patients with HF with reduced ejection fraction and in symptomatic patiens with inappropriate sinus tachycardia. Moreover, interesting effect of ivabradine on endothelial and myocardial function and on oxidative stress and inflamation pathways are progressively emerging. The aim of this paper is to highlight newer evidences about ivabradine effect (and consequently possible future application of the drug) in pathological settings different from guidelines-based clinical practice.

Five-year results of heart rate control with ivabradine or metoprolol succinate in patients after heart transplantation

Background

Cardiac graft denervation causes inadequate sinus tachycardia in patients after heart transplantation (HTX) which is associated with reduced survival. This study investigated the 5-year results of heart rate control with ivabradine or metoprolol succinate in patients after HTX.

Methods

This registry study analyzed 104 patients receiving either ivabradine (n = 50) or metoprolol succinate (n = 54) within 5 years after HTX. Analysis included patient characteristics, medication, echocardiographic features, cardiac catheterization data, cardiac biomarkers, heart rates, and post-transplant survival including causes of death.

Results

Demographics and post-transplant medication revealed no significant differences except for ivabradine and metoprolol succinate use. At 5-year follow-up, patients with ivabradine had a significantly lower heart rate (73.3 bpm) compared to baseline (88.6 bpm; P < 0.01) and to metoprolol succinate (80.4 bpm; P < 0.01), a reduced left ventricular mass (154.8 g) compared to baseline (179.5 g; P < 0.01) and to metoprolol succinate (177.3 g; P < 0.01), a lower left ventricular end-diastolic pressure (LVEDP; 12.0 mmHg) compared to baseline (15.5 mmHg; P < 0.01) and to metoprolol succinate (17.1 mmHg; P < 0.01), and a reduced NT-proBNP level (525.4 pg/ml) compared to baseline (3826.3 pg/ml; P < 0.01) and to metoprolol succinate (1038.9 pg/ml; P < 0.01). Five-year post-transplant survival was significantly better in patients with ivabradine (90.0%) versus metoprolol succinate (68.5%; P < 0.01).

Conclusion

Patients receiving ivabradine showed a superior heart rate reduction and a better left ventricular diastolic function along with an improved 5-year survival after HTX.

Effects of heart rate reduction with ivabradine on vascular stiffness and endothelial function in chronic stable coronary artery disease

INTRODUCTION

Epidemiological and clinical studies have shown a relevant association between heart rate and cardiovascular mortality. Experimental studies identified vascular effects of heart rate reduction with the If channel inhibitor ivabradine. Therefore, the effects of heart rate reduction on endothelial function and indices of arterial stiffness were examined in patients with stable coronary artery disease in a prospective, placebo-controlled clinical crossover study.

METHODS AND RESULTS

Twenty-three patients (18 men and 5 women) with a resting heart rate (HR) of at least 70 beats per minute (bpm) and stable coronary artery disease were enrolled in this study. In a cross-over design, all patients were treated with ivabradine (Iva, 7.5 mg b.i.d.) and placebo for 6 months each. Iva reduced heart rate by 11.4 bpm (Iva 58.8 ± 8.2 bpm vs. placebo 70.2 ± 8.3 bpm, P < 0.0001). Augmentation index (AIx75), carotid-femoral pulse wave velocity (cfPWV) and central aortic blood pressure were measured using applanation tonometry (SphygmoCor). HRR by Iva increased AIx75 by 12.4% (Iva 24.3 ± 10.5% vs. placebo 21.3 ± 10.1%, P < 0.05) and reduced cfPWV by 14.1% (Iva 6.3 ± 1.7 m/s vs. placebo 7.3 ± 1.4 m/s, P < 0.01). Iva increased mean central blood pressure by 7.8% (Iva 107.5 ± 15.4 mmHg vs. placebo 99.1 ± 12.2 mmHg, P < 0.001). Endothelial function was determined measuring the flow-mediated vasodilation (FMD) of the brachial artery. HRR by Iva increased FMD by 18.5% (Iva 7.3 ± 2.2% vs. placebo 6.0 ± 2.0%, P < 0.001). Aortic distensibility was characterized by MRI. HRR by Iva increased aortic distensibility by 33.3% (Iva 0.003 ± 0.001/mmHg vs. placebo 0.002 ± 0.010/mmHg, P < 0.01) and circumferential cyclic strain by 37.1% (Iva 0.062 ± 0.027 vs. placebo 0.039 ± 0.018, P < 0.0001).

CONCLUSION

Heart rate reduction with Iva increased endothelium-dependent vasodilation and reduced arterial stiffness in patients with stable CAD. These findings corroborate and expand the results collected in experimental studies and indicate the importance of heart rate as a determinant of vascular function.

Effect of Ivabradine on a Hypertensive Heart and the Renin-Angiotensin-Aldosterone System in L-NAME-Induced Hypertension

Ivabradine, the selective inhibitor of the If current in the sinoatrial node, exerts cardiovascular protection by its bradycardic effect and potentially pleiotropic actions. However, there is a shortage of data regarding ivabradine's interaction with the renin-angiotensin-aldosterone system (RAAS). This study investigated whether ivabradine is able to protect a hypertensive heart in the model of L-NAME-induced hypertension and to interfere with the RAAS. Four groups (n = 10/group) of adult male Wistar rats were treated as follows for four weeks: control, ivabradine (10 mg/kg/day), L-NAME (40 mg/kg/day), and L-NAME plus ivabradine. L-NAME administration increased systolic blood pressure (SBP) and left ventricular (LV) weight, enhanced hydroxyproline concentration in the LV, and deteriorated the systolic and diastolic LV function. Ivabradine reduced heart rate (HR) and SBP, and improved the LV function. The serum concentrations of angiotensin Ang 1⁻8 (Ang II), Ang 1⁻5, Ang 1⁻7, Ang 1⁻10, Ang 2⁻8, and Ang 3⁻8 were decreased in the L-NAME group and ivabradine did not modify them. The serum concentration of aldosterone and the aldosterone/Ang II ratio were enhanced by L-NAME and ivabradine reduced these changes. We conclude that ivabradine improved the LV function of the hypertensive heart in L-NAME-induced hypertension. The protective effect of ivabradine might have been associated with the reduction of the aldosterone level.

The effect of the heart rate lowering drug Ivabradine on hemodynamics in atherosclerotic mice

The heart rate lowering drug Ivabradine was shown to improve cardiac outcome in patients with previous heart failure. However, in patients without heart failure, no beneficial effect of Ivabradine was observed. Animal studies suggested a preventive effect of Ivabradine on atherosclerosis which was due to an increase in wall shear stress (WSS), the blood flow-induced frictional force exerted on the endothelium, triggering anti-inflammatory responses. However, data on the effect of Ivabradine on WSS is sparse. We aim to study the effect of Ivabradine on (i) the 3D WSS distribution over a growing plaque and (ii) plaque composition. We induced atherosclerosis in ApoE-/- mice by placing a tapered cast around the right common carotid artery (RCCA). Five weeks after cast placement, Ivabradine was administered via drinking water (15 mg/kg/day) for 2 weeks, after which the RCCA was excised for histology analyses. Before and after Ivabradine treatment, animals were imaged with Doppler Ultrasound to measure blood velocity. Vessel geometry was obtained using contrast-enhanced micro-CT. Time-averaged WSS during systole, diastole and peak WSS was subsequently computed. Ivabradine significantly decreased heart rate (459 ± 28 bpm vs. 567 ± 32 bpm, p < 0.001). Normalized peak flow significantly increased in the Ivabradine group (124.2% ± 40.5% vs. 87.3% ± 25.4%, p < 0.05), reflected by an increased normalized WSS level during systole (110.7% ± 18.4% vs. 75.4% ± 24.6%, p < 0.05). However, plaque size or composition including plaque area, relative necrotic core area and macrophage content were not altered in mice treated with Ivabradine compared to controls. We conclude that increased WSS in response to Ivabradine treatment did not affect plaque progression in a murine model.

Taking up the cudgels for the traditional reactive oxygen and nitrogen species detection assays and their use in the cardiovascular system

Reactive oxygen and nitrogen species (RONS such as H2O2, nitric oxide) confer redox regulation of essential cellular functions (e.g. differentiation, proliferation, migration, apoptosis), initiate and catalyze adaptive stress responses. In contrast, excessive formation of RONS caused by impaired break-down by cellular antioxidant systems and/or insufficient repair of the resulting oxidative damage of biomolecules may lead to appreciable impairment of cellular function and in the worst case to cell death, organ dysfunction and severe disease phenotypes of the entire organism. Therefore, the knowledge of the severity of oxidative stress and tissue specific localization is of great biological and clinical importance. However, at this level of investigation quantitative information may be enough. For the development of specific drugs, the cellular and subcellular localization of the sources of RONS or even the nature of the reactive species may be of great importance, and accordingly, more qualitative information is required. These two different philosophies currently compete with each other and their different needs (also reflected by different detection assays) often lead to controversial discussions within the redox research community. With the present review we want to shed some light on these different philosophies and needs (based on our personal views), but also to defend some of the traditional assays for the detection of RONS that work very well in our hands and to provide some guidelines how to use and interpret the results of these assays. We will also provide an overview on the "new assays" with a brief discussion on their strengths but also weaknesses and limitations.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

Heart Rate reduction by IVabradine for improvement of ENDothELial function in patients with coronary artery disease: the RIVENDEL study

AIMS

Data from experimental studies suggest that the _f current-inhibitor ivabradine may reduce oxidative stress and improve endothelial function. We aimed to evaluate the effect of ivabradine on endothelial function in patients with coronary artery disease (CAD) after complete revascularization with percutaneous coronary angioplasty (PCI).

METHODS AND RESULTS

At least 30 days after PCI, 70 patients were randomized (T0) to receive ivabradine 5 mg twice daily (ivabradine group, n = 36) or to continue with standard medical therapy (control group, n = 34). After 4 weeks (T1), ivabradine dose was adjusted up to 7.5 mg twice daily in patients with heart rate (HR) at rest >60 bpm, and thereafter continued for additional 4 weeks (T2). At all timings, brachial artery reactivity was assessed by flow-mediated dilatation (FMD) and nitroglycerin-mediated dilatation (NMD). No significant differences were observed at T0 between ivabradine and control groups in terms of HR (68.0 ± 6.4 vs. 67.6 ± 6.4 bpm; p = 0.803), FMD (8.7 ± 4.9 vs. 8.0 ± 5.5 %; p = 0.577) and NMD (12.7 ± 6.7 vs. 13.3 ± 6.2 %; p = 0.715). Over the study period, a significant reduction of HR (65.2 ± 5.9 bpm at T1, 62.2 ± 5.7 bpm at T2; p < 0.001), and improvement of FMD (12.2 ± 6.2 % at T1, 15.0 ± 7.7 % at T2; p < 0.001) and NMD (16.6 ± 10.4 % at T1, 17.7 ± 10.8 at T2; p < 0.001) were observed in the ivabradine group, while no significant changes were observed in the control group. In the ivabradine group, a moderate negative correlation was observed between the HR variation and FMD variation from T1 to T3 (r = -0.448; p = 0.006).

CONCLUSIONS

In patients with CAD undergoing complete revascularization with PCI, addition of ivabradine to the standard medical therapy produces a significant improvement in endothelial function. This effect seems to be related to HR reduction. ClinicalTrials.gov number, NCT02681978.

Heart Rate Reduction With Ivabradine Protects Against Left Ventricular Remodeling by Attenuating Infarct Expansion and Preserving Remote-Zone Contractile Function and Synchrony in a Mouse Model of Reperfused Myocardial Infarction

BACKGROUND

Ivabradine selectively inhibits the pacemaker current of the sinoatrial node, slowing heart rate. Few studies have examined the effects of ivabradine on the mechanical properties of the heart after reperfused myocardial infarction (MI). Advances in ultrasound speckle-tracking allow strain analyses to be performed in small-animal models, enabling the assessment of regional mechanical function.

METHODS AND RESULTS

After 1 hour of coronary occlusion followed by reperfusion, mice received 10 mg/kg per day of ivabradine dissolved in drinking water (n=10), or were treated as infarcted controls (n=9). Three-dimensional high-frequency echocardiography was performed at baseline and at days 2, 7, 14, and 28 post-MI. Speckle-tracking software was used to calculate intramural longitudinal myocardial strain (Ell) and strain rate. Standard deviation time to peak radial strain (SD Tpeak Err) and temporal uniformity of strain were calculated from short-axis cines acquired in the left ventricular remote zone. Ivabradine reduced heart rate by 8% to 16% over the course of 28 days compared to controls (P<0.001). On day 28 post-MI, the ivabradine group was found to have significantly smaller end-systolic volumes, greater ejection fraction, reduced wall thinning, and greater peak Ell and Ell rate in the remote zone, as well as globally. Temporal uniformity of strain and SD Tpeak Err were significantly smaller in the ivabradine-treated group by day 28 (P<0.05).

CONCLUSIONS

High-frequency ultrasound speckle-tracking demonstrated decreased left ventricular remodeling and dyssynchrony, as well as improved mechanical performance in remote myocardium after heart rate reduction with ivabradine.

Inhibition of Atherosclerosis Progression, Intimal Hyperplasia, and Oxidative Stress by Simvastatin and Ivabradine May Reduce Thoracic Aorta's Stiffness in Hypercholesterolemic Rabbits

AIMS

This study aims to evaluate atherosclerosis, oxidative stress, and arterial stiffness attenuation by simvastatin and ivabradine in hyperlipidemic rabbits.

METHODS AND RESULTS

Forty rabbits were randomly divided into 4 groups: atherogenic diet (group C), atherogenic diet plus simvastatin (group S), atherogenic diet plus ivabradine (group I), and atherogenic diet plus simvastatin and ivabradine (group S + I). After 9 weeks, rabbits were euthanized and descending aortas excised for mechanical testing. Atherogenic diet induced the development of significant atherosclerotic lesions in group C animals but in none of groups S, I, and S + I. RAM-11 and HHF-35-positive cells were significantly reduced in groups S, I, and S + I compared with group C (P < .001). A significant neointimal hyperplasia and intima-media ratio reduction was demonstrated in groups S (P = .015 and P < .001), I (P = .021 and P < .001), and S + I (P = .019 and P < .001) compared with group C. Protein nitrotyrosine levels were significantly decreased in group S compared with group C (P = .009), and reactive oxygen species levels were decreased in group I compared with group C (P = .011). Aortic stiffness was significantly reduced in groups S, I, and S + I compared with group C (P = .003, P = .011, and P = .029).

CONCLUSION

Simvastatin and ivabradine significantly inhibited intimal hyperplasia and oxidative stress contributing to aortic stiffness reduction in hyperlipidemic rabbits.

Ivabradine reduces myocardial stunning in patients with exercise-inducible ischaemia

Ivabradine is an effective treatment for angina in patients with stable coronary artery disease (CAD) and for heart failure. Experiments in a canine model have shown that ivabradine reduces both acute left ventricular (LV) dysfunction and post-ischaemic stunning. Aim of this study was to investigate the effect of ivabradine on LV dysfunction and stunning in patients with CAD and exercise-inducible ischaemia. Fifteen patients with ejection fraction >40 % and heart rate >70 bpm were enrolled. After pharmacologic washout, echocardiography was performed at rest, at peak treadmill exercise and during recovery until return to baseline. After 2 weeks of ivabradine (7.5 mg bid) stress echocardiography was repeated at the same workload achieved during washout. Peak global and segmental (ischaemic vs. remote normal segments) LV longitudinal strain (LS) was assessed by 2D speckle tracking analysis. At washout, LS was significantly impaired in ischaemic compared to remote segments at peak stress and for several minutes during recovery. After ivabradine a smaller, albeit still significant, impairment of LS in ischaemic segments was observed at peak whilst no difference with remote segments was present during recovery. Furthermore, the average global LS value improved significantly after treatment. In conclusion, ivabradine reduces both acute LV dysfunction and stunning in patients with CAD and exercise-inducible ischaemia. We hypothesise that this mechanism might contribute to reduce chronic LV dysfunction in patients with CAD. In this setting the drug might limit the development of hibernating myocardium which is believed to result from repeated episodes of ischaemia and stunning.

Heart rate and ischemic stroke: the REasons for Geographic And Racial Differences in Stroke (REGARDS) study

BACKGROUND

The association between resting heart rate and ischemic stroke remains unclear.

AIM

To examine the association between resting heart rate and ischemic stroke.

METHODS

A total of 24 730 participants (mean age: 64 ± 9·3 years; 59% women; 41% blacks) from the REasons for Geographic And Racial Differences in Stroke (REGARDS) study who were free of stroke at the time of enrollment (2003-2007) were included in this analysis. Resting heart rate was determined from baseline electrocardiogram data. Heart rate was examined as a continuous variable per 10 bpm increase and also as a categorical variable using tertiles ( <61 bpm, 61 to 70 bpm, and >70 bpm). First-time ischemic stroke events were identified during follow-up and adjudicated by physician review.

RESULTS

Over a median follow-up of 7·6 years, a total of 646 ischemic strokes occurred. In a Cox regression model adjusted for socio-demographics, cardiovascular risk factors, and potential confounders, each 10 bpm increase in heart rate was associated with a 10% increase in the risk of ischemic stroke (hazard ratio = 1·10, 95% confidence interval = 1·02, 1·18). In the categorical model, an increased risk of ischemic stroke was observed for heart rates in the middle (hazard ratio = 1·29, 95% confidence interval = 1·06, 1·57) and upper (hazard ratio = 1·37, 95% confidence interval = 1·12, 1·67) tertiles compared with the lower tertile. The results were consistent when the analysis was stratified by age, gender, race, exercise habits, hypertension, and coronary heart disease.

CONCLUSION

In REGARDS, high resting heart rates were associated with an increased risk of ischemic stroke compared with low heart rates. Further research is needed to examine whether interventions aimed to reduce heart rate decrease stroke risk.

Pleiotropic, heart rate-independent cardioprotection by ivabradine

BACKGROUND AND PURPOSE

In pigs, ivabradine reduces infarct size even when given only at reperfusion and in the absence of heart rate reduction. The mechanism of this non-heart rate-related cardioprotection is unknown. Hence, in the present study we assessed the pleiotropic action of ivabradine in more detail.

EXPERIMENTAL APPROACH

Anaesthetized mice were pretreated with ivabradine (1.7 mg · kg(-1) i.v.) or placebo (control) before a cycle of coronary occlusion/reperfusion (30/120 min ± left atrial pacing). Infarct size was determined. Isolated ventricular cardiomyocytes were exposed to simulated ischaemia/reperfusion (60/5 min) in the absence and presence of ivabradine, viability was then quantified and intra- and extracellular reactive oxygen species (ROS) formation was detected. Mitochondria were isolated from mouse hearts and exposed to simulated ischaemia/reperfusion (6/3 min) in glutamate/malate- and ADP-containing buffer in the absence and presence of ivabradine respectively. Mitochondrial respiration, extramitochondrial ROS, mitochondrial ATP production and calcium retention capacity (CRC) were assessed.

KEY RESULTS

Ivabradine decreased infarct size even with atrial pacing. Cardiomyocyte viability after simulated ischaemia/reperfusion was better preserved with ivabradine, the accumulation of intra- and extracellular ROS decreased in parallel. Mitochondrial complex I respiration was not different without/with ivabradine, but ivabradine significantly inhibited the accumulation of extramitochondrial ROS, increased mitochondrial ATP production and increased CRC.

CONCLUSION AND IMPLICATIONS

Ivabradine reduces infarct size independently of a reduction in heart rate and improves ventricular cardiomyocyte viability, possibly by reducing mitochondrial ROS formation, increasing ATP production and CRC.

Impact of Hey2 and COUP-TFII on genes involved in arteriovenous differentiation in primary human arterial and venous endothelial cells

Arteries and veins show marked differences in their anatomy, physiology and genetic expression pattern. In this study, we analyzed impact of overexpression or downregulation of arterial marker gene Hey2 and venous marker gene COUP-TFII in human venous and arterial endothelial cells on genes involved in arteriovenous differentiation. Lentiviral overexpression of venous marker gene COUP-TFII in arterial endothelial cells led to downregulation of NICD4, arterial marker gene Hey2 and EphrinB2. Downregulation of Hey2 could be mediated by direct binding of COUP-TFII to Hey2 promoter as shown by ChIP, EMSA and promoter analysis. Downregulation of Hey2 by shRNA causes downregulation of EphrinB2 expression. Overexpression of arterial marker Hey2 in venous endothelial cells did not change expression pattern of COUP-TFII. Downregulation of venous marker gene COUP-TFII in venous endothelial cells resulted in upregulation of VEGF-A, Dll4 and EphrinB2 expression. Our data support an important role of Hey2 and COUP-TFII in arteriovenous differentiation of human endothelial cells.

Transcriptional regulation of Nox4 by histone deacetylases in human endothelial cells

Nox4 is a member of the NADPH oxidase family, which represents a major source of reactive oxygen species (ROS) in the vascular wall. Nox4-mediated ROS production mainly depends on the expression levels of the enzyme. The present study was aimed to investigate the mechanisms of Nox4 transcription regulation by histone deacetylases (HDAC). In human umbilical vein endothelial cells (HUVEC) and HUVEC-derived EA.hy 926 cells, treatment with the pan-HDAC inhibitor scriptaid led to a marked decrease in Nox4 mRNA expression. A similar down-regulation of Nox4 mRNA expression was observed by siRNA-mediated knockdown of HDAC3. HDAC inhibition in endothelial cells was associated with enhanced histone acetylation, increased chromatin accessibility in the human Nox4 promoter region, with no significant changes in DNA methylation. In addition, we provided evidence that c-Jun played an important role in controlling Nox4 transcription. Knockdown of c-Jun with siRNA led to a down-regulation of Nox4 mRNA expression. In response to scriptaid treatment, the binding of c-Jun to the Nox4 promoter region was reduced despite the open chromatin structure. In parallel, the binding of RNA polymerase IIa to the Nox4 promoter was significantly inhibited as well, which may explain the reduction in Nox4 transcription. In conclusion, HDAC inhibition decreases Nox4 transcription in human endothelial cells by preventing the binding of transcription factor(s) and polymerase(s) to the Nox4 promoter, most likely because of a hyperacetylation-mediated steric inhibition.

Comparison of effects of ivabradine versus carvedilol in murine model with the Coxsackievirus B3-induced viral myocarditis

BACKGROUND

Elevated heart rate is associated with increased cardiovascular morbidity. The selective I(f) current inhibitor ivabradine reduces heart rate without affecting cardiac contractility, and has been shown to be cardioprotective in the failing heart. Ivabradine also exerts some of its beneficial effects by decreasing cardiac proinflammatory cytokines and inhibiting peroxidants and collagen accumulation in atherosclerosis or congestive heart failure. However, the effects of ivabradine in the setting of acute viral myocarditis and on the cytokines, oxidative stress and cardiomyocyte apoptosis have not been investigated.

METHODOLOGY/PRINCIPAL FINDINGS

The study was designed to compare the effects of ivabradine and carvedilol in acute viral myocarditis. In a coxsackievirus B3 murine myocarditis model (Balb/c), effects of ivabradine and carvedilol (a nonselective β-adrenoceptor antagonist) on myocardial histopathological changes, cardiac function, plasma noradrenaline, cytokine levels, cardiomyocyte apoptosis, malondialdehyde and superoxide dismutase contents were studied. Both ivabradine and carvedilol similarly and significantly reduced heart rate, attenuated myocardial lesions and improved the impairment of left ventricular function. In addition, ivabradine treatment as well as carvedilol treatment showed significant effects on altered myocardial cytokines with a decrease in the amount of plasma noradrenaline. The increased myocardial MCP-1, IL-6, and TNF-α. in the infected mice was significantly attenuated in the ivabradine treatment group. Only carvedilol had significant anti-oxidative and anti-apoptoic effects in coxsackievirus B3-infected mice.

CONCLUSIONS/SIGNIFICANCE

These results show that the protective effects of heart rate reduction with ivabradine and carvedilol observed in the acute phase of coxsackievirus B3 murine myocarditis may be due not only to the heart rate reduction itself but also to the downregulation of inflammatory cytokines.

The biological effects of ivabradine in cardiovascular disease

A large number of studies in healthy and asymptomatic subjects, as well as patients with already established cardiovascular disease (CAD) have demonstrated that heart rate (HR) is a very important and major independent cardiovascular risk factor for prognosis. Lowering heart rate reduces cardiac work, thereby diminishing myocardial oxygen demand. Several experimental studies in animals, including dogs and pigs, have clarified the beneficial effects of ivabradine associated with HR lowering. Ivabradine is a selective inhibitor of the hyperpolarisation activated cyclic-nucleotide-gated funny current (If) involved in pacemaker generation and responsiveness of the sino-atrial node (SAN), which result in HR reduction with no other apparent direct cardiovascular effects. Several studies show that ivabradine substantially and significantly reduces major risks associated with heart failure when added to guideline-based and evidence-based treatment. However the biological effect of ivabradine have yet to be studied. This effects can appear directly on myocardium or on a systemic level improving endothelial function and modulating immune cell migration. Indeed ivabradine is an 'open-channel' blocker of human hyperpolarization-activated cyclic nucleotide gated channels of type-4 (hHCN4), and a 'closed-channel' blocker of mouse HCN1 channels in a dose-dependent manner. At endothelial level ivabradine decreased monocyte chemotactin protein-1 mRNA expression and exerted a potent anti-oxidative effect through reduction of vascular NADPH oxidase activity. Finally, on an immune level, ivabradine inhibits the chemokine-induced migration of CD4-positive lymphocytes. In this review, we discuss the biological effects of ivabradine and highlight its effects on CAD.