Differential effects of heart rate reduction by atenolol or ivabradine on peripheral endothelial function in type 2 diabetic patients

Update on clinical and experimental management of diabetic cardiomyopathy: addressing current and future therapy

Diabetic cardiomyopathy (DCM) is a severe secondary complication of type 2 diabetes mellitus (T2DM) that is diagnosed as a heart disease occurring in the absence of any previous cardiovascular pathology in diabetic patients. Although it is still lacking an exact definition as it combines aspects of both pathologies - T2DM and heart failure, more evidence comes forward that declares DCM as one complex disease that should be treated separately. It is the ambiguous pathological phenotype, symptoms or biomarkers that makes DCM hard to diagnose and screen for its early onset. This re-view provides an updated look on the novel advances in DCM diagnosis and treatment in the experimental and clinical settings. Management of patients with DCM proposes a challenge by itself and we aim to help navigate and advice clinicians with early screening and pharmacotherapy of DCM.

Endothelial dysfunction: developmental mechanisms and therapeutic strategies

Introduction: Every year the importance of the normal functioning of the endothelial layer of the vascular wall in maintaining the health of the body becomes more and more obvious.

The physiological role of the endothelium: The endothelium is a metabolically active organ actively involved in the regulation of hemostasis, modulation of inflammation, maintenance of hemovascular homeostasis, regulation of angiogenesis, vascular tone, and permeability.

Risk factors for the development of endothelial dysfunction: Currently, insufficient bioavailability of nitric oxide is considered the most significant risk factor for endothelial dysfunction.

Mechanisms of development of endothelial dysfunction: The genesis of endothelial dysfunction is a multifactorial process. Among various complex mechanisms, this review examines oxidative stress, inflammation, hyperglycemia, vitamin D deficiency, dyslipidemia, excess visceral fat, hyperhomocysteinemia, hyperuricemia, as well as primary genetic defect of endotheliocytes, as the most common causes in the population underlying the development of endothelial dysfunction.

Markers of endothelial dysfunction in various diseases: This article discusses the main biomarkers of endothelial dysfunction currently used, as well as promising biomarkers in the future for laboratory diagnosis of this pathology.

Therapeutic strategies: Therapeutic approaches to the endothelium in order to prevent or reduce a degree of damage to the vascular wall are briefly described.

Conclusion: Endothelial dysfunction is a typical pathological process involved in the pathogenesis of many diseases. Thus, pharmacological agents with endothelioprotective properties can provide more therapeutic benefits than a drug without such an effect.

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.

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.

Heart Rate Control during Experimental Sepsis in Mice: Comparison of Ivabradine and β-Blockers

BACKGROUND

Tachycardia is a hallmark of sepsis. An elevated heart rate could impair ventricular filling and increase myocardial oxygen demand. β-Blockers and ivabradine (a selective inhibitor of If channels in the sinoatrial node) are both able to control sinus tachycardia, with the latter drug being devoid of negative inotropic effect. This work aimed at assessing the hemodynamic effects of ivabradine as compared with a β-blocker (atenolol) during murine peritonitis.

METHODS

Ivabradine (3 μg/g), atenolol (3 μg/g), or placebo was administered intraperitoneally 2 h after induction of peritonitis (cecal ligation and puncture) in male C57BL6 mice. The authors used invasive (left ventricular catheterization) and noninvasive (transthoracic echocardiography) monitoring to assess hemodynamics 20 h after surgery, including heart rate, blood pressure, left ventricular systolic, and diastolic function (n = 10 mice/group). The authors also assessed overall mortality 30 and 60 h after surgery in a distinct subset of animals (n = 20 mice/group). Descriptive data are presented as median (25th to 75th percentile).

RESULTS

As compared with placebo (601 beats/min [547 to 612]), ivabradine (447 beats/min [430 to 496]) and atenolol (482 beats/min [412 to 505]) blunted sepsis-induced tachycardia assessed by transthoracic echocardiography in awake animals (P < 0.001 and P = 0.004, respectively). Unlike ivabradine, atenolol reduced cardiac output, systolic blood pressure, and left ventricular systolic function (as assessed by ejection fraction, maximal left ventricular pressure rise, and anterior wall strain rate) as compared with septic mice receiving placebo. There was no difference in survival 60 h after sepsis induction with ivabradine (6 of 20, 30%) or atenolol (7 of 20, 35%), as compared with placebo (5 of 20, 25%; P = 0.224).

CONCLUSIONS

Heart rate control could be similarly achieved by ivabradine or atenolol, with preservation of blood pressure, cardiac output, and left ventricular systolic function with the former drug.

Cardiac autonomic neuropathy: Risk factors, diagnosis and treatment

Cardiac autonomic neuropathy (CAN) is a serious complication of diabetes mellitus (DM) that is strongly associated with approximately five-fold increased risk of cardiovascular mortality. CAN manifests in a spectrum of things, ranging from resting tachycardia and fixed heart rate (HR) to development of "silent" myocardial infarction. Clinical correlates or risk markers for CAN are age, DM duration, glycemic control, hypertension, and dyslipidemia (DLP), development of other microvascular complications. Established risk factors for CAN are poor glycemic control in type 1 DM and a combination of hypertension, DLP, obesity, and unsatisfactory glycemic control in type 2 DM. Symptomatic manifestations of CAN include sinus tachycardia, exercise intolerance, orthostatic hypotension (OH), abnormal blood pressure (BP) regulation, dizziness, presyncope and syncope, intraoperative cardiovascular instability, asymptomatic myocardial ischemia and infarction. Methods of CAN assessment in clinical practice include assessment of symptoms and signs, cardiovascular reflex tests based on HR and BP, short-term electrocardiography (ECG), QT interval prolongation, HR variability (24 h, classic 24 h Holter ECG), ambulatory BP monitoring, HR turbulence, baroreflex sensitivity, muscle sympathetic nerve activity, catecholamine assessment and cardiovascular sympathetic tests, heart sympathetic imaging. Although it is common complication, the significance of CAN has not been fully appreciated and there are no unified treatment algorithms for today. Treatment is based on early diagnosis, life style changes, optimization of glycemic control and management of cardiovascular risk factors. Pathogenetic treatment of CAN includes: Balanced diet and physical activity; optimization of glycemic control; treatment of DLP; antioxidants, first of all α-lipoic acid (ALA), aldose reductase inhibitors, acetyl-L-carnitine; vitamins, first of all fat-soluble vitamin B1; correction of vascular endothelial dysfunction; prevention and treatment of thrombosis; in severe cases-treatment of OH. The promising methods include prescription of prostacyclin analogues, thromboxane A2 blockers and drugs that contribute into strengthening and/or normalization of Na+, K+-ATPase (phosphodiesterase inhibitor), ALA, dihomo-γ-linolenic acid (DGLA), ω-3 polyunsaturated fatty acids (ω-3 PUFAs), and the simultaneous prescription of ALA, ω-3 PUFAs and DGLA, but the future investigations are needed. Development of OH is associated with severe or advanced CAN and prescription of nonpharmacological and pharmacological, in the foreground midodrine and fludrocortisone acetate, treatment methods are necessary.

The effects of linagliptin on endothelial function and global arginine bioavailability ratio in coronary artery disease patients with early diabetes: study protocol for a randomized controlled trial

BACKGROUND

Patients with type 2 diabetes (T2DM) are at increased risk for macrovascular events as well as for microvascular complications. There is evidence that in patients with coronary artery disease (CAD), about 35 % suffer from manifest T2DM. Early glucose-lowering intervention in subjects with T2DM has been demonstrated to be beneficial in terms of cardiovascular risk reduction. But thus far, no data are available regarding investigating the impact of linagliptin treatment in patients with early diabetes on cardiovascular endpoints or surrogate parameters. Therefore, the aim of this study is to investigate the effects of linagliptin in CAD patients with early T2DM on various cardiovascular surrogate measurements including mechanical and biochemical endothelial function assessments.

METHODS/DESIGN

Forty-two subjects with early diabetes and CAD are included in this investigator-driven, randomized, placebo-controlled, double-blind, phase IV, single-center study. Participants will be randomized to receive either linagliptin (5 mg) administered once daily per os or placebo for 12 weeks. Before and after the intervention, evaluation of endothelial function (flow-mediated dilatation and biochemical biomarkers) and a Meal Tolerance Test are performed.

DISCUSSION

Cardiovascular surrogate parameters, such as endothelial function, are able to provide insights into the potential mechanisms of the cardiovascular effects of antihyperglycemic agents. Currently ongoing trials do not specifically focus on early diabetes as a target of intervention and we therefore believe that our study will contribute to a better understanding of the cardiovascular effects of dipeptidylpeptidase-4 (DPP-4) inhibitors in early diabetes.

TRIAL REGISTRATION

NCT02350478 . Registered 26 January 2015. Protocol date/version 24 October 2014/version 2.4 EudraCT number: 2013-000330-35.

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.

The Risk of Atrial Fibrillation With Ivabradine Treatment: A Meta-analysis With Trial Sequential Analysis of More Than 40000 Patients

Recent trials reported that risk of atrial fibrillation (AF) is increased in patients using ivabradine compared with controls. We performed this meta-analysis to investigate the risk of AF association with ivabradine treatment on the basis of data obtained from randomized controlled trials (RCTs). We searched PubMed, EMBASE, Scopus, and the Cochrane Library for RCTs that comprised >100 patients. The incidence of AF was assessed. We obtained data from European Medicines Agency (EMA) scientific reports for the RCTs in which the incidence of AF was not reported. We used trial sequential analysis (TSA) to provide information on when we had reached firm evidence of new AF based on a 15% relative risk increase (RRI) in ivabradine treatment. Three RCTs and 1 EMA overall oral safety set (OOSS) pooled analysis (included 5 RCTs) were included in the meta-analysis (N = 40 437). The incidence of AF was 5.34% in patients using ivabradine and 4.56% in placebo. There was significantly higher incidence of AF (24% RRI) in the ivabradine group when compared with placebo before (RR: 1.24, 95% confidence interval: 1.08-1.42, P = 0.003, I 1980 = 53%) and after excluding OOSS (RR: 1.24, 95% confidence interval: 1.06-1.44, P = 0.008). In the TSA, the cumulative z-curve crossed both the traditional boundary (P = 0.05) and the trial sequential monitoring boundary, indicating firm evidence for ≥15% increase in ivabradine treatment when compared with placebo. Study results indicate that AF is more common in the ivabradine group (24% RRI) than in controls.

Vascular endothelial dysfunction and pharmacological treatment

The endothelium exerts multiple actions involving regulation of vascular permeability and tone, coagulation and fibrinolysis, inflammatory and immunological reactions and cell growth. Alterations of one or more such actions may cause vascular endothelial dysfunction. Different risk factors such as hypercholesterolemia, homocystinemia, hyperglycemia, hypertension, smoking, inflammation, and aging contribute to the development of endothelial dysfunction. Mechanisms underlying endothelial dysfunction are multiple, including impaired endothelium-derived vasodilators, enhanced endothelium-derived vasoconstrictors, over production of reactive oxygen species and reactive nitrogen species, activation of inflammatory and immune reactions, and imbalance of coagulation and fibrinolysis. Endothelial dysfunction occurs in many cardiovascular diseases, which involves different mechanisms, depending on specific risk factors affecting the disease. Among these mechanisms, a reduction in nitric oxide (NO) bioavailability plays a central role in the development of endothelial dysfunction because NO exerts diverse physiological actions, including vasodilation, anti-inflammation, antiplatelet, antiproliferation and antimigration. Experimental and clinical studies have demonstrated that a variety of currently used or investigational drugs, such as angiotensin-converting enzyme inhibitors, angiotensin AT1 receptors blockers, angiotensin-(1-7), antioxidants, beta-blockers, calcium channel blockers, endothelial NO synthase enhancers, phosphodiesterase 5 inhibitors, sphingosine-1-phosphate and statins, exert endothelial protective effects. Due to the difference in mechanisms of action, these drugs need to be used according to specific mechanisms underlying endothelial dysfunction of the disease.

Effect of Ivabradine on Endothelial Function in Patients with Stable Angina Pectoris: Assessment with the Endo-PAT 2000 Device

INTRODUCTION

Ivabradine has opened up new possibilities for treating stable angina and chronic heart failure by lowering heart rate. Ivabradine lowers heart rate by selectively inhibiting the I f current in the sinoatrial node. This study aimed to determine whether the decrease in heart rate achieved with ivabradine was accompanied by hemodynamic changes that might lead to an enhancement of endothelial function.

METHODS

Thirty patients with stable angina pectoris were included in the study. Ivabradine (5 mg bid) was added to the recommended standard treatment. Endothelial function was assessed at baseline and after 3 months of ivabradine therapy, with an Endo-PAT 2000 device (Itamar Medical, Israel). This device was recently developed for the noninvasive assessment for endothelial dysfunction. We evaluated reactive hyperemia index (RHI), which reflects endothelial function, and augmentation index (AI), which provides an indication of arterial stiffness.

RESULTS

The study population consisted of 25 (83.3%) men and five (16.7%) women. The mean age of the patients was 65.4 ± 6.7 years. Twenty-eight (93.3%) patients had a history of myocardial infarction (ST-segment elevation myocardial infarction or non-ST-segment elevation myocardial infarction), 23 (76.6%) had undergone revascularization (percutaneous coronary intervention or coronary artery bypass graft), 16 (53.3%) had type 2 diabetes mellitus, and 29 (96.6%) had arterial hypertension. The mean resting heart rate decreased significantly, from 77 ± 7 bpm at the start of the study to 65 ± 6 bpm after treatment (P < 0.0001). Endothelial function was found to have improved significantly after 3 months of ivabradine therapy. Mean RHI before treatment was 1.54 ± 0.30, suggesting probable endothelial dysfunction, whereas mean RHI at the end of the study was 1.83 ± 0.36 (P < 0.0001). AI also improved significantly on treatment, from 21 ± 20% to 10 ± 21% (P < 0.0001).

CONCLUSION

The addition of ivabradine to the treatment regimen of patients with stable angina pectoris both lowered heart rate and improved endothelial function. However, broader, randomized, double-blind, placebo-controlled clinical trials are required to confirm these findings.

Vascular and Microvascular Endothelial Function in Heart Failure With Preserved Ejection Fraction

BACKGROUND

Assessment of vascular endothelial function lacks consistency, and microvascular endothelial function has been only partly assessed in heart failure with preserved ejection fraction (HFpEF).

METHODS

The study population consisted of 90 patients: 45 had well documented HFpEF, and 45 had hypertension and no history or evidence of heart failure. Patients with hypertension but no heart failure were matched with HFpEF patients for age, sex, and diabetes. They served as control subjects. All patients underwent 2-dimensional Doppler echocardiography and vascular function measurements, including assessment of arterial wave reflections and arterial stiffness, brachial artery flow-mediated dilation (FMD), and forearm cutaneous blood flow with the use of a laser Doppler flow probe at rest and after release of arterial occlusion for 5 minutes.

RESULTS

Brachial artery FMD was lower in HFpEF than in control subjects (median (IQR) 3.6 (0.4-7.4) vs. 7.2 (3.2-17.2)%, P = .001). Forearm cutaneous blood flow at rest was similar in HFpEF and control subjects (P = .68). After release of arterial occlusion, forearm cutaneous peak blood flow was lower in HFpEF than in control subjects (P = .03). Estimated aortic systolic and mean blood pressures were similar in HFpEF and control subjects, whereas pulse pressure and pressure augmentation were greater in HFPEF than in control subjects (both P < .05).

CONCLUSION

Compared with hypertensive control subjects, patients with HFpEF had a depressed endothelial function in the forearm vasculature and microvasculature.

The Effect of Ivabradine on the Heart Rate and Sympathovagal Balance in Postural Tachycardia Syndrome Patients

BACKGROUND

Postural tachycardia syndrome (POTS) is a common form of chronic orthostatic intolerance. The remarkable increase in heart rate (HR) upon standing is the hallmark of this syndrome. Treatment of POTS patients is challenging and includes drugs that slow the HR. Ivabradine is a selective If channel blocker designed to slow the HR, as an anti-anginal agent. In view of its ability to slow the HR, we posited that ivabradine may be an ideal medication for treating POTS patients. This report provides the results of an investigation in which we studied ivabradine's effect on the hemodynamics and sympathovagal balance in POTS patients.

METHODS

An open-label trial, without a placebo control, was performed in eight patients with POTS of two years' standing. Characterization of symptoms, hemodynamics, autonomic function tests, and HR and blood pressure (BP) variability were determined while patients were in a supine position and during a 20-minute head-up tilt before and after a single oral dose of 7.5 mg ivabradine.

RESULTS

Ivabradine slowed the HR of POTS patients at rest by 4±1 bpm (P<0.05). During a 5-minute head-up tilt, the HR decreased from 118±4 bpm to 101±5 bpm (P<0.01). Ivabradine did not affect the BP when patients were at rest in a supine position or in head-up tilt position. Cardiovascular vagal and sympathetic tone, extrapolated from the time and frequency domains of the HR and BP variability, were also not affected by ivabradine.

CONCLUSIONS

Ivabradine is an effective drug for slowing the HR of POTS patients at rest and during tilting, without producing significant adverse effects. Moreover, ivabradine exerts its effects without influencing the sympathovagal balance.

Effects of Celiprolol and Bisoprolol on Blood Pressure, Vascular Stiffness, and Baroreflex Sensitivity

BACKGROUND

We tested the hypothesis that celiprolol and bisoprolol have differential effects on blood pressure (BP), flow-mediated dilation (FMD), and vascular stiffness.

METHODS

We analyzed 102 hypertensives (mean age: 59±14 years) who were being treated other than beta-blockers. They were randomized to receive add-on treatment with either celiprolol 100-200mg (C group) or bisoprolol 2.5-5mg (B group), and followed up for 3 months. In addition to clinic, home, and ambulatory BP monitoring, the FMD, radial augmentation index (AI), brachial-ankle pulse wave velocity (baPWV), urine albumin-to-creatinine ratio, and baroreflex sensitivity (BRS) were measured at baseline and at the end of the study.

RESULTS

Compared to the baseline values, home and 24-hour BP were significantly lowered in the third month in both groups (all Ps < 0.05). Pulse rate (PR) and baPWV were reduced (P < 0.001), and BRS was increased significantly only in the B group (P = 0.02). Radial AI was unchanged in the C group but was significantly increased in the B group (P < 0.001). Central BP was significantly reduced in the C group (P = 0.003) but was unchanged in the B group. FMD was significantly increased in both groups (both P < 0.01).

CONCLUSION

Bisoprolol achieved the greater reduction of PR and improved BRS and vascular stiffness, whereas, celiprolol reduced the central BP level. In treated hypertensive patients, add-on use of celiprolol may be favorable in uncomplicated stage of hypertension. On the other hand, bisoprolol may be useful in hypertensives with cardiac or vascular diseases who have advanced atherosclerotic changes and sympathetic nervous system activation.

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.

New Insight into Effects of β-Blockers on Arterial Functions

The effects of β-blockers on arterial properties are not well investigated. In our recent study, we compared the effects of the two β-blockers celiprolol and bisoprolol on blood pressure, baroreflex sensitivity (BRS), flow-mediated vasodilatation, and vascular stiffness. We found that bisoprolol achieved a greater reduction in the pulse rate and improved BRS and vascular stiffness, whereas celiprolol reduced the central blood pressure level. In this review, the mechanisms of different types of β-blockers and their effects on arteries are discussed, and the appropriate use of β-blockers in hypertensive subjects will be proposed.

Flow-mediated dilation is associated with cardiovascular events in non-valvular atrial fibrillation patients

BACKGROUND

Atrial fibrillation is associated with multiple atherosclerotic risk factors and predisposes to cardiovascular events (CVE). Endothelial dysfunction is associated with atherosclerosis and independently predicts CVE. The aim of the study was to evaluate the association between endothelial dysfunction, as assessed by flow-mediated dilation (FMD), and CVE in AF patients.

METHODS

We prospectively measured FMD in 514 non-valvular AF patients on anticoagulant treatment with vitamin K antagonists. Patients were followed-up for a mean time of 23.5 months. The main composite outcome of the study was the occurrence of stroke/TIA, myocardial infarction, urgent revascularization and cardiovascular death.

RESULTS

Median value of FMD was 4.6% [IQR 1.46-8.00]. A CVE occurred in 44 patients (8.56%):non-fatal myocardial infarction (MI) in 7, fatal MI in 2, stent/coronary artery by-pass graft (CABG) in 10, ischemic non-fatal stroke in 10, fatal stroke in 3, transient ischemic attack (TIA) in 1, and cardiovascular death in 11 patients. Patients who experienced a CVE showed significantly reduced FMD compared to those who did not (3.06% [IQR 0.00-6.00] vs 4.67% [IQR 1.58-8.22], p=0.027). During a mean follow-up of 23.5 months, the rate of CVE was significantly higher in subjects with FMD below median (<4.6%) than in those with FMD above median (27 vs 17, log-rank test p=0.006). COX analysis demonstrated that low FMD (below median) (HR: 2.20, CI 95%:1.13-4.28, p=0.020), age (HR: 1.08, CI 95%: 1.03-1.12, p<0.001), smoking (HR: 4.15, CI 95%: 1.63-10.6, p=0.003) and history of stroke/TIA (HR: 2.38, CI 95%: 1.13-5.04, p=0.023) independently predicted CVE.

CONCLUSIONS

In AF patients low FMD is associated with increased risk of CVE suggesting that impaired artery dilatation predisposes to atherosclerotic complications.

Atrial fibrillation associated with ivabradine treatment: meta-analysis of randomised controlled trials

Objective

To quantify any risk of atrial fibrillation (AF) associated with ivabradine treatment by meta-analysis of clinical trial data.

Methods

Medline, Embase, Web of Knowledge and the Cochrane central register of controlled trials were searched for double-blinded randomised controlled trials of ivabradine with a minimum follow-up period of 4 weeks. For studies where AF data were unpublished, safety data were obtained from the European Medicines Agency (EMeA) website and personal communications. Studies were appraised for risk of bias using components recommended by the Cochrane Collaboration. Meta-analyses were performed of relative risk of AF and absolute risk difference of AF per year of treatment. The main outcome measure was incident AF during the follow-up period.

Results

AF data were available from 11 studies: one from the published report, six from the EMeA and four from personal communications. Ivabradine treatment was associated with a relative risk of AF of 1.15 (95% CI 1.07 to 1.24, p=0.0027) among 21 571 patients in the meta-analysis. From this we estimated that the number needed to harm for ivabradine would be 208 (95% CI 122 to 667) per year of treatment.

Conclusions

AF is a substantially more common side effect of ivabradine treatment than one patient in 10 000, the risk presently reported in the product literature. The incidence of AF has not routinely been reported in clinical trials of ivabradine.

Effect of ivabradine-induced heart rate reduction on flow-mediated dilation measured with high-sensitivity ultrasound in patients with stable coronary heart disease

Background

Experimental data suggests that exclusive heart rate reduction with ivabradine is associated with the amelioration of the endothelial function. Since it is presently unknown whether this also applies to humans, the aim of this pilot study was to investigate whether heart rate reduction with ivabradine modulates the endothelial function in humans with an established coronary heart disease.

Methods

Using high-sensitivity ultrasound, we analysed the flow-mediated (FMD) and nitro-mediated dilation (NMD) of the brachial artery in 25 patients (62.9 ± 8.4 years) with a stable coronary heart disease and a resting heart rate of ≥70 beats per minute (bpm). To assess acute effects, measurements were performed before and 4 hours after the first intake of ivabradine 7.5 mg. Sustained effects of an ivabradine therapy (5 mg to 7.5 mg twice daily) were investigated after 4 weeks.

Results

We found a significant decrease in heart rate, both 4 hours after the intake of 7.5 mg of ivabradine (median -8 [interquartile range (IQR) -14 to -4] bpm) and after 4 weeks of twice daily intake (median -10 [IQR-17 to -5] bpm) (p < 0.05). However, the FMD did not change significantly: neither after first dose of ivabradine nor after sustained therapy (baseline FMD: median 5.0 [IQR 2.4 to 7.9]%; FMD 4 hours after 7.5 mg of ivabradine: median 4.9 [IQR 2.7 to 9.8]%; FMD after 4 weeks of ivabradine therapy: median 6.1 [IQR 4.3 to 8.2]%). No significant changes of the NMD were observed. In regression analysis, the heart rate and FMD did not correlated, irrespective of the ivabradine intake (r² = 0.086).

Conclusion

In conclusion, in our study heart rate reduction through ivabradine does not improve the endothelial function in patients with a stable coronary heart disease. Moreover, we found no correlation between the heart rate and the endothelial function.

An evaluation of the pharmacokinetics and pharmacodynamics of ivabradine for the treatment of heart failure

INTRODUCTION

Ivabradine is a new heart-rate-lowering drug; the aim of this review was to analyze its role in heart failure (HF).

AREAS COVERED

This systematic review on the role of ivabradine in HF is based on material searched and obtained through Pubmed and Medline up to September 2013.

EXPERT OPINION

Heart rate (HR) is a risk factor in patients with HF, and its reduction is considered an important goal of therapy. The BEAUTIFUL trial demonstrated the benefits of ivabradine on prognosis (only on ischemic endpoints) in patients with coronary artery disease (CAD) and left ventricular systolic dysfunction (LVSD) and HR ≥ 60 bpm. In the SHIFT trial, which enrolled patients with LVSD, HF and HR ≥ 70 bpm, ivabradine administration (on top of guideline-based therapy, including β-blockers [BB]) was associated with a reduction of cardiovascular death and hospitalizations for HF, but BB were underutilized. Further studies are needed to test the efficacy of ivabradine in CAD patients with high HR and to shed light on the comparison between ivabradine and a more aggressive therapy with higher doses of BB in HF patients.