Differential effects of heart rate reduction and beta-blockade on left ventricular relaxation during exercise

Physiological effects of ivabradine in heart failure and beyond

Ivabradine is a pharmacologic agent that inhibits the funny current responsible for determining heart rate in the sinoatrial node. Ivabradine's clinical potential has been investigated in the context of heart failure since it is associated with reduced myocardial oxygen demand, enhanced diastolic filling, stroke volume, and coronary perfusion time; however, it is yet to demonstrate definitive mortality benefit. Alternative effects of ivabradine include modulation of the renin-angiotensin-aldosterone system, sympathetic activation, and endothelial function. Here, we review key clinical trials informing the clinical use of ivabradine and explore opportunities for leveraging its potential pleiotropic effects in other diseases, including treatment of hyperadrenergic states and mitigating complications of COVID-19 infection.

Inappropriate sinus tachycardia-induced cardiomyopathy with severe functional mitral regurgitation and successful treatment with ivabradine

Ivabradine increases stroke volume, but does not have a negative impact on blood pressure (BP). Thus, a patient with low BP can benefit from treatment with ivabradine. A 72-year-old Japanese woman with asthma and chronic bronchitis presented with dyspnea. Her heart rate (HR) was 126 beats per minute and an electrocardiogram showed sinus tachycardia. The chest X-ray showed cardiomegaly and pulmonary congestion. A transthoracic echocardiogram (TTE) showed reduced left ventricular ejection function (LVEF) and severe functional mitral regurgitation (MR). We diagnosed her with inappropriate sinus tachycardia (IST) and heart failure (HF) due to tachycardia-induced cardiomyopathy. After resolving the pulmonary congestion with diuretics, we administered a minimum dose of bisoprolol, which resulted in re-exacerbation of the HF. Because IST was persistent, we initiated treatment with ivabradine. As soon as ivabradine was started, the HR decreased, the BP gradually increased, and HF compensation was achieved. Bisoprolol was continued and losartan was started. In summary, we used ivabradine for a patient with tachycardia, low BP, a low LVEF, and severe MR. By optimizing the medical therapy, exercise tolerance improved and she was discharged. The serum brain natriuretic peptide was significantly reduced and TTE showed an improved LVEF and reduced MR. <Learning objective: We managed a patient who had low blood pressure (BP) due to tachycardia, reduced left ventricular ejection function (LVEF), and severe mitral regulation (MR). In this case, ivabradine had a novel effect; specifically, heart rate was reduced and BP increased. As a result of the drug effects, we could prescribe a renin-angiotensin-system inhibitor. With optimal medical therapy, LVEF was restored and functional MR was reduced. In similar cases, ivabradine can be a key drug for medical therapy of heart failure.>.

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.

Heart Rate Reduction Improves Right Ventricular Function and Fibrosis in Pulmonary Hypertension

The potential benefit of heart rate reduction (HRR), independent of β-blockade, on right ventricular (RV) function in pulmonary hypertension (PH) remains undecided. We studied HRR effects on RV fibrosis and function in PH and RV pressure-loading models. Adult rats were randomized to 1) sham controls, 2) monocrotaline (MCT)-induced PH, 3) SU5416 + hypoxia (SUHX)-induced PH, or 4) pulmonary artery banding (PAB). Ivabradine (IVA) (10 mg/kg/d) was administered from 2 weeks after PH induction or PAB. Exercise tolerance, echocardiography, and pressure-volume hemodynamics were obtained at a terminal experiment 3 weeks later. RV myocardial samples were analyzed for putative mechanisms of HRR effects through fibrosis, profibrotic molecular signaling, and Ca⁺⁺ handling. The effects of IVA versus carvedilol on human induced pluripotent stem cell-derived cardiomyocytes beat rate and relaxation properties were evaluated in vitro. Despite unabated severely elevated RV systolic pressures, IVA improved RV systolic and diastolic function, profibrotic signaling, and RV fibrosis in PH/PAB rats. RV systolic-elastance (control, 121 ± 116; MCT, 49 ± 36 vs. MCT+IVA, 120 ± 54; PAB, 70 ± 20 vs. PAB+IVA, 168 ± 76; SUHX, 86 ± 56 vs. SUHX +IVA, 218 ± 111; all P < 0.05), the time constant of RV relaxation, echo indices of RV function, and fibrosis (fibrosis: control, 4.6 ± 1%; MCT, 13.4 ± 6.5 vs. MCT+IVA, 6.7 ± 2.6%; PAB, 11.4 ± 4.5 vs. PAB+IVA, 6.4 ± 5.1%; SUHX, 10 ± 4.6 vs. SUHX+IVA, 3.9 ± 2.2%; all P < 0.001) were improved by IVA versus controls. IVA had a dose-response effect on induced pluripotent stem cell-derived cardiomyocytes beat rate by delaying Ca⁺⁺ loss from the cytoplasm. In experimental PH or RV pressure loading, HRR improves RV fibrosis, function, and exercise endurance independent of β-blockade. The balance between adverse tachycardia and bradycardia requires further study, but judicious HRR may provide a promising strategy to improve RV function in clinical PH.

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.

Left Atrial Phasic Function in Patients with Hypertension and Recurrent Atrial Fibrillation: Gender Differences of the Relationship with Diastolic Dysfunction and Central Aortic Pressure

Aim. To evaluate gender-related differences of left atrial (LA) phasic function and structural remodeling in conjunction with the parameters of left ventricular (LV) diastolic dysfunction and central aortic pressure in patients with hypertension and recurrent atrial fibrillation (AF).

Material and methods. The comparative study included 30 men and 37 women with non-valvular AF, hypertension and LV hypertrophy. Conventional echocardiographic measures were extended with LA measures, including its volume in three phases, LAemptying fraction (LAEF), passive and active ejection fraction. The parameters of central aortic pressure were estimated by applanation tonometry method.

Results. No difference was observed between LA and LV structural parameters in men and women. However, in women LAEF (39 [28;50] vs 50 [42;55]%; p=0.02) and E/E’(9.7 [7.8;12] vs 7.1 [5.6;8.6]; p=0.001) were worse than in men. Active LA ejection fraction was higher in women (31 [21;42] vs 24 [19;31]%; p=0.04), whereas passive one – in men (12 [10;14] vs 33 [23;38]%; p<0.001), respectively. Men and women had comparable heart rate (HR), central and peripheral systolic and diastolic pressure, pulse wave velocity (PWV), but women had higher augmentation index (AI) values [33 [28;39] vs 23 [21;28]%; p<0.001], even adjusted by HR (AI 75) (34 [27;39] vs 26 [20;29]%; p<0.001). Only in men PWV weakly correlated with AI 75 (r=0.44; p=0.02 versus r=-0.11; p=0.51, respectively for men and women; intergroup differences: z=2.26; p=0.012). In a multivariate regression analysis in men LAEF was significantly associated with height, weight, E’, E/E’ and glomerular filtration rate (GFR), whereas in women – with E’ and AI 75.

Conclusion. Patients of different genders with recurrent AF and hypertension have comparable LA structuralremodeling. However, women characterized by a more pronounced decrease in LAEF and impaired LV diastolic function than men. In women as distinct from men LV filling is predominantly due to LA systole. In a multivariate regression analysis in men LAEF was significantly associated with height, weight, E’, E/E’ and GFR, whereas in women – with E’ and AI 75. 

Effects of Ivabradine on Residual Myocardial Ischemia after PCI Evaluated by Stress Echocardiography

Background

Residual angina after PCI is a frequently occurring disease. Ivabradine improves symptoms but its role in patients without left ventricular systolic dysfunction is still unclear. The aim was to quantify the effects of ivabradine in terms of MVO₂ indicators and diastolic function.

Methods

Twenty-eight consecutive patients with residual angina after PCI were randomized to ivabradine 5 mg twice/day (IG) or standard therapy (CG). All patients performed a stress echocardiography at the enrollment and after 30 days. MVO₂ was estimated from double product (DP) and triple product (TP) integrating DP with ejection time (ET). Diastolic function was evaluated determining E and A waves, E' measurements, and E/E' ratio both at rest and at the peak of exercise.

Results

The exercise time was longer in IG 9'49″ ± 48″ vs 8'09″ ± 59″ in CG (p=0.0001), reaching a greater workload (IG 139.3 ± 13.4 vs CG 118.7 ± 19.6 Watts; p=0.003). MVO₂ expressed with DP and TP was significantly higher in IG (DP: IG 24194 ± 2697 vs CG 20358 ± 4671.8, p=0.01; TP: IG 17239 ± 4710 vs CG 12206 ± 4413, p=0.007). At peak exercise, the ET was diminished in IG than CG. The analysis of diastolic function after the exercise revealed an increase of E and A waves, without difference in the E/A ratio. The E' wave was higher in IG than CG, and in the same group, the differences between baseline and peak exercise were greater (∆E'3.14 ± 0.7 vs 2.4 ± 1.13, p=0.047). The E/E' ratio was reduced in patients treated with ivabradine (IG 10.2 ± 2.0 vs CG 7.9 ± 1.6, p=0.002).

Conclusions

Ivabradine seems to produce a significant improvement of ischemic threshold, chronotropic reserve, and diastolic function.

Acute Heart Rate-Dependent Hemodynamic Function of the Heart in the Post-Myocardial Infarction Rat Model: Change Over Time

BACKGROUND

Optimal heart rate (HR) for acute hemodynamic efficiency in heart failure (HF) is unknown.

METHODS

Wistar-Kyoto rats were followed-up for 3 and 7 days, 1 or 2 months after myocardial infarction (MI) or sham operation (ShO) and left ventricle (LV) pressure-volume (PV) loops were obtained at various HRs: baseline 400 beats per minute (bpm), reduced by ivabradine to 320 bpm, increased by atrial pacing to 480 bpm, under normal conditions and after preload increase (PI).

RESULTS

In the ShO group, PI augmented cardiac output (CO) by 55%, 67%, 84% at reduced, baseline, and increased HR, respectively. In post-MI rats, PI augmented CO 3 and 7 days, but not 1 and 2 months after MI. At increased HR, in response to PI, CO increased 3 and 7 days, tended to fall 1 and 2 months after MI; this hemodynamic response was salvaged by HR reduction. Further beneficial effects of HR reduction included reduction of LV end-diastolic pressure, increase of ejection fraction, contractility and relaxation velocity 1 and 2 months after MI.

CONCLUSIONS

In a rat HF model, optimal HR with regard to acute hemodynamic performance is shifted. Whereas in ShO rats increased HR facilitates CO increase induced by PI, in HF rats, such increase reduces CO, and HR reduction has beneficial effects. Thus, besides reducing progression of HF, HR-reducing interventions also offer immediate hemodynamic benefits.

Pharmacological heart rate lowering in patients with a preserved ejection fraction-review of a failing concept

Epidemiological studies have demonstrated that high resting heart rates are associated with increased mortality. Clinical studies in patients with heart failure and reduced ejection fraction have shown that heart rate lowering with beta-blockers and ivabradine improves survival. It is therefore often assumed that heart rate lowering is beneficial in other patients as well. Here, we critically appraise the effects of pharmacological heart rate lowering in patients with both normal and reduced ejection fraction with an emphasis on the effects of pharmacological heart rate lowering in hypertension and heart failure. Emerging evidence from recent clinical trials and meta-analyses suggest that pharmacological heart rate lowering is not beneficial in patients with a normal or preserved ejection fraction. This has just begun to be reflected in some but not all guideline recommendations. The detrimental effects of pharmacological heart rate lowering are due to an increase in central blood pressures, higher left ventricular systolic and diastolic pressures, and increased ventricular wall stress. Therefore, we propose that heart rate lowering per se reproduces the hemodynamic effects of diastolic dysfunction and imposes an increased arterial load on the left ventricle, which combine to increase the risk of heart failure and atrial fibrillation. Pharmacologic heart rate lowering is clearly beneficial in patients with a dilated cardiomyopathy but not in patients with normal chamber dimensions and normal systolic function. These conflicting effects can be explained based on a model that considers the hemodynamic and ventricular structural effects of heart rate changes.

Role of ivabradine and heart rate lowering in chronic heart failure: guideline update

INTRODUCTION

This review summarizes the current management of heart failure (HF) in patients with reduced ejection fraction and the potential role of heart rate lowering agents in select populations, as recommended in the updated guidelines. Areas covered: PubMed was searched for studies that evaluated the role of heart rate lowering or ivabradine in HF management. Expert commentary: Targeting heart rate may offer benefit when added to renin-angiotensin aldosterone antagonists, and beta-blockers. Ivabradine is a heart rate lowering agent that acts on the funny current (I_f) in the sinoatrial node, thereby reducing heart rate without directly affecting cardiac contraction and relaxation. Clinical data from a phase III trial demonstrated that ivabradine reduced the composite end point of cardiovascular death or hospital admission for worsening systolic HF, while maintaining an acceptable safety profile in patients receiving standard of care therapy. These data, in addition to more recently published guidelines, suggest ivabradine as a promising new treatment option for lowering heart rate after optimizing standard therapy in select patients with chronic HF.

Heart failure with preserved ejection fraction: current management and future strategies : Expert opinion on the behalf of the Nucleus of the "Heart Failure Working Group" of the German Society of Cardiology (DKG)

About 50% of all patients suffering from heart failure (HF) exhibit a reduced ejection fraction (EF ≤ 40%), termed HFrEF. The others may be classified into HF with midrange EF (HFmrEF 40-50%) or preserved ejection fraction (HFpEF, EF ≥ 50%). Presentation and pathophysiology of HFpEF is heterogeneous and its management remains a challenge since evidence of therapeutic benefits on outcome is scarce. Up to now, there are no therapies improving survival in patients with HFpEF. Thus, the treatment targets symptom relief, quality of life and reduction of cardiac decompensations by controlling fluid retention and managing risk factors and comorbidities. As such, renin-angiotensin-aldosterone inhibitors, diuretics, calcium channel blockers (CBB) and beta-blockers, diet and exercise recommendations are still important in HFpEF, although these interventions are not proven to reduce mortality in large randomized controlled trials. Recently, numerous new treatment targets have been identified, which are further investigated in studies using, e.g. soluble guanylate cyclase stimulators, inorganic nitrates, the angiotensin receptor neprilysin inhibitor LCZ 696, and SGLT2 inhibitors. In addition, several devices such as the CardioMEMS, interatrial septal devices (IASD), cardiac contractility modulation (CCM), renal denervation, and baroreflex activation therapy (BAT) were investigated in different forms of HFpEF populations and some of them have the potency to offer new hopes for patients suffering from HFpEF. On the basic research field side, lot of new disease-modifying strategies are under development including anti-inflammatory drugs, mitochondrial-targeted antioxidants, new anti-fibrotic and microRNA-guided interventions are under investigation and showed already promising results. This review addresses available data of current best clinical practice and management approaches based on expert experiences and summarizes novel approaches towards HFpEF.

The role of Ivabradine in Diastolic Heart Failure with preserved Ejection Fraction. A Doppler-Echocardiographic study

Background:

Ivabradine (IVA) is effective in patients with coronary artery disease (CAD) or systolic heart failure in sinus rhythm. Its action consists in reducing heart rate (HR) and improving the time of left ventricular (LV) diastolic filling. The aim of this study was to evaluate the effects of IVA added to conventional therapy on patients with diastolic heart failure (DHF) and preserved ejection fraction (HFpEF).

Methods:

We evaluated 25 patients with DHF in the New York Heart Association (NYHA) Class II-III and sinus rhythm. In these, IVA per os (5 mg/twice a day) was added to the conventional medical therapy and given for 12 weeks. Immediately before the beginning of IVA therapy and 3 months later, patients underwent echocardiographic evaluation by two-dimensional (2D) ultrasound and tissue Doppler imaging (TDI). The patterns of diastolic mitral inflow and pulmonary venous flow were recorded using 2D echocardiography, while the diastolic phase of mitral flow was recorded by TDI, from the lateral mitral annulus.

Results:

Three months after the addition of IVA to conventional treatment, HR significantly decreased in comparison to the baseline values. On the contrary, the echocardiographic indexes of LV diastolic dysfunction improved.

Conclusions:

These results testify that the addition of IVA to conventional therapy in patients with HFpEF can improve LV diastolic function evaluated by 2D and tissue Doppler-echocardiographic patterns. These Doppler-echocardiographic results match with the clinical improvement of patients evaluated.

Ivabradine in Patients with Stable Coronary Artery Disease: A Rationale for Use in Addition to and Beyond Percutaneous Coronary Intervention

Heart rate is an established prognostic marker for longevity and is an important contributor in the pathophysiology of various cardiovascular diseases, including ischemic heart disease and heart failure. Most ischemic episodes are triggered by an increase in heart rate, which causes an imbalance between myocardial oxygen delivery and consumption. In addition, increased heart rate is a modifiable risk factor for chronic heart failure. Ivabradine, an inhibitor of I_f ion channels, is an approved second-line anti-ischemic drug for the treatment of angina. Ivabradine has been shown to decrease the risk of hospitalization in patients with chronic heart failure who were previously treated with β-blockers, renin-angiotensin system blockers or mineralocorticoid receptor antagonists. This review describes the rationale for the pathophysiological and clinical use of ivabradine as an anti-ischemic agent in patients with stable coronary disease and highlights its benefits and drawbacks compared with other first- and second-line anti-anginal drugs. The review also highlights the role of ivabradine as a treatment for patients with high-risk coronary artery disease in whom first-line anti-anginal drugs are insufficient or inadequate and percutaneous coronary intervention is contraindicated or revascularization is incomplete or unsuitable.

Improvement of left ventricular filling by ivabradine during chronic hypertension: involvement of contraction-relaxation coupling

Chronic hypertension is associated with left ventricular (LV) hypertrophy and LV diastolic dysfunction with impaired isovolumic relaxation and abnormal LV filling. Increased heart rate (HR) worsens these alterations. We investigated whether the I f channel blocker ivabradine exerts beneficial effects on LV filling dynamic. In this setting, we also evaluated the relationship between LV filling and isovolumic contraction as a consequence of contraction-relaxation coupling. Therefore, hypertension was induced by a continuous infusion of angiotensin II during 28 days in 10 chronically instrumented pigs. LV function was investigated after stopping angiotensin II infusion to offset the changes in loading conditions. In the normal heart, LV relaxation filling, LV early filling, LV peak early filling rate were positively correlated to HR. In contrast, these parameters were significantly reduced at day 28 vs. day 0 (18, 42, and 26 %, respectively) despite the increase in HR (108 ± 6 beats/min vs. 73 ± 2 beats/min, respectively). These abnormalities were corrected by acute administration of ivabradine (1 mg/kg, iv). Ivabradine still exerted these effects when HR was controlled at 150 beats/min by atrial pacing. Interestingly, LV relaxation filling, LV early filling and LV peak early filling were strongly correlated with both isovolumic contraction and relaxation. In conclusion, ivabradine improves LV filling during chronic hypertension. The mechanism involves LV contraction-relaxation coupling through normalization of isovolumic contraction and relaxation as well as HR-independent mechanisms.

Effectiveness of Ivabradine in Treating Stable Angina Pectoris

Many studies show that ivabradine is effective for stable angina.This meta-analysis was performed to determine the effect of treatment duration and control group type on ivabradine efficacy in stable angina pectoris.Relevant articles in the English language in the PUBMED and EMBASE databases and related websites were identified by using the search terms "ivabradine," "angina," "randomized controlled trials," and "Iva." The final search date was November 2, 2015.Articles were included if they were published randomized controlled trials that related to ivabradine treatment of stable angina pectoris.Patients with stable angina pectoris were included.The patients were classified according to treatment duration (<3 vs ≥3 months) or type of control group (placebo vs beta-receptor blocker). Angina outcomes were heart rate at rest or peak, exercise duration, and time to angina onset.Seven articles were selected. There were 3747 patients: 2100 and 1647 were in the ivabradine and control groups, respectively. The ivabradine group had significantly longer exercise duration when they had been treated for at least 3 months, but not when treatment time was less than 3 months. Ivabradine significantly improved time to angina onset regardless of treatment duration. Control group type did not influence the effect of exercise duration (significant) or time to angina onset (significant).Compared with beta-blocker and placebo, ivabradine improved exercise duration and time to onset of angina in patients with stable angina. However, its ability to improve exercise duration only became significant after at least 3 months of treatment.

Ivabradine: A Unique and Intriguing Medication for Treating Cardiovascular Disease

There has been much research linking elevated resting heart rate to cardiovascular morbidity and mortality. Based on these findings, a lower resting heart rate would be of theoretical benefit in patients with cardiovascular disease. From a pathophysiologic perspective, a lower resting heart rate would be of particular benefit in patients with ischemic heart disease and/or heart failure. Although β-blockers and nondihydropyridine calcium channel blockers are effective at lowering heart rate, they have many other pharmacologic effects that may not be desirable in some patients, such as negative inotropy. Ivabradine is a drug designed to lower heart rate without any other demonstrable pharmacologic effects; in other words, a pure heart rate-lowering drug. It functions by blocking the hyperpolarization-activated cyclic nucleotide gated channels (f-channels) specific for the sinoatrial node and disrupting If ion current flow. This effectively prolongs diastolic depolarization and slows firing in the sinoatrial node, which lowers heart rate. The effects of ivabradine are most pronounced at higher heart rates (use-dependence), which is important in minimizing the development of symptomatic bradycardia. Clinical trials have demonstrated ivabradine to be an effective antianginal drug both alone and in combination with β-blocker therapy, although it has not been shown to produce a demonstrable effect on reducing major adverse cardiovascular events. In patients with heart failure, ivabradine has demonstrated many hemodynamic benefits, but its effect on clinical outcomes have been mixed and dependent on baseline heart rate, ie, the drug may be of benefit with higher baseline heart rates, but detrimental with low baseline heart rates. The adverse effects of ivabradine are not uncommon, but are rarely severe and include visual disturbances, bradycardia, and atrial fibrillation. Although ivabradine is a very interesting new agent, its variable benefits in large-scale clinical trials leave its exact place in therapy still somewhat nebulous. Unanswered questions include which patient populations would benefit most from this drug, and which concomitant medications would produce the best clinical outcomes when used with ivabradine.

Treatment of Stable Angina Pectoris With Ivabradine in Everyday Practice: A Pan-Hellenic, Prospective, Noninterventional Study

Introduction

In coronary artery disease (CAD), medical treatment is the main clinical strategy for controlling ischemia and angina symptoms while restoring a satisfactory level of usual activities and improving quality of life (QOL). This study's purpose was to evaluate in CAD patients the antianginal efficacy of 4‐month treatment with ivabradine plus a β‐blocker and to record patient compliance and the effect of treatment on QOL.

Methods

In this noninterventional study, 2403 patients with chronic stable angina were prospectively studied from 245 private cardiology offices. Data were recorded at baseline and at 1 and 4 months after inclusion. Patient quality of life was assessed using the EuroQol 5 dimensions (EQ‐5D) questionnaire.

Results

From baseline to study completion, mean heart rate decreased from 81.5 ± 9.7 bpm to 63.9 ± 6.0 bpm (P <‐0.001), mean number of anginal attacks decreased from 2.0 ± 2.0 times/wk to 0.2 ± 0.6 times/wk (P < 0.001) and nitroglycerin consumption decreased from 1.4 ± 2.0 times/wk to 0.1 ± 0.4 times/wk (P < 0.001). The percentage of patients with Canadian Cardiovascular Society angina class I increased from approximately 38% (baseline) to 84% (study completion; P < 0.001). The reduction in anginal attacks, nitroglycerin consumption, and angina score was correlated with reduction in heart rate (P < 0.001). The mean EQ‐5D visual analogue scale index increased by 16.1 points (P < 0.001), and compliance with treatment was high throughout the trial (96%).

Conclusions

Ivabradine administration on top of optimal individualized dose of β‐blockers is associated with decreased anginal events and with improvement of QOL in CAD patients.

Cardiac and Hemodynamic Benefits: Mode of Action of Ivabradine in Heart Failure

Heart failure has seen a number of therapeutic advances in recent years. Despite this, heart failure is still related to increasing rates of morbidity, repeated hospitalizations, and mortality. Ivabradine is a recent treatment option for heart failure. It has a mode of action that includes reduction in heart rate, and leads to improvement in outcomes related to heart failure mortality and morbidity, as demonstrated by the results of the SHIFT trial in patients with systolic heart failure, functional classes II and III on the New York Heart Association classification, and left ventricular ejection fraction ≤ 35%. These results are intriguing since many heart failure drugs reduce heart rate without such benefits, or with quite different effects, making it more difficult to understand the novelty of ivabradine in this setting. Many of the drugs used in heart failure modify heart rate, but most have other pathophysiological effects beyond their chronotropic action, which affect their efficacy in preventing morbidity and mortality outcomes. For instance, heart rate reduction at rest or exercise with ivabradine prolongs diastolic perfusion time, improves coronary blood flow, and increases exercise capacity. Another major difference is the increase in stroke volume observed with ivabradine, which may underlie its beneficial cardiac effects. Finally, there is mounting evidence from both preclinical and clinical studies that ivabradine has an anti-remodeling effect, improving left ventricular structures and functions. All together, these mechanisms have a positive impact on the prognosis of ivabradine-treated patients with heart failure, making a compelling argument for use of ivabradine in combination with other treatments.

Ivabradine and Bisoprolol on Doppler-derived Coronary Flow Velocity Reserve in Patients with Stable Coronary Artery Disease: Beyond the Heart Rate

Introduction

Coronary flow velocity reserve (CFVR) is an important prognostic marker in patients with stable coronary artery disease (CAD). Beta-blockers and ivabradine have been shown to improve CFVR in patients with stable CAD, but their effects were never compared. The aim of the current study was to compare the effects of bisoprolol and ivabradine on CFVR in patients with stable CAD.

Methods

Patients in sinus rhythm with stable CAD were enrolled in this prospective, randomized, double-blind trial. Patients had to be in a stable condition for at least 15 days before enrollment, on their usual therapy. Patients who were receiving beta-blockers or ivabradine entered a 2-week washout period from these drugs before randomization. Transthoracic Doppler-derived CFVR was assessed in left anterior descending coronary artery, and was calculated as the ratio of hyperemic to baseline diastolic coronary flow velocity (CFV). Hyperemic CFV was obtained using dipyridamole administration using standard protocols. After CFVR assessment, patients were randomized to ivabradine or bisoprolol and entered an up-titration phase, and CFVR was assessed again 1 month after the end of the up-titration phase.

Results

Fifty-nine patients (38 male, 21 female; mean age 69 ± 9 years) were enrolled. Transthoracic Doppler-derived assessment of CFV and CFVR was successfully performed in all patients. Baseline characteristics were similar between the bisoprolol and ivabradine groups. No patient dropped out during the study. At baseline, rest and hyperemic peak CFV as well as CFVR was not significantly different in the ivabradine and bisoprolol groups. After the therapy, resting peak CFV significantly decreased in both the ivabradine and bisoprolol groups, but there was no significant difference between the groups (ivabradine group 20.7 ± 4.6 vs. 22.8 ± 5.2, P < 0.001; bisoprolol group 20.1 ± 4.1 vs. 22.1 ± 4.3, P < 0.001). However, hyperemic peak CFV significantly increased in both groups, but to a greater extent in patients treated with ivabradine (ivabradine: 70.7 ± 9.4 vs. 58.8 ± 9.2, P < 0.001; bisoprolol: 65 ± 8.3 vs. 58.7 ± 8.2, P < 0.001). Accordingly, CFVR significantly increased in both groups (ivabradine 3.52 ± 0.64 vs. 2.67 ± 0.55, P < 0.001; bisoprolol 3.35 ± 0.70 vs. 2.72 ± 0.55, P < 0.001), but it was significantly higher in ivabradine group, despite a similar decrease in heart rate (63 ± 7 vs. 61 ± 6; P not significant).

Conclusion

Ivabradine improves hyperemic peak CFV and CFVR to a greater extent than bisoprolol in patients with stable CAD, despite a similar decrease in heart rate. These data demonstrate that the benefits from ivabradine therapy go beyond the heart rate. This could be due to a different mechanism such as diastolic perfusion time, isovolumic ventricular relaxation, end-diastolic pressure, and collaterals.

Funding

Servier.

Electronic supplementary material

The online version of this article (doi:10.1007/s12325-015-0237-x) contains supplementary material, which is available to authorized users.

The Role of Ivabradine in Cardiac Rehabilitation in Patients With Recent Coronary Artery Bypass Graft

BACKGROUND

Little is known about ivabradine in cardiac rehabilitation in patients with coronary artery bypass graft (CABG).

METHODS

In this prospective, randomized study, suitable patients admitted for cardiac rehabilitation after recent CABG were randomized to ivabradine 5 mg twice a day + standard medical therapy including bisoprolol 1.25 mg once daily (group I-BB, n = 38) or standard medical therapy including bisoprolol 2.5 to 3.75 mg once daily (group BB, n = 43). Patients were evaluated at admission, discharge, and 3 months. The primary end point was improvement in functional status, and other end points were improvement in diastolic function and recovery of systolic function. End points were assessed by distance covered in 6-minute walking test (6MWT), percentage with normal diastolic function, and percentage increase in left ventricular ejection fraction (LVEF).

RESULTS

Cardiac rehabilitation improved functional capacity in both groups. In group BB, distances covered in the 6MWT at admission, discharge, and 3 months were 215 ± 53, 314 ± 32, and 347 ± 42 m, respectively. Corresponding distances in group I-BB were 180 ± 91, 311 ± 58, and 370 ± 55 m. Normal diastolic function was restored in I-BB patients, increasing from 24% at admission to 50% and 79% at discharge and 3 months; in BB patients, it decreased from 23% to 19% and 16%. The LVEF improved in I-BB patients, from 57% ± 3% at admission to 62% ± 4% at discharge and 66% ± 3% at 3 months, while remaining unchanged in BB patients (57% ± 3%, 59% ± 4%, and 59% ± 3%).

CONCLUSION

Adding ivabradine to low-dose bisoprolol during cardiac rehabilitation in patients with CABG improved functional capacity, enhanced recovery of systolic function, and reduced diastolic dysfunction.

[New therapy concepts for heart failure with preserved ejection fraction]

The management of patients with heart failure and preserved ejection fraction (HFpEF) remains challenging and requires an accurate diagnosis. Although currently no convincing therapy that can prolong survival in patients with HFpEF has been established, treatment of fluid retention, heart rate and control of comorbidities are important cornerstones to improve the quality of life and symptoms. In recent years many new therapy targets have been tested for development of successful interventional strategies for HFpEF. Insights into new mechanisms of HFpEF have shown that heart failure is associated with dysregulation of the nitric oxide-cyclic guanosine monophosphate-protein kinase (NO-cGMP-PK) pathway. Two new drugs are currently under investigation to test whether this pathway can be significantly improved by either the neprilysin inhibitor LCZ 696 due to an increase in natriuretic peptides or by the soluble guanylate cyclase stimulator vericiguat, which is also able to increase cGMP. In addition, several preclinical or early phase studies which are currently investigating new mechanisms for matrix, intracellular calcium and energy regulation including the role of microRNAs and new devices are presented and discussed.

Addition of ivabradine to β-blocker improves exercise capacity in systolic heart failure patients in a prospective, open-label study

INTRODUCTION

Difficulties initiating and uptitrating β-blockers due to tolerability can complicate management of heart failure. Among other actions, β-blockers reduce heart rate, which is an important cardiovascular risk factor in heart failure. A new therapeutic strategy is ivabradine, which reduces resting heart rate and is associated with improved outcomes.

METHODS

A 5-month, prospective, open-label, nonrandomized single-center study was performed in 69 patients. All patients had chronic heart failure with left ventricular systolic dysfunction in sinus rhythm, each were initiated on 3.125 mg twice daily (bid) carvedilol alone (n = 36) or 3.125 mg bid carvedilol/5 mg bid ivabradine (n = 33), on top of background therapy including angiotensin-converting enzyme inhibitor (88%), diuretics (86%), antiplatelet agents (91%), and statins (90%). Dosages were uptitrated every 2 weeks to 25 mg bid carvedilol in both groups and 7.5 mg bid ivabradine maximum in the carvedilol/ivabradine group. Uptitration of carvedilol lasted 1.9 ± 0.4 months with carvedilol/ivabradine and 2.8 ± 0.6 months with carvedilol alone (P < 0.05).

RESULTS

The patients receiving ivabradine had lower resting heart rate at 5 months (61.6 ± 3.1 versus 70.2 ± 4.4 bpm, P < 0.05). Adding ivabradine to carvedilol in patients with heart failure was associated with increases in the 6-min walk test and ejection fraction (all P < 0.05). Treatment tolerability was satisfactory. Patients receiving ivabradine and carvedilol had lower heart rates and better exercise capacity than those on carvedilol alone.

CONCLUSION

Adding ivabradine to carvedilol in patients with chronic heart failure improves the uptitration of β-blocker. The results merit further verification in a prospective double-blind study.

Ivabradine improves left ventricular function during chronic hypertension in conscious pigs

During chronic hypertension, increases in heart rate (HR) or adrenergic stimulation are associated with maladaptive left ventricular responses as isovolumic contraction and relaxation durations failed to reduce, impeding filling. We, therefore, investigated the effects of acute selective HR reduction with ivabradine on left ventricular dysfunction during chronic hypertension. Accordingly, chronically instrumented pigs received angiotensin II infusion during 4 weeks to induce chronic hypertension. Left ventricular function was investigated while angiotensin II infusion was stopped. A single intravenous dose of ivabradine was administered at days 0 and 28. Dobutamine infusion was also performed. HR was increased at day 28 versus day 0. Paradoxically, both isovolumic contraction and relaxation times failed to reduce and remained unchanged (57±3 versus 58±3 ms and 74±3 versus 70±3 at day 28 versus day 0, respectively). At day 28, ivabradine significantly reduced HR by 27%. Concomitantly, abnormal ventricular responses were corrected because both isovolumic contraction and relaxation times were significantly reduced while filling time was improved. Similarly at day 28, maladaptive responses of isovolumic contraction and relaxation to dobutamine were no longer observed during HR reduction with ivabradine. Correction of HR reduction with pacing showed that non-HR-related mechanisms also participated to these beneficial effects. In this model of chronic hypertension and left ventricular hypertrophy, acute HR reduction with ivabradine corrects the maladaptive responses of cardiac cycle phases by restoring a normal profile for isovolumic contraction and relaxation both at rest and under adrenergic stimuli, ultimately favoring filling.

Heart failure with preserved ejection fraction

As part of this series devoted to heart failure (HF), we review the epidemiology, diagnosis, pathophysiology, and treatment of HF with preserved ejection fraction (HFpEF). Gaps in knowledge and needed future research are discussed.

Selective and specific inhibition of If with ivabradine for the treatment of coronary artery disease or heart failure

Heart rate is an important contributor in the pathophysiology of both coronary artery disease (CAD) and heart failure (HF). Ivabradine is an anti-anginal and anti-ischaemic agent, which selectively and specifically inhibits the I_f current in the sino-atrial node and provides pure heart rate reduction without altering other cardiac parameters, including conduction, and without directly affecting other haemodynamic parameters. It is approved for the treatment of CAD and HF. This article summarises the pharmacological properties, pharmacokinetics, clinical efficacy and tolerability of ivabradine in the treatment of CAD and HF, and presents evidence demonstrating that the pharmacological and clinical properties and clinical efficacy of ivabradine make it an important therapeutic choice for patients with stable CAD or HF. The positive effect of ivabradine on angina pectoris symptoms and its ability to reduce myocardial ischemia make it an important agent in the management of patients with stable CAD or chronic HF. Further studies are underway to add to the already robust evidence of ivabradine for the prevention of cardiovascular events in patients with CAD but without clinical HF. The SIGNIFY (Study assessInG the morbidity–mortality beNefits of the I_f inhibitor ivabradine in patients with coronarY artery disease) trial includes patients with stable CAD and an LVEF above 40 %, with no clinical sign of HF, and is investigating the long-term effects (over a period of 48 months) of ivabradine in a large study population. So far, this study has included more than 19,000 patients from 51 countries.

Beta-blockers and ivabradine in chronic heart failure: from clinical trials to clinical practice

Beta-blockers have become one of the cornerstones of treatment of patients with heart failure (HF) and depressed left ventricular function, but in clinical practice only 30-35% of patients achieve the therapeutic target dose as established in randomized clinical trials. Moreover, high resting heart rate (HR) has emerged as a simple but relevant risk factor for cardiovascular events, including coronary artery disease and HF; also, it was found to have an independent prognostic value in patients with HF. Evidence that HR could be considered a good parameter to evaluate the quality of treatment in patients with HF has been suggested; of note, many patients maintain a resting HR ≥70 beats per minute despite optimal beta-blocker therapy. In recent years, a new drug able to reduce HR, ivabradine, has been introduced in clinical practice, and its use in the clinical setting of HF patients has been recommended by current European Society of Cardiology (ESC) guidelines. Here we review the evidence of the prognostic role of HR in systolic HF and the potential relationship between HR lowering and the beneficial effects of beta-blockers; we will also analyze the reasons why an appropriate use of these drugs is seldom achieved in clinical practice, and review the evidence for the use of ivabradine in systolic HF in the clinical setting.

Effect of If-channel inhibition on hemodynamic status and exercise tolerance in heart failure with preserved ejection fraction: a randomized trial

OBJECTIVES

The aim of this study was to test the effects of treatment with ivabradine on exercise capacity and left ventricular filling in patients with heart failure with preserved ejection fraction (HFpEF).

BACKGROUND

Because symptoms of HFpEF are typically exertional, optimization of diastolic filling time by controlling heart rate may delay the onset of symptoms.

METHODS

Sixty-one patients with HFpEF were randomly assigned to ivabradine 5 mg twice daily (n = 30) or placebo (n = 31) for 7 days in this double-blind trial. Cardiopulmonary exercise testing with echocardiographic assessment of myocardial function and left ventricular filling were undertaken at rest and after exercise.

RESULTS

The ivabradine group demonstrated significant improvement between baseline and follow-up exercise capacity (4.2 ± 1.8 METs vs. 5.7 ± 1.9 METs, p = 0.001) and peak oxygen uptake (14.0 ± 6.1 ml/min/kg vs. 17.0 ± 3.3 ml/min/kg, p = 0.001), with simultaneous reduction in exercise-induced increase in the ratio of peak early diastolic mitral flow velocity to peak early diastolic mitral annular velocity (3.1 ± 2.7 vs. 1.3 ± 2.0, p = 0.004). Work load-corrected chronotropic response (the difference in heart rate at the same exercise time at the baseline and follow-up tests) showed a slower increase in heart rate during exercise than in the placebo-treated group. Therapy with ivabradine (β = 0.34, p = 0.04) and change with treatment in exertional increase in the ratio of peak early diastolic mitral flow velocity to peak early diastolic mitral annular velocity (β = -0.30, p = 0.02) were independent correlates of increase in exercise capacity, and therapy with ivabradine (β = 0.32, p = 0.007) was independently correlated with increase in peak oxygen uptake.

CONCLUSIONS

In patients with HFpEF, short-term treatment with ivabradine increased exercise capacity, with a contribution from improved left ventricular filling pressure response to exercise as reflected by the ratio of peak early diastolic mitral flow velocity to peak early diastolic mitral annular velocity. Because this patient population is symptomatic on exertion, therapeutic treatments targeting abnormal exercise hemodynamic status may prove useful. (Use of Exercise and Medical Therapies to Improve Cardiac Function Among Patients With Exertional Shortness of Breath Due to Lung Congestion; ACTRN12610001087044).

Impaired left ventricular function in the presence of preserved ejection in chronic hypertensive conscious pigs

Systolic function is often evaluated by measuring ejection fraction and its preservation is often assimilated with the lack of impairment of systolic left ventricular (LV) function. Considering the left ventricle as a muscular pump, we explored LV function during chronic hypertension independently of increased afterload conditions. Fourteen conscious and chronically instrumented pigs received continuous infusion of either angiotensin II (n = 8) or saline (n = 6) during 28 days. Hemodynamic recordings were regularly performed in the presence and 1 h after stopping angiotensin II infusion to evaluate intrinsic LV function. Throughout the protocol, the mean arterial pressure steadily increased by 55 ± 4 mmHg in angiotensin II-treated animals. There were no significant changes in stroke volume, LV fractional shortening or LV wall thickening, indicating the lack of alterations in LV ejection. In contrast, we observed maladaptive changes with (1) the lack of reduction in isovolumic contraction and relaxation durations with heart rate increases, (2) abnormally blunted isovolumic contraction and relaxation responses to dobutamine and (3) a linear correlation between isovolumic contraction and relaxation durations. None of these changes were observed in saline-infused animals. In conclusion, we provide evidence of impaired LV function with concomitant isovolumic contraction and relaxation abnormalities during chronic hypertension while ejection remains preserved and no sign of heart failure is present. The evaluation under unloaded conditions shows intrinsic LV abnormalities.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSION

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

Heart rate: a forgotten link in coronary artery disease?

A considerable body of evidence indicates that elevated resting heart rate is an independent, modifiable risk factor for cardiovascular events and mortality in patients with coronary artery disease. Elevated heart rate can produce adverse effects in several ways. Firstly, myocardial oxygen consumption is increased at high heart rates, but the time available for myocardial perfusion is reduced, increasing the likelihood of myocardial ischemia. Secondly, exposure of the large elastic arteries to cyclical stretch is increased at high heart rates. This effect can increase the rate at which components of the arterial wall deteriorate. Elastin fibers, which have an extremely slow rate of turnover in adult life, might be particularly vulnerable. Thirdly, elevated heart rate can predispose the myocardium to arrhythmias, and favor the development and progression of coronary atherosclerosis, by adversely affecting the balance between systolic and diastolic flow. Comparisons of the effects of the specific heart-rate-lowering drug ivabradine with those of β-blockers could help clarify the pathophysiological effects of elevated heart rate. Effective heart rate control among patients with coronary artery disease is uncommon in clinical practice, representing a missed therapeutic opportunity.

Ivabradine reduces heart rate while preserving metabolic fluxes and energy status of healthy normoxic working hearts

Heart rate reduction (HRR) is an important target in the management of patients with chronic stable angina. Most available drugs for HRR, such as β-blockers, have adverse effects, including on cardiac energy substrate metabolism, a well-recognized determinant of cardiac homeostasis. This study aimed at 1) testing whether HRR by ivabradine (IVA) alters substrate metabolism in the healthy normoxic working heart and 2) comparing the effect of IVA with that of the β-blocker metoprolol (METO). This was assessed using our well-established model of ex vivo mouse heart perfusion in the working mode, which enables concomitant evaluation of myocardial contractility and metabolic fluxes using (13)C-labeled substrates. Hearts were perfused in the absence (controls; n = 10) or presence of IVA (n = 10, 3 μM) with or without atrial pacing to abolish HRR in the IVA group. IVA significantly reduced HR (35 ± 5%) and increased stroke volume (39 ± 9%) while maintaining similar cardiac output, contractility, power, and efficiency. Effects of IVA on HR and stroke volume were reversed by atrial pacing. At the metabolic level, IVA did not impact on substrate selection to citrate formation, rates of glycolysis, or tissue levels of high-energy phosphates. In contrast, METO, at concentrations up to 40 μM, decreased markedly cardiac function (flow: 25 ± 6%; stroke volume: 30 ± 10%; contractility: 31 ± 9%) as well as glycolysis (2.9-fold) but marginally affected HR. Collectively, these results demonstrate that IVA selectively reduces HR while preserving energy substrate metabolism of normoxic healthy working mouse hearts perfused ex vivo, a model that mimics to some extent the denervated transplanted heart. Our results provide the impetus for testing selective HRR by IVA on cardiac substrate metabolism in pathological models.

Safety, efficacy, and indications of beta-adrenergic receptor blockade to reduce heart rate prior to coronary CT angiography

For selected indications, coronary computed tomographic (CT) angiography is an established clinical technology for evaluation in patients suspected of having or known to have coronary artery disease. In coronary CT angiography, image quality is highly dependent on heart rate, with heart rate reduction to less than 60 beats per minute being important for both image quality and radiation dose reduction, especially when single-source CT scanners are used. β-Blockers are the first-line option for short-term reduction of heart rate prior to coronary CT angiography. In recent years, multiple β-blocker administration protocols with oral and/or intravenous application have been proposed. This review article provides an overview of the indications, efficacy, and safety of β-blockade protocols prior to coronary CT angiography with respect to different scanner techniques. Moreover, implications for radiation exposure and left ventricular function analysis are discussed.

Chronic heart rate reduction with ivabradine improves systolic function of the reperfused heart through a dual mechanism involving a direct mechanical effect and a long-term increase in FKBP12/12.6 expression

AIMS

To investigate the adaptations of left ventricular function and calcium handling to chronic heart rate reduction with ivabradine in the reperfused heart.

METHODS AND RESULTS

Rabbits underwent 20 min coronary artery occlusion followed by 3 weeks of reperfusion. Throughout reperfusion, rabbits received ivabradine (10 mg/kg/day) or vehicle (control). Ivabradine reduced heart rate by about 20% and improved both ejection fraction (+35%) and systolic displacement (+26%) after 3 weeks of treatment. Interestingly, this was associated with a two-fold increase expression of FKBP12/12.6. There was no difference in the expressions of phospholamban, SERCA2a, calsequestrin, ryanodine, phospho-ryanodine, and Na(2+)/Ca(2+) exchanger in the two groups. Infarct scar and vascular density were similar in both groups. Administration of a single intravenous bolus of ivabradine (1 mg/kg) in control rabbits at 3 weeks of reperfusion also significantly improved acutely ejection fraction and systolic displacement.

CONCLUSION

Chronic heart rate reduction protects the myocardium against ventricular dysfunction induced by myocardial ischaemia followed by 3 weeks of reperfusion. Beyond pure heart rate reduction, ivabradine improves global and regional systolic function of the reperfused heart through a dual mechanism involving a direct mechanical effect and a long-term adaptation in calcium handling, as supported by the increase in FKBP12/12.6 expression.

Heart failure with preserved ejection fraction in older adults

Age-associated physiologic changes predispose older adults to develop heart failure, even when left ventricular ejection fraction is normal or near normal. Heart failure with a preserved ejection fraction is particularly common in older hypertensive women, and hypertension plays a key role in its pathophysiology. In contrast with heart failure with a reduced ejection fraction, the treatment of heart failure with a preserved ejection fraction has a limited empiric basis, although some basic principles are useful. Ongoing studies provide hope of improving care of these patients.

Postmyocardial infarction remodeling and coronary reserve: effects of ivabradine and beta blockade therapy

We compared the effects of heart rate reduction (HRR) by the hyperpolarization-activated pacemaker current (I(f)) channel inhibitor ivabradine (MI+Iva) and the beta(1)-blocker atenolol (MI+Aten) on ventricular remodeling and perfusion after myocardial infarction (MI) in middle-aged (12 mo) Sprague-Dawley rats. Mean HRR was virtually identical in the two treated groups (19%). Four weeks after coronary artery ligation, maximal myocardial perfusion fell in the MI group but was preserved in infarcted rats treated with either Iva or Aten. However, coronary reserve in the remodeled hearts was preserved only with Iva, since Aten treatment elevated baseline perfusion in response to a higher wall stress. The higher maximal perfusion noted in the two treated groups was not due to arteriogenesis or angiogenesis. Plasma levels of angiotensin (ANG) II and myocardial ANG type 1 (AT(1)) receptor and transforming growth factor (TGF)-beta1 were reduced during the first week of treatment by both Iva and Aten. Moreover, treatment also reduced arteriolar perivascular collagen density. Despite these similar effects of Iva and Aten on vascularity and ANG II, Iva, but not Aten, attenuated the decline in ejection fraction and lowered left ventricular (LV) end-diastolic volume (LVEDV)-to-LV mass ratio, determined by echocardiography. In conclusion, 1) Iva has advantages over Aten in postinfarction therapy that are not due to differential effects of the drugs on heart rate, and 2) age limits growth factor upregulation, angiogenesis, and arteriogenesis in the postinfarcted heart.

Ivabradine induces an increase in ventricular fibrillation threshold during acute myocardial ischemia: an experimental study

BACKGROUND

Tachycardia often facilitates ischemic ventricular fibrillation (VF).

OBJECTIVE

This study assessed the impact of ivabradine (IVA), a selective inhibitor of the cardiac pacemaker If current, on ventricular fibrillation threshold (VFT) during acute myocardial ischemia.

METHODS

The experiments were conducted on a total of 54 domestic pigs. Myocardial ischemia was induced in anesthetized pigs by total 1-minute coronary occlusion at baseline and then on 2 occasions after intravenous administration of saline or 0.5 mg/kg of IVA. VF was triggered by electrical stimuli of increasing intensity at a fixed rate. Heart rate (HR), VFT, monophasic action potential duration, and peak of the time derivative of left ventricular pressure (LV dP/dt max) were monitored on each occasion. The activity of mitochondrial succinodehydrogenase was measured on heart sections.

RESULTS

Compared with controls, IVA induced a 31% reduction in HR, a 2.9-fold increase in VFT, and prevented ischemia-induced monophasic action potential duration shortening (+1 +/- 12 vs. -14 +/- 11 milliseconds) without affecting peak LV dP/dt. This beneficial effect on VFT was mainly due to HR reduction and was accompanied by a significant reduction in the hypoxic area (26% +/- 1% vs. 38% +/- 1%, P < 0.0001).

CONCLUSION

HR reduction and the decrease in myocardial damage induced by IVA protected against primary ischemic VF without altering myocardial contractility.

Genesis and regulation of the heart automaticity

The heart automaticity is a fundamental physiological function in higher organisms. The spontaneous activity is initiated by specialized populations of cardiac cells generating periodical electrical oscillations. The exact cascade of steps initiating the pacemaker cycle in automatic cells has not yet been entirely elucidated. Nevertheless, ion channels and intracellular Ca(2+) signaling are necessary for the proper setting of the pacemaker mechanism. Here, we review the current knowledge on the cellular mechanisms underlying the generation and regulation of cardiac automaticity. We discuss evidence on the functional role of different families of ion channels in cardiac pacemaking and review recent results obtained on genetically engineered mouse strains displaying dysfunction in heart automaticity. Beside ion channels, intracellular Ca(2+) release has been indicated as an important mechanism for promoting automaticity at rest as well as for acceleration of the heart rate under sympathetic nerve input. The potential links between the activity of ion channels and Ca(2+) release will be discussed with the aim to propose an integrated framework of the mechanism of automaticity.