Ivabradine in heart failure--no paradigm SHIFT…yet

Viral Myocarditis-Incidence, Diagnosis and Management

Viral myocarditis has an incidence rate of 10 to 22 per 100,000 individuals. The presentation pattern of viral myocarditis can range from nonspecific symptoms of fatigue and shortness of breath to more aggressive symptoms that mimic acute coronary syndrome. After the initial acute phase presentation of viral myocarditis, the virus may be cleared, resulting in full clinical recovery; the viral infection may persist; or the viral infection may lead to a persistent autoimmune-mediated inflammatory process with continuing symptoms of heart failure. As a result of these 3 possibilities, the diagnosis, prognosis, and treatment of viral myocarditis can be extremely unpredictable and challenging for the clinician. Herein, the incidence, etiology, definition and classification, clinical manifestation, diagnosis, pathogenesis, prognosis, and treatment of viral myocarditis are reviewed, and how acute clinical care teams might differentiate between viral myocarditis and other acute cardiac conditions is discussed.

Association between systolic ejection time and outcomes in heart failure by ejection fraction

AIMS

Worsening heart failure (HF) is associated with shorter left ventricular systolic ejection time (SET), but there are limited data describing the relationship between SET and clinical outcomes. Thus, the objective was to describe the association between SET and clinical outcomes in an ambulatory HF population irrespective of ejection fraction (EF).

METHODS AND RESULTS

We identified ambulatory patients with HF with reduced EF (HFrEF) and HF with preserved EF (HFpEF) who had an outpatient transthoracic echocardiogram performed between August 2008 and July 2010 at a tertiary referral centre. Multivariable logistic regression was used to evaluate the association between SET and 1-year outcomes. A total of 545 HF patients (171 HFrEF, 374 HFpEF) met eligibility criteria. Compared with HFpEF, HFrEF patients were younger [median age 60 years (25th-75th percentiles 50-69) vs. 64 years (25th-75th percentiles 53-74], with fewer females (30% vs. 56%) and a similar percentage of African Americans (36% vs. 35%). Median (25th-75th percentiles) EF with HFrEF was 30% (25-35%) and with HFpEF was 54% (48-58%). Median SET was shorter (280 ms vs. 315 ms, P < 0.001), median pre-ejection period was longer (114 ms vs. 89 ms, P < 0.001), and median relaxation time was shorter (78.7 ms vs. 93.3 ms, P < 0.001) among patients with HFrEF vs. HFpEF. Death or HF hospitalization occurred in 26.9% (n = 46) HFrEF and 11.8% (n = 44) HFpEF patients. After adjustment, longer SET was associated with lower odds of the composite of death or HF hospitalization at 1 year among HFrEF but not HFpEF patients.

CONCLUSION

Longer SET is independently associated with improved outcomes among HFrEF patients but not HFpEF patients, supporting a potential role for normalizing SET as a therapeutic strategy with systolic dysfunction.

Medication dosing for heart failure with reduced ejection fraction - opportunities and challenges

Multiple drug classes have shown incremental benefits in heart failure with reduced ejection fraction. Most of these trials were designed to achieve specific doses of the investigational agent. Clinical practice guidelines recommend using the same target dosing of therapies, as tolerated. However, with the increasing number of available therapies, clinicians face the challenge of simultaneously using several drugs, achieving target doses, and managing side effects that are often overlapping. Blood pressure, renal function, hyperkalaemia, and other factors may impede achieving target doses of all medications, leaving clinicians with dilemmas as to how to sequence and dose these various classes of drugs. The guideline-directed eligibility for certain drugs and devices requires stability on maximally tolerated doses of background therapies. However, significant variability exists in dosing achieved in clinical practice. We discuss the existing background data regarding the doses of heart failure medications in clinical trials and in practice, and provide recommendations on how to navigate this complex therapeutic decision-making.

Limited role and benefit of ivabradine in the treatment of angina and heart failure with reduced ejection fraction

Ivabradine is an original drug that has been approved in two indications (systolic heart failure and angina). The aim of this short review is to draw the attention of clinician prescribers to the evidence base of ivabradine. Three large randomized trials testing ivabradine versus placebo have been performed. The BEAUTIFUL and SIGNIFY trials were in fact negative in the treatment of angina while the SHIFT trial found a marginal benefit of ivabradine over placebo in the treatment of heart failure. These important results are put into perspective in order to improve the assessment of risk-cost/benefit balances when ivabradine is considered. Ideally, a further clinical trial investigating the use of ivabradine in heart failure should be carried out with optimal treatment of the patient population in order to identify the subgroup of patients who respond to ivabradine.

New Novel Treatment Approaches for Heart Failure With Reduced Ejection Fraction

Despite availability of standardized drug therapies with proven beneficial outcomes, heart failure is associated with poor quality of life, increased hospital readmission, and high mortality rate. In the recent years, comprehensive understanding of the pathophysiological mechanisms of heart failure has led to the development and approval of 2 new pharmacological agents, sacubitril–valsartan and ivabradine. These agents are currently approved for use in heart failure with reduced ejection fraction (HFrEF) and present as novel approaches to further improve prognosis and outcomes in patients with HF. They offer alternative treatment options for patients who are intolerant or continue to be symptomatic despite utilization of standard HF drug therapies at optimally tolerated dosages. A review of these 2 novel agents in HFrEF, including information on pivotal trials that led to its approval and its place in therapy for HFrEF, is presented.

Heart rate and heart failure

PURPOSE OF REVIEW

Resting heart rate has long been thought to be a risk factor in cardiovascular disease and a prognostic factor in heart failure. β-Blockers were originally used in heart failure for their heart rate control abilities. However, they also have negative inotropic effects contributing to their overall benefit. The role of isolated heart rate modification is unclear in left ventricular systolic dysfunction.

RECENT FINDINGS

Two recent studies looked at the heart rate-lowering effects of the If, or funny current inhibitor ivabradine and its potential role in heart failure therapy. At the doses chosen for the studies, ivabradine is presumed to have only effects on heart rate with no other cardiotropic effects. Thus, the cardiovascular outcome benefits are presumed to be secondary to heart rate modification.

SUMMARY

The two recent trials showed both heart rate and cardiovascular events to be significantly lower in the ivabradine-treated group of patients with left ventricular systolic dysfunction and initial heart rate at least 70 beats/min. However, neither of these trials proved causality. Hence, the link between heart rate and improved cardiovascular outcomes still remains muddled.

Present and future pharmacotherapeutic agents in heart failure: an evolving paradigm

Many conditions culminate in heart failure (HF), a multi‐organ systemic syndrome with an intrinsically poor prognosis. Pharmacotherapeutic agents that correct neurohormonal dysregulation and haemodynamic instability have occupied the forefront of developments within the treatment of HF in the past. Indeed, multiple trials aimed to validate these agents in the 1980s and early 1990s, resulting in a large and robust evidence‐base supporting their use clinically. An established treatment paradigm now exists for the treatment of HF with reduced ejection fraction (HFrEF), but there have been very few notable developments in recent years. HF remains a significant health concern with an increasing incidence as the population ages. We may indeed be entering the surgical era for HF treatment, but these therapies remain expensive and inaccessible to many. Newer pharmacotherapeutic agents are slowly emerging, many targeting alternative therapeutic pathways, but with mixed results. Metabolic modulation and manipulation of the nitrate/nitrite/nitric oxide pathway have shown promise and could provide the answers to fill the therapeutic gap between medical interventions and surgery, but further definitive trials are warranted. We review the significant evidence base behind the current medical treatments for HFrEF, the physiology of metabolic impairment in HF, and discuss two promising novel agents, perhexiline and nitrite.

Evaluation of the SIGNIFY trial

A reduction in the heart rate has been thought to be beneficial in coronary artery disease. The study assessing the morbidity-mortality Benefits of the If Inhibitor, Ivabradine, in patients with coronary artery disease (SIGNIFY) tested this hypothesis. It specifically evaluated the effects of ivabradine, administered at the dosage of 5 - 10 mg/bid in addition to current drug treatment, on cardiovascular outcome in 19102 patients with heart rate ≥ 70 bpm in normal sinus rhythm and stable coronary artery disease without heart failure. The primary endpoint of the trial, whose follow-up averaged for 2.3 years, was a composite of death from cardiovascular causes or nonfatal myocardial infarction whereas the secondary endpoint was represented by the primary endpoint plus total mortality. The incidence of the primary endpoint was at the study end similar in the ivabradine-treated and in the placebo-treated group (6.8 vs 6.4%, p = NS). Superimposable was also the incidence of death for cardiovascular events and for nonfatal myocardial infarction. However, in the 12049 patients with angina class II or higher ivabradine significantly increased the incidence of primary endpoint as compared to placebo (7.6 vs 6.5%, p < 0.02). This was associated with a significantly greater incidence of bradycardia, atrial fibrillation and Q-T prolongation. Taken together the results of the SIGNIFY do not support the clinical benefits of ivabradine in patients with stable coronary artery disease.

HCN channels--modulators of cardiac and neuronal excitability

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels comprise a family of cation channels activated by hyperpolarized membrane potentials and stimulated by intracellular cyclic nucleotides. The four members of this family, HCN1-4, show distinct biophysical properties which are most evident in the kinetics of activation and deactivation, the sensitivity towards cyclic nucleotides and the modulation by tyrosine phosphorylation. The four isoforms are differentially expressed in various excitable tissues. This review will mainly focus on recent insights into the functional role of the channels apart from their classic role as pacemakers. The importance of HCN channels in the cardiac ventricle and ventricular hypertrophy will be discussed. In addition, their functional significance in the peripheral nervous system and nociception will be examined. The data, which are mainly derived from studies using transgenic mice, suggest that HCN channels contribute significantly to cellular excitability in these tissues. Remarkably, the impact of the channels is clearly more pronounced in pathophysiological states including ventricular hypertrophy as well as neural inflammation and neuropathy suggesting that HCN channels may constitute promising drug targets in the treatment of these conditions. This perspective as well as the current therapeutic use of HCN blockers will also be addressed.

Ivabradine: a new rate-limiting therapy for coronary artery disease and heart failure

Ivabradine is a new bradycardic agent acting on the I f channels of sinoatrial nodal cells to decrease the rate of diastolic depolarization and thus heart rate. The benefit of ivabradine over other negatively chronotropic agents is its absence of negative inotropy. Effective management of coronary artery disease, in terms of reducing morbidity and mortality, is reliant on controlling heart rate. Ivabradine has been shown to safely and effectively reduce heart rate without compromising cardiac function in patients with coronary artery disease and more recently in patients with heart failure and raised heart rate. Furthermore, ivabradine has been shown to have a favourable side-effect profile compared with alternative bradycardic agents. This article reviews the evidence for ivabradine in coronary artery disease and heart failure and compares its safety with alternative bradycardic agents for these conditions.

Ivabradine, coronary artery disease, and heart failure: beyond rhythm control

Elevated heart rate could negatively influence cardiovascular risk in the general population. It can induce and promote the atherosclerotic process by means of several mechanisms involving endothelial shear stress and biochemical activities. Furthermore, elevated heart rate can directly increase heart ischemic conditions because of its skill in unbalancing demand/supply of oxygen and decreasing the diastolic period. Thus, many pharmacological treatments have been proposed in order to reduce heart rate and ameliorate the cardiovascular risk profile of individuals, especially those suffering from coronary artery diseases (CAD) and chronic heart failure (CHF). Ivabradine is the first pure heart rate reductive drug approved and currently used in humans, created in order to selectively reduce sinus node function and to overcome the many side effects of similar pharmacological tools (ie, β-blockers or calcium channel antagonists). The aim of our review is to evaluate the role and the safety of this molecule on CAD and CHF therapeutic strategies.

Heart rate: a prognostic factor and therapeutic target in chronic heart failure. The distinct roles of drugs with heart rate-lowering properties

Heart rate not only predicts outcome but may also be a therapeutic target in patients with chronic heart failure. Several classes of pharmacological agents can be used to modulate heart rate, including beta-blockers, ivabradine, digoxin, amiodarone, and verapamil. Choice of agent will depend on heart rhythm, co-morbidities, and disease phenotype. Beneficial and harmful interactions may also exist. The aim of this paper is to summarize the current body of knowledge regarding the relevance of heart rate as a prognostic factor (risk marker) and particularly as a therapeutic target (risk factor) in patients with chronic heart failure, with a special focus on ivabradine, a novel agent that is currently the only available purely bradycardic agent.

Do general practitioners follow treatment recommendations from guidelines in their decisions on heart failure management? A cross-sectional study

OBJECTIVE

To investigate whether general practitioners (GPs) follow treatment recommendations from clinical practice guidelines in their decisions on the management of heart failure patients, and assess whether doctors' characteristics are related to their decisions.

DESIGN

Cross-sectional vignette study.

SETTING

Continuing Medical Education meeting.

PARTICIPANTS

451 Dutch GPs.

MAIN OUTCOME MEASURES

Answers to four multiple-choice treatment decisions in clinical vignettes of a patient with heart failure and a reduced ejection fraction. With univariable and multivariable regression analyses, respondent characteristics were related to optimal treatment decisions.

RESULTS

Of the 451 GPs, none took four optimal decisions: 7% considered stopping statin treatment, 36% initiated β-blocker treatment at a low-dose and 4% doubled the β-blocker in the up-titration phase. Finally, for our vignette patient now also suffering from chronic obstructive pulmonary disease, 45% of the GPs continued β-blocker therapy even when they considered prescribing a long-acting β2-agonist. While the relation between respondent characteristics and each decision was very different, none was independently associated with all four decisions. Giving priority to evidence-based medicine was independently related to stopping statin treatment and doubling the β-blocker in the up-titration phase.

CONCLUSIONS

GPs seem not to follow treatment recommendations from clinical practice guidelines in their decisions on the management of heart failure patients. The recommendations from guidelines may appear counterintuitive when statin treatment needs to be stopped when a patient feels comfortable, or when a β-blocker should be up-titrated in patients who experience more symptoms. Giving priority to evidence-based medicine is possibly positively related to difficult treatment decisions.

Molecular and functional evidence of HCN4 and caveolin-3 interaction during cardiomyocyte differentiation from human embryonic stem cells

Maturation of human embryonic stem cell-derived cardiomyocytes (hESC-CM) is accompanied by changes in ion channel expression, with relevant electrophysiological consequences. In rodent CM, the properties of hyperpolarization-activated cyclic nucleotide-gated channel (HCN)4, a major f-channel isoform, depends on the association with caveolin-3 (Cav3). To date, no information exists on changes in Cav3 expression and its associative relationship with HCN4 upon hESC-CM maturation. We hypothesize that Cav3 expression and its compartmentalization with HCN4 channels during hESC-CM maturation accounts for the progression of f-current properties toward adult phenotypes. To address this, hESC were differentiated into spontaneously beating CM and examined at ∼30, ∼60, and ∼110 days of differentiation. Human adult and fetal CM served as references. HCN4 and Cav3 expression and localization were analyzed by real time PCR and immunocyto/histochemistry. F-current was measured in patch-clamped single cells. HCN4 and Cav3 colocalize in adult human atrial and ventricular CM, but not in fetal CM. Proteins and mRNA for Cav3 were not detected in undifferentiated hESC, but expression increased during hESC-CM maturation. At 110 days, HCN4 appeared to be colocalized with Cav3. Voltage-dependent activation of the f-current was significantly more positive in fetal CM and 60-day hESC-CM (midpoint activation, V1/2, ∼ -82 mV) than in 110-day hESC-CM or adult CM (V1/2∼-100 mV). In the latter cells, caveolae disruption reversed voltage dependence toward a more positive or an immature phenotype, with V1/2 at -75 mV, while in fetal CM voltage dependence was not affected. Our data show, for the first time, a developmental change in HCN4-Cav3 association in hESC-CM. Cav3 expression and its association with ionic channels likely represent a crucial step of cardiac maturation.

Heart failure

Despite major improvements in the treatment of virtually all cardiac disorders, heart failure (HF) is an exception, in that its prevalence is rising, and only small prolongations in survival are occurring. An increasing fraction, especially older women with diabetes, obesity, and atrial fibrillation exhibit HF with preserved systolic function. Several pathogenetic mechanisms appear to be operative in HF. These include increased hemodynamic overload, ischemia-related dysfunction, ventricular remodeling, excessive neurohumoral stimulation, abnormal myocyte calcium cycling, excessive or inadequate proliferation of the extracellular matrix, accelerated apoptosis, and genetic mutations. Biomarkers released as a consequence of myocardial stretch, imbalance between formation and breakdown of extracellular matrix, inflammation, and renal failure are useful in the identification of the pathogenetic mechanism and, when used in combination, may become helpful in estimating prognosis and selecting appropriate therapy. Promising new therapies that are now undergoing intensive investigation include an angiotensin receptor neprilysin inhibitor, a naturally-occurring vasodilator peptide, a myofilament sensitizer and several drugs that enhance Ca++ uptake by the sarcoplasmic reticulum. Cell therapy, using autologous bone marrow and cardiac progenitor cells, appears to be promising, as does gene therapy. Chronic left ventricular assistance with continuous flow pumps is being applied more frequently and successfully as destination therapy, as a bridge to transplantation, and even as a bridge to recovery and explantation. While many of these therapies will improve the care of patients with HF, significant reductions in prevalence will require vigorous, multifaceted, preventive approaches.

HCN channels in the heart: lessons from mouse mutants

Hyperpolarization-activated cation channels generate the I(f) current in the heart. In the sino-atrial node (SAN), I(f) is thought to play an essential role in setting the heart rate and mediating its autonomic control. This review focuses on the role of I(f) in pacemaking and non-pacemaking cardiomyocytes and the resulting therapeutic implications. HCN4 represents the principal isoform underlying sino-atrial I(f) , but other isoforms may also be of importance. To examine the functional role of cardiac channels, several mouse mutants, most of them targeting HCN4, have been generated by different groups. Unexpectedly, these lines display greatly different and as yet unexplained phenotypes. We provide an overview about these HCN mutants and suggest an interpretation of the functional significance of I(f) in the SAN in light of these studies. HCN channels are also present in ventricular myocytes, and an up-regulation of I(f) in the hypertrophic and failing heart may contribute to arrhythmogenesis. Inhibition of I(f) by HCN channel blockers is a novel approach in the treatment of cardiac disorders, and ivabradine is approved for treatment of stable angina pectoris. Remarkably, a recent clinical trial assessing this substance in heart failure showed a significantly improved outcome. The mechanism underlying this beneficial effect is not yet clear and might lie beyond heart rate slowing. Thus, the growing knowledge about cardiac HCN channels will undoubtedly promote the development of the promising class of HCN channel blockers.

Long-term treatment with ivabradine in post-myocardial infarcted rats counteracts f-channel overexpression

BACKGROUND AND PURPOSE

Recent clinical data suggest beneficial effects of ivabradine, a specific heart rate (HR)-lowering drug, in heart failure patients. However, the mechanisms responsible for these effects have not been completely clarified. Thus, we investigated functional/molecular changes in I(f), the specific target of ivabradine, in the failing atrial and ventricular myocytes where this current is up-regulated as a consequence of maladaptive remodelling.

EXPERIMENTAL APPROACH

We investigated the effects of ivabradine (IVA; 10 mg·kg(-1) ·day(-1) for 90 days) on electrophysiological remodelling in left atrial (LA), left ventricular (LV) and right ventricular (RV) myocytes from post-mycardial infarcted (MI) rats, with sham-operated (sham or sham + IVA) rats as controls. I(f) current was measured by patch-clamp; hyperpolarization-activated cyclic nucleotide-gated (HCN) channel isoforms and microRNA (miRNA-1 and miR-133) expression were evaluated by reverse transcription quantitative PCR.

KEY RESULTS

Maximal specific conductance of I(f) was increased in MI, versus sham, in LV (P < 0.01) and LA myocytes (P < 0.05). Ivabradine reduced HR in both MI and sham rats (P < 0.05). In MI + IVA, I(f) overexpression was attenuated and HCN4 transcription reduced by 66% and 54% in LV and RV tissue, respectively, versus MI rats (all P < 0.05). miR-1 and miR-133, which modulate post-transcriptional expression of HCN2 and HCN4 genes, were significantly increased in myocytes from MI + IVA.

CONCLUSION AND IMPLICATION

The beneficial effects of ivabradine may be due to the reversal of electrophysiological cardiac remodelling in post-MI rats by reduction of functional overexpression of HCN channels. This is attributable to transcriptional and post-transcriptional mechanisms.

Implications of geographical variation on clinical outcomes of cardiovascular trials

Cardiovascular clinical trials are increasingly conducted globally as a means to reduce costs, expedite timelines, provide broad applicability, and satisfy regulatory authorities. Potential problems with trial globalization include regional differences in patient characteristics, medical practice patterns, and health policies which may influence outcomes and limit generalizability. Moreover, concerns have been raised about ethical misconduct and unsatisfactory quality oversight in regions with less trial experience and infrastructure. This article reviews geographical differences in cardiovascular trials in heart failure, acute coronary syndromes, hypertension and atrial fibrillation. It also explores potential explanations for these differences and methods to standardize the presentation of trial results. This review is based on discussions between basic scientists and clinical trialists at the 8th Global Cardio Vascular Clinical Trialists Forum 2011 in Paris, France, from December 2 to 3.

Ventricular HCN channels decrease the repolarization reserve in the hypertrophic heart

AIMS

Cardiac hypertrophy is accompanied by reprogramming of gene expression, where the altered expression of ion channels decreases electrical stability and increases the risk of life-threatening arrhythmias. However, the underlying mechanisms are not fully understood. Here, we analysed the role of the depolarizing current I(f) which has been hypothesized to contribute to arrhythmogenesis in the hypertrophied ventricle.

METHODS AND RESULTS

We used transverse aortic constriction in mice to induce ventricular hypertrophy. This resulted in an increased number of I(f) positive ventricular myocytes as well as a strongly enhanced and accelerated I(f) when compared with controls. Of the four HCN (hyperpolarization-activated cyclic nucleotide-gated channels) isoforms mediating I(f), HCN2 and HCN4 were the predominantly expressed subunits in healthy as well as hypertrophied hearts. Unexpectedly, only the HCN1 transcript was significantly upregulated in response to hypertrophy. However, the combined deletion of HCN2 and HCN4 disrupted ventricular I(f) completely. The lack of I(f) in hypertrophic double-knockouts resulted in a strong attenuation of pro-arrhythmogenic parameters characteristically observed in hypertrophic hearts. In particular, prolongation of the action potential was significantly decreased and lengthening of the QT interval was reduced.

CONCLUSIONS

We suggest that the strongly increased HCN channel activity in hypertrophied myocytes prolongs the repolarization of the ventricular action potential and thereby may increase the arrhythmogenic potential. Our results provide for the first time a direct link between an upregulation of ventricular I(f) and a diminished repolarization reserve in cardiac hypertrophy.

Medical therapy for chronic heart failure

Understanding of contemporary pharmacological therapy for chronic heart failure continues to evolve. In this Review, we discuss how findings from clinical trials have caused the roles of old therapies to be expanded and past treatment algorithms to be challenged. Several trials investigating preserved ejection fraction as a measure of heart failure had disappointing results, although important studies are in progress. Many novel therapeutic approaches for heart failure have emerged and are discussed in this review. The pharmacological treatments for heart failure continue to change, with many exciting possibilities for the future.

β-blockers and their mortality benefits: underprescribed in heart failure and chronic obstructive pulmonary disease

This article discusses the most recent insights into the actions of β-blockers on the heart and lungs, highlighting that β-blockers should have a place in the treatment of patients with chronic obstructive pulmonary disease (COPD), especially in those with coexisting cardiovascular disease or arterial hypertension. Practical studies clearly show underutilization of β-blockers in patients with heart failure and COPD, which seems to be caused by an unnecessary fear for adverse effects on the lungs, and the ‘outdated’ adverse effects mentioned on instruction leaflets.