Importance of heart rate in determining beta-blocker efficacy in acute and long-term acute myocardial infarction intervention trials

Beta blocker use after acute myocardial infarction in the patient with normal systolic function: when is it "ok" to discontinue?

Beta-Blockers [BB] have been used extensively in the last 40 years after acute myocardial infarction [AMI] as part of therapy and in secondary prevention. The evidence for “routine” therapy with beta-blocker use post AMI rests largely on results of trials conducted over 25 years ago. However, there remains no clear recommendation regarding the appropriate duration of treatment with BBs in post AMI patients with normal left ventricular ejection fraction [LVEF] who are not experiencing angina, or who require BB for hypertension or dysrhythmia. Based on the latest ACC/AHA guidelines, BBs are recommended for early use in the setting of AMI, except in patients who are at low risk and then indefinitely as secondary prevention after AMI. This recommendation was downgraded to class IIa in low risk patients and the updated 2007 ACC/AHA guidelines suggest that the rationale for BB for secondary prevention is from limited data derived from extrapolations of chronic angina and heart failure trials. In this review, we examine the key trials that have shaped the current guidelines and recommendations. In addition, we attempt to answer the question of the duration of BB use in patients with preserved LVEF after acute MI, as well as which subgroups of patients benefits most from post AMI use of beta blockers.

'Inappropriate' sinus tachycardia: does the 100 beats per min cut-off matter?

Sinus tachycardia is commonly encountered in clinical practice and when persistent, can result in significant symptoms and impaired quality of life, warranting further evaluation. On the other hand, a growing body of epidemiological and clinical evidence has shown that high resting heart rate (HR) within the accepted normal range is independently associated with increased risk of all-cause and cardiovascular mortality. However, higher HR as a risk factor for adverse cardiovascular outcomes is frequently underappreciated. In this review, we focus on two challenging problems that span the spectrum of abnormally fast sinus HR. The first section reviews inappropriate sinus tachycardia, a complex disorder characterized by rapid sinus HR without a clear underlying cause, with particular emphasis on current management options. The latter section discusses the prognostic significance of elevated resting HR and reviews clinical evidence aimed at modifying this simple, yet highly important risk factor.

Novel postoperative use of beta-blocking medication for infants with left ventricular outflow obstruction and diastolic myocardial dysfunction

Severe left ventricular outflow obstruction often is associated with diastolic left ventricular myocardial dysfunction and tachycardia despite successful initial treatment. The authors have used esmolol to lower heart rate in this setting for successful weaning of patients from ventilation in postoperative recovery. Their limited experience supports the beneficial effect of continuous esmolol administration on infants with persistent tachycardia and severe left ventricular diastolic dysfunction in postoperative cardiac intensive care.

Adherence to the Mediterranean dietary pattern and heart rate in the SUN project

BACKGROUND

A higher heart rate has been related to an increase of total and cardiovascular mortality. The aim of this study was to assess the relation between adherence to the Mediterranean diet and heart rate.

DESIGN

The SUN project is an ongoing multipurpose cohort study based on university graduates from Spain.

METHODS

This cross-sectional study included 15,863 participants of the SUN project. Adherence to the Mediterranean dietary pattern was assessed through a validated 136-item food frequency questionnaire and calculated according to the 9-point score proposed by Trichopoulou. Multiple linear regression models were fitted to assess the relationship between adherence to the Mediterranean dietary pattern and heart rate and 95% confidence intervals were calculated.

RESULTS

The multivariable-adjusted models revealed that participants with a high adherence (7--9 points) to the Mediterranean dietary pattern had a heart rate 2.2 bpm (95% CI 1.4-3.1) lower than participants with a low adherence (0--2 points).

CONCLUSIONS

Adherence to the Mediterranean dietary pattern seems to be related to a lower heart rate.

Heart rate-lowering efficacy and respiratory safety of ivabradine in patients with obstructive airway disease: a randomized, double-blind, placebo-controlled, crossover study

BACKGROUND

There is substantial evidence that heart rate (HR) is a powerful predictor of mortality in both normal individuals and in patients with cardiovascular disease. The use of β-adrenoceptor antagonists (β-blockers) has confirmed the importance of lowering elevated HR in a patient's prognosis. However, these agents can have undesirable adverse effects (AEs) and due to the risk of bronchoconstriction are contraindicated in patients with obstructive airway disease. A selective bradycardic agent, without such undesirable effects, could be of therapeutic interest. Ivabradine, a new I(f) inhibitor that acts specifically on the sino-atrial node, is a pure HR-lowering agent.

OBJECTIVE

The objective of this study was to assess HR-lowering efficacy and respiratory safety of ivabradine in patients with asthma and chronic obstructive pulmonary disease (COPD).

METHODS

This was a randomized, single-center, double-blind, placebo-controlled, crossover trial. Enrolment began in May 2009, and the last patient completed the study in January 2011. The study was conducted in an ambulatory setting. A total of 40 patients completed the study (20 asthmatic patients and 20 COPD patients). Inclusion criteria were: documented diagnosis of asthma or COPD according to international guidelines, age 18-75 years, and mean HR on Holter ECG recording of ≥60 beats/min. Exclusion criteria included disease exacerbation in a previous month or inability to understand instructions on the study procedures. All patients received ivabradine 7.5 mg twice daily for 5 days and placebo twice daily for 5 days in a crossover manner, in one of the two arms of the study, with at least 2 days of washout between treatments. The main outcome measures included the difference in HR between ivabradine and placebo treatment and change in HR in comparison with baseline. Other evaluated outcomes were differences in the peak expiratory flow rate (PEFR), the daily symptom score, rescue medication consumption, and AEs.

RESULTS

Ivabradine produced significantly lower mean HR than placebo in both groups of patients: asthma 67.4 ± 8.38 versus 82.85 ± 11.19 beats/min (p < 0.001) and COPD 69.75 ± 8.9 versus 81.05 ± 9.75 beats/min (p < 0.001). Similar results were observed for the minimal HR as well as for the maximal noted HR. In comparision with baseline, ivabradine significantly reduced HR in both groups of studied patients (all p < 0.05), whereas placebo did not have such an effect. No significant difference, in either the asthma or the COPD group, was found between ivabradine and placebo in morning and evening peak expiratory flow rate, peak expiratory flow diurnal variability, daily symptom scores, and rescue medication usage (all p > 0.05). Both treatments were well tolerated. The incidence of AEs was low and generally similar in both periods of treatment, except for visual symptoms during treatment with ivabradine, which was reported by 5% of the patients.

CONCLUSION

Our study demonstrated that selective HR reduction with ivabradine is effective in patients with asthma and COPD, with no alteration in respiratory function or symptoms over the duration of the study. Ivabradine offers an interesting alternative, as an HR-lowering agent, in patients with respiratory disease and contraindications to β-blockers.

CLINICAL TRIAL REGISTRATION

Registered at www.clinicaltrials.gov (NCT01365286).

Comparing marginal structural models to standard methods for estimating treatment effects of antihypertensive combination therapy

Background

Due to time-dependent confounding by blood pressure and differential loss to follow-up, it is difficult to estimate the effectiveness of aggressive versus conventional antihypertensive combination therapies in non-randomized comparisons.

Methods

We utilized data from 22,576 hypertensive coronary artery disease patients, prospectively enrolled in the INternational VErapamil-Trandolapril STudy (INVEST). Our post-hoc analyses did not consider the randomized treatment strategies, but instead defined exposure time-dependently as aggressive treatment (≥3 concomitantly used antihypertensive medications) versus conventional treatment (≤2 concomitantly used antihypertensive medications). Study outcome was defined as time to first serious cardiovascular event (non-fatal myocardial infarction, non-fatal stroke, or all-cause death). We compared hazard ratio (HR) estimates for aggressive vs. conventional treatment from a Marginal Structural Cox Model (MSCM) to estimates from a standard Cox model. Both models included exposure to antihypertensive treatment at each follow-up visit, demographics, and baseline cardiovascular risk factors, including blood pressure. The MSCM further adjusted for systolic blood pressure at each follow-up visit, through inverse probability of treatment weights.

Results

2,269 (10.1%) patients experienced a cardiovascular event over a total follow-up of 60,939 person-years. The HR for aggressive treatment estimated by the standard Cox model was 0.96 (95% confidence interval 0.87-1.07). The equivalent MSCM, which was able to account for changes in systolic blood pressure during follow-up, estimated a HR of 0.81 (95% CI 0.71-0.92).

Conclusions

Using a MSCM, aggressive treatment was associated with a lower risk for serious cardiovascular outcomes compared to conventional treatment. In contrast, a standard Cox model estimated similar risks for aggressive and conventional treatments.

Trial registration

Clinicaltrials.gov Identifier: NCT00133692

Acidosis differentially modulates inactivation in na(v)1.2, na(v)1.4, and na(v)1.5 channels

Na(V) channels play a crucial role in neuronal and muscle excitability. Using whole-cell recordings we studied effects of low extracellular pH on the biophysical properties of Na(V)1.2, Na(V)1.4, and Na(V)1.5, expressed in cultured mammalian cells. Low pH produced different effects on different channel subtypes. Whereas Na(V)1.4 exhibited very low sensitivity to acidosis, primarily limited to partial block of macroscopic currents, the effects of low pH on gating in Na(V)1.2 and Na(V)1.5 were profound. In Na(V)1.2 low pH reduced apparent valence of steady-state fast inactivation, shifted the τ(V) to depolarizing potentials and decreased channels availability during onset to slow and use-dependent inactivation (UDI). In contrast, low pH delayed open-state inactivation in Na(V)1.5, right-shifted the voltage-dependence of window current, and increased channel availability during onset to slow and UDI. These results suggest that protons affect channel availability in an isoform-specific manner. A computer model incorporating these results demonstrates their effects on membrane excitability.

Resting heart rate and the risk of death and cardiovascular complications in patients with type 2 diabetes mellitus

AIMS/HYPOTHESIS

An association between resting heart rate and mortality has been described in the general population and in patients with cardiovascular disease. There are, however, few data exploring this relationship in patients with type 2 diabetes mellitus. The current study addresses this issue.

METHODS

The relationship between baseline resting heart rate and all-cause mortality, cardiovascular death and major cardiovascular events (cardiovascular death, non-fatal myocardial infarction or non-fatal stroke) was examined in 11,140 patients who participated in the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) Study.

RESULTS

A higher resting heart rate was associated with a significantly increased risk of all-cause mortality (fully adjusted HR 1.15 per 10 bpm [95% CI 1.08, 1.21], p<0.001), cardiovascular death and major cardiovascular outcomes without adjustment and after adjusting for age and sex and multiple covariates. The increased risk associated with a higher baseline resting heart rate was most obvious in patients with previous macrovascular complications (fully adjusted HR for death 1.79 for upper [mean 91 bpm] vs lowest [mean 58 bpm] fifth of resting heart rate in this subgroup [95% CI 1.28, 2.50], p = .001).

CONCLUSIONS/INTERPRETATION

Among patients with type 2 diabetes, a higher resting heart rate is associated with an increased risk of death and cardiovascular complications. It remains unclear whether a higher heart rate directly mediates the increased risk or is a marker for other factors that determine a poor outcome.

Heart rate reduction as a therapeutic goal: focus on primary prevention

Recently published studies have demonstrated a direct link between heart rate (HR) and prognosis across various populations and clinical groups, including elderly people, patients with arterial hypertension, myocardial infarction, and coronary artery stenting, overweight patients, or even young people with relatively low cardiovascular risk levels. HR is considered as an additional independent risk factor (RF) of cardiovascular disease (CVD). However, thus far, pharmaceutical HR reduction has been demonstrated to improve prognosis only in patients with coronary heart disease or chronic heart failure. The results in CVD-free patients have been contradictory. The review discusses the potential of different HR-reducing therapeutic regimens, as a part of primary CVD prevention.

Prognostic significance of heart rate in hospitalized patients presenting with myocardial infarction

AIM

To investigate the prognostic significance of resting heart rate in patients with acute coronary syndrome (ACS), independent of other known factors.

METHODS

Patients 40 years of age or older who had been admitted with acute coronary syndrome (ACS) to one of the 94 hospitals participating in the Prevalence of Peripheral Arterial Disease in Patients with Acute Coronary Syndrome (PAMISCA) study were included. Patients were divided into two groups based on their resting heart rate (HR ≥ or < 70 bpm). Complications were recording during a follow-up period of 1 year.

RESULTS

There were 1054 ACS patients analyzed (43.5% with ST segment elevation and 56.5% without elevation). Mean age was 66.6 ± 11.7 years, 70.6% were male and 29.4% of subjects were female. During follow-up, more patients in the HR ≥ 70 bpm group were hospitalized for heart failure and they also had a higher mortality rate. In the multivariate analysis, a heart rate of ≥ 70 bpm was independently related to overall mortality during the follow-up period (hazard ratio 2.5; 95% confidence interval, 1.26-4.97, P = 0.009).

CONCLUSION

A resting heart rate ≥ 70 bpm in patients who survive an ACS is an indicator of a high risk of suffering cardiovascular events during follow-up.

Differential effect of β-blockers for heart rate control in coronary artery disease

BACKGROUND

Resting heart rate is an independent risk factor for cardiovascular disease and is mainly controlled by β-blockers (BBs). BBs are part of the optimal medical treatment for coronary artery disease (CAD), and their benefit correlates with resting heart rate (RHR) reduction.

HYPOTHESIS

RHR is poorly controlled in daily practice among patients with stable cardiovascular disease, and control is only achieved by some BBs.

METHODS

Observational, cross-sectional, and multicenter study of CAD patients recruited nationwide from 20 institutions. Antecedents, risk factors, and treatments were collected. Controlled RHR was considered at <70 bpm.

RESULTS

The mean age of the 2897 patients included was 67.4 years (11.4%), and 75.9% were males. Patients treated with a BB (56.5%) had a lower mean age and comorbidities. The mean RHR was 69.6 bpm (12.6). A significantly lower RHR was observed in patients treated with a BB compared to the rest (67.2 vs 73.0 bpm; P<0.01), and no difference was observed in patients treated with a calciumchannel blocker (CCB). The analysis by individual agents identified that only patients treated with atenolol, bisoprolol, and metoprolol had significantly lower RHR than those not receiving a BB. No differences were observed in mean doses of each agent according to RHR control, except for verapamil. BB treatment was independently associated with RHR control (odds ratio [OR]: 2.42, 95% CI: 2.05-2.87; P<0.01), and no association was found for nondihydropyridine CCBs (OR: 0.99, 95% CI: 0.96-1.02; P = 0.38). Bisoprolol (OR: 1.56, 95% CI: 1.38-1.78; P<0.01), atenolol (OR: 2.01, 95% CI: 1.57-3.49; P<0.01), and metoprolol (OR: 1.29, 95% CI: 1.04-1618; P = 0.04) were independently associated with RHR control.

CONCLUSIONS

RHR is poorly controlled in CAD patients, and although BBs are the most efficient therapy, in daily clinical practice RHR <70 bpm is only independently associated with atenolol, bisoprolol, or metoprolol.

Respiratory muscle training improves hemodynamics, autonomic function, baroreceptor sensitivity, and respiratory mechanics in rats with heart failure

Respiratory muscle training (RMT) improves functional capacity in chronic heart-failure (HF) patients, but the basis for this improvement remains unclear. We evaluate the effects of RMT on the hemodynamic and autonomic function, arterial baroreflex sensitivity (BRS), and respiratory mechanics in rats with HF. Rats were assigned to one of four groups: sedentary sham (n = 8), trained sham (n = 8), sedentary HF (n = 8), or trained HF (n = 8). Trained animals underwent a RMT protocol (30 min/day, 5 day/wk, 6 wk of breathing through a resistor), whereas sedentary animals did not. In HF rats, RMT had significant effects on several parameters. It reduced left ventricular (LV) end-diastolic pressure (P < 0.01), increased LV systolic pressure (P < 0.01), and reduced right ventricular hypertrophy (P < 0.01) and pulmonary (P < 0.001) and hepatic (P < 0.001) congestion. It also decreased resting heart rate (HR; P < 0.05), indicating a decrease in the sympathetic and an increase in the vagal modulation of HR. There was also an increase in baroreflex gain (P < 0.05). The respiratory system resistance was reduced (P < 0.001), which was associated with the reduction in tissue resistance after RMT (P < 0.01). The respiratory system and tissue elastance (Est) were also reduced by RMT (P < 0.01 and P < 0.05, respectively). Additionally, the quasistatic Est was reduced after RMT (P < 0.01). These findings show that a 6-wk RMT protocol in HF rats promotes an improvement in hemodynamic function, sympathetic and vagal heart modulation, arterial BRS, and respiratory mechanics, all of which are benefits associated with improvements in cardiopulmonary interaction.

Effect of Carvedilol, Ivabradine or their combination on exercise capacity in patients with Heart Failure (the CARVIVA HF trial)

AIM

Patients with heart failure (HF) have reduced exercise capacity. The beneficial effect of beta-blocker on prognosis is not matched by an impact on exercise capacity and quality of life. We performed a randomised open blinded endpoint study to assess the effect of heart rate reduction with carvedilol, ivabradine, and their combination on exercise capacity in HF patients receiving maximal dose of ACE inhibitor.

METHODS AND RESULTS

After a run-in phase patients were randomly allocated to 3 groups: carvedilol up to 25mg bid (n=38); ivabradine up to 7.5mg bid (n=41); and carvedilol/ivabradine up to 12.5/7.5mg bid (n=42). The maximal dose of study treatment was more frequently tolerated in patients receiving ivabradine (36/41) than in those receiving carvedilol (18/38) or combination therapy (32/42) (P<0.01 ivabradine versus carvedilol). Heart rate was reduced in all three groups, but to a greater extent by the combination. The distance walked on the 6-min walking test and the exercise time on MVO(2) test significantly improved in the ivabradine and combination groups (both P<0.01 versus baseline), as did peak VO(2) and VAT (P<0.01 for ivabradine and P<0.03 for combination versus carvedilol, respectively). No changes in these parameters were found with carvedilol. The patients receiving ivabradine or the combination had better quality of life (P<0.01 versus baseline for ivabradine and P<0.02 for combination), versus no change with carvedilol.

CONCLUSION

Ivabradine alone or in combination with carvedilol is more effective than carvedilol alone at improving exercise tolerance and quality of life in HF patients.

Reducing elevated heart rate in patients with multiple organ dysfunction syndrome by the I (f) (funny channel current) inhibitor ivabradine : MODI (f)Y trial

BACKGROUND

Heart rate (HR) is of relevant prognostic value not only in the general population and patients with cardiovascular disease, but also in critically ill patients with multiple organ dysfunction syndrome (MODS). An elevated HR in MODS patients is associated with a worse prognosis. Beta-blocker (BB) administration has been shown to reduce mortality in MODS. In most cases, negative inotropic effects prevent administration of BBs in MODS patients. In this trial we investigate, whether the "funny current" (I (f)) channel inhibitor ivabradine is able and apt to reduce pathologically elevated HR in MODS patients. We hypothesize that critically ill patients could derive particular benefit from the specific HR-lowering agent ivabradine.

METHODS

MODI (f)Y is a prospective, single centre, open label, randomized, controlled two arms, phase II-trial to evaluate the potential of ivabradine to reduce an elevated HR in MODS patients. The primary end point is the proportion of patients with a reduction of HR by at least 10 beats per minute (bpm) within 4 days. This trial will randomize 70 patients (men and women, aged ≥18 years) with newly diagnosed MODS, with an elevated HR (sinus rhythm with HR ≥90 bpm) and contraindications to BB therapy. Treatment period will last for 4 days. All patients will be followed for 6 months.

RESULTS

The first patient was randomized on May 21, 2010.

CONCLUSIONS

The MODI (f)Y trial is the first application of ivabradine as a pure heart rate reducing agent in MODS patients.

Evaluation of aggressive heart rate reduction in patients with stable angina

BACKGROUND

There is a strong correlation between heart rate and myocardial ischemia, cardiovascular diseases, and life expectancy in general; however, heart rate has been neglected as an important risk factor as well as a therapeutic opportunity.

PURPOSE

To investigate the effect of aggressive heart rate reduction (50 ⩽ HR ⩽ 60 bpm) on anti-ischemic and anti-anginal efficacy, left ventricular function, exercise tolerance and quality of life in patients with stable coronary artery disease with or without left ventricular dysfunction during 4 months.

METHODS

A total of 159 patients presented with stable CAD without clinical heart failure symptoms were included in a open-label, non-comparative, prospective clinical study between June 2009 to February 2010 in King Abdul Aziz Specialist Hospital, Taif, KSA, Al Hayah National Hospital, Khamis Mushyt, KSA and Critical care department, Cairo University, Egypt. All included patients were, in addition to the ant ischemic treatment, subjected to aggressive heart rate control starting by beta blocker titrated to the maximum dose as tolerated, then Ivabradine added if the target heart rate is not achieved or rate control started by Ivabradine if beta blockers are contraindicated. Exercise treadmill test (ETT) to assess exercise capacity using time to 1 mm ST-segment depression in milliseconds, ejection fraction (EF) assessed by transthoracic echocardiography and frequency of angina attacks and the use of sublingual nitroglycerin per week during the last week were evaluated during a follow-up for 4 months. The patients were divided into two groups, group-I (patients achieved a resting heart rate between 50 and 60 bpm with heart rate reduction treatment) and group-II (patients with resting HR >60 bpm in spite of maximum treatment for heart rate reduction).

RESULTS

The resting heart rate was significantly reduced from 77.98 ± 8.7 at baseline to 60.68 ± 4.34 bpm after 4 months of treatment, P < 0.001. The frequency of angina pectoris attacks had been significantly reduced from 2.14 ± 1.27 to 0.48 ± 0.58 attacks per week, P < 0.001 and the highest significant reduction was observed with group-I. Also, the frequency of use sublingual nitrate therapy was significantly reduced from 1.38 ± 1.1 tablet per week at the last week before the study to 0.12 ± 0.33 tablet per week during the last week after 4 months of treatment, P < 0.001 and the reduction was more significantly with group-I. Exercise treadmill test demonstrated statistically significant increase in the time to 1 mm ST-segment depression from 357.36 ± 66.73 at baseline to 387.96 ± 65.19 ms. after 4 months with P < 0.001. The degree of improvement was significantly higher for group-I (from 358.06 ± 68.81 at baseline to 391.71 ± 69.01 after 4 months with P < 0.001) than that of group-II (from 356.11 ± 64.8 at baseline to 381.27 ± 59.08 after 4 months with P < 0.001). Ejection fraction showed a statistically significant increase from 59.76 ± 6.86 at baseline to 61.04 ± 5.35 after 4 months with P < 0.001.

CONCLUSION

This study indicates that heart rate reduction has been associated with an improvement in quality of life in patients with stable coronary artery disease, presenting new opportunities for treatment.

[Ivabradine in coronary heart disease: experimental and clinical pharmacology]

The present paper reviews clinical evidence underlining the role of ivabradine in the management of patient with ischemic heart disease. Reduction in heart rate mediated by this selective I(f) current inhibitor has been associated with anti-ischemic efficacy without any effect on haemodynamic or myocardial contractility. The antianginal efficacy of ivabradine is similar or superior to that of conventional anti-ischemic agents. Moreover combination therapy with ivabradine provides substantial benefit in patients already receiving beta-blocker. Prognostic efficacy of ivabradine is evaluated in a large program of studies, among which BEAUTIFUL in coronary patients with left ventricular dysfunction. The SIGNIFY study is ongoing in stable coronary patients without ventricular dysfunction. Furthermore the SHIFT trial will evaluate ivabradine benefits in heart failure patients, whatever the origin, ischemic or not.

[Antiarrhythmic therapy with β-receptor antagonists]

β-Blockers are an essential component of medical therapy in patients with ischemic heart disease or cardiac dysfunction of any genesis. They have an effect at the level of the sinus and the atrioventricular node, as well as on the atrial and ventricular refractory period of the myocardium. Overall, there are complicated antifibrillatory effects which are involved in the reduction of morbidity and mortality of this the therapy. According to the guidelines, it is important to uptitrate to highest tolerated dose. In patients with atrial fibrillation, antiadrenergic therapy should be the first line treatment; if well tolerated, then β-blockers alone or as a combination with an antiarrhythmic drug is preferable. Future prospective studies on the antiarrhythmic effects in this therapeutic area should include comparisons of different α - and β-selective active substances. Increasing knowledge of the differential therapy with the available active substances including intravenously applicable short-acting β-blockers, e.g., in intensive care therapy - should distinguish the different therapeutic effects.

Impact of ‘‘Off-Label’’ Use of Ivabradine on Exercise Capacity, Gas Exchange, Functional Class, Quality of Life, and Neurohormonal Modulation in Patients With Ischemic Chronic Heart Failure

Background: Epidemiologic studies indicate that elevated heart rate (HR) is an independent risk factor for mortality and morbidity in patients (pts) with chronic heart failure (CHF). Clinical trials with β-blockers suggest that HR reduction is an important mechanism of their benefit in pts with stable CHF. Pharmacologic inhibition of the If current now provides the opportunity of pure HR reduction. The purpose of this study was to evaluate the impact of ‘‘Off-Label’’ use of ivabradine on exercise capacity, gas exchange, functional class, quality of life, and neurohormonal modulation in pts with ischemic CHF. Methods: Between January 2008 and June 2008, a graded maximal exercise test with respiratory gas analysis and an endurance test with constant workload corresponding to 85% of the peak VO2 at the baseline and after 3 months were performed, and at the same times, N-terminal probrain natriuretic peptide (NT-proBNP) levels were also measured, in 60 pts (45 M, 15 F, mean age 52.7 ± 5.3 years), with stable ischemic CHF, New York Heart Association (NYHA) functional classes II (n = 35)—III (n = 25), with left ventricular ejection fraction (LVEF) ≤ 40%, randomized to a ‘‘off-label’’ ivabradine use (n = 30) and a control group (n = 30). Results: The exercise capacity increased from 14.8 ± 2.5 to 28.2 ± 3.5 min (P < .0001) and the peak oxygen consumption tended to improve from 13.5 ± 1.3 to 17.9 ± 2.4 mL/kg per minute (P < .0001) in ivabradine group. Oxygen consumption at the anaerobic threshold (AT) increased from 11.9 ± 1.4 to 15.3 ± 1.4 mL/kg per minute (P < .0001). NTproBNP levels decreased from 2356 ± 2113 pg/mL to 1434 ± 1273 pg/mL (P = .045). No significant differences were found in control group at 3 months. The positive ivabradine effects were also associated with an improvement in the NYHA functional class and quality of life. Conclusion: The ‘‘Off-Label’’ use of ivabradine significantly improves the exercise capacity, gas exchange, functional heart failure class, quality of life, and neurohormonal modulation in pts with ischemic CHF.

β-blocker therapy and heart rate control during exercise testing in the general population: role of a common G-protein β-3 subunit variant

AIM

Impaired heart rate (HR) response to exercise is associated with increased cardiovascular morbidity and mortality. We analyzed whether common variants (rs5443/C825T and rs5442/G814A) in the G-protein β3 subunit (GNB3) gene modulate interindividual variation in β-blocker responses with respect to HR.

MATERIALS & METHODS

Among 1614 subjects (347 current β-blocker users) of a population-based study, HR during symptom-limited exercise testing was analyzed by multilevel linear regression models adjusted for potential confounders.

RESULTS

In β-blocker users, but not in nonusers, HR was attenuated in rs5443 T allele carriers (TC/TT vs CC) with lower adjusted HR over the entire exercise period from rest to peak workload (3.5 bpm; 95% CI: 1.1-5.8; p < 0.01), and during recovery (4.2 bpm; 95% CI: 0.6-7.8; p = 0.02). The genotype-related HR reducing effect at peak exercise varied by up to 7.5 bpm (CC vs TT), more than a third (35.9%) of the total β-blocker effect (20.9 bpm). By contrast, rs5442 had no impact on any HR-related parameter.

CONCLUSION

In this population-based sample, a common GNB3 polymorphism (C825T) was significantly related with response to β-blocker therapy with respect to HR during exercise and HR recovery, respectively. Further prospective studies are needed to confirm these associations and to examine their potential clinical relevance.

[ProCor: an extramural screening on heart rate reduction in patients with chronic stable angina pectoris in Austria]

Based on the evidence from large clinical and epidemiological studies indicating an independent prognostic role of heart rate in cardiovascular disease, the assessment and correction of elevated heart rate is of significant prognostic relevance. In the present study conducted with the support of 74 specialists of Internal Medicine in 2009 in Austria, heart rate in patients with coronary heart disease (CHD) and chronic stable angina pectoris was evaluated in relation to pre-existing and concomitant diseases, angina-severity (CCS), angina-symptoms and treatment. For all variables, descriptive statistical analyses were performed according to three predefined groups with heart rates <60 bpm (HR-1), 60-70 bpm (HR-2), and >70 bpm (HR-3). Of the 1280 patients 21.8% had a heart rate of <60 bpm, 39.6% of 60-70 bpm, and 38.5% of >70 bpm. A significant association was shown between elevated heart rate and concomitant disease, e.g., peripheral artery disease (p = 0.046), psoriasis (p = 0.029), previous acute coronary syndrome (p = 0.001), COPD (p < 0.001), diabetes mellitus (p = 0.004), and depression (p < 0.001). CCS-severity was correlated with heart rates (mean values; CCS-0: 66.8 bpm, CCS-IV: 77.5 bpm). Angina-pectoris (AP) symptoms were more common in patients with heart rates of >70 bpm (HR-3: 1,2 AP-events/week; HR-2: 1 AP-events/week; HR-1: 0,7 AP events/week; each time p < 0.001). The majority of patients were treated with betablockers (74%); yet, the average dose was approximately half the maximal recommended dose. Despite inadequate heart rate reduction in patients on betablockers, selective heart rate lowering agents such as ivabradine were used in only 1.6% of patients. Overall, these results illustrate that heart rate as an important therapeutic target in CHD-patients with chronic stable angina is still underestimated in contemporary clinical practice.

Heart rate control with adrenergic blockade: clinical outcomes in cardiovascular medicine

The sympathetic nervous system is involved in regulating various cardiovascular parameters including heart rate (HR) and HR variability. Aberrant sympathetic nervous system expression may result in elevated HR or decreased HR variability, and both are independent risk factors for development of cardiovascular disease, including heart failure, myocardial infarction, and hypertension. Epidemiologic studies have established that impaired HR control is linked to increased cardiovascular morbidity and mortality. One successful way of decreasing HR and cardiovascular mortality has been by utilizing β-blockers, because their ability to alter cell signaling at the receptor level has been shown to mitigate the pathogenic effects of sympathetic nervous system hyperactivation. Numerous clinical studies have demonstrated that β-blocker-mediated HR control improvements are associated with decreased mortality in postinfarct and heart failure patients. Although improved HR control benefits have yet to be established in hypertension, both traditional and vasodilating β-blockers exert positive HR control effects in this patient population. However, differences exist between traditional and vasodilating β-blockers; the latter reduce peripheral vascular resistance and exert neutral or positive effects on important metabolic parameters. Clinical evidence suggests that attainment of HR control is an important treatment objective for patients with cardiovascular conditions, and vasodilating β-blocker efficacy may aid in accomplishing improved outcomes.

Heart Rate Control in an Unselected Consecutive Population of Outpatients With Stable Coronary Artery Disease: Analysis of the CARDIf Study Cohort

Background: Despite increasing pharmacological and mechanical treatment options, coronary artery disease (CAD) continues to be associated with considerable mortality and morbidity. The detrimental effects of elevated heart rate (HR) on cardiac morbidity and mortality are well established. Although β-blockers represent the mainstay of treatment of patients with CAD and heart failure (HF), according to current guidelines, these drugs are most often undertitrated for various reasons despite the lack of real contraindications. This observational, cross-sectional, multicenter survey was designed to assess which clinical variables influence HR and whether HR is adequately controlled; and the rate of administration of β-blockers in patients with chronic CAD attending outpatient clinics. Methods: Over 6 months 2226 (of 2362 screened) outpatients with stable CAD and resting HR > 60 beats/min (bpm) were enrolled. Left ventricular systolic function was not a criterion of inclusion. Each patient had a full clinical examination and the past medical history, angina, or HF-related symptoms were evaluated. In each patient, the demographics and cardiovascular risk factors were assessed; weight, height, and body mass index (BMI) was calculated; sitting blood pressure and a HR by a 12-lead electrocardiogram was obtained. Results: Overall, 45.4% of patients with CAD were not under β-blocker therapy. Male patients featured a significantly lower HR than females, corrected from β-blockers use. In multiple regression analysis, which also included the use/nonuse of β-blockers as independent variable, not using β-blockers, female sex (OR 2.55), New York Heart Association (NYHA) classes I and II (OR 1.62 vs classes III-IV), smoking (OR 0.89), and increased BMI (OR 0.14) were all independent determinants of resting HR, with the lack of β-blockade therapy (OR 3.35) being the main determinant of the magnitude of HR increase. Heart rate in patients under β-blocker therapy was significantly less than in untreated patients (73.6 10.0 vs 77.1 10.4, P < .0001), although it often did not reach target values of <70 bpm. Among patients with HF symptoms, 56.6% were under β-blocker therapy. In patients free of symptoms of HF, HR was significantly less in those receiving a β-blocker (72.3 10 vs 76.7 11 bpm, P < .0001). Conclusion: This survey demonstrates that HR is poorly controlled in a broadly representative cohort of outpatients with CAD, even in those on β-blocker therapy, mainly because of undertitration of therapy—almost half of the patients with CAD and elevated resting HR are not on β-blockers. This might be related to absolute or relative controindications and to haemodynamic and chronotropic intolerance to beta-blockers.

Heart rate in ischemic heart disease. The innovation of ivabradine: more than pure heart rate reduction

A wealth of data suggests that heart rate (HR) is an independent predictor of cardiovascular and all-cause mortality in men and women of all ages with and without cardiovascular disease. Data gathered from clinical trials suggest that HR reduction is an important mechanism of benefit of HR-lowering drugs. A high HR has direct detrimental effects not only on myocardial ischemia but also on the progression of atherosclerosis, ventricular arrhythmias, and on left ventricular function. The risk increases with HR >60 b.p.m. Ivabradine, a drug that slows HR though an effect on the If channels, has been approved for the control of myocardial ischemia in patients with coronary artery disease intolerant to beta-blockers. More recently, the indication of ivabradine has been extended for use in association with beta-blockers in patients with coronary artery disease. The effects of ivabradine on myocardial ischemia are greater than those predicted by pure HR reduction with beta-blockers, suggesting additional mechanisms of action.

Usefulness of heart rate at rest as a predictor of mortality, hospitalization for heart failure, myocardial infarction, and stroke in patients with stable coronary heart disease (Data from the Treating to New Targets [TNT] trial)

The heart rate at rest (HR) is a predictor of cardiovascular (CV) mortality. However, its effect on nonfatal CV events is unknown. The aim of the present post hoc analysis of the Treating New Targets (TNT) trial was to assess the effect of the HR at rest on major CV events in patients with stable coronary heart disease. A total of 9,580 subjects were included in the present analysis and were followed up for a median of 4.9 years. The rate of major CV events was 11.9% in those with a baseline HR of > or =70 beats/min versus 8.8% in those with a baseline HR of <70 beats/min. An increased HR at rest was associated with CV events, even after adjustment for differences in baseline characteristics (unadjusted hazard ratio 1.16 for every 10-beats/min increase, 95% confidence interval [CI] 1.10 to 1.23, p <0.0001; adjusted hazard ratio 1.08 per 10-beats/min increase, 95% CI 1.02 to 1.16, p = 0.018). A HR > or =70 beats/min was a significant independent predictor of all-cause mortality (hazard ratio 1.40, 95% CI 1.14 to 1.71, p = 0.001) and heart failure hospitalization (hazard ratio 2.30, 95% CI 1.80 to 2.95, p > or =0.0001). However, this association was not observed for stroke or myocardial infarction (p = 0.11 and p = 0.68, respectively). In conclusion, in patients with stable coronary heart disease, every 10-beats/min increase in the HR at rest was associated with an 8% increase in major CV events. In particular, a HR at rest of > or =70 beats/min was associated with a 40% increased risk of all-cause mortality and more than doubled the risk of heart failure hospitalization, but not the risk of stroke or myocardial infarction.

beta-Adrenergic receptor blockers and heart failure risk after myocardial infarction: a critical review

Remodeling after myocardial infarction is a complex biological process that leads to progressive left ventricular dilation and clinical heart failure. Multiple influences, including autonomic imbalance with sympathetic activation, contribute to the process. This article reviews clinical data in favor of early- and long-term use of beta-adrenergic receptor blockers in patients after myocardial infarction. Areas of uncertainty, such as the selection of dose and duration of therapy, current guidelines, and patterns of underuse of therapy with this important class of drugs are outlined and highlighted.

Elevated heart rate and cardiovascular outcomes in patients with coronary artery disease: clinical evidence and pathophysiological mechanisms

There is an established body of evidence from epidemiological studies which indicates that an elevated resting heart rate is independently associated with atherosclerosis and increased cardiovascular morbidity and mortality, in both the general population and in patients with established cardiovascular disease. Clinical trial data suggest that in patients with coronary artery disease, an elevated heart rate identifies those at increased risk of adverse cardiovascular outcomes, and that lowering of heart rate may reduce major cardiovascular events in patients with an elevated heart rate and symptom-limiting angina. These results suggest that an increased heart rate may have an adverse impact on the atherosclerotic process and increase the risk of a cardiovascular event in patients with coronary artery disease. The precise pathophysiological mechanisms that link heart rate and cardiovascular outcomes have yet to be defined. Possibilities may include indirect mechanisms related to autonomic dysregulation and those due to an increase in heart rate per se, which can increase the ischaemic burden and exert local haemodynamic forces that can adversely impact on the endothelium and arterial wall. For these reasons, heart rate should be considered as a therapeutic target in the treatment of patients with coronary artery disease.

Muscle sympathetic nervous activity in depressed patients before and after treatment with sertraline

BACKGROUND

Sympathetic hyperactivity is one of the mechanisms involved in the increased cardiovascular risk associated with depression, and there is evidence that antidepressants decrease sympathetic activity.

OBJECTIVES

We tested the following two hypotheses: patients with major depressive disorder with high scores of depressive symptoms (HMDD) have augmented muscle sympathetic nervous system activity (MSNA) at rest and during mental stress compared with patients with major depressive disorder with low scores of depressive symptoms (LMDD) and controls; sertraline decreases MSNA in depressed patients.

METHODS

Ten HMDD, nine LMDD and 11 body weight-matched controls were studied. MSNA was directly measured from the peroneal nerve using microneurography for 3 min at rest and 4 min during the Stroop color word test. For the LMDD and HMDD groups, the tests were repeated after treatment with sertraline (103.3 +/- 40 mg).

RESULTS

Resting MSNA was significantly higher in the HMDD [29.1 bursts/min (SE 2.9)] compared with LMDD [19.9 (1.6)] and controls [22.2 (2.0)] groups (P = 0.026 and 0.046, respectively). There was a significant positive correlation between resting MSNA and severity of depression. MSNA increased significantly and similarly during stress in all the studied groups. Sertraline significantly decreased resting MSNA in the LMDD group and MSNA during mental stress in LMDD and HMDD groups. Sertraline significantly decreased resting heart rate and heart rate response to mental stress in the HMDD group.

CONCLUSION

Moderate-to-severe depression is associated with increased MSNA. Sertraline treatment reduces MSNA at rest and during mental challenge in depressed patients, which may have prognostic implications in this group.

The relationship between high resting heart rate and ventricular arrhythmogenesis in patients referred to ambulatory 24 h electrocardiographic recording

AIMS

High resting heart rate (HR) has been associated with sudden cardiac death (SCD). This association is not fully explained by the reported association between HR with coronary heart disease (CHD) or left ventricular systolic dysfunction, the major pathological substrates for SCD. Ventricular arrhythmia is the most common antecedent event before SCD. Examining associations between resting HR and ventricular arrhythmogenesis may enhance our understanding of the association between high resting HR and SCD.

METHODS AND RESULTS

This study included 867 patients (age 54 +/- 5, 57% females) who underwent 24 h ambulatory electrocardiographic (ECG) recording (Holter) in the period from 1998 to 2000. We examined the unadjusted and multivariable-adjusted associations between resting HR with factors involved in ventricular arrhythmogenesis [ventricular late potentials (LPs) detected by signal-averaged ECG, heart rate variability (HRV), and premature ventricular complexes (PVCs)]. Linear regression models were used for continuous outcomes and logistic regression analysis was used for categorical outcomes. The multivariable models included first age and sex, then history of hypertension, diabetes, hypercholesterolaemia, CHD, heart failure, left ventricular ejection fraction (LVEF), smoking, body mass index, the use of anti-arrhythmic drugs, and ST-depression in the 24 h ambulatory ECG recording (Holter) were included in the final models. In the unadjusted and multivariable-adjusted analysis, high resting HR was significantly associated with positive ventricular LPs, depressed HRV indices, and increased prevalence of PVCs/24 h independently from demographic and clinical variables including LVEF, history of CHD, and the presence of ST-depression in Holter (P-value <0.05 in all comparisons and models).

CONCLUSION

High resting HR is independently associated with ventricular arrhythmogenesis, the major cause of SCD. These findings could partially explain the reported association between increased HR and SCD.

Cardioprotection with beta-blockers: myths, facts and Pascal's wager

Beta-blockers were documented to reduce reinfarction rate more than 3 decades ago and subsequently touted as being cardioprotective for a broad spectrum of cardiovascular indications such as hypertension, diabetes, angina, atrial fibrillation as well as perioperatively in patients undergoing surgery. However, despite lowering blood pressure, beta-blockers have never shown to reduce morbidity and mortality in uncomplicated hypertension. Also, beta-blockers do not prevent heart failure in hypertension any better than any other antihypertensive drug class. Beta-blockers have been shown to increase the risk on new onset diabetes. When compared with nondiuretic antihypertensive drugs, beta-blockers increase all-cause mortality by 8% and stroke by 30% in patients with new onset diabetes. Beta-blockers are useful for rate control in patients with chronic atrial fibrillation but do not help restore sinus rhythm or have antifibrillatory effects in the atria. Beta-blockers provide symptomatic relief in patients with chronic stable angina but do not reduce the risk of myocardial infarction. Adverse effects of beta-blockers are common including fatigue, dizziness, depression and sexual dysfunction. However, beta-blockers remain a cornerstone in the management of patients having suffered a myocardial infarction and for patients with heart failure. Thus, recent evidence argues against universal cardioprotective properties of beta-blockers but attest to their usefulness for specific cardiovascular indications.