Pharmacodynamics ofβ-Blockers in Heart Failure: Lessons from the Carvedilol Or Metoprolol European Trial

Investigating the effects of beta-blockers on circadian heart rhythm using heart rate variability in ischemic heart disease with preserved ejection fraction

Heart failure is characterized by sympathetic activation and parasympathetic withdrawal leading to an abnormal autonomic modulation. Beta-blockers (BB) inhibit overstimulation of the sympathetic system and are indicated in heart failure patients with reduced ejection fraction. However, the effect of beta-blocker therapy on heart failure with preserved ejection fraction (HFpEF) is unclear. ECGs of 73 patients with HFpEF > 55% were recruited. There were 56 patients in the BB group and 17 patients in the without BB (NBB) group. The HRV analysis was performed for the 24-h period using a window size of 1,4 and 8-h. HRV measures between day and night for both the groups were also compared. Percentage change in the BB group relative to the NBB group was used as a measure of difference. RMSSD (13.27%), pNN50 (2.44%), HF power (44.25%) and LF power (13.53%) showed an increase in the BB group relative to the NBB group during the day and were statistically significant between the two groups for periods associated with high cardiac risk during the morning hours. LF:HF ratio showed a decrease of 3.59% during the day. The relative increase in vagal modulated RMSSD, pNN50 and HF power with a decrease in LF:HF ratio show an improvement in the parasympathetic tone and an overall decreased risk of a cardiac event especially during the morning hours that is characterized by a sympathetic surge.

Pharmacokinetics and pharmacodynamics of oral and intravenous metoprolol tartrate in clinically healthy horses

Cardiac drugs with defined pharmacological parameters in horses are limited. The objective of this study was to characterize the pharmacokinetic properties and cardiovascular effects of intravenous and oral metoprolol tartrate (MET) in horses. In a 2-period randomized cross-over design, MET was administered IV (0.04 mg/kg) and PO (6 mg/kg) once to six healthy adult horses. Horses were monitored via continuous telemetry and non-invasive blood pressure (NIBP). Blood samples were serially collected for 72 h post-administration, and concentrations were determined by LC-MS/MS. Pharmacokinetics were modeled using a 3-compartment model and non-linear least squares regression. Median (range) MET concentration was 110 (40.1-197) ng/ml collected 1 min (0.0167 h) after a bolus IV administration. Maximum concentration (C_max ) after PO administration was 2135 (1590-4170) ng/ml at 0.5 (0.25-0.5) hours. Oral bioavailability was 54% (17-100%). Median apparent volume of distribution was 0.39 (0.17-0.58) l/kg, clearance was 12.63 (11.41-18.94) ml/kg/min, and elimination half-life was 21.1 (7.46-34.36) minutes. No clinically relevant effects of IV or PO metoprolol were noted on cardiac rhythm or NIBP. Sweating was the most common side effect. The metoprolol doses used in this study achieve plasma concentrations reported to achieve ß-blockade in humans.

Photobiomodulation therapy combined with carvedilol attenuates post-infarction heart failure by suppressing excessive inflammation and oxidative stress in rats

The post-myocardial infarction heart failure (HF) still carries a huge burden since current therapy is unsuccessful to abrogate poor prognosis. Thus, new approaches are needed, and photobiomodulation therapy (PBMt) may be a way. However, it is not known whether PBMt added to a standard HF therapy provides additional improvement in cardiac remodeling in infarcted rats. This study sought to determine the combined carvedilol-drug and PBMt with low-level laser therapy value in HF. Rats with large infarcts were treated for 30 days. The functional fitness was evaluated using a motorized treadmill. Echocardiography and hemodynamic measurements were used for functional evaluations of left ventricular (LV). ELISA, Western blot and biochemical assays were used to evaluate inflammation and oxidative stress in the myocardium. Carvedilol and PBMt had a similar action in normalizing pulmonary congestion and LV end-diastolic pressure, attenuating LV dilation, and improving LV systolic function. Moreover, the application of PBMt to carvedilol-treated rats inhibited myocardial hypertrophy and improved +dP/dt of LV. PBMt alone prevented inflammation with a superior effect than carvedilol. Carvedilol and PBMt normalized 4-hydroxynonenal (a lipoperoxidation marker) levels in the myocardium. However, importantly, the addition of PBMt to carvedilol attenuated oxidized protein content and triggered a high activity of the anti-oxidant catalase enzyme. In conclusion, these data show that the use of PBMt plus carvedilol therapy results in a significant additional improvement in HF in a rat model of myocardial infarction. These beneficial effects were observed to be due, at least in part, to decreased myocardial inflammation and oxidative stress.

Simultaneous measurement of left and right ventricular volumes and ejection fraction during dobutamine stress cardiovascular magnetic resonance

OBJECTIVE

During cardiovascular stress, if right ventricular (RV) stroke volume exceeds left ventricular (LV) stroke volume, then a large volume of blood is displaced into the pulmonary circulation that may precipitate pulmonary edema. We sought to determine the metrics by which cardiovascular magnetic resonance (CMR) could measure simultaneous displacement of RV and LV stroke volumes during dobutamine stress.

METHODS

Thirteen healthy subjects (5 women) aged 53 ± 10 years without medical conditions and taking no medications underwent 2 CMR examinations at 1.5 T separated by 4 to 8 weeks in which RV and LV stroke volumes were determined during intravenous dobutamine and atropine infused to achieve 80% of the maximum predicted heart rate response for age.

RESULTS

The RV and LV stroke volumes were highly correlated at each level of stress (rest: r = 0.98, P = 0.007; low stress: r = 0.87, P = 0.001; and peak stress: r = 0.88, P = 0.001), and the mean difference in SV at each level of stress (rest, low stress, and peak stress was 0 to 2 mL on examinations 1 and 2.

CONCLUSIONS

Simultaneous change in right and left ventricular stroke volumes can be assessed in a highly reproducible manner throughout the course of dobutamine CMR stress administered to achieve 80% of maximum predicted heart rate response for age. This technology may help identify discrepancies in RV and LV stroke volumes during cardiovascular stress that are associated with the development of pulmonary edema.

Influence of metoprolol on systolic and diastolic function in children with heart failure

The aim of this study was to assess the effect ofmetoprolol on cardiac function in children with heart failure. This randomized double-blind placebo controlled clinical trial was performed in children with heart failure due to left ventricle volume overload structural heart disease such as VSD, PDA, AI and MR who referred to pediatric cardiology clinics in sari in 2007. The patients divided into case and control groups. All cases were matched as viewpoints of age, sex, weight, kinds of primary disease and cardiac drugs (except for metoprolol).Metoprolol with single daily dose of 1 mg kg(-1) and placebo were given to patients in case and control groups respectively. Echocardiography with cardiac indices of systolic and diastolic function was done as baseline and monthly for 3 months in all the patients. Data were analyzed using SPSS software and statistical t-test. Thirty patients (16 cases and 14 controls) were enrolled in the study. CI, MPI and dv/dt (dt) decreased significantly at first month. Significant changes in LVEF and EPSS appeared on the second month and in E wave and E/A appeared on the third month. The results were in favor of systolic and diastolic improvement. Metoprolol causes improvement of cardiac systolic and diastolic function in children with heart failure due to cardiac defect. Therefore, metoprolol is recommended in patients with heart failure in above mentioned diseases that have not been controlled adequately in spite of receiving standard cardiac failure drug therapy such as an inotrope, a diuretic and a vasodilator agent.

Atenolol is inferior to metoprolol in improving left ventricular function and preventing ventricular remodeling in dogs with heart failure

OBJECTIVES

beta-Blockers are standard therapy for patients with heart failure (HF). This study compared the effects of chronic monotherapy with 2 different beta(1)-selective adrenoceptor blockers, namely atenolol and metoprolol succinate, on left ventricular (LV) function and remodeling in dogs with coronary microembolization-induced HF [LV ejection fraction (EF) 30-40%].

METHODS

Twenty HF dogs were randomized to 3 months of therapy with atenolol (50 mg once daily, n = 6), metoprolol succinate (100 mg, once daily, n = 7) or to no therapy (control, n = 7). LV EF and volumes were measured before initiating therapy and after 3 months of therapy. The change (Delta) in EF and volumes between measurements before and after therapy was calculated and compared among study groups.

RESULTS

In controls, EF decreased and end-systolic volume increased. Atenolol prevented the decrease in EF and the increase in ESV. In contrast, metoprolol succinate significantly increased EF and decreased end-systolic volume. DeltaEF was significantly higher and Deltaend-systolic volume significantly lower in metoprolol succinate-treated dogs compared to atenolol-treated dogs (EF: 6.0 +/- 0.86% vs. 0.8 +/- 0.85%, p < 0.05; end-systolic volume: -4.3 +/- 0.81 ml vs. -1 +/- 0.52 ml, p <0.05).

CONCLUSIONS

In HF dogs, chronic therapy with atenolol does not elicit the same LV function and remodeling benefits as those achieved with metoprolol succinate.

Pharmacological prevention of atherothrombotic events in patients with peripheral arterial disease

Peripheral arterial disease (PAD) is strongly associated with atherosclerosis in the coronary and carotid arteries, leading to a highly increased incidence of myocardial infarction, ischaemic stroke and cardiovascular death. Fortunately, pharmacological interventions in large clinical trials have been as effective in subgroups of patients with PAD as in subjects with other atherosclerotic disease. Antiplatelet treatment is indicated in virtually all patients with PAD. Aspirin 75-325 mg day(-1) is considered as first-line treatment, and clopidogrel 75 mg day(-1) is an effective alternative. Statin therapy is indicated to achieve a target low-density lipoprotein cholesterol level of < or = 2.5 mmol L(-1) in patients with PAD and there is emerging evidence that even lower levels are beneficial. Lowering of plasma homocysteine by supplementing folic acid, vitamin B(12) and vitamin B(6) is not recommended in patients with mild to moderate hyperhomocysteinaemia in the 12-25 micromol L(-1) range, since it does not reduce the incidence of cardiovascular events. Antihypertensive treatment is indicated to achieve a goal blood pressure of < or = 140/90 mmHg or < or = 130/80 mmHg in the presence of diabetes or chronic kidney disease. All classes of antihypertensive drugs are acceptable for treatment of hypertension in patients with PAD, but angiotensin-converting enzyme inhibitors ramipril or perindopril are especially appropriate because they reduce the incidence of cardiovascular events beyond their blood pressure-lowering effects. Beta-blockers should not be used as first-line antihypertensive treatment. Diabetic patients with PAD should reduce their glycosylated haemoglobin to < or = 7%. In conclusion, pharmacological secondary prevention of cardiovascular morbidity and mortality in patients with PAD should be as comprehensive as that in patients with established coronary or cerebrovascular disease.