Use of beta-adrenoceptor blockers in patients with congestive heart failure

A bioenergetics assessment of aortic regurgitation: A new tool to assess severity?

Aortic regurgitation is frequently classified as mild, moderate or severe based on echocardiography. Patients with mild aortic regurgitation are usually managed medically. Decisions with regard to moderate aortic regurgitation can be difficult. We hypothesise that mild aortic regurgitation as assessed volumetrically can in fact be moderate to severe when analysed from a bioenergetics point of view. The conservation of energy predicts that any regurgitant volume will require the heart to provide more work energy to support the circulation. Aortic regurgitation involves the left ventricle imparting potential energy, via blood pressure, and kinetic energy, via increased ejected volume and velocity respectively. This implies that regurgitant volume, ejection velocity, diastolic and systolic blood pressure, heart rate, and regurgitant orifice area are all important factors. We present limited data to demonstrate our hypothesis. A bioenergetic analysis of aortic regurgitation, reveals that correlation between regurgitant volume and effective regurgitant orifice can be poor in certain physiological circumstances. In addition we identify the importance of systolic and diastolic blood pressure, and heart rate control in patients with aortic regurgitation. The concept that mild aortic regurgitation can be ignored is from an engineering point fundamentally flawed in some cases.

Cardiovascular function in large to small hibernators: bears to ground squirrels

Mammalian hibernation has intrigued scientists due to extreme variations in normal seasonal physiological homeostasis. Numerous species manifest a hibernation phenotype although the characteristics of the hypometabolic state can be quite different. Ground squirrels (e.g., Sciuridae) are often considered the prototypical hibernator as individuals in this genus transition from an active, euthermic state (37 °C) to a nonresponsive hibernating state where torpid body temperature commonly falls to 3-5 °C. However, the hibernating state is not continuous as periodic warming and arousals occur. In contrast, the larger hibernators of genus Ursus are less hypothermic (body temperatures decline from approximately 37°-33 °C), are more reactive, and cyclical arousals do not occur. Both species dramatically reduce cardiac output during hibernation from the active state (bears ~75 % reduction in bears and ~97 % reduction in ground squirrels), and both species demonstrate hypokinetic atrial chamber activity. However, there are several important differences in cardiac function between the two groups during hibernation. Left ventricular diastolic filling volumes and stroke volumes do not differ in bears between seasons, but increased diastolic and stroke volumes during hibernation are important contributors to cardiac output in ground squirrels. Decreased cardiac muscle mass and increased ventricular stiffness have been found in bears, whereas ground squirrels have increased cardiac muscle mass and decreased ventricular stiffness during hibernation. Molecular pathways of cardiac muscle plasticity reveal differences between the species in the modification of sarcomeric proteins such as titin and α myosin heavy chain during hibernation. The differences in hibernation character are likely to account for the alternative cardiac phenotypes and functional strategies manifested by the two species. Molecular investigation coupled with better knowledge of seasonal physiological alterations is dramatically advancing our understanding of small and large hibernators and their evolutionary differences.

A bioenergetic assessment of mitral regurgitation: a new tool to assess severity?

Mitral regurgitation is frequently classified as mild, moderate or severe based on echocardiography. Patients with mild mitral regurgitation are usually managed medically. We hypothesise that mild mitral regurgitation as assessed volumetrically can in fact be severe when analysed from a bioenergetics point of view. The conservation of energy predicts that any regurgitant volume will require the heart to provide more work energy to support the circulation. Mitral regurgitation involves the left ventricle imparting potential energy, via blood pressure, and kinetic energy, via regurgitant velocity, to the regurgitant blood volume. This implies that regurgitant volume, regurgitant velocity, systolic blood pressure, heart rate, regurgitant orifice area and cardiac output are all important factors. We present limited data to demonstrate our hypothesis. A bioenergetic analysis of mitral regurgitation, may identify patients whose mitral regurgitation, assessed via echocardiography as mild, is actually clinically significant. In addition we identify the importance of blood pressure and heart rate control in patients with mitral regurgitation. The concept that a bit of mitral regurgitation in patients with poor left ventricles is a good thing, as it helps offload the left ventricle is from an engineering point fundamentally flawed.

Managing beta-blockers in acute heart failure: when to start and when to stop?

The role of beta-blockers in heart failure has been long debated. Data from chronic heart failure studies clearly indicate that beta-blockers save lives. However, data concerning use of beta-blockers in patients with acute heart failure are limited, and only recently have emerged to help guide therapy. In this review, we provide an overview of when to stop and when to start beta-blockers in patients with acute heart failure.

Nebivolol in the treatment of cardiac failure: a double-blind controlled clinical trial

BACKGROUND

Nebivolol is a highly cardioselective long-acting beta-blocker with vasodilating properties, which acts in part via the endothelial L-arginine/nitric oxide pathway. As an antihypertensive drug it is effective in once-daily dosage. Nebivolol has previously been shown to improve left ventricular function in patients with cardiac impairment.

METHODS AND RESULTS

This paper reports a double-blind randomized trial comparing, in patients with heart failure, once-daily nebivolol 2.5 or 5.0 mg (initiated in all at 2.5 mg) with placebo on a constant background of digitalis plus diuretic. There was with nebivolol no overall deterioration of cardiac function or cardiac symptoms, and especially not of exercise capacity, in comparison with placebo. One patient on nebivolol 2.5 mg developed hypotension and pulmonary edema, and one patient on nebivolol 5 mg, bradycardia. All the remaining patients continued with unchanged diuretic and digitalis dosage. Nebivolol was accompanied by a trend toward clinical and functional improvement; rather better results were obtained with 2.5 than 5.0 mg.

CONCLUSIONS

In view of increasing interest in beta-blockade in heart failure, nebivolol merits further study in this context. The capacity of nebivolol to enhance endothelial nitric oxide production appears potentially attractive.

Prognostic value of bisoprolol-induced hemodynamic effects in heart failure during the Cardiac Insufficiency BIsoprolol Study (CIBIS)

BACKGROUND

To further evaluate the mechanism of beta-blocker-induced benefits in heart failure, the relationships between bisoprolol-induced hemodynamic effects and survival were studied during the Cardiac Insufficiency BIsoprolol Study (CIBIS).

METHODS AND RESULTS

In 557 patients studied, bisoprolol significantly reduced heart rate (-16.3+/-15.3 versus -1.6+/-13.4 bpm, respectively; P<.001) compared with placebo at 2 months after inclusion in the study. Heart rate change over time had the highest predictive value for survival (P<.01). Left ventricular fractional shortening (LVFS) significantly increased in the bisoprolol group compared with the placebo group 5 months after inclusion (+0.04+/-0.06 versus -0.001+/-0.05, respectively; P<.001; n=160). LVFS change over time was also significantly correlated with further survival (P<.02 by Cox analysis). Using a nonparametric approach, we demonstrated a significant interaction between study treatment group and LVFS over time. Patients who demonstrated improvement of LVFS over time (82% and 51% of patients in the bisoprolol and the placebo groups, respectively; P<.02) were at lower risk, but the hazard did not further decrease with a further increase of fractional shortening, and there was no significant difference between study treatment groups. Finally, it could be demonstrated that each of the three factors (heart rate change over time, LVFS change over time, and bisoprolol treatment) made a specific contribution to mortality rate.

CONCLUSIONS

Preservation of left ventricular function appears to play a key role in the bisoprolol-induced beneficial effects on prognosis in heart failure. Short-term beta-blocker-induced cardiac effects could provide a means to identify those patients who will experience improved survival over the long term.

Current and newer approaches in the drug treatment of congestive heart failure

Most patients with chronic congestive heart failure (CHF) are subjected to symptomatic treatment, predominantly with drugs. Over the years, it has become clear that treatment with unloading drugs is probably more beneficial than treatment with inotropic agents. In addition, it has been widely recognized that the neuroendocrine compensatory changes associated with CHF afford and important target for drug treatment. This may also hold for some of the changes in receptor density, such as the downregulation of cardiac beta-adrenoceptors. The present and clearly changing insights into the backgrounds of drugs for the treatment of CHF are critically discussed. Apart from the changing views and appreciation of the currently used drugs (diuretics, ACE inhibitors, digoxin, beta-adrenoceptor agonists), the following new approaches are discussed: beta-blockers, angiotensin II receptor antagonists, ibopamine, calcium antagonists, inhibitors of ANP degradation, vasopression antagonist, vesnarinone, and calcium sensitizers.

Changes in cardiovascular responsiveness to dopexamine and beta 1- and beta 2-adrenoceptor function after the chronic treatment of beta-adrenoceptor antagonists and agonists in anaesthetized dogs

1. The studies were designed to investigate the changes in responsiveness to beta-adrenoceptor agonists induced by chronic administration of beta-adrenoceptor antagonists and agonists. 2. Dose-response curves for dopexamine, isoprenaline, noradrenaline and impromidine on heart rate, blood pressure and myocardial contractility (dP/dt:integrated isometric tension) were obtained in untreated dogs and compared to those measured in dogs which had been pretreated with propranolol (8 mg kg-1 day-1), atenolol (6 mg kg-1 day-1), isoprenaline (0.5 microgram kg-1 min-1) or noradrenaline (0.5 microgram kg-1 min-1) for 14 days. 3. Propranolol pretreatment significantly enhanced the inotropic and chronotropic responses to isoprenaline. There were noticeable, but non-significant increases in inotropic sensitivity to noradrenaline and dopexamine, especially at higher dose levels. In the atenolol treatment group, there were significant increases in inotropic responses to dopexamine and isoprenaline and in depressor responses to isoprenaline. 4. Thus, chronic administration of propranolol increased responses mediated by both beta 1- and beta 2-adrenoceptors, whereas, atenolol selectively enhanced the inotropic responsiveness to dopexamine, which is mediated mainly by beta 2-adrenoceptors. 5. Isoprenaline pretreatment caused a significant decrease in inotropic sensitivity to dopexamine, isoprenaline and noradrenaline and a significant reduction in chronotropic responses to dopexamine. The tendency to reduced depressor responses to isoprenaline and dopexamine failed to reach significance. Pretreatment with noradrenaline decreased only the inotropic response to noradrenaline. 6. Thus, chronic isoprenaline treatment reduced the responsiveness of both beta 1- and beta 2-adrenoceptors, while chronic noradrenaline infusion only reduced beta 1-adrenoceptor-mediated responses. 7. There was no significant change in any of the dose-response curves to impromidine after any beta-adrenoceptor antagonist or agonist treatment. This indicates that there was no non-specific alteration in responsiveness and that the observed changes were likely to be associated with specific alterations in beta-adrenoceptor number or function.