Nonselective versus selective beta-adrenergic receptor blockade in congestive heart failure: differential effects on sympathetic activity

Beta-adrenergic blockers in heart failure: review of mechanisms of action and clinical outcomes

Better understanding of the pathophysiology of heart failure has shifted the treatment of heart failure away from enhancing myocardial contractility to a new paradigm that targets the root cause of disease progression by blocking the adverse effects of excessive neurohormonal activation. Beta-adrenergic receptor-blockers have emerged as a cornerstone in the management of symptomatic heart failure. This article reviews the normal functioning of the beta-adrenergic pathway, the consequences of hyperadrenergism on this crucial signaling pathway, and the mechanisms by which chronic beta-blocker therapy reverses these abnormalities. The clinical evidence from controlled trials of the efficacy of beta-blockers in treating heart failure is summarized. Finally, the concomitant use of beta-blockers and positive inotropic agents in advanced heart failure is discussed.

Emerging Trends in the Management of Heart Failure: Beta Blocker Therapy

There is overwhelming evidence that beta blocker therapy in the form of metoprolol, bisoprolol, and carvedilol can have positive outcomes on morbidity, mortality, and quality of life in patients who have been diagnosed with mild to severe heart failure. Barring contraindications, beta blockers should be considered a cornerstone of therapy for these patients along with ACE inhibitors and diuretics. Beta blocking drugs are effective in modifying the cascade of events that occur as a result of the neurohormonal response that leads to the devastating effects evident during heart failure. Long-term effects of beta blockade include an increase in cardiac output, an increase in exercise tolerance, a decrease in the number of hospitalizations, and an overall improvement in symptoms.

Betablockers in heart failure: Carvedilol Safety Assessment (CASA 2-trial)

BACKGROUND

Betablockers are a cornerstone in the treatment of patients with chronic heart failure (CHF). The purpose of the present study was to assess safety and tolerability of carvedilol in CHF-patients.

METHODS

66 general practitioners, who were supervised by a local cardiologist, enrolled 151 CHF-patients. All patients were on standard therapy with ACE-inhibitors and diuretics. Carvedilol treatment was started with 3.125 mg twice daily and slowly uptitrated in 2-week intervals to 2x25 mg per day. Mean follow-up was 12 weeks.

RESULTS

145 of the 151 patients (96%) finished the study according to protocol, six patients were lost to follow-up (4%). 59 patients (41%) experienced minor and nine (6%) serious adverse events. 68 were under maximal therapy with 50 mg daily, 33 received 25 mg, and 15 12.5 mg. Overall tolerability was good and NYHA-class fell significantly from 2.2 to 1.8 (P<0.001). Mean heart rate decreased from 78 to 69 bpm (P<0.001), mean systolic blood pressure from 137 to 132 mmHg (P<0.001) and mean diastolic blood pressure from 80 to 76 mmHg (P<0.001). Quality of life significantly improved under carvedilol with a reduction in the Minnesota living with heart failure score from 1.28 to 0.88 (P<0.001).

CONCLUSIONS

Carvedilol is well tolerated in CHF-patients treated by general practitioners. Serious adverse events and hospitalisations are rare. Thus, carvedilol is a safe drug in the treatment of CHF-patients and can be easily initiated and managed by the general practitioner.

Sympathetic hyperactivity in chronic kidney disease: pathogenesis, clinical relevance, and treatment

Cardiovascular morbidity and mortality importantly influence live expectancy of patients with chronic renal disease (CKD). Traditional risk factors are usually present, but several other factors have recently been identified. There is now evidence that CKD is often characterized by an activated sympathetic nervous system. This may contribute to the pathogenesis of renal hypertension, but it may also adversely affect prognosis independently of its effect on blood pressure. The purpose of this review is to summarize available knowledge on the role of the sympathetic nervous system in the pathogenesis of renal hypertension, its clinical relevance, and the consequences of this knowledge for the choice of treatment.

Impact of 6 months of therapy with carvedilol on muscle sympathetic nerve activity in heart failure patients

BACKGROUND

The long-term effects of carvedilol on muscle sympathetic nerve activity (MSNA) and muscle blood flow at rest and exercise in patients with chronic heart failure (CHF) remain unknown.

METHODS AND RESULTS

Twenty-six patients (New York Heart Association class II-III) were randomized to carvedilol or placebo. Blood pressure, heart rate, MSNA, and forearm vascular resistance (FVR) at rest and during isometric forearm exercise (10% and 30% maximal voluntary contraction) were assessed before and after 6 months. Seven patients did not complete the study. Paired data were obtained in 19 (carvedilol 12, placebo 7). Carvedilol significantly decreased MSNA levels and heart rate at rest (-13 +/- 2 versus 3 +/- 8 bursts/min, P = .0001 and -16 +/- 3 vs -4 +/- 6 bpm, P = .05, respectively) and peak exercise (30% = -20 +/- 5 versus -3 +/- 7 bursts/min, P = 0.05 and -19 +/- 4 versus -4 +/- 6 bpm, P = 0.03, respectively) when compared with placebo. Carvedilol did not change a magnitude of response of MSNA and heart rate during exercise (-10 +/- 3 versus -7 +/- 2 bursts/min, P = 0.7 and 11 +/- 3 versus 6 +/- 1, P = .6, respectively). FVR was unchanged by carvedilol. When MSNA was quantified by burst incidence, the strength of reduction in MSNA was attenuated but still greater than placebo.

CONCLUSIONS

Carvedilol reduces MSNA in patients with CHF. Carvedilol does not reduce FVR at rest or during isometric exercise.

Volume-independent mechanisms of hypertension in hemodialysis patients: clinical implications

The renin-angiotensin and sympathetic nervous systems are often activated in hemodialysis (HD) patients; the pathogenesis of this condition is discussed. Medications aimed at reducing renin and sympathetic activity may improve the cardiovascular prognosis, independent of its effect on blood pressure. This knowledge has important implications for the choice of treatment in HD patients.

PPAR-gamma agonist rosiglitazone ameliorates ventricular dysfunction in experimental chronic mitral regurgitation

Previously we reported that the beneficial effects of beta-adrenergic blockade in chronic mitral regurgitation (MR) were in part due to induction of bradycardia, which obviously affects myocardial energy requirements. From this observation we hypothesized that part of the pathophysiology of MR may involve faulty energy substrate utilization, which in turn might lead to potentially harmful lipid accumulation as observed in other models of heart failure. To explore this hypothesis, we measured triglyceride accumulation in the myocardia of dogs with chronic MR and then attempted to enhance myocardial metabolism by chronic administration of the peroxisome proliferator-activated receptor (PPAR)-gamma agonist rosiglitazone. Cardiac tissues were obtained from three groups of dogs that included control animals, dogs with MR for 3 mo without treatment, and dogs with MR for 6 mo that were treated with rosiglitazone (8 mg/day) for the last 3 mo of observation. Hemodynamics and contractile function (end-systolic stress-strain relationship, as measured by K index) were assessed at baseline, 3 mo of MR, and 6 mo of MR (3 mo of the treatment). Lipid accumulation in MR (as indicated by oil red O staining score and TLC analysis) was marked and showed an inverse correlation with the left ventricular (LV) contractility. LV contractility was significantly restored after PPAR therapy (K index: therapy, 3.01 +/- 0.11*; 3 mo MR, 2.12 +/- 0.34; baseline, 4.01 +/- 0.29; ANOVA, P = 0.038; *P < 0.05 vs. 3 mo of MR). At the same time, therapy resulted in a marked reduction of intramyocyte lipid. We conclude that 1) chronic MR leads to intramyocyte myocardial lipid accumulation and contractile dysfunction, and 2) administration of the PPAR-gamma agonist rosiglitazone ameliorates MR-induced LV dysfunction accompanied by a decline in lipid content.

Beta-blockade in the management of systolic dysfunction

The concept that heart failure is simply the consequence of impaired pump function is now outmoded. Congestive heart failure is a neuroendocrine syndrome in with activation of the adrenergic nervous system and specific endocrine pathways is integral to its pathogenesis. It is now clear that chronic increases in adrenergic drive associated with heart failure have detrimental effects on myocardial function. The use of BAAs is now standard therapy for people who develop heart failure caused by systolic dysfunction. Beta-blockade may have a role in the management of dogs with heart failure.

Presynaptic modulation of evoked NE release contributes to sympathetic activation after pressure overload

Activation of the sympathetic nervous system is well documented in heart failure. Our previous studies demonstrated an increase in evoked norepinephrine (NE) release from left ventricle (LV) slices at 10 days of pressure overload. The purpose of this study was to test the hypothesis that presynaptic modulation of NE release contributes to sympathetic activation after pressure overload. We examined the functional status of the presynaptic α2- and β2-receptors and ANG II subtype 1 (AT1) receptors in LV slices from 10-day aortic constricted (AC) and sham-operated (SO) rats. Evoked 3H overflow from LV slices preloaded with [3H]NE was increased in AC rats. The α2-agonist UK-14,304 decreased evoked 3H overflow with no differences between groups. The β2-agonist salbutamol increased evoked 3H overflow with greater sensitivity in slices from AC rats. The β-antagonist propranolol decreased evoked 3H overflow from LV slices of AC rats but not controls. ANG II increased evoked 3H overflow with greater sensitivity in slices from AC rats. These data support the hypothesis that aberrant presynaptic modulation of catecholamine release contributes to sympathetic activation after pressure overload.

Do β-blockers prolong survival in heart failure only by inhibiting the β1-receptor? A perspective on the results of the COMET trial

Experimental and clinical studies indicate that carvedilol exerts multiple antiadrenergic effects in addition to beta(1)-receptor blockade, but the prognostic importance of these actions has long been debated. This controversy has now been substantially advanced by the results of the recently completed Carvedilol Or Metoprolol European Trial (COMET), which showed that carvedilol (25 mg twice daily) reduced mortality by 17% when compared with metoprolol (50 mg twice daily), P=.0017--a result that was consistent with the differences seen across earlier controlled trials with beta-blockers in survivors of an acute myocardial infarction and in patients with chronic heart failure. Questions have been raised about the interpretation of these findings in view of the fact that the trial did not use the dose or formulation of metoprolol that was shown to prolong life in a placebo-controlled trial (ie, Metoprolol CR/XL [Controlled Release] Randomized Intervention Trial in Heart Failure). Pharmacokinetic and pharmacodynamic analyses, however, indicate that the dosing regimen of metoprolol selected for use in the COMET trial produces a magnitude and time course of beta(1)-blockade during a 24-hour period that is similar to the dose of carvedilol targeted for use in the trial. These analyses suggest that the observed difference in the mortality effects of metoprolol and carvedilol is not related to a difference in the magnitude or time course of their beta(1)-blocking effects but instead reflect antiadrenergic effects of carvedilol in addition to beta(1)-blockade.

Comparison of effectiveness of carvedilol versus metoprolol or atenolol for atrial fibrillation appearing after coronary artery bypass grafting or cardiac valve operation

A retrospective review of 115 patients who underwent cardiac surgery demonstrated a marked reduction in postoperative atrial fibrillation (8% vs 32%, p <0.05) in patients who received carvedilol versus metoprolol or atenolol immediately after surgery. A prospective study examining the possibility of carvedilol's greater efficacy in preventing postoperative atrial fibrillation appears warranted.

The effects of exercise training on sympathetic neural activation in advanced heart failure: a randomized controlled trial

OBJECTIVES

The goal of this study was to test the hypothesis that exercise training reduces resting sympathetic neural activation in patients with chronic advanced heart failure.

BACKGROUND

Exercise training in heart failure has been shown to be beneficial, but its mechanisms of benefit remain unknown.

METHODS

Sixteen New York Heart Association class II to III heart failure patients, age 35 to 60 years, ejection fraction < or =40% were divided into two groups: 1) exercise-trained (n = 7), and 2) sedentary control (n = 9). A normal control exercise-trained group was also studied (n = 8). The four-month supervised exercise training program consisted of three 60 min exercise sessions per week, at heart rate levels that corresponded up to 10% below the respiratory compensation point. Muscle sympathetic nerve activity (MSNA) was recorded directly from peroneal nerve using the technique of microneurography. Forearm blood flow was measured by venous plethysmography.

RESULTS

Baseline MSNA was greater in heart failure patients compared with normal controls; MSNA was uniformly decreased after exercise training in heart failure patients (60 +/- 3 vs. 38 +/- 3 bursts/100 heart beats), and the mean difference in the change was significantly (p < 0.05) greater than the mean difference in the change in sedentary heart failure or trained normal controls. In fact, resting MSNA in trained heart failure patients was no longer significantly greater than in trained normal controls. In heart failure patients, peak VO(2) and forearm blood flow, but not left ventricular ejection fraction, increased after training.

CONCLUSIONS

These findings demonstrate that exercise training in heart failure patients results in dramatic reductions in directly recorded resting sympathetic nerve activity. In fact, MSNA was no longer greater than in trained, healthy controls.

Long-term treatment with the beta-blocker carvedilol restores autonomic tone and responsiveness in patients with moderate heart failure

The authors performed two studies on the effects of carvedilol on autonomic tone and responsiveness in patients with heart failure. In study 1, the autonomic responses of 25 patients (age, 60 years+/-2; New York Heart Association [NYHA] class, 2.6+/-0.5; pVO2, 16.6 mL/Kg/min+/-1.1) treated with angiotensin-converting enzyme inhibitors, diuretics, and carvedilol (38.0 mg/d+/-2.5) were compared to those of 25 patients of similar age, therapy, NYHA class, and pVO2 in whom carvedilol was not yet administered. In study 2, autonomic tone and responsiveness were studied in 20 patients (age, 57 years+/-9; NYHA class, 2.5+/-0.2; pVO2, 15.6 mL/Kg/min+/-3.4), before and 6 months after additional carvedilol treatment (40.0 mg/d+/-12.5). Autonomic evaluation was performed with autoregressive power spectral analysis of RR variability during 10 minutes of supine rest (control), breathing 20 times per minute (vagal stimulus), and standing (sympathetic activation). The ratio between low-frequency (LF) and high-frequency (HF) components of the autospectra indicated the sympathovagal interaction. In study 1, spectral analysis in controls showed sympathetic hyperactivity which was blunted in patients receiving carvedilol (LF/HF ratio: 10.4+/-1.4 vs. 7.0+/-1.1; P<0.05) who responded to vagal and adrenergic stimuli (LF/HF, -35% with regular breathing and 72% standing). In study 2, left ventricular function, volumes, and exercise performance improved with carvedilol (EF, 31%; EDLV volume, -22%; pVO2, 11%; P<0.05). Sympathetic hyperactivity in control was reduced (LF/HF ratio, 4.9+/-0.8 from 7.9+/-1.3; P<0.05), whereas a response to vagal and adrenergic activation on breathing and standing reemerged (LF/HF ratio, -31% during regular breathing and 88% on standing). Therefore, combined autonomic and hemodynamic effects may determine the favorable effects of beta-blockers in heart failure.

Beta-blocker benefit according to severity of heart failure

BACKGROUND AND AIMS

Beta-blockers are an established treatment for chronic heart failure. However, the relationship between their benefit and the severity of the disease remains to be determined.

METHODS AND RESULTS

We studied the relationship between amplitude of benefit of beta-blockers and severity of chronic heart failure, based on data for mortality and hospitalizations for worsening heart failure, using a meta-analysis of randomized controlled trials, complementary subgroup analyses and analysis of individual data from the CIBIS II trial. In the meta-analysis, mortality was reduced by 22% (95%CI: 16 to 28) and hospitalizations for worsening heart failure by 24% (95%CI: 20 to 29). Benefit was similar with metoprolol, bisoprolol and carvedilol. After exclusion of bucindolol trials, due to the heterogeneity of results for mortality, the reduction in mortality was similar according to the severity of heart failure, assessed either by left ventricular ejection fraction or by New York Heart Association classification. In CIBIS II, beta-blockers induced a significant reduction in mortality of 45% (95%CI: 9 to 66), 41% (95%CI: 17 to 59) and 23% (95%CI: 1 to 40) in the low, intermediate and high risk groups, respectively. Hospitalizations were reduced by 35% (95%CI: 2 to 57), 41% (95%CI: 18 to 58) and 23% (95%CI: 0 to 41), there was no significant difference between the three score groups.

CONCLUSION

We conclude that the amplitude of benefit of the beta-blockers carvedilol, metoprolol and bisoprolol on mortality and morbidity is similar, regardless of the severity of chronic heart failure.

Characterization of adrenoceptor involvement in skeletal and cardiac myotoxicity Induced by sympathomimetic agents: toward a new bioassay for beta-blockers

Excessive levels of catecholamines have long been known to be cardiotoxic, but less well known are their toxic effects on skeletal muscle. By using an antimyosin monoclonal antibody and quantitative methods to measure the extent of myocyte necrosis, and by employing modulators of adrenoceptors (ARs), including clenbuterol, bupranolol, propranolol, bisoprolol, atenolol, ICI-118551, phenoxybenzamine, prazosin, and yohimbine, the involvement of ARs in isoproterenol-induced myotoxicity was characterized. In the myocardium, the toxic effects were predominantly mediated via the beta(1)-ARs. In the soleus muscle, it was almost solely via the beta(2)-ARs. Myotoxicity was also observed in the myocardium when challenged with the beta(2)-AR agonist clenbuterol. This was found to be mediated via sympathetic presynaptic beta(2)-ARs, leading to enhanced release of norepinephrine. This effect was abolished by prior treatment with reserpine. The skeletal muscle was found to be more sensitive to the myotoxic effects than cardiac muscle at lower doses of beta-AR agonists. These experiments introduce a new way of assaying beta-AR antagonists by classifying them according to their ability to prevent catecholamine-induced myotoxicity. Further research along these lines may deepen understanding of which beta-blockers work best in heart failure therapy.

Beta-blockers for heart failure: why, which, when, and where

Beta-blockers are a highly effective treatment for patients with all grades of heart failure secondary to LV systolic dysfunction. Beta-blockers are best deployed as a form of tertiary prevention in heart failure but have a very limited role for the treatment of a heart failure crisis. Physicians and patients need to understand the time course of the effects of beta-blocker therapy. The initial effects are often neutral or adverse, though the benefits, at least of carvedilol, may be apparent within days in patients with severe heart failure. Benefits accumulate gradually over a period of weeks to months. Some patience, perseverance, and education are required in order to allow patients to reap the full benefits of beta-blocker therapy for this malignant disease. Initiation of treatment early in the course of the disease maximizes the effectiveness and acceptance of therapy. Trials are under way to determine whether the benefits of beta-blockers extend to patients over 80 years of age and to those with preserved LV systolic function. It is likely that important differences exist between beta-blockers in terms of their clinical benefit, though whether differences exist between the agents that have been reported to be effective so far awaits the outcome of a large clinical trial. It is unclear whether the target doses of beta-blockers currently recommended are optimal.

Sympathetic activation in human heart failure: diverse mechanisms, therapeutic opportunities

Plasma noradrenaline (NA) concentrations relate both to the severity of heart failure, and to its impact on survival, but have shortcomings that limit their usefulness as measures of sympathetic discharge. Neural recordings and the isotopic dilution method for determining organ-specific rates of NA spillover into plasma have enhanced our understanding of mechanisms responsible for sympathetic activation. Because the arterial baroreceptor reflex control of heart rate is impaired in heart failure, a parallel reduction in the reflex inhibition of sympathetic outflow has been assumed. However, human heart failure is characterized by rapidly responsive arterial baroreflex regulation of muscle sympathetic nerve activity (MSNA), attenuated cardiopulmonary reflex modulation of MSNA, and activation of a cardiac-specific sympatho-excitatory reflex related to increased cardiopulmonary filling pressures. Together, these baroreceptor mediated mechanisms account only, in part, for the time course and magnitude of adrenergic activation in heart failure. Non-baroreflex sympatho-excitatory mechanisms include: a metaboreflex arising from exercising skeletal muscle, mediated, in part, by adenosine, co-existing sleep apnoea, and pre-junctional facilitation of NA release. Thus, sympathetic activation in the setting of impaired systolic function reflects the net balance and interaction between augmented excitatory and diminished inhibitory influences. Variation, between patients, in the dynamics, magnitude and progression of sympathetic activation mandates an individualized approach to investigation and therapy. Excessive sympathetic outflow to the heart and periphery can be addressed by several complimentary strategies: attenuating these sympatho-excitatory stimuli, modulating the neural regulation of NA release, and blocking the actions of catecholamines at post-junctional receptors.

Differential effects of carvedilol and atenolol on plasma noradrenaline during exercise in humans

AIMS

Evidence of long-term beneficial effects of beta-blockers on mortality and morbidity in patients with heart failure has been demonstrated in recent randomized trials. However, not all beta-blockers are identical. Carvedilol, a nonselective beta- and alpha-adrenergic blocker, can potentially blunt the release of noradrenaline by blocking presynaptic beta2-adrenergic receptors. To test this hypothesis, we have compared the effects of carvedilol and atenolol on plasma noradrenaline during exercise in healthy young volunteers.

METHODS

This study investigated the differential effects of 2 weeks pretreatment with carvedilol 25 mg day(-1) and atenolol 50 mg day(-1) on plasma noradrenaline at rest and during exercise on a treadmill in a double-blind randomized crossover study, involving 12 healthy male volunteers (mean age 21.6 +/- 0.3 years).

RESULTS

Haemodynamic parameters at rest and during exercise were not significantly different in either carvedilol or atenolol pretreatment groups. However, carvedilol pretreatment significantly blunted the increase in plasma noradrenaline during exercise [393.8 +/- 51.7 pg ml(-1) (pretreatment) to 259.7 +/- 21.2 pg ml(-1) (post-treatment)], when compared with atenolol [340.4 +/- 54.6 pg ml(-1) (pretreatment) to 396.2 +/- 32.0 pg ml(-1) (post-treatment)]. The difference between carvedilol and atenolol (95% confidence interval) was -145.2, -351.0, P < 0.05.

CONCLUSIONS

We have demonstrated that carvedilol but not atenolol significantly blunted the increase in plasma noradrenaline during exercise. These findings may suggest a sympathoinhibitory effect of carvedilol that may enhance its ability to attenuate the cardiotoxicity associated with adrenergic stimulation in patients with heart failure.

Effect of selective and nonselective beta-blockers on resting energy production rate and total body substrate utilization in chronic heart failure

BACKGROUND

In chronic heart failure (CHF) beta-blockers reduce myocardial oxygen consumption and improve myocardial efficiency by shifting myocardial substrate utilization from increased free fatty acid oxidation to increased glucose oxidation. The effect of selective and nonselective beta-blockers on total body resting energy production rate (EPR) and substrate utilization is not known.

METHODS

Twenty-six noncachectic patients with moderately severe heart failure (New York Heart Association class II or III, left ventricular ejection fraction < 0.40) were treated with carvedilol (37.5 +/- 13.5 mg/12 h) or bisoprolol (5.4 +/- 3.0 mg/d) for 6 months. Indirect calorimetry was performed before and after 6 months of treatment.

RESULTS

Resting EPR was decreased in carvedilol (5.021 +/- 0.803 to 4.552 +/- 0.615 kJ/min, P <.001) and bisoprolol group (5.230 +/- 0.828 to 4.978 +/- 0.640 kJ/min, P <.05; nonsignificant difference between groups). Lipid oxidation rate decreased in carvedilol and remained unchanged in bisoprolol group (2.4 +/- 1.4 to 1.5 +/- 0.9 mg m(2)/kg min versus 2.7 +/- 1.1 to 2.5 +/- 1.1 mg m(2)/kg min, P <.05). Glucose oxidation rate was increased only in carvedilol (2.6 +/- 1.4 to 4.4 +/- 1.6 mg m(2)/kg min, P <.05), but did not change in bisoprolol group.

CONCLUSIONS

Both selective and nonselective beta-blockers reduce total body resting EPR in noncachectic CHF patients. Carvedilol compared to bisoprolol shifts total body substrate utilization from lipid to glucose oxidation.

Differential effects of the angiotensin-converting enzyme inhibitor lisinopril versus the beta-adrenergic receptor blocker atenolol on hemodynamics and left ventricular contractile function in experimental mitral regurgitation

OBJECTIVES

The goal of this study was to determine the therapeutic efficacy of angiotensin-converting enzyme (ACE) inhibitors and beta-adrenergic receptor blockers in experimental chronic mitral regurgitation (MR), gaining knowledge using methods difficult to apply in humans.

BACKGROUND

Both ACE inhibitors and beta-blockers are cornerstones in the treatment of human congestive heart failure. However, the roles of these treatments for chronic MR is unclear.

METHODS

Mitral regurgitation was created in 11 closed-chest dogs. Three months after the creation, the ACE inhibitor lisinopril 20 mg was given orally daily. After three months of lisinopril therapy, the beta-blocker atenolol was added to lisinopril for another three months. Atenolol was begun at a dose of 12.5 mg daily and increased gradually to 100 mg daily. Hemodynamics and left ventricular (LV) function were assessed throughout the study.

RESULTS

Regurgitant fraction was consistently >50% over the course of this study. Pulmonary capillary wedge pressure and LV end-diastolic pressure were significantly increased after three months of MR and decreased during both lisinopril and the combined therapy in which it was not different from baseline. Left ventricular contractility measured by the end-systolic stiffness constant was depressed from 3.66 +/- 0.20 to 2.65 +/- 0.12 (p < 0.05) at three months of MR and rose insignificantly after lisinopril treatment (2.99 +/- 0.17). When atenolol was added, it rose significantly and returned to normal (3.50 +/- 0.22, p < 0.05).

CONCLUSIONS

Although lisinopril significantly reduced preload, its effect on LV contractility was insignificant in experimental MR. Conversely, atenolol, when added to lisinopril, achieved maximum hemodynamic benefit and also restored LV contractility.

Present and future pharmacotherapy for heart failure

The pharmacotherapy currently recommended by the American College of Cardiology and the American Heart Association for heart failure (HF) is a diuretic, an angiotensin-converting enzyme inhibitor (ACEI), a beta-adrenoceptor antagonist and (usually) digitalis. This current treatment of HF may be improved by optimising the dose of ACEI used, as increasing the dose of lisinopril increases its benefits in HF. Selective angiotensin receptor-1 (AT(1)) antagonists are effective alternatives for those who cannot tolerate ACEIs. AT(1) antagonists may also be used in combination with ACEIs, as some studies have shown cumulative benefits for the combination. In addition to being used in Stage IV HF patients, in whom it has a marked benefit, spironolactone should be studied in less severe HF and in the presence of beta-blockers. The use of carvedilol, extended-release metoprolol and bisoprolol should be extended to severe HF patients as these agents have been shown to decrease mortality in this group. The ancillary properties of carvedilol, particularly antagonism at prejunctional beta -adrenoceptors, may give it additional benefits to selective beta(1)-adrenoceptor antagonists. Celiprolol and bucindolol are not the beta-blockers of choice in HF, as they do not decrease mortality. Although digitalis does not reduce mortality, it remains the only option for a long-term positive inotropic effect, as the long-term use of the phosphodiesterase inhibitors is associated with increased mortality. The calcium sensitising drug levosimendan may be useful in the hospital treatment of decompensated HF to increase cardiac output and improve dyspnoea and fatigue. The antiarrhythmic drug amiodarone should probably be used in patients at high risk of arrhythmic or sudden death, although this treatment may soon be superseded by the more expensive implanted cardioverter defibrillators, which are probably more effective and have fewer side effects. The natriuretic peptide nesiritide has recently been introduced for the hospital treatment of decompensated HF. Novel drugs that may be beneficial in the treatment of HF include the vasopeptidase inhibitors and the selective endothelin-A receptor antagonists but these require much more investigation. However, disappointing results have been obtained in a large clinical trial of the tumour necrosis factor alpha antagonist etanercept, where no likelihood of a difference between placebo and etanercept was observed. Small clinical trials with recombinant growth hormone to thicken ventricles in dilated cardiomyopathy have given variable results.