A comparison of oral milrinone, digoxin, and their combination in the treatment of patients with chronic heart failure

How should physicians view heart failure? The philosophical and physiological evolution of three conceptual models of the disease

During the last 50 years, physicians have developed three distinct conceptual models of heart failure that have provided a rational basis for the treatment of the disease. In the 1940s through the 1960s, physicians regarded heart failure principally as an edematous disorder and formulated a cardiorenal model of the disease in an attempt to explain the sodium retention of these patients. This model led to the widespread use of digitalis and diuretics. In the 1970s and 1980s, physicians viewed heart failure principally as a hemodynamic disorder and formulated a cardiocirculatory model of the disease in an attempt to explain patients' symptoms and disability. This model led to the widespread use of peripheral vasodilators and the development of novel positive inotropic agents. Now, in the 1990s, physicians are beginning to think about heart failure as a neurohormonal disorder in an attempt to explain the progression of the disease and its poor long-term survival. This new conceptual framework has led to the widespread use of converting-enzyme inhibitors and the development of beta blockers for the treatment of heart failure. Which conceptual model most accurately describes the syndrome of heart failure and leads physicians to utilize the most effective treatment? This paper critically reviews the available evidence supporting and refuting the validity of all three models of heart failure. We conclude that, to varying degrees, all three approaches provide useful, but incomplete, insights into this physiologically complex and therapeutically challenging disease.

Effects of bucindolol in heart failure

Bucindolol hydrochloride is a phenoxypropanolamine with potent nonselective beta antagonist and mild vasodilatory properties. In humans with congestive heart failure, it is extremely well tolerated and produces improvements in left ventricular systolic (ejection fraction, systolic elastance, cardiac index, and stroke work) and diastolic (isovolumic relaxation) performance while reducing pulmonary artery pressures and heart rate. These improvements occur without an increase in myocardial oxygen extraction or oxygen consumption. In addition, functional class improves with this agent although exercise tolerance and maximal oxygen consumption (VO2max) does not change, an effect that is not unexpected with a beta-adrenergic antagonist. Bucindolol produces a decrease in plasma renin activity and plasma norepinephrine, effects that may be beneficial for the long-term treatment of congestive heart failure. However, these effects are most marked in patients with idiopathic dilated cardiomyopathy compared with patients with ischemic heart disease. This agent holds great promise for the treatment of heart failure patients.

Effect of milrinone on thromboxane A2 synthesis, cAMP phosphodiesterase and 45Ca2+ uptake by human platelets

The phosphodiesterase inhibitors milrinone and isobutylmethylxanthine (IBMX) inhibited the conversion of [3H]cAMP to [3H]AMP by washed human platelets in concentration-dependent manners (IC50: milrinone, 2.6 x 10(-6) M; IBMX, 4.6 x 10(-6) M). Milrinone and IBMX increased cAMP levels when stimulated by a single concentration (0.3 microM) of iloprost. EC50:milrinone, 5.6 x 10(-5) M; IBMX, 3 x 10(-5) M. Milrinone was a potent inhibitor of platelet thromboxane A2 (TXA2) synthesis when stimulated by median stimulatory doses of collagen (IC50: 3 x 10(-7) M), sodium fluoride (NaF) (a non-specific G protein activator; IC50: 3 x 10(-7) M) and phorbol ester myristate acetate (PMA) (a protein kinase C activator; IC50: 2.2 x 10(-7) M). In contrast, at median stimulatory doses of A23187 and arachidonate there was a marked decrease in the potency of milrinone in inhibiting TXA2 synthesis. Milrinone had a weak inhibitory effect on TXA2 synthesis when elicited by freeze fracturing. In all experiments IBMX was a weaker inhibitor of TXA2 synthesis, although the general pattern of effects was similar to milrinone. Milrinone inhibited both collagen- and adrenaline-stimulated 45Ca2+ uptake by human platelets in dose-dependent manners. Since platelet TXA2 synthesis is dependent on Ca2+, and milrinone inhibited 45Ca2+ uptake, it is concluded that milrinone exerts its inhibitory effect on platelet activity, principally through an action on Ca2+ mobilisation/binding to effector proteins (protein kinase C and/or phospholipase A2).

Long-term outcome of enoximone therapy in patients with refractory heart failure

Few options are available for patients with severe heart failure that is unresponsive to therapy with digoxin, diuretics, and vasodilators. The clinical responses and predictors of survival were studied in 41 consecutive patients with New York Heart Association (NYHA) class IV heart failure during long-term oral enoximone therapy (mean dose 232 +/- 15 mg/day). The mean age was 60 +/- 1 years, and the initial left ventricular ejection fraction was 0.19 +/- 0.01. The cause of heart failure was either coronary artery disease (n = 23) or dilated cardiomyopathy (n = 18). Symptomatic improvement occurred in the majority (83%) of patients; 24% improved two or more NYHA classes. Although the 12-month mortality rate for the entire group was high (54 +/- 8%), a subgroup of patients with dilated cardiomyopathy achieved a sustained benefit with a decrease in symptoms > 1 NYHA class, fewer hospitalizations, and a survival rate at 24 months of 60%. Multivariate analysis identified the cause of heart failure, left ventricular ejection fraction, and clinical improvement within 60 days of enoximone therapy as predictors of a favorable long-term outcome. The presence of coronary artery disease was most predictive of early mortality (p < 0.0002), with only 5% of patients surviving > 18 months compared to 66% of those with dilated cardiomyopathy. Median survival rates were 132 +/- 31 and 921 +/- 214 days (p < 0.001) for the coronary artery disease and dilated cardiomyopathy populations, respectively. Oral enoximone can provide symptomatic improvement and a palliative option for the majority of patients with refractory heart failure resulting from cardiomyopathy.

The role of phosphodiesterase inhibitors in heart failure

Myocardial contractility is dependent on available intracellular calcium and this can be enhanced by increasing intracellular cyclic adenosine monophosphate. One way of achieving this is by inhibiting the phosphodiesterase III enzyme. Over the last 15 years, a number of new drugs with this mechanism of action have been studied in man and have been found not only to have a positive inotropic action on the heart but also a vasodilating action on peripheral blood vessels. This combination of effects produces favourable haemodynamic improvement in patients with chronic heart failure. While some smaller studies showed that this did translate into an improvement in symptoms and functional capacity, a large well-designed and controlled clinical trial showed that survival was decreased when milrinone was used in target daily doses of 40 mg. For this reason, chronic long-term oral therapy with phosphodiesterase III inhibitors is not currently being actively pursued. They may still have a role as acute short-term therapy in severely ill patients who do not respond adequately to optimal standard drug therapy. Milrinone has been one of the most widely studied drugs in this regard. Even during short-term administration, its use should be closely monitored for any evidence of an increase in ventricular arrhythmias or decrease in ventricular function.

Inotropic therapy of the failing myocardium

The clinical syndrome of congestive heart failure remains a therapeutic dilemma and challenge for the physician in 1992. This is a disease process that appears to be increasing in frequency and continues to carry an unacceptably high mortality rate. For years it has been well recognized that the combination of digoxin, Lasix and vasodilator therapy improved symptoms in these patients and decreased hospitalization, but did not increase survival. It was not until 1986 that the combination of digoxin, Lasix, Isordil, and hydralazine was shown to increase survival. Further significant improvement in quality of life and survival has recently been established in three large clinical trials, and it is now safe to say that the standard of care for symptomatic congestive heart failure in 1992 is digoxin, furosemide, and an ACE inhibitor, with the survival trials favoring the ACE inhibitor enalapril. The IV inotropic drug dobutamine remains the mainstay of pharmacological therapy for the treatment of severely refractory heart failure. Unfortunately, the phosphodiesterase inhibitors--amrinone, milrinone, and enoximone--have demonstrated unacceptable clinical side effects and have been withdrawn from further clinical study. In spite of these promising developments, the mortality and morbidity of congestive heart failure remains unacceptably high, and continued investigation in the new fields of pharmacology and the pathophysiology of congestive heart failure still must be aggressively pursued.

Cardiac effects of R 79595 and its isomers (R 80122 and R 80123) in an acute heart failure model. A new class of cardiotonic agents with highly selective phosphodiesterase III inhibitory properties

R 79595 (N-cyclohexyl-N-methyl-2-[[[phenyl (1,2,3,5-tetrahydro-2 oxoimidazo [2,1-b]-quinazolin-7-yl) methylene] amin] oxy] acetamide) and its isomers represent a novel class of compounds with phosphodiesterase (PDE) inhibitory and cardiotonic (positive inotropic) actions. The cardiac effects of this class of compounds were investigated in the hexobarbital-depressed heart-lung preparation of the guinea-pig. After induction of heart failure (reduction of cardiac output to 25% of the initial value) cumulative addition of R 79595 or its isomers R 80122 (E-isomer) and R 80123 (Z-isomer) concentration-dependently reversed the cardiac depressant effects of hexobarbitone-Na. With regard to reconstitution of contractility and cardiac function R 80122 (E-isomer) was 10 fold more potent than R 79595 (1:1 mixture of the isomers) and nearly 100 fold more potent than R 80123 (Z-isomer). Furthermore, the cardiotonic action of the most potent isomer (R 80122) was compared to the effects of several positive inotropic reference compounds. The order of cardiotonic potency was as follows: (-)-adrenaline > R 80122 = adibendan > digitoxin > milrinone = enoximone > theophylline. Adibendan (EC50 value: 6.7 +/- 1.8 x 10.-8 mol/l), which showed cardiotonic effects in the same concentration range as R 80122 (EC50 value: 6.1 +/- 1.3 x 10(-8) mol/l), was significantly (p < 0.01) less effective than R 80122 with respect to the maximally induceable increase in cardiac output (CO). The cardiotonic effects of R 80122 could be observed in the low concentration range of 3 x 10(-8) to 1 x 10(-6) mol/l, whereas enoximone (EC50 value: 1.2 +/- 0.1 x 10(-5) mol/l) and milrinone (EC50 value: 8.9 +/- 3.5 x 10(-6) mol/l) elicited positive inotropic effects at 100 fold higher concentrations. Digitoxin was 10 fold less and theophylline was 300 fold less potent than R 80122 with regard to reconstitution of heart function. The cardiotonic effects of R 80122 were not accompanied by an increase in heart rate as found with milrinone, theophylline or (-)-adrenaline in this model. Furthermore, the PDE inhibitory effect of R 79595 and its E-isomer R 80122 were investigated in partially purified isoenzymes from guinea-pig ventricles. The IC50 values of R 79595 and R 80122 on PDE I-IV were compared to the IC50 values of adibendan, milrinone, enoximone and theophylline. The selectivity of an inhibitor for PDE III was evaluated by division of its IC50 values on PDE I, II and IV by the IC50 value on PDE III. R 80122 was the most potent and selective PDE III inhibitor.(ABSTRACT TRUNCATED AT 400 WORDS)

Angiotensin-converting enzyme inhibitors, left ventricular dysfunction, and early heart failure

A study was undertaken to examine the effects of the angiotensin-converting enzyme inhibitor lisinopril on exercise performance in 18 patients with major impairment of left ventricular systolic function. The study was a randomized, double-blind, crossover design, and patients received treatment with either once-daily lisinopril (2.5-10 mg) or placebo for a period of 6 weeks. A total of 15 patients completed the study. Compared with placebo, lisinopril had no significant effect on supine or standing blood pressure or heart rate. Although lisinopril had no effect on exercise duration during a low-intensity exercise protocol, in patients undergoing a high-intensity exercise protocol, there was a trend toward improved exercise time and peak oxygen consumption improved significantly. In addition, treatment with lisinopril resulted in an increase in renal blood flow and a reduction in glomerular filtration rate. Moreover, administration of once-daily lisinopril 10 mg resulted in a decrease in plasma concentrations of angiotensin II, aldosterone, and atrial natriuretic peptide, and an increase in plasma concentrations of active renin.

Heart failure: to digitalise or not? The view against

Despite extensive clinical experience the role of digoxin is still not well defined. In patients with atrial fibrillation digoxin is beneficial for ventricular rate control. For patients in sinus rhythm and heart failure the situation is less clear. Digoxin has a narrow therapeutic:toxic ratio and concentrations are affected by a number of drugs. Also, digoxin has undesirable effects such as increasing peripheral resistance and myocardial demands, and causing arrhythmias. There is a paucity of data from well-designed trials. The trials that are available are generally small with limitations in design and these show variation in patient benefit. More convincing evidence is required showing that digoxin improves symptoms or exercise capacity. Furthermore, no trial has had sufficient power to evaluate mortality. Pooled analysis of the effects of other inotropic drugs shows an excess mortality and there is a possibility that digoxin may increase mortality after myocardial infarction (MI). Angiotensin-converting enzyme (ACE) inhibitors should be used first as they are safer, do not require blood level monitoring, modify progression of disease, relieve symptoms, improve exercise tolerance and reduce mortality. Caution should be exercised in using digoxin until large mortality trials are completed showing either benefit or harm. Until then digoxin should be considered a third-line therapy.

The rational pharmacology of digoxin

Although digoxin remains one of the most widely prescribed drugs in the United States, potential pharmacodynamic and pharmacokinetic interactions between this compound and other drugs, diseases, and events commonly encountered in the perioperative period remain largely unappreciated. Furthermore, the therapeutic benefit of discontinuing or initiating digoxin treatment preoperatively remains unclear. We present a basic review of current knowledge regarding digoxin pharmacology and examine those concepts from the perspective of clinical anesthesiologists.

Current issues in advanced heart failure

In the past 50 years, an increased understanding of the pathophysiologic mechanisms associated with the development of heart failure has produced a more precise treatment of this syndrome. The effects of the agents used for the treatment of patients with advanced heart failure have been summarized in this article and demonstrate the importance of vasodilatory drugs on the survival and progression of dilated cardiomyopathy.

Effect of flosequinan on exercise capacity and cardiac function in patients with chronic mild heart failure: a double-blind placebo-controlled study

Although beneficial effects of a new vasodilating agent, flosequinan, have been demonstrated in patients with severe heart failure, its efficacy has not been studied in patients with a less severe form of chronic heart failure. In this study, the effects of 4 weeks' administration of flosequinan, 50 mg daily, and placebo on exercise capacity, cardiac function, and symptoms of heart failure were investigated in 24 patients with chronic mild heart failure (New York Heart Association functional class, mainly class II) in a double-blind clinical trial. When the parameter changes during the treatment period of the flosequinan and placebo groups were compared, no significant difference was found in any of the measurements except for left ventricular fractional shortening determined from M-mode echocardiograms; it was increased by 2.9 +/- 1.3% in the flosequinan group whereas it was decreased by 1.3 +/- 0.9% in the placebo group (P less than 0.05 vs flosequinan treatment). However, when compared to baseline values, flosequinan significantly increased exercise time in the symptom-limited maximal exercise test (704 +/- 103 to 763 +/- 107 s, P less than 0.05) and the oxygen uptake at the anaerobic threshold (13.8 +/- 1.3 to 16.7 +/- 1.4 ml/min kg, P less than 0.05), and improved symptoms assessed with a new heart failure severity classification (a median value of 2.0-1.5, P less than 0.05). These improvements were not observed in the placebo group. Serious adverse effects were not observed in either group. These results suggest that flosequinan is useful for the treatment of chronic mild heart failure as well as severe heart failure.

The neurohormonal hypothesis: a theory to explain the mechanism of disease progression in heart failure

Because physicians have traditionally considered heart failure to be a hemodynamic disorder, they have described the syndrome of heart failure using hemodynamic concepts and have designed treatment strategies to correct the hemodynamic derangements of the disease. However, although hemodynamic abnormalities may explain the symptoms of heart failure, they are not sufficient to explain the progression of heart failure and, ultimately, the death of the patient. Therapeutic interventions may improve the hemodynamic status of patients but adversely affect their long-term outcome. These findings have raised questions about the validity of the hemodynamic hypothesis and suggest that alternative mechanisms must play a primary role in advancing the disease process. Several lines of evidence suggest that neurohormonal mechanisms play a central role in the progression of heart failure. Activation of the sympathetic nervous system and renin-angiotensin system exerts a direct deleterious effect on the heart that is independent of the hemodynamic actions of these endogenous mechanisms. Therapeutic interventions that block the effects of these neurohormonal systems favorably alter the natural history of heart failure, and such benefits cannot be explained by the effect of these treatments on cardiac contractility and ejection fraction. Conversely, pharmacologic agents that adversely influence neurohormonal systems in heart failure may increase cardiovascular morbidity and mortality, even though they exert favorable hemodynamic effects. These observations support the formulation of a neurohormonal hypothesis of heart failure and provide the basis for the development of novel therapeutic strategies in the next decade.

Review of randomized trials of digoxin therapy in patients with chronic heart failure

Although digitalis glycosides were introduced in the treatment of cardiac maladies greater than 200 years ago, controversy persists regarding the precise role of digoxin in any multidrug approach to the treatment of congestive heart failure (CHF). Despite its widespread use for more than 2 centuries, only recently have double-blind, randomized, placebo-controlled trials of digoxin therapy been conducted in patients with moderate CHF and sinus rhythm. These trials demonstrate that digoxin is superior to placebo in improving left ventricular (LV) ejection fraction, increasing exercise capacity, and preventing CHF worsening. Digoxin produces benefits similar to those seen with angiotensin converting enzyme (ACE) inhibitors with regard to clinical compensation and improvement in LV function. However, improved survival is demonstrated only in response to ACE inhibitors. The recently completed RADIANCE study addresses the value of combining digoxin with ACE inhibitor therapy in patients with mild-to-moderate CHF. Because increased mortality has been reported with the newer oral inotropic agents, it currently appears that digoxin is the only oral inotropic agent useful in clinical practice in the treatment of CHF. However, the effects of digoxin on mortality in patients with CHF remain unknown. In the large, double-blind, randomized trial conducted by the National Heart, Lung, and Blood Institute, the effects of digoxin on mortality in patients with CHF and already being treated with ACE inhibitors are currently being evaluated. Presently, based on the results of placebo-controlled studies, it appears that digoxin, alone or in combination with ACE inhibitors, is beneficial in patients with any signs or symptoms of CHF due to systolic LV dysfunction.

Recognition and management of asymptomatic patients with left ventricular dysfunction

In recent years there have been encouraging developments in the therapy for congestive heart failure. Vasodilator therapy, as an adjunct to digitalis and diuretics, has made a major impact. Vasodilator therapy results in improved left ventricular (LV) ejection fraction, improved functional capacity, and enhanced quality of life. When an angiotensin-converting enzyme (ACE) inhibitor is used, several studies published since 1988 show that these improvements are accompanied by improved survival. Yet many questions remain. Principal among these is how to approach the patient who has significantly depressed LV function, but is asymptomatic or has only minimal symptoms. In these patients the prognosis cannot be based on New York Heart Association (NYHA) functional class, but must reflect objective measurements of ventricular function. Any intervention should be specifically designed to improve survival, since functional capacity and quality of life are apparently unimpaired. On the other hand, there are no data at present to suggest that intervention in these patients will improve survival. This article considers the evaluation of such asymptomatic patients and potential therapeutic approaches. These are the use of cardiac glycosides, the use of ACE inhibitors, or their combination. Circumstantial evidence supporting their use in this select patient population is considered. It is stressed that any decision to intervene therapeutically in the asymptomatic patient must be made by the physician on an individual basis.

Management of refractory congestive heart failure

Despite recent advances in the treatment of congestive heart failure (CHF), many patients continue to present with symptoms refractory to digoxin, diuretic, and vasodilatory therapy. Since it is unlikely that this population will decrease in the near future, practical approaches to management of refractory CHF are reviewed. Refractory CHF here is defined as New York Heart Association (NYHA) functional class III-IV heart failure, despite maximal drug therapy. Before such a diagnosis is made, the patient should be treated with digoxin, diuretics, and a vasodilator. Approach to therapy requires assessment of changing clinical status and pathophysiology, optimizing oral drug treatment, and providing temporary parenteral support when indicated. Specific attention should be given to factors that influence the optimal response to each of these 3 treatment classes. A theoretical, but unproven, concept suggests that combined vasodilatory therapy may be appropriate as long as excessive hypotension is avoided. In the course of management, a decision is required as to whether further optimization of therapy can be achieved on an outpatient basis. Hospital-based intravenous inotropic support given for 2-4 days will often provide the opportunity to restructure patient therapy.

Need for a large randomized trial to evaluate the effects of digitalis on morbidity and mortality in congestive heart failure

Despite major advances in the prevention and treatment of cardiovascular diseases, the incidence and prevalence of congestive heart failure (CHF) have been increasing in recent years. As the average age of the population increases, the prevalence of CHF is expected to continue to increase. The number of deaths in which CHF was considered the underlying or contributing cause increased from 51,000 in 1955 to 274,000 by 1988 in the United States. Even accounting for population growth and an increase in the number of elderly, this represents a 2-fold increase. Additionally, CHF was responsible for about 643,000 hospitalizations in 1988. Digitalis is one of the drugs most commonly prescribed for CHF and has been used for greater than 200 years. In 1990, digoxin was one of the most commonly prescribed drugs in the United States, accounting for greater than 21 million prescriptions. There has been little decline in the drug's use over the last 5 years, indicating that newer treatments for CHF have not replaced the widespread use of digitalis. Despite these findings, considerable controversy surrounds the appropriateness of its role and value in treating CHF patients who are in sinus rhythm. A number of recent, uncontrolled studies have arrived at apparently contradictory conclusions concerning the effects of digitalis on mortality in postmyocardial infarction and heart failure patients. A large, double-blind, randomized, controlled clinical trial to evaluate the effects of digitalis on mortality, morbidity and quality of life is being sponsored by the National Heart, Lung, and Blood Institute in conjunction with the Department of Veterans Affairs Cooperative Studies Program.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term strategies in the management of heart failure: looking beyond ventricular function and symptoms

Therapeutic approaches to the management of heart failure have traditionally focused on shortterm hemodynamic and symptomatic goals, but present evidence suggests that most therapeutic decisions have long-term consequences. Treatment may change the rate of disease progression, modify the need for additional therapy, influence the number of hospitalizations, and alter the risk of death. However, there may be little relation between a drug's short-term effect on cardiac function or cardiovascular symptoms and its long-term effect on survival. Some therapeutic interventions favorably influence the outcome of patients with heart failure, even though they exert negative inotropic effects; others adversely affect the outcome of patients, even though they markedly improve cardiac performance. This discordance might be explained if the most important predictor of response to a therapeutic intervention in heart failure were the effect of the pharmacologic agent on neurohormonal systems rather than on hemodynamic variables. In general, drugs that decrease the effects of the sympathetic nervous system (digitalis glycosides) and the renin-angiotensin system (angiotensin-converting enzyme [ACE] inhibitors) reduce the risk of worsening heart failure. Conversely, drugs that potentiate the effects, or increase the activity, of the sympathetic nervous system (phosphodiesterase inhibitors) or the renin-angiotensin system (calcium antagonists) increase cardiovascular morbidity and mortality. These observations suggest that physicians should no longer focus on short-term hemodynamic or symptomatic goals in the treatment of heart failure but, instead, should manage patients to improve both the quality and quantity of life.

Ventricular arrhythmia in congestive heart failure

The importance of ventricular arrhythmia is based on its association with sudden death. In certain groups of patients, ventricular arrhythmia--primarily runs of nonsustained ventricular tachycardia (NSVT)--is associated with an increased risk for sudden death. Although this relationship has been most often reported in patients with recent myocardial infarction, it has also been recognized in patients with dilated cardiomyopathy, regardless of etiology. Therefore, ventricular arrhythmia is common in patients with CHF due to cardiomyopathy. A number of studies have reported that 70-95% of patients with cardiomyopathy and congestive heart failure (CHF) have frequent ventricular premature beats, and 40-80% will manifest runs of NSVT. Many factors are responsible for ventricular arrhythmia in such patients, including structural abnormalities, electrolyte imbalance, hemodynamic impairment, activation of neurohormonal mechanisms, and pharmacologic therapy. Many studies have reported a high yearly mortality in patients with cardiomyopathy and CHF; greater than 40% of deaths are sudden, most often the result of sustained ventricular tachyarrhythmia. Most studies have noted an association between presence (and frequency) of NSVT and risk of sudden cardiac death in these patients. Unfortunately, other techniques--such as the signal-averaged electrocardiogram and electrophysiologic testing--are not helpful in identifying the individual at risk. Although several drug interventions will reduce mortality from progressive CHF, these drugs have not been shown to reduce sudden death and, indeed, have a variable effect on ventricular arrhythmia. Although NSVT is a marker for increased risk for sudden death, it is uncertain if antiarrhythmic drugs will prevent this outcome. Antiarrhythmic drugs have not been shown to be effective for preventing sudden death, although there are as yet no well-controlled randomized trials. Several studies suggest that amiodarone and beta blockers are beneficial, but this requires confirmation. For patients who have been resuscitated following an episode of sudden death due to a sustained ventricular tachyarrhythmia, antiarrhythmic therapy guided by invasive and noninvasive techniques appears to reduce risk of recurrent arrhythmia. However, the response rate to antiarrhythmic agents is low and side effects are common in patients with CHF. Especially important is the increased risk of precipitating CHF and aggravating the arrhythmia being treated. For many such patients who have had serious ventricular tachyarrhythmia, the automatic implantable cardioverter defibrillator may prove a better option. Other drugs used for management of CHF reduce overall mortality, but not risk of sudden death.

Current status of non-digitalis positive inotropic drugs

Considerable effort and resources have been directed at the development and study of positive inotropic drugs over the past 10-15 years. Much has been learned about the physiology and pharmacology of myocardial contraction, the application of agents to augment contractility, and, importantly, the general and specific limitations of positive inotropic therapy. Studies on acute inotropic intervention have now shown that a drug's ability to augment overall cardiac performance is heavily dependent on its effects on vasculature, vascular control, and ventricular-vascular coupling. The clinical research on new agents has served to remind us how difficult it is to formulate the "ideal" positive inotropic or cardiovascular support drug for the critical care setting. The vast effort to develop a chronically and orally administrable drug to replace or even supplement digitalis has generally been disappointing. The dopaminergic agents (e.g., ibopamine, levodopa) act primarily via vasodilation and their effectiveness and role in managing heart failure remain unresolved. The initial excitement about the phosphodiesterase III inhibitors (e.g., amrinone, milrinone, enoximone) has been tempered by the results of large well-designed trials indicating variable effectiveness and a prominent adverse effect profile. During long-term oral administration none of these agents has been shown to improve clinical status or exercise capacity beyond that achieved by digoxin, when administered either separately or in combination with digoxin. The Prospective Randomized Milrinone Survival Evaluation (PROMISE) trial, showing that repeated oral administration of milrinone can increase mortality in heart failure, is having a devastating effect on the further development of this class of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

The paradox of beta-adrenergic blockade for the management of congestive heart failure

PURPOSE

To review the current data regarding the use of beta-adrenergic blockers for the treatment of congestive heart failure.

MATERIAL AND METHODS

Relevant studies published between 1975 and 1991 were reviewed. Key data from each study were extracted. The significance of conclusions reached by each author(s) was identified.

RESULTS

beta-adrenergic blockade, although still considered an investigational therapy for the treatment of congestive heart failure, has been proven in several studies to improve ventricular function, including myocardial contractility and relaxation. In addition, since beta-blockade up-regulates myocardial beta-receptors, the myocardium becomes more responsive to graded doses of beta-agonists. Speculation regarding the possible mechanisms of these effects is presented. In addition, since beta-blockers have been shown to reduce neurohormonal activation, they may have a beneficial effect on survival. Although small pilot studies or subgroup analysis of larger studies suggest beta-blockade therapy improves survival in heart failure, this has yet to be proven. Large prospective trials are warranted to study this issue.

CONCLUSIONS

As current data suggest, beta-blockers improve ventricular function and reduce neurohormonal activation in heart failure. beta-blockers should be considered as adjunctive therapy in patients with congestive heart failure. In addition, future studies are warranted to better elucidate their effects on ventricular function and survival.

The effect of treatment on survival in congestive heart failure

Congestive heart failure (CHF) is a disorder characterized by a variety of clinical, biochemical, electrophysiological, and hemodynamic abnormalities. During the past two decades, numerous drugs have been employed in the treatment of this complex syndrome, and many agents have been shown to improve symptoms and ventricular function in patients with CHF. Because CHF is associated with a high risk of death, treatment should be directed not only toward the relief of symptoms, but also toward a reduction in mortality. Many variables have been shown to be related to survival; taken individually, however, each is limited in its utility in predicting prognosis. In recent years, large-scale studies with large sample sizes have directly assessed the effects of treatment on mortality in CHF. Results from these trials indicate that vasodilators and angiotensin-converting enzyme (ACE) inhibitors may improve mortality in patients with symptoms of heart failure. Additional trials are now in progress to evaluate the effect of treatment on patients with asymptomatic left ventricular dysfunction.

Impact of converting enzyme inhibition on progression of chronic heart failure: results of the Munich Mild Heart Failure Trial

OBJECTIVE

Neurohormonal activation has major impact on the pathophysiology of congestive heart failure. The Munich Mild Heart Failure Trial was designed to test the hypothesis that interference with the renin-angiotensin system by angiotensin converting enzyme inhibition favourably influences the natural history of heart failure.

DESIGN AND PATIENTS

170 patients, median New York Heart Association (NYHA) class II, were randomised to double blind treatment with 25 mg captopril twice a day or placebo in addition to standard treatment for a median observation period of 2.7 years.

MAIN OUTCOME MEASURES

Progression of heart failure to NYHA class IV on an optimally adjusted standard treatment, death due to progressive heart failure, and sudden death.

RESULTS

Heart failure progressed to class IV in nine patients (10.8%) treated with captopril and in 23 patients (26.4%) treated with placebo (p = 0.01). The mean survival time until this end point was 223 days longer in the captopril group (Kaplan-Meier life table analysis; p = 0.02). Also, progressive deterioration to severe heart failure was a powerful predictor of total mortality and death from heart failure; 80% of deaths due to progressive heart failure occurred after this end point. There were fewer deaths caused by progressive heart failure in the captopril group than in the placebo group (4 v 11; p = 0.10) but similar numbers of sudden deaths (11 v 10). Progressive heart failure was the cause of death in 18.2% of all deaths in the captopril group and 50% in the placebo group. Total heart failure events (the end point on which power calculation was based) were also more common in the placebo group (19 v 32 events) but not significantly so. Total mortality was similar to both groups (22 of 83 v 22 of 87).

CONCLUSIONS

Angiotensin converting enzyme inhibition in conjunction with standard therapy early in the course of congestive heart failure slowed the progress of heart failure and thus favourably altered the natural history of the disease.

Beneficial effects of pimobendan on exercise tolerance and quality of life in patients with heart failure. Results of a multicenter trial. The Pimobendan Multicenter Research Group

BACKGROUND

This multicenter trial was conducted to determine the efficacy and safety of pimobendan, an inotropic agent with calcium-sensitizing properties and activity as a phosphodiesterase inhibitor, in patients with heart failure.

METHODS AND RESULTS

One hundred ninety-eight ambulatory patients with symptoms of moderate to severe heart failure despite therapy with digitalis and diuretics with or without a single vasodilator were randomly assigned to receive either placebo (n = 49) or pimobendan (n = 149) in a double-blind fashion for 12 weeks. A dose range of pimobendan was used including 2.5 (n = 49), 5 (n = 51), or 10 mg/day (n = 49). One hundred fifty-eight (80%) patients were taking a converting enzyme inhibitor (CEI) and 28 (14%) patients were taking a non-CEI vasodilator. At end point, the 5-mg dose of pimobendan significantly increase exercise duration compared with placebo (121.6 +/- 19.1 seconds, p less than 0.001), whereas the 10-mg dose produced an increase of borderline significance (81.1 +/- 19.5 seconds, p = 0.05). Peak VO2 was significantly increased by 2.23 +/- 0.58 ml/kg/min in the 5-mg group (p less than 0.01 versus placebo). Furthermore, quality of life measured with the Minnesota Living With Heart Failure Questionnaire improved by 8.5 +/- 2.3 units in the 5-mg group compared with 1.3 +/- 2.2 units in the placebo group (p less than 0.01). There were a total of 23 all-cause hospitalizations in the placebo group, which was significantly greater compared with 33 in the three groups treated with pimobendan (p less than 0.01). There were no significant differences between the placebo and pimobendan groups with respect to changes in ejection fraction and plasma norepinephrine measured at baseline and at the completion of the 12-week study, proarrhythmic effect, or the number of patients with a significant adjustment in background therapy. Eleven patients died, including three (6%) on placebo and eight (5%) on pimobendan (p = NS). Among all adverse events, headache tended to be more common in the pimobendan groups compared with placebo, with the incidence increasing with dose (p less than 0.05).

CONCLUSIONS

These data demonstrate that pimobendan significantly increases exercise duration, peak VO2, and quality of life in patients with heart failure. Pimobendan appears to be useful adjunctive therapy when added to digitalis, diuretics, and vasodilators.

A multicenter, randomized, double-blind, placebo-controlled trial of pimobendan, a new cardiotonic and vasodilator agent, in patients with severe congestive heart failure

Pimobendan, a new oral cardiotonic and vasodilator agent, increases myocardial contractile force through specific inhibition of phosphodiesterase type III and increased calcium sensitivity of the myocardial contractile elements. The effects of pimobendan on left ventricular performance and maximal exercise capacity were studied in a multicenter, randomized, double-blind, placebo-controlled trial involving 52 patients with severe congestive heart failure despite diuretics, digoxin, and angiotensin-converting enzyme inhibitors. The acute hemodynamic evaluation included three single doses of 2.5, 5.0, and 10.0 mg of oral pimobendan, which was subsequently administered at a daily dose of 5 or 10 mg for 4 weeks. Acute administration of pimobendan significantly increased the resting cardiac index and lowered pulmonary capillary wedge pressure in a dose-dependent manner, whereas heart rate and systemic arterial pressure were not substantially altered. Patients receiving pimobendan, 5 and 10 mg daily, had a significantly greater increase in maximal exercise duration than those receiving placebo, that is, 144 +/- 30 and 124 +/- 33 seconds versus 58 +/- 25 seconds (p = 0.05). Peak oxygen uptake increased by 1.7 +/- 0.8 and 2.2 +/- 1.3 ml/kg/min in patients receiving pimobendan at a daily dose of 5 and 10 mg, respectively, whereas it decreased by 0.1 +/- 0.6 ml/kg/min in patients receiving placebo (p = 0.06). Thus pimobendan acutely improves resting left ventricular performance and chronically increases exercise duration and peak oxygen uptake in patients with severe congestive heart failure concomitantly treated with digoxin, diuretics, and angiotensin-converting enzyme inhibitors.

Control of arteriolar resistance in heart failure. Partial attenuation of specific phosphodiesterase inhibitor-mediated vasodilation by digitalis glycosides

BACKGROUND

The vasodilatory response to local specific type III phosphodiesterase inhibition with amrinone was evaluated before and immediately after local administration of digoxin in 14 patients with severe congestive heart failure (CHF).

METHODS AND RESULTS

A 3F polyethylene catheter was inserted into the common femoral artery for drug administration and pressure monitoring. Mean blood flow velocity (MBFV) was continuously determined in the superficial femoral artery by transcutaneous Doppler ultrasonography. After intra-arterial administration of 10 mg amrinone, group MBFV increased from 7.7 +/- 1.4 to 16.0 +/- 2.1 cm/sec (p less than 0.05, n = 10). Local administration of 20 micrograms digoxin, which was infused over 20 minutes, did not alter group MBFV (i.e., 8.2 +/- 1.6 versus 7.6 +/- 1.5 cm/sec; p = NS, n = 10). The second administration of 10 mg amrinone, which immediately followed completion of local digoxin infusion, increased group MBFV but to a lesser extent than that produced by the first amrinone administration (i.e., 11.9 +/- 1.9 versus 16.0 +/- 2.1 cm/sec; p less than 0.05, n = 10). When placebo was administered instead of digoxin, group MBFV was similar after the first and second administrations of amrinone (i.e., 15.3 +/- 3.3 versus 15.6 +/- 3.8 cm/sec; p = NS, n = 4).

CONCLUSIONS

Although local administration of digoxin did not significantly alter baseline vascular tone in patients with CHF, it substantially decreased the direct vasodilatory effect induced by specific type III phosphodiesterase with amrinone.

Changing strategies in the management of chronic congestive heart failure

Recent studies have more clearly defined the role of drug therapy in patients with chronic congestive heart failure (CHF). Treatment of patients with asymptomatic left ventricular dysfunction (New York Heart Association [NYHA] class I) cannot be recommended at this time. The benefit of prophylactic treatment with angiotensin-converting enzyme inhibitors (ACEIs) or vasodilators in patients at high risk for developing symptomatic CHF is currently being evaluated. Treatment of patients with symptomatic CHF (NYHA class II-IV) should be initiated with a combination of a diuretic, digoxin, and an ACEI. This combination has been shown to reduce the mortality rate in patients with NYHA class II-IV CHF. Patients who remain symptomatic despite treatment with this combination may benefit from the addition of the direct-acting, nonspecific vasodilators--hydralazine and a nitrate. The addition of the nonspecific vasodilators to an ACEI has not been tested in controlled trials. In patients who remain symptomatic despite treatment with diuretics, digoxin, ACEIs, and nonspecific vasodilators, treatment options are not clear. The use of beta-agonists, phosphodiesterase inhibitors, and intermittent fixed-dose, fixed-interval dobutamine should be avoided as these agents are associated with a high mortality rate. Heart transplantation should be considered early in the course of CHF to allow for preservation of other vital organ systems. Unfortunately, heart transplantation is available to only a very small minority of potential transplant candidates.

Calcium-sensitizing inotropic agents in the treatment of heart failure: a critical view

Interventions that augment the contractile state of the heart are associated with, or caused by, alterations in Ca2+ exchange in heart muscles. New inotropic agents have been developed that increase the sensitivity of the myofilaments to Ca2+. To examine the effect of calcium-sensitizing agents on force development, we measured systolic and diastolic intracellular Ca2+ concentration [( Ca2+]i) and constructed [Ca2+]i-force relationships in normal (n = 6) and myopathic human hearts (n = 10). Using the bioluminescent calcium indicator aequorin, we found that the diastolic [Ca2+]i was 225 +/- 52 nM in normal muscles, whereas in myopathic muscles diastolic [Ca2+]i was significantly higher at 361 +/- 68 nM. Calcium-sensitizing agents that shift the [Ca2+]i-force relationship toward lower [Ca2+]i increase the diastolic force of myopathic hearts significantly more than in normal human hearts. This leads us to the conclusion that inotropic agents that increase the sensitivity of the myofilaments to Ca2+ further impair relaxation in myopathic hearts, resulting in a reduced contractile reserve and diminished active force production.

Enalapril versus digoxin in patients with congestive heart failure: a multicenter study. Canadian Enalapril Versus Digoxin Study Group

Patients with New York Heart Association functional class II or III heart failure stabilized on furosemide therapy were entered into a randomized controlled trial comparing enalapril (n = 72) and digoxin (n = 73). End points were clinical outcome, treadmill exercise capacity and echocardiographic left ventricular dimensions. Improvement in clinical outcome was defined as a reduction of at least one functional class or withdrawal because of an adverse clinical event. After 4 weeks, 13 patients receiving enalapril showed improvement, 55 had no change and 9 manifested deterioration compared with 7, 49 and 17, respectively, in the digoxin group (p less than 0.01). After 14 weeks, 13 patients receiving enalapril showed improvement, 50 had no change and 9 manifested deterioration, compared with 14, 37 and 22, respectively, in the digoxin group (p less than 0.025). More patients in the digoxin group were withdrawn because of an adverse clinical event (p less than 0.05). Exercise time and percent fractional shortening improved in both groups (p less than 0.001 and less than 0.05, respectively), with no significant difference between groups (p greater than 0.50). Both rate-pressure product and subjectively evaluated exertion during submaximal exercise were reduced only in the enalapril group. Although the majority of patients in both groups did well, those receiving enalapril experienced fewer adverse clinical events and had less fatigue during submaximal exercise.

Effect of oral milrinone on mortality in severe chronic heart failure. The PROMISE Study Research Group

BACKGROUND

Milrinone, a phosphodiesterase inhibitor, enhances cardiac contractility by increasing intracellular levels of cyclic AMP, but the long-term effect of this type of positive inotropic agent on the survival of patients with chronic heart failure has not been determined.

METHODS

We randomly assigned 1,088 patients with severe chronic heart failure (New York Heart Association class III or IV) and advanced left ventricular dysfunction to double-blind treatment with (40 mg of oral milrinone daily (561 patients) or placebo (527 patients). In addition, all patients received conventional therapy with digoxin, diuretics, and a converting-enzyme inhibitor throughout the trial. The median period of follow-up was 6.1 months (range, 1 day to 20 months).

RESULTS

As compared with placebo, milrinone therapy was associated with a 28 percent increase in mortality from all causes (95 percent confidence interval, 1 to 61 percent; P = 0.038) and a 34 percent increase in cardiovascular mortality (95 percent confidence interval, 6 to 69 percent; P = 0.016). The adverse effect of milrinone was greatest in patients with the most severe symptoms (New York Heart Association class IV), who had a 53 percent increase in mortality (95 percent confidence interval, 13 to 107 percent; P = 0.006). Milrinone did not have a beneficial effect on the survival of any subgroup. Patients treated with milrinone had more hospitalizations (44 vs. 39 percent, P = 0.041), were withdrawn from double-blind therapy more frequently (12.7 vs. 8.7 percent, P = 0.041), and had serious adverse cardiovascular reactions, including hypotension (P = 0.006) and syncope (P = 0.002), more often than the patients given placebo.

CONCLUSIONS

Our findings indicate that despite its beneficial hemodynamic actions, long-term therapy with oral milrinone increases the morbidity and mortality of patients with severe chronic heart failure. The mechanism by which the drug exerts its deleterious effects is unknown.

Usefulness of OPC-8212, a quinolinone derivative, for chronic congestive heart failure in patients with ischemic heart disease or idiopathic dilated cardiomyopathy

To evaluate the safety and efficacy of the inotropic agent OPC-8212 in patients with chronic congestive heart failure, 76 patients with impaired cardiac function and diminished exercise tolerance were studied. They were randomized to 12 weeks of double-blind therapy with either 60 mg/day of OPC-8212 or placebo. The study drug was added to their baseline medical regimen. The primary study outcome was the combined outcome of the time to either mortality (of all cause) or substantial worsening of heart failure (major morbidity), whichever occurred first. Treatment with OPC-8212 significantly (p less than 0.01) decreased the combination of major morbidity/mortality over 12 weeks of therapy. Quality of life, assessed by the Sickness Impact Profile questionnaire, was significantly improved in patients receiving OPC-8212 (p less than 0.01). Furthermore, ventricular premature contractions as assessed by 24-hour Holter monitoring were not increased with OPC-8212 treatment. Although patients treated with OPC-8212 were able to reach a significantly higher peak oxygen uptake and exercise longer during symptom-limited exercise, when data were analyzed as percent change from baseline, the absolute increases were small. These results suggest that OPC-8212 is beneficial in treating patients with congestive heart failure and that further evaluation of this new inotropic agent is warranted.

Electrophysiologic profile of ibopamine in patients with congestive heart failure and ventricular tachycardia and relation to its effects on hemodynamics and plasma catecholamines

Programmed electrical stimulation was performed in 12 patients with moderate to severe congestive heart failure and ventricular tachycardia (VT) to study possible arrhythmogenic properties of ibopamine, a new orally active dopamine agonist. Ibopamine induced no significant changes in spontaneous cycle length, PR, QRS, QTc, AH or HV intervals, and also right ventricular effective refractory periods were unaffected (for paced cycle lengths of 600 and 430 ms, respectively, using 1 extrastimulus: 287 +/- 16 ms at baseline vs 283 +/- 27 ms after ibopamine and 270 +/- 23 ms during the control study vs 262 +/- 19 ms after ibopamine). In 6 of the 8 patients with coronary artery disease but in none of the 4 patients with dilated cardiomyopathy, sustained VT was induced before and after ibopamine. Proarrhythmia was present in 1 patient, who became inducible after ibopamine. However, 1 patient had sustained VT only at baseline but not after ibopamine. The number of extrastimuli required for VT induction was equal (2.7 +/- 0.2 vs 2.7 +/- 0.2). Holter monitoring showed no changes in ventricular premature complexes, ventricular couplets and runs of VT after 1 week of ibopamine therapy. The signal-averaged electrocardiogram was abnormal in 11 and showed late potentials in 5 patients, but no changes occurred after ibopamine. During hemodynamic evaluation, increases in cardiac (32%) and stroke volume (34%) indexes were seen after administration of 100 mg of ibopamine, accompanied by a decrease in vascular resistance and filling pressures. Plasma norepinephrine decreased significantly after ibopamine (p = 0.02) but plasma epinephrine was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)