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

Insights from Second-Line Treatments for Idiopathic Dilated Cardiomyopathy

Background: Dilated cardiomyopathy (DCM) is an independent nosographic entity characterized by left ventricular dilatation and contractile dysfunction leading to heart failure (HF). The idiopathic form of DCM (iDCM) occurs in the absence of coronaropathy or other known causes of DCM. Despite being different from other forms of HF for demographic, clinical, and prognostic features, its current pharmacological treatment does not significantly diverge. Methods: In this study we performed a Pubmed library search for placebo-controlled clinical investigations and a post-hoc analysis recruiting iDCM from 1985 to 2016. We searched for second-line pharmacologic treatments to reconsider drugs for iDCM management and pinpoint pathological mechanisms. Results: We found 33 clinical studies recruiting a total of 3392 patients of various durations and sizes, as well as studies that tested different drug classes (statins, pentoxifylline, inotropes). A metanalysis was unfeasible, although a statistical significance for changes upon treatment for molecular results, morphofunctional parameters, and clinical endpoints was reported. Statins appeared to be beneficial in light of their pleiotropic effects; inotropes might be tolerated more for longer times in iDCM compared to ischemic patients. General anti-inflammatory therapies do not significantly improve outcomes. Metabolic and growth modulation remain appealing fields to be investigated. Conclusions: The evaluation of drug effectiveness based on direct clinical benefit is an inductive method providing evidence-based insights. This backward approach sheds light on putative and underestimated pathologic mechanisms and thus therapeutic targets for iDCM management.

In silico risk assessment for drug-induction of cardiac arrhythmia

The main components of repolarization reserve for the ventricular action potential (AP) are the rapid (I(Kr)) and slow (I(Ks)) delayed outward K(+) currents. While many drugs block I(Kr) and cause life-threatening arrhythmias including torsades de pointes, the frequency of arrhythmias varies between different I(Kr)-blockers. Different types of block of I(Kr) cause distinct phenotypes of prolongation of action potential duration (APD), increase in transmural dispersion of repolarization (TDR) and, accordingly, occurrence of torsades de pointes. Therefore the assessment of a drug's proarrhythmic risk requires a method that provides quantitative and comprehensive comparison of the effects of different forms of I(Kr)-blockade upon APDs and TDR. However, most currently available methods are not adapted to such an extensive comparison. Here, we introduce I(Kr)-I(Ks) two-dimensional maps of APD and TDR as a novel risk-assessment method. Taking the kinetics of I(Kr)-blockade into account, APDs can be calculated upon a ventricular AP model which systematically alters the magnitudes of I(Kr) and I(Ks). The calculated APDs are then plotted on a map where the x axis represents the conductance of I(Kr) while the y axis represents that of I(Ks). TDR is simulated with models corresponding to APs in epicardial, midcardial and endocardial myocardium. These two-dimensional maps of APD and TDR successfully account for differences in the risk resulting from three distinct types of I(Kr)-blockade which correspond to the effects of dofetilide, quinidine and vesnarinone. This method may be of use to assess the arrhythmogenic risk of various I(Kr)-blockers.

Heart failure and a controlled trial investigating outcomes of exercise training (HF-ACTION): design and rationale

BACKGROUND

Although there are limited clinical data to support the use of exercise training as a means to reduce mortality and morbidity in patients with heart failure, current guidelines state that exercise is beneficial.

TRIAL DESIGN

The objective of this trial is to determine whether exercise training reduces all-cause mortality or all-cause hospitalization for patients with left ventricular systolic dysfunction and heart failure symptoms. After undergoing baseline assessments to determine whether they can safely exercise, patients are randomized to either usual care or exercise training. Patients in the exercise training arm attend 36 supervised facility-based exercise training sessions. Exercise modalities are cycling or walking. After completing 18 sessions, patients initiate home-based exercise and then transition to solely home-based exercise after completing all 36 sessions. Patients return for facility-based training every 3 months to reinforce their exercise training program. Patients are followed for up to 4 years. Physiologic, quality-of-life, and economic end points that characterize the effect of exercise training in this patient population will be measured at baseline and at intervals throughout the trial. Blood samples will be collected to examine biomarkers such as brain natriuretic peptide, tumor necrosis factor, and C-reactive protein.

CONCLUSIONS

Because of its relatively low cost, high availability, and ease of use, exercise training is an intervention that could be accessible to most patients with heart failure. The HF-ACTION trial is designed to definitively assess the effect of exercise training on the clinically relevant end points of mortality, hospitalization, and quality of life in patients with heart failure.

Frequency-dependent effects of various IKr blockers on cardiac action potential duration in a human atrial model

Rapidly activating K(+) current (I(Kr)) blockers prolong action potential (AP) duration (APD) in a reverse-frequency-dependent manner and may induce arrhythmias, including torsade de pointes in the ventricle. The I(Kr) blocker dofetilide has been approved for treatment of atrial arrhythmias, including fibrillation. There are, however, a limited number of studies on the action of I(Kr) blockers on atrial AP. When we tested a mathematical model of the human atrial AP (M Courtemanche, RJ Ramirez, S Nattel. Am J Physiol Heart Circ Physiol 275: H301-H321, 1998) to examine the effects of dofetilide-type I(Kr) blockade, this model could not reproduce the reverse-frequency-dependent nature of I(Kr) blockade on atrial APD. We modified the model by introducing a slowly activating K(+) current activation parameter. As the slow time constant was increased, dofetilide-type blockade induced more prominent reverse-frequency-dependent APD prolongation. Using the modified model, we also examined the effects of two more types of I(Kr) blockade similar to those of quinidine and vesnarinone. Voltage- and time-dependent block of I(Kr) through the onset of inhibition by quinidine is much faster than by vesnarinone. When we incorporated the kinetics of the effects of these drugs on I(Kr) into the model, we found that quinidine-type blockade caused a reverse-frequency-dependent prolongation of APD that was similar to the effect of dofetilide-type blockade, whereas vesnarinone-type blockade did not. This finding coincides with experimental observations. The lack of the reverse frequency dependence in vesnarinone-type blockade was accounted for by the slow development of I(Kr) blockade at depolarized potentials. These results suggest that the voltage- and time-dependent nature of I(Kr) blockade by drugs may be critical for the phenotype of the drug effect on atrial AP.

Acute heart failure: inotropic agents and their clinical uses

Inotropic agents are indispensable for the improvement of cardiac contractile dysfunction in acute or decompensated heart failure. Clinically available agents, including sympathomimetic amines (dopamine, dobutamine, noradrenaline) and selective phosphodiesterase-3 inhibitors (amrinone, milrinone, olprinone and enoximone) act via cAMP/protein kinase A (PKA)-mediated facilitation of intracellular Ca2+ mobilisation. Phosphodiesterase-3 inhibitors also have a vasodilatory action, which plays a role in improving haemodynamic parameters in certain patients, and are termed inodilators. The available inotropic agents suffer from risks of Ca2+ overload leading to arrhythmias, myocardial cell injury and ultimately, cell death. In addition, they are energetically disadvantageous because of an increase in activation energy and cellular metabolism. Furthermore, they lose their effectiveness under pathophysiological conditions, such as acidosis, stunned myocardium and heart failure. Pimobendan and levosimendan (that act by a combination of an increase in Ca2+ sensitivity and phosphodiesterase-3 inhibition) appear to be more beneficial among existing agents. Novel Ca2+ sensitisers that are under basic research warrant clinical trials to replace available inotropic agents.

Clinical and analytical considerations in the study of health status in device trials for heart failure

BACKGROUND

Measures of health status (including symptoms, functional status, or quality of life) assess patients' experiences of their disease, and may therefore be used to quantify the benefits and risks of treatment. The aim of this article is to provide recommendations to regulatory agencies and research sponsors regarding the use of health status measures in medical device trials.

METHODS AND RESULTS

A workshop jointly planned by the Heart Failure Society of America and the US Food and Drug Administration was convened in October 2003 in Washington, DC. A Working Group to address health status measures initiated its collaboration at the workshop and continued its efforts throughout the next year. The Working Group recommended assessment of health status in all studies of heart failure therapy. Standardized instruments known to be valid, reliable, responsive to changes, and available in the languages of target populations should be used. Minimizing bias may be accomplished by using blinded, independent evaluators; collecting multiple health status measures; using valid statistical methods; and creating a health status resource bank.

CONCLUSION

Assessment of health status should be part of any device trial and should occur regardless of whether the device is intended as destination or bridging therapy. Health status endpoints should be chosen, collected, and analyzed with the same level of scientific rigor as traditional clinical endpoints. Regulatory agencies should require use of analytic methods that handle the complexity of health status data in addition to usual protocol protections.

Phosphodiesterase III inhibitors for heart failure

BACKGROUND

In the treatment of chronic heart failure, vasodilating agents, ACE inhibitors and beta-blockers have shown an increase of life expectancy. Another strategy is to increase the inotropic state of the myocardium : phosphodiesterase inhibitors (PDIs) act by increasing intra-cellular cyclic AMP, thereby increasing the concentration of intracellular calcium, and lead to a positive inotropic effect.

OBJECTIVES

This overview on summarised data aims to review the data from all randomised controlled trials of PDIs III versus placebo in symptomatic patients with chronic heart failure. The primary endpoint is total mortality. Secondary endpoints are considered such as cause-specific mortality, worsening of heart failure (requiring intervention), myocardial infarction, arrhythmias and vertigos. We also examine whether the therapeutic effect is consistent in the subgroups based on the use of concomitant vasodilators, the severity of heart failure, and the type of PDI derivative and/or molecule. This overview updates our previous meta-analysis published in 1994.

SEARCH STRATEGY

Randomised trials of PDIs versus placebo in heart failure were searched using MEDLINE (1966 to 2004 January), EMBASE (1980 to 2003 December), Cochrane CENTRAL trials (The Cochrane Library Issue 1, 2004) and McMaster CVD trials registries, and through an exhaustive handsearching of international abstracting publications (abstracts published in the last 22 years in the "European Heart Journal", the "Journal of the American College of Cardiology" and "Circulation").

SELECTION CRITERIA

All randomised controlled trials of PDIs versus placebo with a follow-up duration of more than three months.

DATA COLLECTION AND ANALYSIS

21 trials (8408 patients) were eligible for inclusion in the review. 4 specific PDI derivatives and 8 molecules of PDIs have been considered.

MAIN RESULTS

As compared with placebo, treatment with PDIs was found to be associated with a significant 17% increased mortality rate (The relative risk was 1.17 (95% confidence interval 1.06 to 1.30; p<0.001). In addition, PDIs significantly increase cardiac death, sudden death, arrhythmias and vertigos. Considering mortality from all causes, the deleterious effect of PDIs appears homogeneous whatever the concomitant use (or non-use) of vasodilating agents, the severity of heart failure, the derivative or the molecule of PDI used.

AUTHORS' CONCLUSIONS

Our results confirm that PDIs are responsible for an increase in mortality rate compared with placebo in patients suffering from chronic heart failure. Currently available results do not support the hypothesis that the increased mortality rate is due to additional vasodilator treatment. Consequently, the chronic use of PDIs should be avoided in heart failure patients.

Clinical characteristics of vesnarinone

Congestive heart failure is a common condition with a poor prognosis. Its high rates of morbidity and mortality produce a huge societal burden. Current pharmacological treatment approaches are based on angiotensin-converting enzyme inhibitors, diuretics and digoxin, but up to 5% of patients may have refractory disease with persistent symptoms at rest. Such patients with advanced-stage disease may be candidates for treatment with the novel agent vesnarinone, a mixed phosphodiesterase inhibitor and ion-channel modifier that has modest, dose-dependent, positive inotropic activity, but minimal negative chronotropic activity. Vesnarinone improves ventricular performance most in patients with the worst degree of heart failure. However, before the initiation of vesnarinone therapy, risk-benefit profiles in individual patients should be considered, because in two large-scale studies [i.e. of the high dosage used in the Vesnarinone Study Group Trial (VSGT), and of both dosages used in the Vesnarinone Trial (VEST)] a dose-dependent increase in mortality was identified for vesnarinone 30-120 mg/day. The two studies also found significant vesnarinone-induced, short-term improvements in quality of life (QOL) in patients with refractory end-stage heart failure. Such patients are the most willing to trade-off a slightly increased risk of mortality for improved QOL. It is thus in these patients with refractory end-stage heart failure that vesnarinone may ultimately establish an important treatment role. However, detailed further investigation of the overall place of vesnarinone in heart failure management, with particular reference to the clinical potential of vesnarinone plus beta-blocker combination therapy, for example, is certainly warranted.

Comparison of kinetic properties of quinidine and dofetilide block of HERG channels

Many drugs inhibit human ether-a-go-go related gene (HERG) current and prolong cardiac action potential duration. We examined the kinetic properties of quinidine block of HERG channels expressed in Xenopus oocytes in comparison with those of the block by a class III antiarrhythmic dofetilide. Both of the drugs inhibited HERG currents in a use-dependent and frequency-independent manner. However, the underlying mechanisms were different. Under the steady state, quinidine block was voltage- and time-dependent. At positive membrane potentials, the onset of block was very fast. Thus, quinidine caused frequency-independent block mainly through this fast blocking kinetic. In contrast, dofetilide blocked HERG currents in a voltage- and time-independent manner under the steady state because of very slow unblocking at negative potentials, which also caused frequency-independent block. Therefore, quinidine and dofetilide might cause the reverse frequency-dependent prolongation of action potential duration through distinct mechanisms with regard to blocking and unblocking kinetics.

Precautions for Use and Adverse Effects of Vesnarinone Potential Mechanisms and Future Therapies

This article reviews the precautions and adverse effects associated with vesnarinone use, and the potential mechanisms responsible for these complications as well as suggested treatment strategies. Vesnarinone, a quinolinone derivative, improves the haemodynamics and quality of life in patients with congestive heart failure (CHF); however, it is associated with the adverse effects of increased sudden cardiac death and neutropenia. These adverse effects have limited the application of vesnarinone to the general population but perhaps with continued research into vesnarinone-induced neutropenia and advances in arrhythmia management, the risk/ benefit ratio of vesnarinone may become favourable. For now, the use of vesnarinone should be limited to patients with CHF who have demonstrated a poor response to other cardiac medications and devices. These patients should be closely monitored for both cardiac and non-cardiac adverse effects.

Worst-rank score analysis with informatively missing observations in clinical trials

Many randomized clinical trials schedule subjects to undergo some assessment at a fixed time (or times) after the initiation of treatment. Often, these follow-up measurements may be missing for some subjects because a disease-related event occurred prior to the time of the follow-up observation. For example, a study of congestive heart failure may schedule patients to undergo exercise testing at 12 weeks, but this measurement may be missing for those who died of heart disease during the study. In such cases, the measurements are informatively missing because mortality from heart disease and a decline in exercise both indicate progression of the underlying disease. It is inappropriate, therefore, to treat these missing observations as missing-at-random and ignore them in the analysis. In one approach to this problem, investigators have included such patients in the analysis of the follow-up data by assigning a rank that represents a "worst-rank score" relative to those actually observed. Some, however, have criticized this procedure as having the potential to produce biased results. In this paper, we explore the statistical properties of such an analysis. We show under a specific model that the imputation of a worst-rank score for informatively missing observations provides an unbiased test against a restricted alternative. We also describe generalizations that employ the actual times of the informative event. We present an example from a study of congestive heart failure. Last, we discuss the implications of this approach and of other methods.

Effect of vesnarinone on cardiac function in patients with severe congestive heart failure

BACKGROUND

Vesnarinone has yielded controversial results on morbidity in patients with congestive heart failure. We tested the hypothesis that vesnarinone may have a beneficial effect on cardiac remodeling and function.

METHODS

Thirty-four patients with left ventricular ejection fraction (LVEF) <30% (17 treated with vesnarinone) underwent an echocardiography at baseline and at 12+/-5 months. Left ventricular end-diastolic and end-systolic volume, mitral regurgitation, diastolic filling, and right ventricular area change were quantified and compared.

RESULTS

When the vesnarinone group was considered as a whole, there was no significant effect of vesnarinone on cardiac systolic and diastolic function or remodeling. However, an increase in LVEF >7% was observed in six of the vesnarinone patients and none of the control group. Vesnarinone improved right and left ventricular systolic function significantly in patients with initial LVEF <25%.

CONCLUSIONS

In severe congestive heart failure, vesnarinone induces variable responses but improves biventricular performance in patients with the most impaired initial function.

Innovations in the pharmacologic management of heart failure

Improved understanding of the pathophysiologic course of heart failure has led to many advances in pharmacologic therapy. Angiotensin-converting enzyme inhibitors represent the first effort at targeting neurohormonal activation in chronic heart failure. More recently, beta-adrenergic receptor antagonists have been shown effective in blocking chronic sympathetic nervous system activation. The roles of digoxin and the newer, vasoselective calcium channel blockers in heart failure have been better defined. Other agents targeting the neurohormonal system are under investigation. These include angiotensin-receptor antagonists, aldosterone inhibitors, and endothelin antagonists. Experience with phosphodiesterase inhibitors and adrenergic agents has confirmed the importance of neurohormonal activation in progression of heart failure. Despite angiotensin-converting enzyme inhibitor, diuretic, and digoxin therapy, mortality in heart failure remains high. Careful manipulation of the neurohormonal response to heart failure holds promise for altering the course of the disease.

Effect of increasing gastric pH with famotidine on the absorption and oral pharmacokinetics of the inotropic agent vesnarinone

The effect of famotidine, an H2 receptor blocker, on the oral absorption and pharmacokinetics of the novel agent vesnarinone was investigated after oral administration of 60 mg vesnarinone with and without pretreatment with intravenous famotidine. The single-blind, randomized, two-way crossover study was conducted in 12 volunteers, with a washout period of 7 days between the two treatments. A pH monitor was used to ensure that gastric pH of the subjects was < or = 3 in the absence of and > or = 5 in the presence of famotidine. A significant decrease in maximum concentration (Cmax) and increase in time to Cmax (tmax) was observed for vesnarinone during treatment with famotidine, whereas area under the concentration-time curve (AUC) was similar for both treatments. The physicochemical properties of the drug support the above observations. Therefore, therapies that increase gastric pH will affect the rate but not the extent of absorption of vesnarinone or the safety or efficacy profile of vesnarinone.

Quality of life in cardiac patient research: a meta-analysis

This article reports a meta-analysis of 84 studies of quality of life (QOL) in cardiac patient populations published in the 5-year period 1987-1991. Selected methodologies and substantive characteristics of the studies are described. An overall effect size of .31 indicated a small but significant positive effect of pharmacologic, mechanical, surgical, nursing, or other treatment on QOL. No negative effect of treatment was found for any cardiovascular diagnostic category. Homogeneity analysis revealed eight potential moderators of the overall effect size: quality of study, gender of sample, time dimension, sampling method, intervention, marital status of subjects, quality-of-life dimension measured, and sample size.

Acute cardiovascular effects of OPC-18790 in patients with congestive heart failure. Time- and dose-dependence analysis based on pressure-volume relations

BACKGROUND

OPC-18790 is a water-soluble quinolinone derivative that shares the pharmacological properties of vesnarinone and that may be useful for treating heart failure. We studied the contribution and relative dose sensitivities of the inotropic, lusitropic, and vascular effects of OPC-18790 in patients with dilated cardiomyopathy.

METHODS AND RESULTS

Pressure-volume (PV) analysis was performed in 17 patients who received either 5 micrograms.kg-1.min-1 (low dose, n = 10) or 10 micrograms.kg-1.min-1 (high dose, n = 7) OPC-18790 by 1-hour IV infusion. Right heart pressures and flow and left heart PV relations (conductance catheter) were measured at baseline and every 15 minutes during infusion. Transient inferior vena caval obstruction was used to determine PV relations. Both doses produced venodilation reflected by a 10% decline in left ventricular end-diastolic volume and a 30% fall in atrial and pulmonary artery pressures. Arterial dilation was four times greater at the high dose, with an approximately 40% fall in effective arterial elastance and systemic resistance. Contractility rose by 25% to 100% (depending on PV index) with both doses. Ventricular-arterial coupling (ratio of ventricular end-systolic to arterial elastances) was approximately 0.25 at baseline and doubled (or tripled) at low (or high) dose, correlating with improved efficiency. Isovolumetric relaxation shortened, whereas the diastolic PV relation was generally unchanged. Heart rate was unaltered.

CONCLUSIONS

OPC-18790 has potent venous and arterial vasodilator effects and moderate inotropic and lusitropic effects without a change in heart rate. These combined actions suggest a unique potential of OPC-18790 for heart failure treatment.

Strategies for pharmacologic modulation of the heart failure phenotype

The end-stage heart failure phenotype is characterized by marked dyspnea on exertion, edema, and overwhelming fatigue, and by a high incidence of sudden death. Patients who display the end-stage phenotype have transitioned from a normal phenotype with myocardial damage at a cellular level. This transition appears to be mediated by events at both the cellular and molecular levels. Until recently, it was generally believed that this transition was irreversible. However, recent clinical trials have demonstrated that the phenotype can be changed with pharmacologic agents. These agents have been demonstrated to improve exercise capability, increase ventricular function, and improve symptoms. Important recent studies have shown that pharmacologic agents can substantially alter the high mortality rates associated with the end-stage heart failure phenotype. As we learn more about the molecular and cellular events that initiate and support the transition from cardiac compensation to decompensation, we will be able to improve our pharmacologic targeting and, we hope, be able to delay the development of the end-stage heart failure phenotype to an even greater degree.

Vesnarinone: a new inotropic agent for treating congestive heart failure

Vesnarinone is a new and novel inotropic drug that has unique and complex mechanisms of action. It inhibits phosphodiesterase, thereby leading to increased intracellular calcium, and also affects numerous myocardial ion channels, resulting in the prolongation of the opening time of sodium channels and the decrease in the delayed outward and inward rectifying potassium current. In vitro, it has also demonstrated significant effects on cytokine production, which may account for some of its observed clinical benefits. Hemodynamic studies in humans with congestive heart failure reveal that vesnarinone can improve ventricular function. Placebo-controlled studies in large numbers of patients with heart failure have suggested a morbidity and mortality benefit with a 60 mg daily dose. There is increased mortality with vesnarinone at the 120 mg daily dose, however, suggesting a narrow therapeutic window for the drug. Its predominant toxic side effect is a 2% incidence of reversible neutropenia.

Is there a role for epoprostenol in the management of heart failure?

Prostacyclin (PGI2, epoprostenol), a pulmonary and systemic vasodilating agent, has recently undergone long-term intravenous administration trials in patients with severe congestive heart failure. As in many other agents that have beneficial acute hemodynamic profiles, its effects on mortality have been disappointing. However, the drug continues to have a role in the short-term management of patients with decompensated heart failure because of its short half-life, lack of medium-term toxicity compared to sodium nitroprusside, and lesser tendency toward development of tolerance than intravenous nitrates. There may also be therapeutic effects other than its influence on central hemodynamics; in particular, inhibition of platelet aggregation and thrombus formation in small vessels may be of value in the long-term management of patients with primary pulmonary hypertension. It is possible that, like other agents such as vesnarinone (OPC-8212), achieving beneficial long-term effects may require identification of an ideal dose range. The most effective therapeutic doses in long-term administration may not correlate with the most effective doses during short-term hemodynamic studies.

Treatment of end stage dilated cardiomyopathy

Patients should be referred for cardiac transplantation only after all other means of management of congestive heart failure have been attempted and have been unsuccessful (table 3). An adequate therapeutic trial of conventional and experimental agents including beta blockade and vesnarinone should be completed and be shown to be unsuccessful before transplantation is considered in patients in NYHA class III. Prospective clinical trials need to be completed to define the role of newer therapeutic options. The scarcity of donor organs will probably preclude the use of cardiac transplantation in all patients who may benefit. Alternative methods of cardiac replacement (such as dynamic cardiomyoplasty, permanent implantable mechanical circulatory assistance, and xenografting) must be developed. These methods coupled with better pharmacological treatment will greatly improve the outcome of patients with dilated cardiomyopathy.

Is there a role for positive inotropic agents in congestive heart failure: focus on mortality

Congestive heart failure (CHF) is a common clinical syndrome that may result from a variety of etiologies. Impaired contractility can lead to pump failure and a number of hemodynamic and neurohormonal alterations. Vasodilator therapy improves symptoms and survival in patients with CHF due to systolic dysfunction. Inotropic therapy, on the other hand, has not been shown to improve survival and may even worsen survival. This article reviews the mechanism of action and clinical trials of inotropic therapy in patients with CHF.

Treatment of virus-induced myocardial injury with a novel immunomodulating agent, vesnarinone. Suppression of natural killer cell activity and tumor necrosis factor-alpha production

Controversy still exists concerning the therapy for viral myocarditis which manifests a wide variety of clinical symptoms. Vesnarinone, a quinolinone derivative that was developed as a positive inotropic agent with complex actions, including phosphodiesterase inhibition and cation channel modification, has recently been confirmed to improve the prognosis of patients with chronic heart failure. However, the precise mechanism of this beneficial effect is not yet clearly understood. In this study, using a murine model of acute viral myocarditis resulting from encephalomyocarditis virus infection, survival and myocardial damage were markedly improved by treatment with vesnarinone. In contrast, survival was not improved by treatment with amrinone, a phosphodiesterase inhibitor. Although vesnarinone did not inhibit viral replication or protect myocytes from viral direct cell injury, it did inhibit the increase in natural killer cell activity after viral infection. On the other hand, amrinone failed to inhibit natural killer cell activity. Both vesnarinone and amrinone suppressed the production of tumor necrosis factor-alpha. Therefore, we postulate that vesnarinone exerted its beneficial effects through an inhibition of natural killer cell activity, and that it serves as an immunomodulator providing new therapeutic possibilities for the treatment of viral myocarditis and/or immunological disorders.

Clinical effects of long-term administration of pimobendan in patients with moderate congestive heart failure

The long-term efficacy of the positive inotropic and vasodilator drug, pimobendan, was assessed in 21 patients suffering from symptomatic heart failure. Patients were randomized to 16 weeks of double-blind therapy with either 2.5 or 5.0 mg/day of pimobendan (n = 10), or a matching placebo (n = 11). Patients were blinded on the study drug if their clinical status had not substantially worsened during the study. Of the placebo-treated patients, 5 patients were withdrawn from the study because of a deterioration of their heart failure, while none of the active treated group was withdrawn because of increased symptoms. Quality of life, assessed by the specific activity scale derived from the metabolic costs of individual physical activity, was 3.45 +/- 0.90 (SD) mets in the baseline state and increased significantly after week 16, averaging 5.07 +/- 1.40 and 4.67 +/- 1.47 mets at weeks 16 and 24, respectively. In the placebo-treated group, the specific activity scale was 3.27 +/- 1.21 mets at the baseline and remained unchanged throughout the study period. Patients treated with pimobendan were able to significantly increase their exercise duration. The accompanying increase in peak oxygen uptake was statistically insignificant, due to the limited number of patients enrolled in the study. These results suggest that in contrast to the recent pessimistic view of the long-term efficacy of cardiotonic drugs, pimobendan is beneficial in treating patients with congestive heart failure and may favorably modify their prognosis. Further large-scale evaluation of this agent is warranted.

Medical advances in the treatment of congestive heart failure

The increased incidence and prevalence of congestive heart failure place a high priority on novel treatment strategies. Left ventricular ejection fraction remains the single most valuable measurement providing both diagnostic and prognostic insights. The most systematic approach to heart failure involves an objective assessment of functional disability, to include exercise tests such as a 6-minute walk under standardized conditions. Left ventricular dysfunction incites a host of neurohumoral compensations that are of fundamental importance in the heart failure syndrome expression. Both vasoconstrictor and vasodilator neurohormones are stimulated and provide new therapeutic opportunities. The therapeutic approach to heart failure begins with a strong emphasis on prevention, patient education, and self-participation in therapy with respect to both its monitoring and adjustment. Diuretics remain a mainstay of therapy but, in the face of severe heart failure, may become ineffectual, requiring constant infusion of loop-active diuretics, combination diuretics, or diuretics in association with concomitant low-dose dopamine infusion. Vasodilator therapy has been an important advance: combination hydralazine and nitrate therapy was initially shown to be efficacious in improving survival, and more recently, angiotensin-converting enzyme (ACE) inhibitors, in the form of enalapril, have shown incremental benefit on survival over this combination. Interestingly, there is now evidence from both SOLVD and SAVE to demonstrate an unexpected and, as yet, unexplained reduction in the frequency of both unstable angina and myocardial infarction. Although, on balance, the weight of evidence concerning the long-term efficacy of inotropic agents has been disappointing, especially as it relates to their unfavorable effects on survival, recent information on vesnarinone, an agent with a complex and diversified mechanism of action, suggests that with appropriate doses, improved symptoms and survival are possible. A substantial amount of new information from randomized placebo-controlled trials attests to the symptomatic relief, hemodynamic improvement, and gain in exercise performance achieved by digoxin. A long-term survival study is ongoing to assess its effects on mortality. beta-Blockers, especially metoprolol, appear beneficial in some patients with heart failure, possibly related to their reduction in sympathetic nervous activity and restoration of beta-receptor population, with resultant improved contractile performance, enhanced myocardial relaxation, and overall increase in cardiac efficiency. Based on available evidence, the best contemporary approach to treatment involves the use of ACE inhibitors coupled with diuretic therapy, either continuous or intermittent, to relieve central or peripheral congestion. The addition of digoxin or a hydralazine nitrate combination is a logical next step, with commencement of low-dose beta-blocker a reasonable option.(ABSTRACT TRUNCATED AT 400 WORDS)

Differentiating systolic from diastolic heart failure: pathophysiologic and therapeutic considerations

PURPOSE

To compare and contrast the pathophysiology and therapy of heart failure with normal and abnormal systolic ventricular function.

METHODS

Review of basic pathophysiologic mechanisms, clinical data, and therapeutic trials.

CONCLUSIONS

The clinical features of heart failure may be similar regardless of whether ventricular function is normal or abnormal. However, the pathophysiologic mechanisms leading to heart failure with normal ventricular function differ considerably from those producing heart failure with abnormal systolic function. The key problems in heart failure with abnormal systolic function involve impaired contractility, neuroendocrine activation, increased intracardiac volume and pressure, and enhanced sensitivity to change in afterload. With normal systolic function, the key problem is an abnormal diastolic pressure/volume relationship, which may be due to a variety of active and passive processes affecting diastole. Assessing left ventricular systolic function is crucial before initiating therapy in a patient with heart failure, since treatment for systolic dysfunction may be ineffective or even counterproductive if symptoms are due to abnormal diastolic properties with preserved systolic function.

Efficacy of phosphodiesterase inhibition with milrinone in combination with converting enzyme inhibitors in patients with heart failure. The Milrinone Multicenter Trials Investigators

We describe the results of two placebo-controlled trials (MIL-1077 and MIL-1078) designed to evaluate the clinical efficacy of oral milrinone administered together with converting enzyme inhibitors to patients with congestive heart failure. Although these trials were terminated prematurely, they provide the only controlled data regarding the effect of oral milrinone on exercise capacity in patients receiving converting enzyme inhibitors. Of the 254 patients randomized, 140 completed one of the trials or reached an end point and are the basis of this report. In both trials, there was a clear trend for an increase in exercise capacity in the milrinone-treated patients (+26 +/- 8% vs. +5 +/- 7% in MIL-1077 and +11 +/- 5% vs. +2 +/- 4% in MIL-1078). Symptoms of congestive heart failure were decreased in one trial but not the other. Quality of life, as assessed by a questionnaire, was not effected in either trial. There was an increased incidence of adverse events in milrinone-treated patients. Adverse events related primarily to hypotension and vasodilation led to discontinuation of drug in 18 milrinone-treated patients vs. 1 placebo-treated patient. Milrinone had little or no proarrhythmic effect and cardiovascular deaths were distributed equally between the milrinone and placebo groups. These data suggest that when used in combination with a converting enzyme inhibitor, oral milrinone improves exercise capacity but is associated with a high incidence of adverse events that appear to be related to excessive vasodilation.

Classification of positive inotropic agents

Although there is increasing recognition that all inotropic agents are not alike, they continue to be viewed in the generic sense because of the lack of a classification system. Analogous to the classification system proposed for the antiarrhythmic agents over 20 years ago, a classification system is proposed that categorizes inotropic agents according to their mechanisms of action. Agents are classified as those that augment contractility by increasing intracellular levels of cyclic adenosine monophosphate (class I); affect ion channels or pumps (class II); modulate intracellular calcium regulation (class III), and augment contractility through multiple pathways (class IV). This classification system does not suggest that some classes of inotropic agents might be more effective than others nor does it imply that potential beneficial effects are shared by all members of each class of drugs. However, it provides a framework for better understanding of the potential benefits and limitations of the traditional inotropic agents as well as the increasing number of new investigational drugs.

The development of positive inotropic agents for chronic heart failure: how have we gone astray?

Because cardiac contractility is impaired in chronic heart failure, many pharmacologic agents have been developed to increase the contractile state of the failing heart. These drugs produce impressive hemodynamic effects, but long-term therapy has failed to produce clinical benefits and has increased mortality in treated patients. This experience has led many physicians to suggest that positive inotropic therapy be abandoned as a therapeutic approach for heart failure. However, recent studies suggest that the efficacy and safety of many (if not all) positive inotropic drugs can be greatly enhanced by reducing the dose of these drugs. The importance of dose is dramatically illustrated by the results of trials with vesnarinone, which decreases mortality when used in low doses but increases mortality when administered in doses only twice as large. Although low doses of positive inotropic drugs may be clinically superior to high doses, it is not clear that these low doses exert significant inotropic effects. All positive inotropic drugs exert actions on the circulation in addition to stimulating the heart, and these ancillary properties may be particularly important at low doses of these drugs. Low doses of milrinone and pimobendan may act primarily to dilate peripheral blood vessels; low doses of digitalis may exert only neurohormonal effects, and low doses of vesnarinone may act as an antiarrhythmic agent. If the noninotropic actions of low doses account for the therapeutic benefits of these drugs, then the positive inotropic effects seen at high doses may be primarily responsible for their adverse effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Ionic basis for OPC-8212-induced increase in action potential duration in isolated rabbit, guinea pig and human ventricular myocytes

Changes in transmembrane ionic currents induced by OPC-8212 (3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)-quinoline) , a recently introduced positive inotropic agent which lengthens cardiac action potential duration, were examined using whole-cell voltage-clamp techniques in single rabbit, guinea pig and human ventricular myocytes. In rabbit, OPC-8212 (12 mumol/l) significantly increased membrane action potential duration measured at 90% of repolarization by an average of 88 ms (from 462 +/- 25 to 550 +/- 35 ms, n = 4; P < 0.05). In rabbit this increase in duration was not associated with significant changes in either the inward rectifier or transient outward K+ currents. The magnitude of the secondary inward current evoked from a holding potential of -50 mV was significantly increased by 97 +/- 8% (n = 6; P < 0.01) while a demonstrable delayed rectifier outward current could not be identified in the rabbit myocytes examined at room temperature. In guinea pig ventricular myocytes, where the delayed rectifier was large, 12 mumol/l OPC-8212 significantly depressed the current by 58 +/- 10% (n = 6; P < 0.01). The effects of OPC-8212 in human ventricular myocytes obtained from the explanted heart of a single patient having an idiopathic cardiomyopathy most closely resembled those observed in isolated rabbit ventricular myocytes. Thus, in rabbit and a few human ventricular myocytes examined at room temperature, OPC-8212 appeared to lengthen cardiac membrane action potential duration primarily by increasing the amplitude of the secondary inward current believed to primarily represent current through L-type Ca2+ channels. In guinea pig preparations, OPC-8212 also decreased the delayed rectifier outward K+ current which also would account for an increase in action potential duration. OPC-8212 could not be demonstrated to affect Na+ current inactivation in a manner similar to that produced by 1 mg/l veratrine, a recognized Na+ channel agonist, which dramatically slowed this process.

Effects of vesnarinone on morbidity and mortality in patients with heart failure. Vesnarinone Study Group

BACKGROUND

Inotropic therapy, other than with digitalis glycosides, has had limited success in patients with chronic congestive heart failure. We investigated whether vesnarinone, a new positive inotropic agent, reduces morbidity and mortality and improves the quality of life of patients with symptomatic heart failure.

METHODS

Patients receiving concomitant therapy with digoxin (87 percent) and an angiotensin-converting-enzyme inhibitor (90 percent) who had ejection fractions of 30 percent or less were randomly assigned to receive double-blinded therapy with 60 mg of vesnarinone per day, 120 mg of vesnarinone per day, or placebo. Afer 253 patients had been enrolled, randomization to the 120-mg vesnarinone group had to be stopped because of a significant increase in early mortality in this group. Thereafter, patients were randomly assigned only to 60 mg of vesnarinone per day (a total of 239 patients) or placebo (a total of 238 patients).

RESULTS

Significantly fewer patients in the group receiving 60 mg of vesnarinone than in the group receiving placebo (26 vs. 50 patients; P = 0.003) died or had worsening heart failure during the six-month study period. The reduction in risk was 50 percent (95 percent confidence interval, 20 to 69 percent). Similarly, there was a 62 percent reduction (95 percent confidence interval, 28 to 80 percent) in the risk of dying from any cause among the patients receiving vesnarinone. Furthermore, quality of life improved to a greater extent in the vesnarinone group than in the placebo group over 12 weeks (P = 0.008). The principal side effect associated with vesnarinone was reversible neutropenia, which occurred in 2.5 percent of the patients.

CONCLUSIONS

Six months of therapy with 60 mg of vesnarinone per day resulted in lower morbidity and mortality and improved the quality of life of patients with congestive heart failure. However, a higher dose of vesnarinone (120 mg per day) increased mortality, suggesting that this drug has a narrow therapeutic range; the long-term effects of vesnarinone are unknown.

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.