Milrinone in congestive heart failure: acute and chronic hemodynamic and clinical evaluation

Fe(III)-Catalyzed Tandem Cyclization of Phenylpropiolamides with 3-Formylchromones for the Construction of 2-Pyridones

A highly efficient and atom-economic iron(III)-catalyzed three-component heteroannulation reaction between phenylpropiolamides, 3-formylchromones, and water is described for the construction of diversely multifunctionalized 2-pyridones. This protocol allows rapid access to a variety of 2-pyridones bearing an ortho-hydroxybenzoyl and a benzoyl scaffold under operationally simple conditions. The synthetic utility of the synthesized 2-pyridone scaffolds is demonstrated by transformation into biologically interesting complex heterocycles.

Hemodynamic Effects of Cyclic Guanosine Monophosphate-Dependent Signaling Through β3 Adrenoceptor Stimulation in Patients With Advanced Heart Failure: A Randomized Invasive Clinical Trial

BACKGROUND

β3-AR (β3-adrenergic receptor) stimulation improved systolic function in a sheep model of systolic heart failure (heart failure with reduced ejection fraction [HFrEF]). Exploratory findings in patients with New York Heart Association functional class II HFrEF treated with the β3-AR-agonist mirabegron supported this observation. Here, we measured the hemodynamic response to mirabegron in patients with severe HFrEF.

METHODS

In this randomized, double-blind, placebo-controlled trial we assigned patients with New York Heart Association functional class III-IV HFrEF, left ventricular ejection fraction <35% and increased NT-proBNP (N-terminal pro-B-type natriuretic peptide) levels to receive mirabegron (300 mg daily) or placebo orally for a week, as add on to recommended HF therapy. Invasive hemodynamic measurements during rest and submaximal exercise at baseline, 3 hours after first study dose and repeated after 1 week's treatment were obtained. Predefined parameters for analyses were changes in cardiac- and stroke volume index, pulmonary and systemic vascular resistance, heart rate, and blood pressure.

RESULTS

We randomized 22 patients (age 66±11 years, 18 men, 16, New York Heart Association functional class III), left ventricular ejection fraction 20±7%, median NT-proBNP 1953 ng/L. No significant changes were seen after 3 hours, but after 1 week, there was a significantly larger increase in cardiac index in the mirabegron group compared with the placebo group (mean difference, 0.41 [CI, 0.07-0.75] L/min/BSA; P=0.039). Pulmonary vascular resistance decreased significantly more in the mirabegron group compared with the placebo group (-1.6 [CI, -0.4 to -2.8] Wood units; P=0.02). No significant differences were seen during exercise. There were no differences in changes in heart rate, systemic vascular resistance, blood pressure, or renal function between groups. Mirabegron was well-tolerated.

CONCLUSIONS

Oral treatment with the β3-AR-agonist mirabegron for 1 week increased cardiac index and decreased pulmonary vascular resistance in patients with moderate to severe HFrEF. Mirabegron may be useful in patients with worsening or terminal HF.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: 2016-002367-34.

Repetitive milrinone therapy in ambulatory advanced heart failure patients

BACKGROUND

Advanced heart failure (HF) patients usually poorly tolerate guideline-directed HF medical therapy (GDMT) and suffer high rates of morbidity and mortality. The use of continuous inotropes in the outpatient settings is hampered by previous data showing excess morbidity. We aimed to assess the safety and efficacy of repetitive, intermittent, short-term intravenous milrinone therapy in advanced HF patients with an intention to introduce and up-titrate GDMT and improve functional class.

HYPOTHESIS

Repetitive, intermittent milrinone therapy may assist with the stabilization of advanced HF patients.

METHODS

Advanced HF patients treated with beta-blockers and implanted with defibrillators were initiated with repetitive, intermittent short-term intravenous milrinone therapy at our HF outpatient unit. Patients were prospectively followed with defibrillator interrogation, functional class assessment, B-natriuretic peptide (BNP) levels, and echocardiography parameters.

RESULTS

The cohort included 24 patients with a mean 330 ± 240 days of milrinone therapy exposure. Mean age was 73 ± 6 years with male predominance (96%). Following milrinone therapy, median BNP levels decreased significantly (882 [286-3768] to 631 [278-1378] pg/ml, p = .017) with a significant reduction in the number of patients with New York Heart Association (NYHA) Class III and IV (p = .012, 0.013) and an increase in number of patients on GDMT. Importantly, the number of total sustained ventricular tachycardia events and HF hospitalizations did not change.

CONCLUSIONS

In this small cohort of advanced HF, repetitive, intermittent, short-term milrinone therapy was found to be safe and potentially efficacious.

Ivabradine prevents deleterious effects of dopamine therapy in heart failure: No role for HCN4 overexpression

BACKGROUND

Exacerbations of chronic heart failure (CHF) are often treated with catecholamines to provide short term inotropic support, but this strategy is associated with long-term detrimental hemodynamic effects and increased ventricular arrhythmias (VA), possibly related to increased heart rate (HR). We hypothesized that ivabradine may prevent adverse effects of short-term dopamine treatment in CHF.

METHODS

Rats with post-myocardial infarction CHF received 2-week infusion of saline, dopamine(D), ivabradine(I) or D&I; cardiac function was assessed using echocardiography and pressure-volume loops while VA were assessed using telemetric ECG recording. Expression of HCN4, a potentially proarrhythmic channel blocked by ivabradine, was assessed in left ventricular (LV) myocardium. HCN4 expression was also assessed in human explanted normal and failing hearts and correlated with VA.

FINDINGS

Dopamine infusion had detrimental effects on hemodynamic parameters and LV remodeling and induced VA in CHF rats, while ivabradine completely prevented these effects. CHF rats demonstrated HCN4 overexpression in LV myocardium, and ivabradine and, unexpectedly, dopamine prevented this. Failing human hearts also exhibited HCN4 overexpression in LV myocardium that was unrelated to patient's sex, CHF etiology, VA severity or plasma NT-proBNP.

INTERPRETATION

HR reduction offered by ivabradine may be a feasible strategy to extract benefits of inotropic support in CHF exacerbations, avoiding detrimental effects on CHF biology or VA. Ivabradine may offer additional beneficial effects in this setting, going beyond pure HR reduction, however prevention of ventricular HCN4 overexpression is unlikely to play a major role.

A PDE3A Promoter Polymorphism Regulates cAMP-Induced Transcriptional Activity in Failing Human Myocardium

BACKGROUND

The phosphodiesterase 3A (PDE3A) gene encodes a PDE that regulates cardiac myocyte cyclic adenosine monophosphate (cAMP) levels and myocardial contractile function. PDE3 inhibitors (PDE3i) are used for short-term treatment of refractory heart failure (HF), but do not produce uniform long-term benefit.

OBJECTIVES

The authors tested the hypothesis that drug target genetic variation could explain clinical response heterogeneity to PDE3i in HF.

METHODS

PDE3A promoter studies were performed in a cloned luciferase construct. In human left ventricular (LV) preparations, mRNA expression was measured by reverse transcription polymerase chain reaction, and PDE3 enzyme activity by cAMP-hydrolysis.

RESULTS

The authors identified a 29-nucleotide (nt) insertion (INS)/deletion (DEL) polymorphism in the human PDE3A gene promoter beginning 2,214 nt upstream from the PDE3A1 translation start site. Transcription factor ATF3 binds to the INS and represses cAMP-dependent promoter activity. In explanted failing LVs that were homozygous for PDE3A DEL and had been treated with PDE3i pre-cardiac transplantation, PDE3A1 mRNA abundance and microsomal PDE3 enzyme activity were increased by 1.7-fold to 1.8-fold (p < 0.05) compared with DEL homozygotes not receiving PDE3i. The basis for the selective up-regulation in PDE3A gene expression in DEL homozygotes treated with PDE3i was a cAMP response element enhancer 61 nt downstream from the INS, which was repressed by INS. The DEL homozygous genotype frequency was also enriched in patients with HF.

CONCLUSIONS

A 29-nt INS/DEL polymorphism in the PDE3A promoter regulates cAMP-induced PDE3A gene expression in patients treated with PDE3i. This molecular mechanism may explain response heterogeneity to this drug class, and may inform a pharmacogenetic strategy for a more effective use of PDE3i in HF.

Insights Into Myocardial Oxygen Consumption, Energetics, and Efficiency Under Left Ventricular Assist Device Support Using Noninvasive Pressure-Volume Loops

Background:

Assessment of left ventricular (LV) recovery under continuous-flow LV assist device therapy is hampered by concomitant pump support. We describe derivation of noninvasive pressure-volume loops in continuous-flow LV assist device patients and demonstrate an application in the assessment of recovery.

Methods and Results:

Using pump controller parameters and noninvasive arterial pressure waveforms, central aortic pressure, outflow conduit pressure gradient, and instantaneous LV pressure were calculated. Instantaneous LV volumes were calculated from echocardiographic LV end-diastolic volume accounting for the integral of pump flow with respect to time and aortic ejection volume derived from the pump speed waveform. Pressure-volume loops were derived during pump speed adjustment and following bolus intravenous milrinone to assess changes in loading conditions and contractility, respectively. Fourteen patients were studied. Baseline noninvasive LV end-diastolic pressure correlated with invasive pulmonary arterial wedge pressure ( r 2 =0.57, root mean square error 5.0 mm Hg, P =0.003). Measured noninvasively, milrinone significantly increased LV ejection fraction (40.3±13.6% versus 36.8±14.2%, P <0.0001), maximum dP/dt (623±126 versus 555±122 mm Hg/s, P =0.006), and end-systolic elastance (1.03±0.57 versus 0.89±0.38 mm Hg/mL, P =0.008), consistent with its expected inotropic effect. Milrinone reduced myocardial oxygen consumption (0.15±0.06 versus 0.16±0.07 mL/beat, P =0.003) and improved myocardial efficiency (43.7±14.0% versus 41.2±15.5%, P =0.001). Reduced pump speed caused increased LV end-diastolic volume (190±80 versus 165±71 mL, P <0.0001) and LV end-diastolic pressure (14.3±10.2 versus 9.9±9.3 mm Hg, P =0.024), consistent with a predictable increase in preload. There was increased myocardial oxygen consumption (0.16±0.07 versus 0.14±0.06 mL O 2 /beat, P <0.0001) despite unchanged stroke work ( P =0.24), reflecting decreased myocardial efficiency (39.2±12.7% versus 45.2±17.0%, P =0.003).

Conclusions:

Pressure-volume loops are able to be derived noninvasively in patients with the HeartWare HVAD and can detect induced changes in load and contractility.

Why has positive inotropy failed in chronic heart failure? Lessons from prior inotrope trials

Current pharmacological therapies for heart failure with reduced ejection fraction are largely either repurposed anti‐hypertensives that blunt overactivation of the neurohormonal system or diuretics that decrease congestion. However, they do not address the symptoms of heart failure that result from reductions in cardiac output and reserve. Over the last few decades, numerous attempts have been made to develop and test positive cardiac inotropes that improve cardiac haemodynamics. However, definitive clinical trials have failed to show a survival benefit. As a result, no positive inotrope is currently approved for long‐term use in heart failure. The focus of this state‐of‐the‐art review is to revisit prior clinical trials and to understand the causes for their findings. Using the learnings from those experiences, we propose a framework for future trials of such agents that maximizes their potential for success. This includes enriching the trials with patients who are most likely to derive benefit, using biomarkers and imaging in trial design and execution, evaluating efficacy based on a wider range of intermediate phenotypes, and collecting detailed data on functional status and quality of life. With a rapidly growing population of patients with advanced heart failure, the epidemiologic insignificance of heart transplantation as a therapeutic intervention, and both the cost and morbidity associated with ventricular assist devices, there is an enormous potential for positive inotropic therapies to impact the outcomes that matter most to patients.

Reassessing the Role of Surrogate End Points in Drug Development for Heart Failure

With few notable exceptions, drug development for heart failure (HF) has become progressively more challenging, and there remain no definitively proven therapies for patients with acute HF or HF with preserved ejection fraction. Inspection of temporal trends suggests an increasing rate of disagreement between early-phase and phase III trial end points. Preliminary results from phase II HF trials are frequently promising, but increasingly followed by disappointing phase III results. Given this potential disconnect, it is reasonable to carefully re-evaluate the purpose, design, and execution of phase II HF trials, with particular attention directed toward the surrogate end points commonly used by these studies. In this review, we offer a critical reappraisal of the role of phase II HF trials and surrogate end points, highlighting challenges in their use and interpretation, lessons learned from past experiences, and specific strengths and weaknesses of various surrogate outcomes. We conclude by proposing a series of approaches that should be considered for the goal of optimizing the efficiency of HF drug development. This review is based on discussions between scientists, clinical trialists, industry and government sponsors, and regulators that took place at the Cardiovascular Clinical Trialists Forum in Washington, DC, on December 2, 2016.

Developing Drugs for Heart Failure With Reduced Ejection Fraction: What Have We Learned From Clinical Trials?

There remains a large unmet need for new therapies in the treatment of heart failure with reduced ejection fraction (HFrEF). In the early drug development phase, the therapeutic potential of a drug is not yet fully understood and trial endpoints other than mortality are needed to guide drug development decisions. While a true surrogate marker for mortality in heart failure (HF) remains elusive, the successes and failures of previous trials can reveal markers that support clinical Go/NoGo decisions.

Novel construction of diversely functionalized N-heteroaryl-2-pyridones via copper(ii)-catalyzed [3+2+1] annulation

A facile synthesis of diversely functionalized N-heteroaryl-2-pyridones is achieved by Cu(OTf)₂-catalyzed [3+2+1] annulation of various 2-aminopyridines via cascade reaction.

Milrinone inhibits hypoxia or hydrogen dioxide-induced persistent sodium current in ventricular myocytes

Much evidence indicates that increased persistent sodium current (I(Na.P)) is associated with cellular calcium overload and I(Na.P) is considered to be a potential target for therapeutic intervention in ischaemia and heart failure. By inhibiting type III phosphodiesterase, milrinone increases intracellular cyclic adenosine monophosphate (cAMP), with a positive inotropic effect. However, the effect of milrinone on increased I(Na.P) under pathological conditions remains unknown. Accordingly, we investigated the effect of milrinone on increased I(Na.P) induced by hypoxia or hydrogen dioxide in guinea pig ventricular myocytes. While milrinone (0.01 mM or 0.1mM) or cAMP (0.1 mM) decreased I(Na.P) respectively in control condition, application of 1 microM H-89, a selective cAMP-dependant protein kinase inhibitor, prevented the effect of 0.1mM milrinone in control condition. Milrinone (0.1 mM) reduced the increased I(Na.P) induced by hypoxia. Furthermore, 0.01 mM or 0.1mM milrinone reduced the enhanced I(Na.P) induced by 0.3 mM hydrogen peroxide. In addition, 0.01 mM or 0.1 mM milrinone shortened action potential duration at 90% repolarization (APD(90)). Bath application of 0.3 mM hydrogen dioxide markedly prolonged APD(90), while 2 microM tetrodotoxin (TTX) reversed the prolonged APD(90). In the other two groups, 0.01 mM or 0.1 mM milrinone shortened the prolonged APD(90) induced by 0.3 mM hydrogen peroxide, ultimately 2 microM TTX causing a further decurtation of APD(90). These findings demonstrate that milrinone inhibited I(Na.P) under normal condition, hypoxia or hydrogen dioxide-induced I(Na.P), and the APD(90) prolonged by hydrogen dioxide-induced I(Na.P) in ventricular myocytes, which is associated with the mechanism of milrinone increasing intracellular cAMP.

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.

Role of nonglycosidic inotropic agents: indications, ethics, and limitations

Nonglycosidic inotropic agents have been used for the short-term management of low output states and hypotension complicating acute myocardial infarction for several years. Without adequate reperfusion of the ischemic myocardium, inotropic agents are seldom effective in producing sustained hemodynamic responses. Furthermore, the potential exists for enhancement of ischemia and extension of myocardial necrosis. Thus, inotropic and vasopressors therapy should be regarded as temporary supportive treatment in patients with acute coronary syndrome and should be discontinued as soon as feasible. Parenteral sympathomimetic agents, usually dobutamine, and phosphodiesterase inhibitors, usually milrinone, are used for the management of exacerbations of chronic systolic heart failure. Although hemodynamics, and occasionally clinical status, improve, such therapy is associated with increased mortality and can potentially hasten a patient's demise. Nonparenteral sympathomimetics, such as ibopamine, phosphodiesterase-III inhibitors, such as milrinone and enoximone, calcium-sensitizing agents, such as pimobendan, and other novel inotropic agents, such as vesnarinone, all increase mortality of patients with chronic heart failure. Furthermore, newer noninotropic agents, such as B-natriuretic peptide, have been introduced for treatment of decompensated heart failure. New nonpharmacologic devices, such as biventricular pacing, are available for the treatment of advanced heart failure. Thus, indications for the use of presently available nonglycosidic inotropic agents are limited and should be considered only for short-term therapy or when no other treatment is available.

Milrinone echocardiographic viability test: a pilot study

We assessed the utility of milrinone to predict recovery of function after surgical myocardial revascularization in patients with severe baseline left ventricular systolic dysfunction caused by coronary artery disease (CAD). Prediction of viable myocardial segments that will regain function after revascularization may help in the selection of patients who will benefit from coronary artery bypass graft surgery (CABG) as well as aid in the choice of target sites for coronary revascularization. We investigated 20 consecutive patients with CAD and left ventricular ejection fraction < or = 40% who had evidence of myocardial viability by either thallium scan or dobutamine viability test and were candidates for elective CABG. Left ventricular regional wall motion and global ejection fraction were assessed by transesophageal echocardiography in the operating room. Measurements were done before and 10 minutes after milrinone infusion, and immediately after CABG. Left ventricular wall motion score was derived by means of a 12-segment model. Functional improvement for each segment was defined as a wall motion change > 1. Baseline ejection fraction was 27% +/- 5% (mean +/- SD). Ejection fraction increased to 35% +/- 5% after milrinone infusion (P < .0001) and to 36% +/- 6% after CABG (P < .0001). Post-CABG ejection fraction was significantly correlated with postmilrinone ejection fraction (r = 0.65, P < .0001). Milrinone infusion resulted in augmentation of contraction in 98 of the 209 abnormal segments (wall motion score > or = 2); 91 (92.9%) of these improved after CABG. One hundred nine of the 111 segments that showed no improvement with milrinone did not improve after revascularization (98.2%). Seventy-three segments were akinetic or dyskinetic at baseline; 46 (63.0%) of these improved with milrinone. Improvement in regional wall motion after revascularization was detected in 84.8% of the segments that improved with milrinone versus only 3.7% of the segments that did not improve with milrinone. In patients with ischemic cardiomyopathy, improvement in left ventricular function (segmental wall motion and global ejection fraction) during milrinone infusion is highly predictive of improvement after CABG.

Intermittent milrinone effect on long-term hemodynamic profile in patients with severe congestive heart failure

BACKGROUND

Many reports have suggested that intermittent milrinone infusion (IMI) may be efficacious in the management of end-stage congestive heart failure (CHF), but this issue has not been clearly established. The aim of our study was to investigate the effectiveness of IMI in hospitalized patients with severe CHF undergoing long-term (4 months) post-therapy hemodynamics.

METHODS

Thirty-six patients (28 men, 8 women; mean age 65.6 +/- 8.2 years old) with end-stage CHF (New York Heart Association functional class III-IV) were studied. Each patient received 4 cycles of 3 days per week with milrinone therapy. Each cycle consisted of a loading dose of 50 microgram/kg over 10 minutes and a 72-hour continuous infusion of 0.5 microgram/kg per minute under close monitoring. Hemodynamic changes were determined during the first and fourth cycles and on 4-month reexamination. Full clinical examination was performed at the beginning (baseline) and at the end of 4-month follow-up.

RESULTS

The values of mean pulmonary arterial pressure, pulmonary capillary wedge pressure, systemic vascular resistance, and pulmonary vascular resistance were significantly decreased (P <.01) and cardiac index was significantly increased (P <.01) compared with the baseline of first and fourth cycles. At the end of the 4-month follow-up period all hemodynamic parameters sustained the improvement. Clinical examination at the end of the 4-month period showed that 21 (58.3%) of 36 patients remained in New York Heart Association functional class IV but were hemodynamically improved, 13 (36.2%) of 36 were in functional class III, and 2 (5.5%) of 36 were in class II-III. There were no deaths during the study period.

CONCLUSIONS

Our findings suggest that IMI in hospitalized patients with severe CHF is hemodynamically efficacious. This beneficial hemodynamic effect is maintained for at least 4 months after discontinuation of therapy. These promising results raised the possibility that given appropriately, milrinone may have an important role in end-stage CHF.

Inotropic therapy for the failing myocardium

Congestive heart failure (CHF) is a common clinical entity with diverse causes. Patients may present with acute decompensation or have a more indolent course, with diminishing exercise tolerance and increasing dyspnea. The management of this clinical entity traditionally has focused on restricting fluid intake, decreasing dietary sodium, decreasing afterload with vasodilatory agents, and supporting the failing myocardium with agents which produce a positive inotropic response. In the acutely decompensated patient, short-term therapy with positive inotropics is clearly beneficial. The role of long-term inotropic therapy for chronic CHF remains less clear. A number of clinical trials have recently evaluated the effects of long-term therapy on morbidity and mortality, with disappointing results. For a number of the newer, nonglycocide oral positive inotropics, at doses of drug which produce measurable hemodynamic improvement, increased mortality in treatment groups has been unacceptably high. Ironically, patients with worse left ventricular dysfunction show the most clinical improvement, but have the highest increased mortality. However, as with digoxin, there is some evidence that employing lower doses of drug that do not produce measurable improvement in hemodynamic parameters may result in both improved clinical state and decreased mortality. This review discusses the role of both oral and intravenous inotropic agents, discusses the difficulty in translating short-term hemodynamic improvement into long-term clinical benefit, and presents a rationale for the use of lower-dose inotropic therapy to improve long-term clinical outcome.

Milrinone: systemic and pulmonary hemodynamic effects in neonates after cardiac surgery

OBJECTIVE

To evaluate the hemodynamic effects of intravenous milrinone in neonates with low cardiac output after cardiac surgery.

DESIGN

Prospective cohort study.

SETTING

Pediatric cardiac intensive care unit.

PATIENTS

Ten neonates with low cardiac output (cardiac index of < or = 3.0 L/min/m2) after corrective cardiac surgery were enrolled in the study. The neonates' ages ranged from 3 to 27 days (median 5) and their weights ranged from 2.0 to 4.8 kg (median 3.7). The diagnoses were: transposition of the great arteries (n = 6, including two with ventricular septal defect), tetralogy of Fallot (n = 2), truncus arteriosus (n = 1), and total anomalous pulmonary venous connection (n = 1).

INTERVENTIONS

Milrinone was intravenously administered in three stages: a) baseline stage, in which patients had a stable hemodynamic status, ventilation and gas exchange, hemostasis, and body temperature; b) loading stage, in which a 50 microgram/kg intravenous loading dose of milrinone was administered over 15 mins; and c) infusion stage, in which milrinone was continuously infused at 0.50 microgram/kg/min for 30 mins.

MEASUREMENTS AND MAIN RESULTS

The mean heart rate increased after the loading stage (149 +/- 13 to 163 +/- 12 beats/min, p < .01) but slowed during the infusion stage (154 +/- 11 beats/min, p < .01 vs. loading stage). Both right and left atrial pressures were lowered in all ten neonates. Compared with baseline, mean arterial pressure decreased after the loading stage (66 +/- 12 to 57 +/- 10 mm Hg, p < .01) but did not decrease further at the infusion stage (59 +/- 12 mm Hg); changes in mean pulmonary arterial pressure were comparable. Cardiac index increased from a baseline mean of 2.1 +/- 0.5 to 3.0 +/- 0.8 L/min/m2 (p < .01) with the loading stage, and was maintained at 3.1 +/- 0.6 L/min/m2 during the infusion stage. Systemic vascular resistance index decreased below baseline values with loading, from 2136 +/- 432 to 1336 +/- 400 dyne.sec/cm5.m2 (p < .01), and pulmonary vascular resistance index also decreased with loading dose of milrinone, from 488 +/- 160 to 360 +/- 120 dyne.sec/cm5.m2 (p < .01). There was no change in the rate pressure index, an indirect measurement of myocardial oxygen consumption, throughout the study.

CONCLUSIONS

Administration of milrinone in neonates with low cardiac output after cardiac surgery lowers filling pressures, systemic and pulmonary arterial pressures, and systemic and pulmonary vascular resistances, while improving cardiac index. Milrinone increases heart rate without altering myocardial oxygen consumption. While milrinone appears to be effective and safe during short-term use, the relative distribution of inotropic and vasodilatory properties of milrinone remains to be elucidated.

Making judgements about treatment effectiveness based on health outcomes: theoretical and practical issues

ISSUES

This article considers the problem of deciding which health care outcomes are important and relevant for (1) developing management recommendations for clinical practice guidelines and (2) evaluating patients' responses to treatment.

DECISIONS

The Heart Failure Guideline Panel sponsored by the Agency for Health Care Policy and Research (AHCPR) decided that for both purposes the relevant outcomes are those experienced directly by patients: mortality and health-related quality of life (HRQOL). Changes in intermediate outcomes, such as test results of various kinds, were deemed insufficient evidence of effectiveness.

CONCLUSIONS

In the context of heart failure, mortality risk (prognosis) can be measured using a variety of biochemical and physiological variables, but changes in these variables do not appear to correspond to changes in prognosis. For this reason, the Heart Failure Guideline Panel recommended that patients' responses to treatment be guided by signs and symptoms, rather than test results (for example, echocardiographic measurement of left-ventricular function or exercise-tolerance testing). HRQOL is best assessed by direct patient self-reports. Although patients may be influenced by a host of other variables (for example, mood, adaptation to chronic disease, placebo effect), self-reports will probably always represent the "gold standard" in assessing HRQOL. The reliability and validity of these reports can be enhanced by using standardized instruments or by incorporating questions from such instruments into the history-taking aspect of patient evaluation and monitoring. Finally, physical examination and submaximal exercise testing can provide additional information that can supplement patient reports. Information from these sources must be evaluated carefully in light of patients' self-reported HRQOL.

Reassessment of digoxin and other low-dose positive inotropes in the treatment of chronic heart failure

Digoxin and other low doses of drugs that have inotropic properties may have an important role to play in the therapy of patients with chronic heart failure. There is convincing evidence that digoxin is effective in relieving the signs and symptoms of heart failure due to systolic dysfunction. While earlier results with some of the other agents have been disappointing, recent data suggest that a reevaluation of these agents is necessary. There is now compelling evidence that lower doses of these agents may be clinically useful without necessarily having any significant hemodynamic effects. The recent experience with vesnarinone is especially promising in showing that therapy with these agents may improve survival in addition to improving clinical status. It is becoming recognized that hemodynamic activity should not necessarily be a prerequisite for clinical utility for those agents. The neuroendocrine and electrophysiologic effects of many of these agents, including digitalis, remain incompletely characterized and may play an important role in their therapeutic benefit. It appears that certain drugs that have inotropic properties may be effective only when their inotropic effects are not readily demonstrated. Further research into the appropriate mechanisms of action and proper dosing of these drugs may lead to a renewed interest in the use of positive inotropes for chronic heart failure.

Spontaneous variability of ventricular function in patients with chronic heart failure. The Western Enoximone Study Group and the REFLECT Investigators

PURPOSE

The spontaneous variation of the left and right ventricular ejection fractions (LVEF and RVEF) was evaluated in patients with chronic heart failure receiving only digoxin and diuretics over a 12-week interval.

PATIENTS AND METHODS

Fifty-one patients with stable heart failure were studied with radionuclide angiography. A baseline evaluation and a 12-week follow-up study were performed. Heart failure therapy consisted of digoxin and diuretics alone during this time.

RESULTS

The mean baseline LVEF (n = 51) was 27.2 +/- 9.5 (range: 7 to 50) and the LVEF after 12 weeks was 27.6 +/- 9.7 (range: 11 to 53; p = NS versus baseline). Mean RVEF (n = 19) was 31.9 +/- 11.3 at baseline and 30.3 +/- 11.3 (range: 14 to 50; p = NS versus baseline) after 12 weeks. Although there was no significant change in mean LVEF or RVEF in this group of patients, individual patients demonstrated considerable spontaneous variation. Individual LVEF values changed from 0 to 26 ejection fraction percentage points (mean of individual changes = 5.6 +/- 5.5). Individual RVEF determinations over the 12-week period varied by 0 to 15 percentage units (mean = 5.6 +/- 4.9). Thirty-five percent of patients had an absolute change in LVEF greater than 5 and 37% of patients had an absolute change of RVEF greater than 5. Even after deletion of the two worst outliers from the LVEF and RVEF data, a change in LVEF greater than 13 and a change in RVEF greater than 11% units were necessary to exclude spontaneous variation as a likely cause for the observed changes (95% confidence limits). No relationship between a change in the individual patient's LVEF or RVEF was found when these values were compared with exercise time, systolic or diastolic blood pressure, heart rate, or degree of baseline left or right ventricular dysfunction.

CONCLUSION

In patients with heart failure, large (greater than 5) spontaneous changes in LVEF and RVEF may be seen in over one third of patients during a 12-week period. This variability should be considered when the ejection fraction is used as an index of improved or worsened cardiac function. The use of the LVEF and RVEF to assess interventions or therapy for heart failure should be interpreted with caution.

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)

Phosphodiesterase III inhibitors: long-term risks and short-term benefits

Heart failure is now viewed as a disorder of the circulation, not merely the heart, which becomes manifest only when certain compensatory mechanisms break down. After treatment with diuretics, the two main strategies in treating heart failure involve decreasing the work of the heart by vasodilatation or increasing ventricular contractility by positive inotropic agents. It is now apparent, however, that the resulting hemodynamic benefit need not equate with long-term clinical improvement or increased longevity; indeed, the reverse can be true. Inhibitors of phosphodiesterase III, which is specific for the breakdown of cyclic adenosine monophosphate (cAMP), produce useful hemodynamic effects following intravenous and oral dosing, but have not fulfilled their initial promise in the chronic oral treatment of heart failure patients. The reason for reduced survival in the long-term studies of milrinone is not clear, but cardiac arrhythmias, possibly resulting from the increased intracellular levels of cAMP, may be responsible. However, intravenous usage may not suffer from the same limitations as chronic oral dosing. Short-term intravenous administration produces the expected beneficial hemodynamic effects of positive inotropism and vasodilatation. Though infusions of milrinone have been shown to enhance atrioventricular conduction in some, but not all, studies, there appears to be no significant increase in ventricular premature contractions, or ventricular or sustained tachyarrhythmias. Because milrinone does not have a significant adverse effect on His-Purkinje conduction, its use should be well tolerated in patients with intraventricular conduction disturbances. However, accurate assessment of the mortality risk and benefit of short-term intravenous treatment remains to be made in sufficiently powerful prospective, randomized controlled studies.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

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)

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.

The efficacy and safety of milrinone for treating heart failure in dogs

Milrinone has been studied in a variety of situations. In experimental dogs it has been documented to increase contractility to a similar degree as beta-receptor agonists and to produce mild arteriolar dilation in dogs. In canine patients with heart failure, milrinone produces demonstrable improvement in echocardiographic ventricular function and hemodynamic variables. In addition, it improves clinical signs in these patients, improving their quality of life. Milrinone is superior to digoxin as evidenced by the improvement in clinical signs noted in dogs that were unresponsive or no longer responding to digoxin administration. There is no doubt that milrinone improves short-term prognosis and in so doing prolongs life. Many of the patients that the author has observed would not have gone home without the benefits of milrinone. Milrinone's effects on long-term survival cannot be assessed, but its effects on survival time are certainly not dramatic enough to be evident without a comparison population. Therefore, milrinone administration should be considered palliative, as is administration of all other cardiovascular medications for heart failure. In addition to its beneficial effects, milrinone also appears to be relatively safe when compared with the alternative of digoxin administration. Fatal events attributable to milrinone administration are rare, and those directly attributable to enhanced ventricular arrhythmia can generally be avoided by monitoring an electrocardiogram after initial milrinone administration commences. Milrinone does not increase the incidence of sudden death in Doberman Pinschers. It is possible that a small number of dogs with mitral regurgitation may develop mitral chordal rupture. For this reason and possibly others, milrinone probably will not be indicated in early heart failure due to mitral regurgitation when heart failure is readily responsive to diuretic administration. The risk-to-benefit ratio turns markedly in the favor of milrinone administration in the dog with mitral regurgitation that is partially or completely refractory to other cardiovascular drugs. Milrinone appears to be a more effective and safer positive inotrope for long-term treatment of dogs with congestive heart failure than drugs currently available. The author and all the investigators involved in the milrinone clinical trials hope that it will soon be available for use by the veterinary community.

Effects of milrinone on left ventricular remodeling after acute myocardial infarction

BACKGROUND

Left ventricular remodeling after an acute myocardial infarction may result in progressive left ventricular dilation that may be associated with increased mortality. We studied the effects of the phosphodiesterase inhibitor milrinone on left ventricular remodeling after acute myocardial infarction.

METHODS AND RESULTS

Rats (n = 90) were randomized to undergo either left coronary artery ligation or sham operation. Three weeks after surgery, rats received either no treatment or milrinone, which was continued until 2 days before the rats were killed. Ninety days after the initial surgery, hemodynamic measurements were made before and after volume loading. The rats were killed, the hearts were removed, and passive pressure-volume curves were obtained. The hearts were fixed at a constant pressure and analyzed morphometrically. Compared with untreated infarcted rats, milrinone-treated infarcted rats had a lower left ventricular end-diastolic pressure (1.7 +/- 0.4 versus 4.3 +/- 1.4 mm Hg, p less than 0.05), a lower left ventricular volume (1.25 +/- 0.20 versus 2.37 +/- 0.30 ml/kg, p less than 0.001) and a lower left ventricular wall stress index (1.3 +/- 0.2 versus 1.7 +/- 0.1, p less than 0.05). Left ventricular chamber stiffness was higher in milrinone-treated infarcted rats than in untreated infarcted rats. Milrinone had no cardiac effect on uninfarcted animals.

CONCLUSION

Chronic milrinone therapy after acute myocardial infarction improves cardiac hemodynamic indexes and attenuates progressive left ventricular dilation.

Criteria for the accurate interpretation of changes in left ventricular ejection fraction and cardiac volumes as assessed by rest and exercise gated radionuclide angiography

Although serial left ventricular ejection fraction and volumetric measurements using gated radionuclide angiography are commonly used to evaluate clinical changes and therapeutic outcomes in individual patients, criteria are not available for accurately interpreting whether a change in any of these hemodynamic measurements is clinically meaningful. Accordingly, the magnitude of inherent variability among sequential measurements of hemodynamic variables assessed by gated radionuclide angiography was investigated in a double-blind placebo-controlled fashion in 39 patients during two placebo periods separated by 6 weeks. All patients analyzed had remained clinically stable during the study period. Although the mean values for all hemodynamic variables between the two placebo periods were minimally changed, the differences in individual patients were striking. Criteria were developed to allow meaningful interpretation of changes in hemodynamic variables by estimating the likelihood that an observed change is due to variability alone. On the basis of this analysis of placebo radionuclide angiographic data, variation due to chance alone is unlikely to account for all variability if a change observed between the two rest gated studies in a patient is greater than or equal to 7% units for left ventricular ejection fraction, greater than or equal to 45 ml/m2 for end-diastolic volume index, greater than or equal to 35 ml/m2 for end-systolic volume index, greater than or equal to 20 ml/m2 for stroke volume index and greater than or equal to 1.25 liters/min per m2 for cardiac index. An observed 4% unit change in left ventricular ejection fraction (increase or decrease) after a medical intervention in an individual patient occurs by random variation greater than 25% of the time.(ABSTRACT TRUNCATED AT 250 WORDS)

Medical management of chronic heart failure: inotropic, vasodilator, or inodilator drugs?

On the basis of pathophysiologic mechanisms, the medical therapy of today for chronic heart failure is reviewed. The advantages and disadvantages of the vasodilator drugs and the inotropic drugs are presented. Finally, the therapeutic value of the inodilator drugs, which combine the central myocardial effects of positive inotropic agents with those of peripheral vasodilators, is discussed. In particular, the orally available dopaminergic agents, such as ibopamine, which interact with beta-receptors in the heart (mediating a positive inotropic effect) as well as with dopaminergic receptors in the peripheral vessels (mediating a systemic vasodilator effect) and in the kidneys (potentiating the natriuretic effect of diuresis), seem to be an advancement in the modern medical therapy of chronic heart failure. Data are shown during long-term treatment with ibopamine, in which the sustained clinical benefit in heart failure was not diminished, despite a decrease of the adrenergic receptors in blood cells. Dopamine plasma concentration was permanently normalized during long-term treatment. The discrepancy between clinical improvement and the measured adrenergic downregulation may be due to the interference of the inodilator with neurohormonal systems at multiple sites and is probably independent of receptor activation. It is suggested that the biosynthesis of noradrenaline is improved by increasing intracellular dopamine transport.

Effect of flosequinan (BTS 49465) on myocardial oxygen consumption

BTS 49465 (flosequinan), a putative selective, balanced arterial and venous vasodilator, displays positive inotropic effects in doses lower than those producing vasodilation. Thus rather than unloading the myocardium, flosequinan may increase myocardial work and oxygen consumption (MVO2), and may adversely affect the patient with myocardial ischemia or compromised coronary blood flow. This study compared the effects of flosequinan with milrinone, a mixed positive inotropic agent and vasodilator, and with nitroprusside (SNP), a standard direct-acting vasodilator, on myocardial dP/dT, MVO2, and myocardial energetics in the normal pentobartital-anesthetized dog. The effect of flosequinan on myocardial work was also evaluated in the dog with propranolol-induced heart failure (PIHF). Fifteen minutes after intraduodenal (id) administration of flosequinan (0.3, 1.0, and 3.0 mg/kg) to seven dogs, mean myocardial dP/dT was increased by 11%, 27%, and 54%, respectively, whereas stroke MVO2 was increased by 10%, 24%, and 47%, respectively. Doses of flosequinan greater than 0.3 mg/kg decreased left ventricular (LV) work but LV efficiency decreased in a dose-related manner. Milrinone (0.1, 0.3, and 1.0 mg/kg, id) increased LV dp/dt by 34%, 68%, and 104% above basal values, while increasing stroke MVO2 by 24%, 106%, and 249%, respectively (n = 7). LV work and LV efficiency decreased after each dose of milrinone. SNP (0.001, 0.003, and 0.01 mg/kg/min, intravenously) did not increase dP/dT but decreased LV work by 28%, 42%, and 46% (n = 5). In animals with PIHF, flosequinan (1 and 3 mg/kg, id) increased LV dP/dT 58% and 87% and increased LV work by 58% and 76% above control values. It was concluded that (1) flosequinan is a positive inotropic agent as well as a vasodilator; (2) in the normal animal the energy cost of positive inotropic activity is less with flosequinan than with milrinone, despite the lesser vasodilating action of the former; and (3) in the animal with a depressed myocardium, flosequinan may adversely affect myocardial work and wall tension.

Phosphodiesterase inhibitors: alterations in systemic and coronary hemodynamics

This paper reviews the effect on myocardial contractility, left ventricular afterload and left ventricular distensibility induced by the following phosphodiesterase inhibitors: Enoximone, piroximone, RO 13-6438, amrinone and milrinone. For all these compounds, direct positive inotropic effects have been shown in experimental studies. For amrinone and milrinone, a direct stimulating effect on myocardial contractility has been demonstrated by an increase in dP/dtmax when intracoronary applications of the compounds were performed. A direct stimulating effect on the myocardium was also demonstrated for enoximone and piroximone by analyzing the systolic pressure versus end-systolic volume ratio. For all of the phosphodiesterase inhibitors, a marked decrease of systemic vascular resistance has been observed indicating direct peripheral vasodilation. Although it has been demonstrated that phosphodiesterase inhibition increases left ventricular distensibility, the nature of this effect is not clear. For most of the phosphodiesterase inhibitors an increase in myocardial oxygen requirements was demonstrated due to overall contractility increase. However, these phosphodiesterase inhibitors induce increased coronary blood flow in excess so that a direct effect of these compounds on the coronary vasculature has been postulated. The clinical significance of such changes, however, remains unclear.

Role of milrinone in the management of congestive heart failure

Milrinone is a bipyridine derivative with positive inotropic and vasodilating properties. The intravenous form of the drug has been approved by the Food and Drug Administration (FDA) for short-term management of congestive heart failure (CHF). The FDA has requested additional mortality data prior to approval of the oral form. Milrinone produces positive inotropic and vasodilating effects through unknown mechanisms, and causes a dose-dependent increase in cardiac index and a decrease in systemic vascular resistance and pulmonary capillary wedge pressure. It is extensively absorbed following oral administration with an elimination half-life of approximately 1.5-2 hours and a corresponding duration of action of 3-6 hours. Its major route of elimination is renal (83 percent). The intravenous dose is 50 micrograms/kg given over ten minutes, followed by a maintenance infusion of 0.375-0.75 micrograms/kg/min titrated to the desired hemodynamic response. The average effective oral dosage is 7.5-10 mg four to six times daily. Milrinone is most effective in the short-term management of CHF where the majority (60-80 percent) of patients have symptomatic and hemodynamic improvement as well as increases in exercise duration. However, many patients do not derive long-term benefit from milrinone therapy. Available evidence suggests that milrinone does not arrest the natural progression of CHF, and some investigators feel it may actually worsen CHF and shorten patients' length of survival. Milrinone has been generally well tolerated with a low risk of major organ toxicity. The most common adverse reactions with intravenous milrinone include ventricular arrhythmias (12 percent) and supraventricular arrhythmias (4 percent).(ABSTRACT TRUNCATED AT 250 WORDS)

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

We randomly assigned 230 patients in sinus rhythm with moderately severe heart failure to treatment with digoxin, milrinone, both, or placebo. The effects of each were compared during a 12-week, double-blind trial. Treatment with milrinone or digoxin significantly increased treadmill exercise time as compared with placebo (by 82 and 64 seconds respectively; 95 percent confidence limits, 44 and 123, and 30 and 100). Both treatments reduced the frequency of decompensation from heart failure, from 47 percent with placebo to 34 percent with milrinone (P less than 0.05; 95 percent confidence limits, 22 and 46) and 15 percent with digoxin (P less than 0.01; 95 percent confidence limits, 7 and 26). However, the clinical condition of 20 percent of the patients taking milrinone deteriorated within two weeks after treatment was begun, as compared with only 3 percent of those taking digoxin (P less than 0.05). The left ventricular ejection fraction at rest was not significantly changed by milrinone (+0.2 percent; 95 percent confidence limits, -1.5 and 1.9), but it was increased by digoxin (+1.7 percent; P less than 0.01; 95 percent confidence limits, -0.03 and 3.4) and decreased by placebo (-2.0 percent; 95 percent confidence limits, -3.8 and -0.1). Three-month survival was related inversely to the base-line ejection fraction. Analysis of mortality from all causes according to the intention to treat suggested an adverse effect of milrinone (P = 0.064). After adjustment for an excess of patients with lower ejection fractions randomly assigned to receive milrinone, this trend was not significant (P = 0.26). Increased ventricular arrhythmias occurred more frequently in patients who received milrinone than in those who did not (18 vs. 4 percent; P less than 0.03). We conclude that milrinone significantly increased exercise tolerance and reduced the frequency of worsened heart failure. However, in the population of patients studied, milrinone or the combination of milrinone and digoxin offered no advantage over digoxin alone. Furthermore, our data suggest that milrinone may aggravate ventricular arrhythmias.

The use of inotropic agents in acute and chronic congestive heart failure

This article reviews our current understanding of the physiology of myocardial contraction; recent research into its mechanical, macromolecular, and biochemical foundations; and its role in the clinical syndromes of congestive heart failure. This review serves as a background for discussing the mechanism of action and pharmacology of currently available and experimental inotropic agents. The clinical applications of these drugs are discussed and the successes and failures of the pharmacologic approach to patients with congestive heart failure analyzed.

Congestive heart failure--advances in treatment. Hemodynamic studies--their uses and limitations

Hemodynamic studies are useful in the diagnosis of the pathophysiologic mechanisms of pump failure and low output state in patients with acute heart failure. Hemodynamic monitoring is extremely useful for the appropriate manipulation of the vasoactive drugs to optimize hemodynamic and clinical improvement of patients with acute heart failure and to stabilize patients with severe refractory or unstable chronic heart failure. Determinations of the hemodynamic indexes of left ventricular function during hemodynamic studies also provide information regarding prognosis of patients with acute or chronic heart failure. In patients with stable chronic heart failure, correlations between the changes in hemodynamics after initiation of vasodilator therapy and subsequent changes in the clinical status and exercise tolerance are poor; thus, the value of hemodynamic studies for vasodilator therapy in patients with stable chronic heart failure is limited.

Long-term oral therapy of congestive heart failure with phosphodiesterase inhibitors

The existing management of severe chronic congestive heart failure carries a dismal prognosis. Mortality over 6 months is 50% by some estimates. This fact, coupled with increasing concern for the safety and efficacy of the digitalis glycosides, has stimulated an intense search for new oral cardiotonic agents suitable for chronic administration. Despite the ability of many phosphodiesterase inhibiting agents to affect profound hemodynamic improvements acutely after oral or intravenous administration, none of the four agents here reviewed in 30 clinical trials has been adequately proven to provide benefit over conventional long-term therapy of severe heart failure. The four drugs to have undergone long-term clinical trials are amrinone, milrinone, enoximone (MDL 17043), and piroximone (MDL 19,025). For amrinone, inefficacy was revealed through carefully designed, placebo-controlled studies despite initial enthusiasm generated by open uncontrolled trials. Enoximone has suffered rapid attenuation of its hemodynamic effectiveness in most studies, and piroximone failed in its only long-term trial. Therefore, final judgment on most of these agents must await completion of controlled clinical trials, and any initial optimism stimulated by the current uncontrolled studies should be met with reservation.

Controlled and uncontrolled studies of phosphodiesterase III inhibitors in contemporary cardiovascular medicine

The phosphodiesterase inhibitors are new inotrope vasodilators that have beneficial hemodynamic effects in patients with congestive heart failure (CHF). The most extensively studied agents are milrinone and enoximone. Both drugs have clearly been shown in numerous studies to improve hemodynamics in patients with CHF when given acutely by either the intravenous or oral route. In long-term studies, milrinone has been shown to have sustained beneficial hemodynamic effects during active treatment. Effects on exercise tolerance have been less clear-cut in several uncontrolled trials, but a recent large-scale randomized trial does show sustained improvement in exercise performance. When milrinone is withdrawn after long-term therapy, some studies show worsened cardiac performance; the exact cause remains ill-defined, but could be due to deterioration of baseline ventricular function or to "rebound." Both uncontrolled studies and a large recently reported randomized trial show that the hemodynamic response to readministration of milrinone after withdrawal is well-preserved, i.e., no tolerance is observed. Studies of enoximone show that its acute hemodynamic effects are similar to those of milrinone, but its long-term efficacy, using both hemodynamic and exercise end points, is less clear-cut, and no large-scale randomized trials of enoximone therapy have yet been reported. The studies of both these agents performed thus far indicate that the phosphodiesterase inhibitors have considerable promise for both acute and long-term treatment of patients with CHF.

Effect of phosphodiesterase inhibitors on survival of patients with chronic congestive heart failure

Controlled and uncontrolled hemodynamic and clinical studies have noted that the long-term treatment of patients with chronic heart failure with phosphodiesterase (PDE) inhibitors, such as amrinone, milrinone, enoximone and imazodan, may accelerate progression of the underlying disease and provoke serious ventricular arrhythmias. However, in an experimental model of chronic progressive left ventricular dysfunction, milrinone has been reported to reduce mortality to a degree comparable to that seen with the converting-enzyme inhibitors. These discordant observations suggest that either the deleterious hemodynamic and electrophysiologic effects of the PDE inhibitors are not translated into an adverse effect on mortality, or the animal model used to evaluate the effects of milrinone cannot be used to investigate the action of these drugs in human heart failure. Unfortunately, no trial has prospectively evaluated the effect of PDE inhibition on the survival of patients with heart failure. To address this need, the Prospective Randomized Milrinone Survival Evaluation (PROMISE Trial) has been launched in 75 to 90 clinical research centers in the United States and Canada. This study will enroll 750 patients with severe (class IV) heart failure, who have symptoms refractory to conventional therapy with digitalis, diuretics, converting-enzyme inhibitor and direct-acting vasodilators. Patients will be randomly assigned to additional treatment with either oral milrinone or placebo, and followed until death or to the conclusion of the study. The primary end point will be all-cause mortality, but the effect of milrinone on functional capacity will also be evaluated. The results of the study should define the place of PDE inhibitors in the treatment of chronic heart failure.

OPC-8212 in the treatment of congestive heart failure: results of a pilot study

To characterize the effects of OPC-8212, a quinolone inotropic agent, in patients with heart failure, we utilized invasive hemodynamics, exercise testing, 24-hour ambulatory electrocardiograms, and two patient self-assessment questionnaires, before and after 1 month of treatment with OPC-8212, in 17 patients with moderate to severe congestive heart failure. There were no significant changes from baseline in heart rate (83 +/- 8 beats/min), mean arterial pressure (70 +/- 15 mmHg), pulmonary wedge pressure (18 +/- 7 mmHg), or cardiac index (2.3 +/- 0.4 L/min/m2) following treatment with OPC-8212. Both exercise duration (5.3 +/- 1.6 min) and peak oxygen consumption (12.0 +/- 2.9 mL/kg/min) were unchanged by OPC-8212. Two independent patient self-assessment scores, the Sickness Impact Profile and the Minnesota Living with Heart Failure Questionnaire, showed improvements from 6.8 to 5.4 and 49 to 38, respectively (both p less than .05), suggesting that the patients reported an improvement in daily functioning. The median ventricular premature contraction count and frequency were reduced from 1,118 beats to 243 beats (p less than 0.05) and 11/1,000 beats to 2.4/1,000 beats (0.05 less than p less than 0.10), respectively. Two patients developed agranulocytosis during longer-term treatment following this 1-month study. These data demonstrate that OPC-8212 did not have significant effects on hemodynamics or exercise tolerance. However, the improvement in patient self-assessment scores and the trend for improvement in ventricular arrhythmia profiles suggest that OPC-8212 may have some benefit for patients with congestive heart failure, but additional placebo-controlled, double-blind studies are necessary.

Vasodilator and inotropic drugs for the treatment of chronic heart failure: distinguishing hype from hope

During the past 10 years, more than 80 orally active vasodilator and inotropic agents have been tested in the clinical setting to evaluate their potential utility in the treatment of chronic heart failure. Although the initial reports of all of these drugs suggested that each represented a major therapeutic advance, only three agents--digoxin, captopril and enalapril--have produced consistent long-term hemodynamic and clinical benefits in these severely ill patients. Most of the other drugs that have been tested have not (to date) distinguished themselves from placebo therapy in large-scale, controlled trials, even though these agents produce hemodynamic effects that closely resemble those seen with digitalis and the converting-enzyme inhibitors. These observations suggest that the hemodynamic derangements that characteristically accompany the development of left ventricular dysfunction cannot be considered to be the most important pathophysiologic abnormality in chronic heart failure. Although cardiac contractility is usually depressed in this disease, positive inotropic agents do not consistently improve the clinical status of these patients. Similarly, although the systemic vessels are usually markedly constricted, drugs that ameliorate this vasoconstriction do not consistently relieve symptoms, enhance exercise capacity or prolong life. Hence, correction of the central hemodynamic abnormalities seen in heart failure may not necessarily provide a rational basis for drug development, and future advances in therapy are likely to evolve only by attempting to understand and modify the basic physiologic derangements in this disorder.