Safety and clinical utility of long-term intravenous milrinone in advanced heart failure

Effects of omecamtiv mecarbil on calcium-transients and contractility in a translational canine myocyte model

Omecamtiv mecarbil (OM) is a selective cardiac myosin activator (myotrope), currently in Phase 3 clinical investigation as a novel treatment for heart failure with reduced ejection fraction. OM increases cardiac contractility by enhancing interaction between myosin and actin in a calcium-independent fashion. This study aims to characterize the mechanism of action by evaluating its simultaneous effect on myocyte contractility and calcium-transients (CTs) in healthy canine ventricular myocytes. Left ventricular myocytes were isolated from canines and loaded with Fura-2 AM. With an IonOptix system, contractility parameters including amplitude and duration of sarcomere shortening, contraction and relaxation velocity, and resting sarcomere length were measured. CT parameters including amplitude at systole and diastole, velocity at systole and diastole, and duration at 50% from peak were simultaneously measured. OM was tested at 0.03, 0.1, 0.3, 1, and 3 µmol\L concentrations to simulate therapeutic human plasma exposure levels. OM and isoproterenol (ISO) demonstrated differential effects on CTs and myocyte contractility. OM increased contractility mainly by prolonging duration of contraction while ISO increased contractility mainly by augmenting the amplitude of contraction. ISO increased the amplitude and velocity of CT, shortened duration of CT concurrent with increasing myocyte contraction, while OM did not change the amplitude, velocity, and duration of CT up to 1 µmol\L. Decreases in relaxation velocity and increases in duration were present only at 3 µmol\L. In this translational myocyte model study, therapeutically relevant concentrations of OM increased contractility but did not alter intracellular CTs, a mechanism of action distinct from traditional calcitropes.

Evaluation and Management of Right-Sided Heart Failure: A Scientific Statement From the American Heart Association

Background and Purpose:

The diverse causes of right-sided heart failure (RHF) include, among others, primary cardiomyopathies with right ventricular (RV) involvement, RV ischemia and infarction, volume loading caused by cardiac lesions associated with congenital heart disease and valvular pathologies, and pressure loading resulting from pulmonic stenosis or pulmonary hypertension from a variety of causes, including left-sided heart disease. Progressive RV dysfunction in these disease states is associated with increased morbidity and mortality. The purpose of this scientific statement is to provide guidance on the assessment and management of RHF.

Methods:

The writing group used systematic literature reviews, published translational and clinical studies, clinical practice guidelines, and expert opinion/statements to summarize existing evidence and to identify areas of inadequacy requiring future research. The panel reviewed the most relevant adult medical literature excluding routine laboratory tests using MEDLINE, EMBASE, and Web of Science through September 2017. The document is organized and classified according to the American Heart Association to provide specific suggestions, considerations, or reference to contemporary clinical practice recommendations.

Results:

Chronic RHF is associated with decreased exercise tolerance, poor functional capacity, decreased cardiac output and progressive end-organ damage (caused by a combination of end-organ venous congestion and underperfusion), and cachexia resulting from poor absorption of nutrients, as well as a systemic proinflammatory state. It is the principal cause of death in patients with pulmonary arterial hypertension. Similarly, acute RHF is associated with hemodynamic instability and is the primary cause of death in patients presenting with massive pulmonary embolism, RV myocardial infarction, and postcardiotomy shock associated with cardiac surgery. Functional assessment of the right side of the heart can be hindered by its complex geometry. Multiple hemodynamic and biochemical markers are associated with worsening RHF and can serve to guide clinical assessment and therapeutic decision making. Pharmacological and mechanical interventions targeting isolated acute and chronic RHF have not been well investigated. Specific therapies promoting stabilization and recovery of RV function are lacking.

Conclusions:

RHF is a complex syndrome including diverse causes, pathways, and pathological processes. In this scientific statement, we review the causes and epidemiology of RV dysfunction and the pathophysiology of acute and chronic RHF and provide guidance for the management of the associated conditions leading to and caused by RHF.

Korean Guidelines for Diagnosis and Management of Chronic Heart Failure

The prevalence of heart failure (HF) is skyrocketing worldwide, and is closely associated with serious morbidity and mortality. In particular, HF is one of the main causes for the hospitalization and mortality in elderly individuals. Korea also has these epidemiological problems, and HF is responsible for huge socioeconomic burden. However, there has been no clinical guideline for HF management in Korea. 
The present guideline provides the first set of practical guidelines for the management of HF in Korea and was developed using the guideline adaptation process while including as many data from Korean studies as possible. The scope of the present guideline includes the definition, diagnosis, and treatment of chronic HF with reduced/preserved ejection fraction of various etiologies.

Changing our Approach to Stage D Heart Failure

Despite the tremendous progress made in the management of heart failure (HF), many patients reach advanced stages. This paper aims to present a practical approach to the stage D HF patient who is no longer responding to optimal medical therapy. We discuss all available therapies for this patient population. We also offer some important caveats with regard to identification, risk stratification, evaluation and treatment including early patient referral to a center with an advanced HF program. Given the changing landscape of heart transplantation and an impending change in the allocation system, we also intend to engage a discussion on the need for a paradigm shift towards left ventricular assist device therapy in this population.

Renal Function and Outcomes With Use of Left Ventricular Assist Device Implantation and Inotropes in End-Stage Heart Failure: A Retrospective Single Center Study

Background

Left ventricular assist device (LVAD) and inotrope therapy serve as a bridge to transplant (BTT) or as destination therapy in patients who are not heart transplant candidates. End-stage heart failure patients often have impaired renal function, and renal outcomes after LVAD therapy versus inotrope therapy have not been evaluated.

Methods

In this study, 169 patients with continuous flow LVAD therapy and 20 patients with continuous intravenous inotrope therapy were analyzed. The two groups were evaluated at baseline and at 3 and 6 months after LVAD or inotrope therapy was started. The incidence of acute kidney injury (AKI), need for renal replacement therapy (RRT), BTT rate, and mortality for 6 months following LVAD or inotrope therapy were studied. Results between the groups were compared using Mann-Whitney U test and Chi-square with continuity correction or Fischer’s exact at the significance level of 0.05.

Results

Mean glomerular filtration rate (GFR) was not statistically different between the two groups, with P = 0.471, 0.429, and 0.847 at baseline, 3 and 6 months, respectively. The incidence of AKI, RRT, and BTT was not statistically different. Mortality was less in the inotrope group (P < 0.001).

Conclusion

Intravenous inotrope therapy in end-stage heart failure patients is non-inferior for mortality, incidence of AKI, need for RRT, and renal function for 6-month follow-up when compared to LVAD therapy. Further studies are needed to compare the effectiveness of inotropes versus LVAD implantation on renal function and outcomes over a longer time period.

Novel role of phosphodiesterase inhibitors in the management of end-stage heart failure

In advanced heart failure (HF), chronic inotropic therapy with intravenous milrinone, a phosphodiesterase III inhibitor, is used as a bridge to advanced management that includes transplantation, ventricular assist device implantation, or palliation. This is especially true when repeated attempts to wean off inotropic support result in symptomatic hypotension, worsened symptoms, and/or progressive organ dysfunction. Unfortunately, patients in this clinical predicament are considered hemodynamically labile and may escape the benefits of guideline-directed HF therapy. In this scenario, chronic milrinone infusion may be beneficial as a bridge to introduction of evidence based HF therapy. However, this strategy is not well studied, and in general, chronic inotropic infusion is discouraged due to potential cardiotoxicity that accelerates disease progression and proarrhythmic effects that increase sudden death. Alternatively, chronic inotropic support with milrinone infusion is a unique opportunity in advanced HF. This review discusses evidence that long-term intravenous milrinone support may allow introduction of beta blocker (BB) therapy. When used together, milrinone does not attenuate the clinical benefits of BB therapy while BB mitigates cardiotoxic effects of milrinone. In addition, BB therapy decreases the risk of adverse arrhythmias associated with milrinone. We propose that advanced HF patients who are intolerant to BB therapy may benefit from a trial of intravenous milrinone as a bridge to BB initiation. The discussed clinical scenarios demonstrate that concomitant treatment with milrinone infusion and BB therapy does not adversely impact standard HF therapy and may improve left ventricular function and morbidity associated with advanced HF.

Inotropes do not increase mortality in advanced heart failure

Inotrope use is one of the most controversial topics in the management of heart failure. While the heart failure community utilizes them and recognizes the state of inotrope dependency, retrospective analyses and registry data have overwhelmingly suggested high mortality, which is logically to be expected given the advanced disease states of those requiring their use. Currently, there is a relative paucity of randomized control trials due to the ethical dilemma of creating control groups by withholding inotropes from patients who require them. Nonetheless, results of such trials have been mixed. Many were also performed with agents no longer in use, on patients without an indication for inotropes, or at a time before automatic cardio-defibrillators were recommended for primary prevention. Thus, their results may not be generalizable to current clinical practice. In this review, we discuss current indications for inotrope use, specifically dobutamine and milrinone, depicting their mechanisms of action, delineating their patterns of use in clinical practice, defining the state of inotrope dependency, and ultimately examining the literature to ascertain whether evidence is sufficient to support the current view that these agents increase mortality in patients with heart failure. Our conclusion is that the evidence is insufficient to link inotropes and increased mortality in low output heart failure.

Elevation of Plasma Milrinone Concentrations in Stage D Heart Failure Associated With Renal Dysfunction

Purpose:

To determine steady state milrinone concentrations in patients with stage D heart failure (HF) with and without renal dysfunction

Methods:

We retrospectively identified patients with stage D HF at a single medical center on continuous milrinone infusion at the time of plasma collection for entry into a research registry database. Milrinone was prescribed and titrated to improve hemodynamic and clinical status by a cardiologist. Plasma samples were obtained at steady state milrinone concentrations. Patients were stratified by creatinine clearance (CrCl) into 4 groups: group 1 (CrCl >60 mL/min), group 2 (CrCl 60-30 mL/min), group 3 (CrCl <30 mL/min), and group 4 (intermittent hemodialysis). Retrospective chart review was performed to quantify the postmilrinone hemodynamic changes by cardiac catheterization and electrophysiologic changes by implantable cardiac defibrillator (ICD) interrogation.

Results:

A total of 29 patients were identified: group 1 (n = 14), group 2 (n = 10), group 3 (n = 3), and group 4 (n = 2). The mean infusion rate (0.391 ± 0.08 µg/kg/min) did not differ between groups ( P = 0.14). The mean milrinone concentration was 451± 243 ng/mL in group 1, 591 ± 293 ng/mL in group 2, 1575 ± 962 ng/mL in group 3, and 6252 ± 4409 ng/mL in group 4 ( P<0.05 compared to groups 1). There was no difference in postmilrinone hemodynamic improvements between the groups ( P=0.41). The ICD interrogation revealed limited comparisons, but 6 of the 8 postmilrinone ventricular tachycardia episodes requiring defibrillation occurred in group 4 patients.

Conclusion:

Patients with stage D HF having severe renal dysfunction have elevated milrinone concentrations. Future studies of milrinone concentrations are warranted to investigate the potential risk of life-threatening arrhythmias and potential dosing regimens in renal dysfunction.

Milrinone in Advanced Heart Failure

Advanced chronic heart failure (ACHF) patients often require inotropes before transplantation or ventricular assist device implantation. Milrinone, an inotrope and vasodilator, may accumulate in cardiorenal syndrome with serious adverse effects. We investigated the potential for therapeutic drug monitoring of milrinone levels using High Performance Liquid Chromatography Mass Spectrometry (HPLC-MS). 22 ACHF patients (15 males, 49±9 years) received milrinone 50 µg/kg intravenously (i.v.) during heart catheterization. Milrinone levels were 216±71 ng/ml (within the reported therapeutic range: 100-300 ng/ml), followed by improvements in cardiac index, pulmonary artery and wedge pressures (p < 0.005). 18 ACHF patients (17 males, 50±12 years, 13 had renal dysfunction) received continuous i.v. milrinone (5-26 days) at 0.1-0.2 µg/kg/min, titrated according to plasma milrinone levels. No adverse events occurred. Therapeutic levels were achieved with doses of 0.2±0.06 µg/Kg/min, below those recommended in Summary of Product Characteristics. Milrinone therapy can be noninvasively monitored by HPLC-MS, while avoiding toxicity in ACHF.

Impact of milrinone on mitral annular velocity in patients with congestive heart failure

PURPOSE

The purpose of this study is to assess the impact of milrinone on mitral annular velocity in patients with congestive heart failure.

METHOD

We studied 27 patients with congestive heart failure. All patients underwent transthoracic echocardiography both before and after administration of milrinone. We measured the early transmitral velocity (E) and the mitral annular early diastolic velocity (Ea). The ratio of E to Ea (E/Ea) was calculated. After the baseline echocardiography, milrinone was administered as a continuous infusion at a rate of 0.25 μg/kg/min. Echocardiographic measurements were repeated 4 h after milrinone was begun.

RESULTS

After administration of milrinone, Ea was significantly increased, while E/Ea was significantly decreased. The population of 27 patients was divided into 20 (74 %) with left ventricular ejection fraction (LVEF) <50 % and seven (26 %) with LVEF ≥50 %. Ea was significantly increased in both groups, while E/Ea was significantly decreased.

CONCLUSION

Even low-dose milrinone produced an improvement in left ventricular (LV) diastolic function, as evidenced by an increase in Ea, and falls in LV filling pressures, as determined by a decrease in E/Ea, in patients with congestive heart failure throughout a wide range of LV systolic function.

Positive inotropes in heart failure: a review article

Increasing myocardial contractility has long been considered a big help for patients with systolic heart failure, conferring an augmented haemodynamic profile in terms of higher cardiac output, lower cardiac filling pressure and better organ perfusion. Though concerns have been raised over the safety issues regarding the clinical trials of different inotropes in hearts with systolic dysfunction, they still stand as a main therapeutic strategy in many centres dealing with such patients. They must be used as short in duration, low in dose and stopped as early as possible. Evidence-based guidelines have provided clinicians with valuable data for better applying inotropes in heart failure patients. In this paper, the authors address clinical trials with different agents used for increasing cardiac contractility in heart failure patients. Furthermore, the authors focus on recent guidelines on making the most out of inotropes in heart failure patients.

Pulmonary hypertension related to left-sided cardiac pathology

Pulmonary hypertension (PH) is the end result of a variety of diverse pathologic processes. The chronic elevation in pulmonary artery pressure often leads to right ventricular pressure overload and subsequent right ventricular failure. In patients with left-sided cardiac disease, PH is quite common and associated with increased morbidity and mortality. This article will review the literature as it pertains to the epidemiology, pathogenesis, and diagnosis of PH related to aortic valve disease, mitral valve disease, left ventricular systolic and diastolic dysfunction, and pulmonary veno-occlusive disease. Moreover, therapeutic strategies, which focus on treating the underlying cardiac pathology will be discussed.

Pulmonary hypertension secondary to left ventricular systolic dysfunction: contemporary diagnosis and management

Pulmonary hypertension secondary to left ventricular systolic dysfunction is often a poor prognostic marker in chronic heart failure. In this article, we review evidence supporting modern strategies addressing pulmonary hypertension in patients with left ventricular systolic dysfunction, including right-sided heart catheterization with vasoreactivity testing and subsequent parenteral, oral, and inhaled therapy. We delineate a diagnostic approach to secondary pulmonary hypertension and outline evidence-based therapeutic strategies for management in acute and chronic heart failure.

Arterial pulmonary hypertension in noncardiac intensive care unit

Pulmonary artery pressure elevation complicates the course of many complex disorders treated in a noncardiac intensive care unit. Acute pulmonary hypertension, however, remains underdiagnosed and its treatment frequently begins only after serious complications have developed. Significant pathophysiologic differences between acute and chronic pulmonary hypertension make current classification and treatment recommendations for chronic pulmonary hypertension barely applicable to acute pulmonary hypertension. In order to clarify the terminology of acute pulmonary hypertension and distinguish it from chronic pulmonary hypertension, we provide a classification of acute pulmonary hypertension according to underlying pathophysiologic mechanisms, clinical features, natural history, and response to treatment. Based on available data, therapy of acute arterial pulmonary hypertension should generally be aimed at acutely relieving right ventricular (RV) pressure overload and preventing RV dysfunction. Cases of severe acute pulmonary hypertension complicated by RV failure and systemic arterial hypotension are real clinical challenges requiring tight hemodynamic monitoring and aggressive treatment including combinations of pulmonary vasodilators, inotropic agents and systemic arterial vasoconstrictors. The choice of vasopressor and inotropes in patients with acute pulmonary hypertension should take into consideration their effects on vascular resistance and cardiac output when used alone or in combinations with other agents, and must be individualized based on patient response.

The use of continuous milrinone therapy as bridge to transplant is safe in patients with short waiting times

OBJECTIVE

The limited availability of donor organs creates a need for more effective management of heart disease when bridging a patient to cardiac transplant. Inotropic therapy is becoming more commonly used long term to maintain baseline function. The effectiveness and complications associated with their use have not been fully evaluated, and indications for mechanical versus medical therapy as a bridge have not been delineated.

METHODS AND RESULTS

The purpose of this study is to evaluate the safety and efficacy of milrinone as a bridge to transplant. This was a retrospective study of 60 patients listed for a cardiac transplant and committed to home intravenous milrinone therapy. A subgroup of patients who eventually progressed to the use of a ventricular assist device were analyzed. Complications and survivals were analyzed for each group. Forty-six patients (76%) were successfully bridged to transplant with milrinone alone, and 14 patients' (24%) conditions deteriorated and required a left ventricular assist device (LVAD); 1-year survivals were 83% and 71%, respectively. The mean waiting time was 59.5 days (9-257 days) for patients receiving milrinone who did not require an LVAD and 112 days (24-270 days) for those whose conditions deteriorated to require an LVAD.

CONCLUSIONS

This study suggests that chronic intravenous milrinone provides an adequate strategy as a bridge to transplant if the waiting time is short (<100 days), whereas an elective ventricular assist device implantation may be a safer strategy for patients expected to wait longer. These data provide the basis for a prospective evaluation of inotrope versus LVAD as a bridge to transplantation.

Medically Refractory Pulmonary Hypertension: Treatment With Nonpulsatile Left Ventricular Assist Devices

BACKGROUND

Severe pulmonary hypertension refractory to medical treatment is a contraindication to orthotopic heart transplantation in most centers. We report our experience in treating severe pulmonary hypertension with mechanical left ventricular unloading using implantable nonpulsatile left ventricular assist devices (LVAD) with continuous flow properties.

METHODS

In ten patients with severe pulmonary hypertension, refractory to medical treatment, an implantable nonpulsatile LVAD was placed for continuous mechanical left ventricular support. Pulmonary hemodynamics were assessed by right heart catheterization prior to and during LVAD implantation, and after orthotopic heart transplantation.

RESULTS

The mean (+/-SD) interval of nonpulsatile support was 182 (+/-118) days. Pulmonary artery pressure (mean +/- SD) significantly decreased from 42 +/- 13 to 24 +/- 5 mm Hg (p < 0.005), the transpulmonary gradient (mean +/- SD) decreased from 20 +/- 6 to 11 +/-5 mm Hg (p < 0.005), and the pulmonary vascular resistance (mean +/- SD) from 4.8 +/- 1.8 to 2.2 +/- 0.8 Wood units (p < 0.005) during an interval of one to six months of LVAD support. No significant increases in pulmonary artery pressure, transpulmonary gradient, and pulmonary vascular resistance were observed during an interval of three to six months after orthotopic heart transplantation.

CONCLUSIONS

This study supports that LVAD support and continuous nonpulsatile mechanical unloading of the left ventricle can reverse medically unresponsive pulmonary hypertension and render patients eligible for orthotopic heart transplantation.

A case and review of acromegaly-induced cardiomyopathy and the relationship between growth hormone and heart failure: cause or cure or neither or both?

Growth hormone plays an integral role in the development and maintenance of structure and function of the heart. Specific involvement of the heart in acromegaly is termed acromegalic cardiomyopathy, manifested as concentric left ventricular hypertrophy and diastolic dys-function. Left untreated, it ultimately progresses to systolic heart failure. Heart failure from acromegalic cardiomyopathy is one of the most common causes of death in acromegaly. Current treatment options include different approaches to lower elevated growth hormone levels with improvement in symptoms, exercise tolerance, and echocardiographic improvement in regression of left ventricular hypertrophy and indices of diastolic dysfunction. On the other hand, growth hormone is essential for cardiac growth and function and exerts beneficial and protective effects on the cardiovascular system. Its potential role as adjunctive therapy in the treatment of heart failure as derived from experimental studies and clinical trials is discussed.

Predictors of Clinical Outcome in Advanced Heart Failure Patients on Continuous Intravenous Milrinone Therapy

Home-based milrinone therapy (HMT) is used as a bridge to cardiac transplant (CT). The safety, efficacy, and predictors of success of HMT were assessed. Forty-five patients with heart failure, referred for CT, were prospectively studied. After initial assessment, low-dose milrinone was titrated based on clinical response. Hemodynamic status was then reevaluated. Thirty-nine patients were discharged on HMT. Patients needing a left ventricular assist device (LVAD) despite milrinone (group I) and those not requiring LVAD (group II) were compared. Six of the 45 patients were ineligible for CT; 16 of 39 required LVAD as a bridge to CT despite milrinone (group I); 23 were stable on milrinone and did not require LVAD (group II). Group I was younger than group II (mean age 38.4 +/- 14.5 years vs. 57.3 +/- 5.9 years, p < 0.001). Initial acute response to intravenous milrinone [e.g., fall in the PCWP (-10.7 +/- 9.5 vs. -2.7 +/- 10.4, p = 0.02), rise in pulmonary artery oxygen saturations (16.5 +/- 8.7 vs. 7.3 +/- 10.9, p = 0.05)] was significantly better in group II than in group I. Acute hemodynamic response to milrinone predicts success of HMT as a bridge to CT.

Lower serum sodium is associated with increased short-term mortality in hospitalized patients with worsening heart failure: results from the Outcomes of a Prospective Trial of Intravenous Milrinone for Exacerbations of Chronic Heart Failure (OPTIME-CHF) study

BACKGROUND

The prognostic value of serum sodium in patients hospitalized for worsening heart failure has not been well defined.

METHODS AND RESULTS

The Outcomes of a Prospective Trial of Intravenous Milrinone for Exacerbations of Chronic Heart Failure (OPTIME-CHF) study randomized 949 patients with systolic dysfunction hospitalized for worsening heart failure to receive 48 to 72 hours of intravenous milrinone or placebo in addition to standard therapy. In a retrospective analysis, we investigated the relationship between admission serum sodium and the primary end point of days hospitalized for cardiovascular causes within 60 days of randomization, as well as the secondary end points of in-hospital mortality, 60-day mortality, and 60-day mortality/rehospitalization. The number of days hospitalized for cardiovascular causes was higher in the lowest sodium quartile: 8.0 (4.5, 18.5) versus 6 (4, 13) versus 6 (4, 11.5) versus 6 (4, 12) days (P<0.015 for comparison with the lowest quartile). Lower serum sodium was associated with higher in-hospital and 60-day mortality: 5.9% versus 1% versus 2.3% versus 2.3% (P<0.015) and 15.9% versus 6.4% versus 7.8% versus 7% (P=0.002), respectively. There was a trend toward higher mortality/rehospitalization for patients who were in the lowest sodium quartile. Multivariable-adjusted Cox proportional hazards analysis showed that serum sodium on admission, when modeled linearly, predicted increased 60-day mortality: sodium (per 3-mEq/L decrease) had a hazard ratio of 1.18 with a 95% CI of 1.03 to 1.36 (P=0.018).

CONCLUSIONS

In patients hospitalized for worsening heart failure, admission serum sodium is an independent predictor of increased number of days hospitalized for cardiovascular causes and increased mortality within 60 days of discharge.

Home continuous positive inotropic infusion as a bridge to cardiac transplantation in patients with end-stage heart failure

BACKGROUND

The clinical use of positive inotropic therapy at home in patients awaiting cardiac transplantation has not been reported since United Network for Organ Sharing (UNOS) regulations were changed to allow home infusions in Status 1B patients.

METHODS

We observed 21 consecutive patients with UNOS 1B status during positive inotropic therapy at home. We used hemodynamic monitoring at the initiation of therapy to optimize dosing. We selected for home therapy patients with stable clinical status and improved functional capacity during inotropic treatment. Implantable cardioverter defibrillators were placed in all but 1 patient before discharge.

RESULTS

Initial positive inotropic therapy included dobutamine in 12 patients (mean dose, 4.5 mcg/kg/min; range, 2.5-7.5 mcg/kg/min), milrinone in 8 patients (mean dose, 0.44 mcg/kg/min; range, 0.375-0.55 mcg/kg/min), and dopamine at a dose of 3 mcg/kg/min in 1 patient. Patients had improved functional capacity (New York Heart Association Class 3.7 +/- 0.1 to 2.4 +/- 0.2, p < 0.01), improved renal function (serum creatinine, 1.5 +/- 0.1 to 1.3 +/- 0.1, p < 0.01), improved resting hemodynamics, and decreased number of hospitalizations during positive inotropic infusion therapy when compared with pre-treatment baseline. Implantable cardioverter defibrillator discharges were infrequent (0.19 per 100 patient days of follow-up). Actuarial survival to transplantation at 6 and 12 months was 84%.

CONCLUSIONS

Continuous positive inotropic therapy at home was safe and was associated with decreased health care costs in selected patients awaiting cardiac transplantation.

A prospective study of continuous intravenous milrinone therapy for status IB patients awaiting heart transplant at home

BACKGROUND

We performed a prospective study to determine the feasibility and safety of continuous intravenous milrinone therapy administered at home in patients listed as Status IB for heart transplant.

METHODS

Patients who were Status IB could participate if they met specific criteria including an optimal dose of milrinone < or =0.5 microg/kg/min, presence of an implantable cardioverter-defibrillator (ICD), and no other serious comorbidity. The primary end-point of the study was survival to transplant. Hospitalizations, quality of life and cost comparisons were assessed.

RESULTS

From May 1999 through October 2002, a total of 60 patients (51 men, 9 women), aged 55.5 +/- 8.4 years, entered the study. Before milrinone therapy, cardiac index was 1.98 +/- 0.66 liters/min/m2 and peak oxygen consumption was 11.4 +/- 2.6 ml/kg/min. Mean time in the study was 160.1 +/- 151.8 days. Fifty-three patients (88.3%) underwent heart transplant. There were only 2 deaths during the study. There were 89 hospital admissions in 46 patients over the 43-month follow-up period; 58 of these admissions were for heart failure. There were 6 episodes of ICD firing for ventricular tachycardia. Quality-of-life measures in a sub-group of patients significantly improved 1 month after discharge. Substantial estimated cost savings occurred.

CONCLUSIONS

Continuous intravenous milrinone therapy can be safely administered at home in selected patients with advanced heart failure who are listed for transplant. This strategy may be an acceptable alternative to prolonged hospitalization for patients dependent on continuous inotropic support. Re-hospitalization is to be expected. An implantable cardioverter-defibrillator should be present due to the incidence of ventricular tachycardia.

Tratamiento inotrópico en la insuficiencia cardíaca: aspectos generales y resultados clínicos

Classic inotropic agents such as beta-adrenergic agonists and phosphodiesterase III inhibitors have beneficial but transitory hemodynamic effects in patients with acute and chronic heart failure. In this context, the available data suggest that long term inotropic therapy has a negative impact on morbidity and mortality in patients with heart failure. For this reason, these agents are mainly used for the treatment of refractory episodes of decompensation and they are also used as a "bridge" (transplant, revascularization, recovery) or as a palliative measure. We present a revision of the general aspects of inotropes including main published clinical trials and some findings of its combined use with beta blockers. Furthermore, we describe a promising and differential therapeutic approach represented by calcium sensitizer agents (levosimendan).

Morbidity and mortality of UNOS status 1B cardiac transplant candidates at home

BACKGROUND

On January 20, 1999, UNOS listing regulations changed, allowing stable patients on inotropic support (Status IB) to be discharged home until cardiac transplant. The outcome, morbidity and cost savings of this new strategy has not been evaluated.

METHODS

From 1/20/99 through 1/1/01, 155 patients were classified as UNOS Status 1B at our institution; 64 patients were never discharged and 91 were discharged home. Criteria for discharge were hemodynamic stability on low-dose, single-agent parenteral inotropic infusion, defined as dobutamine at a dose <7.5 microg/kg/min or milrinone <0.5 microg/kg/min. Data on re-admissions were collected prospectively. The frequency of complex ventricular arrhythmias was evaluated in a sub-group discharged with external or internal cardiodefibrillators (n = 38).

RESULTS

Total Status I time to transplant for the 91 discharged patients was 139 +/- 91 days, with 87 +/- 67 days spent at home. Inpatient time to transplant was still high, with a mean of 51 +/- 45 days. The in-hospital time was comparable to that of the 64 patients who were never discharged (51 +/- 41 days). Fifty-nine percent of discharged patients were re-admitted, with 37% of patients requiring more than 1 admission. Sixty-six percent of admissions were for worsening heart failure (CHF), and 34% for infection or occlusion of the indwelling intravenous line. No significant arrhythmic events were recorded in the 38 patients who had internal or external cardiodefibrillators. Two patients died suddenly at home. One patient had declined to wear the external cardiodefibrillator. The other patient was not wearing the defibrillator at the time of the event, and in 634 hours of previous monitoring he had had no events.

CONCLUSIONS

In UNOS Status 1B patients awaiting cardiac transplant on home inotropic therapy, mortality remains low but the re-admission rate was high. There appeared to be a low incidence of complex ventricular arrhythmias.

Evaluation of pulmonary hypertension in heart transplant candidates

Assessment of the pulmonary circulation and right ventricular function is a cornerstone in the evaluation of the patient as a potential heart transplant recipient. The importance of pulmonary hypertension is linked to outcomes in the posttransplant period. Preoperative pulmonary vascular resistance is an independent risk factor for early death after heart transplantation. Pulmonary hypertension can be classified as reversible, or irreversible if not rapidly responsive to pharmacologic maneuvers. However, in most patients, the major component is likely to reverse with vasodilators, because of the central role played by the endothelium in the control of pulmonary vascular tone. To discriminate between patients with reversible and irreversible pulmonary hypertension, provocative therapies are used, and baseline and the postprovocation hemodynamic parameters are measured. To date, there is no reliable hemodynamic threshold beyond which right ventricular failure is certain to occur, nor are there values below which right ventricular failure is always avoidable. Because of this uncertainty, it becomes clear that only through careful preoperative assessment can this life-threatening condition be recognized preoperatively and, hence, managed in the posttransplant recovery period.

Comparison of dobutamine versus milrinone therapy in hospitalized patients awaiting cardiac transplantation: a prospective, randomized trial

BACKGROUND

The use of dobutamine or milrinone for inotropic support in patients with heart failure awaiting cardiac transplantation is largely arbitrary and based on institutional preference. The costs and effectiveness of these drugs have yet to be compared in a prospective, randomized study.

METHODS

We compared clinical outcomes and costs associated with the use of dobutamine or milrinone in 36 hospitalized patients awaiting cardiac transplantation. Patients were randomly assigned to receive either dobutamine or milrinone at the time of initial hospitalization and were followed until death, transplantation, or placement of mechanical cardiac support (intra-aortic balloon pump or left ventricular assist device).

RESULTS

Seventeen patients were randomly assigned to receive dobutamine (mean dose 4.1 +/- 1.4 microg/kg/min) and 19 patients received milrinone (mean dose 0.39 +/- 1.0 microg/kg/min). Therapy lasted 50 +/- 46 days for those in the dobutamine group and 63 +/- 45 days in the milrinone group. We did not detect differences between the 2 groups in right heart hemodynamics, death, need for additional vasodilator/inotropic therapy, or need for mechanical cardiac support before transplantation. Ventricular arrhythmias requiring increased antiarrhythmic therapy occurred frequently in both groups. Total acquisition cost of milrinone was significantly higher than that of dobutamine (16,270 dollars +/- 1334 vs 380 dollars +/- 533 P <.00001).

CONCLUSIONS

Both dobutamine and milrinone can be used successfully as pharmacologic therapy for a bridge to heart transplantation. Despite similar clinical outcomes, treatment with milrinone incurs greater cost.

Effects of cAMP modulators on long-chain fatty-acid uptake and utilization by electrically stimulated rat cardiac myocytes

Recently, we established that cellular contractions increase long-chain fatty-acid (FA) uptake by cardiac myocytes. This increase is dependent on the transport function of an 88 kDa membrane FA transporter, FA translocase (FAT/CD36), and, in analogy to skeletal muscle, is likely to involve its translocation from an intracellular pool to the sarcolemma. In the present study, we investigated whether cAMP-dependent signalling is involved in this translocation process. Isoproterenol, dibutyryl-cAMP and the phosphodiesterase (PDE) inhibitor, amrinone, which markedly raised the intracellular cAMP level, did not affect cellular FA uptake, but influenced the fate of intracellular FAs by directing these to mitochondrial oxidation in electrostimulated cardiac myocytes. The PDE inhibitors 3-isobutyl-1-methylxanthine, milrinone and dipyridamole each significantly stimulated FA uptake as well as intracellular cAMP levels, but these effects were quantitatively unrelated. The stimulatory effects of these PDE inhibitors were antagonized by sulpho- N -succinimidylpalmitate, indicating the involvement of FAT/CD36, albeit that the different PDE inhibitors use different molecular mechanisms to stimulate FAT/CD36-mediated FA uptake. Notably, 3-isobutyl-1-methylxanthine and milrinone increased the intrinsic activity of FAT/CD36, possibly through its covalent modification, and dipyridamole induces translocation of FAT/CD36 to the sarcolemma. Elevation of intracellular cGMP, but not of cAMP, by the PDE inhibitor zaprinast did not have any effect on FA uptake and metabolism by cardiac myocytes. The stimulatory effects of PDE inhibitors on cardiac FA uptake should be considered when applying these agents in clinical medicine.

The dilemma of late-stage heart failure. Rationale for chronic parenteral inotropic support

The available evidence suggests that while chronic inotropic support likely exerts a long-term deleterious effect on survival, their use is accompanied by short-term enhancements in symptomatology and decreases in medical resource use, thereby curtailing the overall medical costs. The decision to use chronic parenteral inotropic support should not be made lightly and must be considered only after all evidence based therapeutic options has been investigated thoroughly and tried (Fig. 1). This should include not only hemodynamic monitoring-based drug therapy but [figure: see text] also appropriate consideration for options such as heart transplantation or patient enrollment into large-scale drug trials that seek to answer pertinent issues relating to various aspects of advanced heart failure therapeutics. The use of parenteral inotropic support as a chronic bridge to transplantation is accepted widely but remains controversial in other scenarios. For instance, when refractory congestion or hypoperfusion is exhibited in the absence of any definitive medical or mechanical option, it may be wise to contemplate inotropic support after appropriate informed consent has been obtained from the patient. Lastly, it is of great importance to continually seek ways to transit the patient from this approach to a definitive therapeutic end point, such as with transition to oral beta-blockade, which may be better tolerated in the patient with advanced heart failure using an inotropic umbrella.

Inotropic therapy for heart failure: an evidence-based approach

BACKGROUND

Agents that increase cardiac contractility (positive inotropes) have beneficial hemodynamic effects in patients with acute and chronic heart failure but have frequently led to increased mortality when given on a long-term basis. Despite this fact, inotropes remain commonly used in the management of heart failure.

METHODS

We reviewed the available data on short- and long-term inotrope use in heart failure, emphasizing high-quality evidence on the basis of randomized trials that were powered to address clinical end points.

RESULTS

Available data suggest that long-term inotropic therapy has a negative impact on survival in patients with heart failure, regardless of the agent used. The data that inotropic therapy improves quality of life are mixed. High-quality randomized evidence is lacking for the use of inotropes for other heart failure indications, such as for acute decompensations or as a "bridge to transplant."

CONCLUSIONS

On the basis of the available evidence, the routine use of inotropes as heart failure therapy is not indicated in either the acute or chronic setting. Potentially appropriate uses of inotropes include as temporary treatment of diuretic-refractory acute heart failure decompensations or as a bridge to definitive treatment such as revascularization or cardiac transplantation. Inotropes also may be appropriate as a palliative measure in patients with truly end-stage heart failure. A model of heart failure pathophysiologic features that combines an understanding of both hemodynamic and neurohormonal factors will be required to best develop and evaluate novel treatments for advanced heart failure.

Rational use of inotropic therapy in heart failure

Despite their theoretic appeal, agents that increase cardiac contractility (positive inotropes) have consistently been shown to increase mortality when given chronically to patients with heart failure. The routine use of inotropes as heart failure therapy in either the acute or the chronic setting is not supported by the available data. Some appropriate uses of inotropes are as temporary treatment of diuretic-refractory acute heart failure decompensations, or as a bridge to definitive treatment such as revascularization or cardiac transplantation. Although controversial, the use of inotropes as a palliative measure in the small subset of patients with truly end-stage heart failure may be appropriate. An understanding of the appropriate goals of therapy is important for both patients and physicians if rational decisions about the use of inotropes are to be made.

Successful weaning from milrinone of a patient with severe congestive heart failure using carvedilol

Congestive heart failure is a major and growing health care concern worldwide, and mortality in patients with severe heart failure is high. Few options are available to patients with New York Heart Association class IV heart failure refractory to oral medical therapy. Over the last 15-20 years milrinone, a phosphodiesterase-III inhibitor, has been used occasionally to treat patients with acute heart failure and as a bridge to heart transplantation and, more recently, has been used intermittently or continuously on an outpatient basis. We report a patient with severe, chronic congestive heart failure, whom we treated successfully with continuous milrinone infusions as an outpatient. We were able to wean him of the milrinone after successful up-titration of carvedilol. Nine months after discontinuation of milrinone the patient remains stable in New York Heart Association class I on high dose carvedilol. Research is required to validate the possibility that patients with severe heart failure may be successfully weaned from milrinone using carvedilol and achieve significant improvement of their functional status and quality of life. This may prove to be an effective strategy for the treatment of selected patients with severe, chronic congestive heart failure. (c)2001 by CHF, Inc.

Pharmacology of inotropic agents in infants and children

Inotropic agents are drugs which increase the stroke work of the heart at a given pre-load and after-load. All of these agents work through a final common pathway involving the modulation of calcium interactions with various myocardial contractile proteins. The agents employed with pediatric patients include the cardial glycosides, catecholamine beta-agonists and the selective phosphodiesterase III inhibitors. Digoxin is the prototypic cardiac glycoside which has a long history of safe and effective use in infants and children. Its utility in improving right ventricular dysfunction in patients with cor pulmonale leading to biventricular dysfunction makes it ideally suited to the pediatric population. Monitoring digoxin pharmacokinetics in infants is confounded by the presence of an endogenous digoxin-like substance. Nevertheless, the drug is well suited for subacute and chronic myocardial support. In contrast, the catecholamines are the drugs of choice for acute intervention. Their pharmacokinetics permit rapid dosing titration. In infants and children the greatest experience has been accrued with dopamine, a mixed alpha- and beta-agonist but both epinephreine and norepinephrine are being used with increasing frequency as the need for drugs with increased potency and pressor activity becomes more common. The phosphodiesterase inhibitors amrinone and milrinone are the newest additions to our therapeutic armamentarium. In addition to their modest inotropic effects, amrinone and to a greater extent, milrinone offer significant pulmonary vasodilatation as part of their therapeutic package. These effects occur with little or any impact on myocardial oxygen consumpton while their lusitropic effects enhance relaxation in hypertrophied ventricular muscle. Of the two agents milrinone is probably preferred due to its greater therapeutic index and shorter elimination half-life. All of these agents remain important tools in the care of critically ill infants and children. The rational use of these drugs based upon their pharmacokinetic and pharmacodynamic properties is essential to achieve their optimal effects.

Bridging patients to cardiac transplantation

Potential recipients of heart transplants have the most advanced form of congestive heart failure, in which standard therapy fails to maintain clinical stability. In the absence of guidelines derived from evidence obtained in clinical trials, caring for these patients becomes a challenge. A successful approach requires the proper coordination of surgical and nonsurgical strategies, including revascularization and valvular surgery as well as mechanical ventricular support and medical strategies. Intensive medical therapy is the most commonly used approach for prolonged bridging to transplantation. Although carefully individualized regimens are necessary to achieve desired goals, most centers adopt a fairly standardized approach involving vasodilators, diuretics, and inotropic support. Bridging patients with cardiac decompensation to transplantation presents a major therapeutic challenge. Appropriate strategies will maximize patients' chances that the bridge from decompensation to transplantation remains intact. (c)2000 by CHF, Inc.

Rationale for the short term use of intravenous milrinone under hemodynamic guidance in patients with severe systolic heart failure

Patients with severe systolic heart failure have a decrease in both number and function of cardiac beta receptors, which may result in a poor inotropic response to I.V. beta-adrenergic agonists such as dobutamine. The I.V. use of the phosphodiesterase inhibitor milrinone, which is a combined positive inotrope/vasodilator in this patient population, is a more rational choice, especially if heart failure is chronic. Many of these patients may also be referred for consideration for cardiac transplantation, for which the use of invasive hemodynamic monitoring is typically necessary to determine whether severe hemodynamic compromise and pulmonary hypertension are reversible with therapy. The use of hemodynamically guided I.V. vasodilator therapy has also been extensively described as a tool to optimize oral vasodilator therapy and predict prognosis in patients evaluated for cardiac transplantation. This review summarizes the important studies supporting the rationale for and benefits of using I.V. milrinone under hemodynamic guidance in this patient population. (c)2000 by CHF, Inc.

Milrinone for long-term pharmacologic support of the status 1 heart transplant candidates

BACKGROUND

We determined the efficacy of long-term therapy with milrinone alone or in combination with inotropic agents in status 1 heart transplant candidates as a pharmacological support until heart transplantation.

METHODS

Hemodynamic and biochemical variables were recorded in 29 status 1 men with symptoms of severe congestive heart failure, who received continuous intravenous milrinone alone (group 1, n = 21) or in combination with inotropic agents (group 2, n = 8) while awaiting heart transplantation.

RESULTS

Symptomatic relief was noted in all patients of both groups without any preoperative deaths. One patient (4.8%) of group 1 died on the second day and 1 patient of group 2 died 16.4 months after transplantation. Although pulmonary capillary wedge pressure (group 1, p = 0.021; group 2, p = 0.0002), mean pulmonary artery pressure (group 1, p = 0.051; group 2, p = 0.004), and pulmonary vascular resistance (group 1, p = 0.0026; group 2, p = 0.056) were reduced by 1 hour after the onset of treatment and maintained unchanged until transplantation, the changes in mean pulmonary artery pressure in group 1 and pulmonary vascular resistance in group 2 were statistically insignificant except in the posttransplantation period.

CONCLUSIONS

Long-term therapy with milrinone in combination with inotropic agents is safe and effective when only milrinone infusion is inadequate for pharmacologic support in status 1 candidates.

Effects of left ventricular assist devices on outcomes in patients undergoing heart transplantation

BACKGROUND

Left ventricular assist devices (LVADs) are increasingly being used to "bridge" patients to heart transplantation.

METHODS

Data from 40 consecutive status 1 heart transplantation patients treated with intravenous inotrope therapy (n = 20) or the HeartMate LVAD (n = 20) were retrospectively analyzed.

RESULTS

Baseline clinical characteristics were similar in the two groups. At the time of transplantation, LVAD patients had significantly higher blood pressure and sodium with significantly lower blood urea nitrogen and creatinine. After transplantation, renal failure (52.6% versus 16.7%) and right heart failure (31.6% versus 5.6%) occurred more frequently (p < 0.05) in the inotrope group. Six-month survival after transplantation did not significantly differ in the inotrope or LVAD groups (73.7% versus 88.9%) but event-free survival was significantly (p < 0.05) lower in the inotrope group (15.8% versus 55.6%). Total hospital charges were significantly lower in the inotrope group ($213,860 +/- $107,560 versus $342,620 +/- $104,420), but average daily hospital charges were not different ($3,990 +/- $1,300 versus $4,130 +/- $2,050).

CONCLUSIONS

Status 1 heart transplant patients treated with an LVAD as opposed to inotrope therapy have improved clinical and metabolic function at the time of transplant and improved survival to 6 months after transplant without major complications. Total costs are higher in the LVAD patients but average daily costs are similar.

Optimising management of patients with advanced heart failure: the importance of preventing progression

Heart failure is a highly complex, progressive and deadly disease. When incorrectly treated, it results in irreversible structural damage to the myocardium and resists any conventional treatment. This stage has been arbitrarily termed refractory heart failure. However, with timely and sufficiently applied neurohumoral antagonists, progression can be prevented, or at least delayed. In contrast, as soon as heart failure has become moderate or severe due to advanced left ventricular dysfunction, polypharmacy is the rule. Physicians should make every effort to maintain or reconsider optimal neurohumoral antagonist therapy in such patients, even if symptomatic improvement from these agents may be slow. Proper use of diuretics is essential not only for symptom relief but also to achieve full benefit from angiotensin converting enzyme inhibitors and beta-blockers. Digitalis may be particularly indicated in severe heart failure, irrespective of rhythm. Adjunctive regimens can be helpful in specific patients, but evidence of their salutary effects to prolong life is lacking. In the decompensated state, tailoring intravenous therapy to haemodynamic goals followed by (re-)institution of optimal oral therapy is an option. Only if these strategies fail is heart transplantation justified. While waiting for a donor, patients have been bridged with various intravenous agents, most often inotropes, but symptom relief is associated with risk of increased mortality due to these drugs. New hope emerges from drugs interfering with endothelin and the cytokines, and from research into increasing contractility with calcium sensitising agents. Even though these developments follow established routes, they may enable a more effective approach to prevent worsening heart failure in every single patient.

Tolerability of extended duration intravenous milrinone in patients hospitalized for advanced heart failure and the usefulness of uptitration of oral angiotensin-converting enzyme inhibitors

Milrinone is a phosphodiesterase inhibitor that has been shown to improve hemodynamic parameters in patients with class III to IV heart failure when administered intravenously for < or =48 hours. This study examines the tolerability of long-term intravenous milrinone therapy and assesses its utility in allowing upward titration of oral vasodilator agents. A retrospective review of hospital records identified 63 patients who underwent hemodynamic monitoring and received intravenous milrinone for >24 hours in a critical care setting. Hemodynamics and medications were recorded before and after 24 hours of milrinone therapy. Additional medications, as well as any adverse events, were recorded throughout milrinone therapy. The mean dose of milrinone was 0.43 +/- 0.10 microg/kg/min, with a mean duration of 12 +/- 15 days (range 1 to 70). Therapy was continued for >48 hours in 89% of patients. After 24 hours of milrinone therapy, patients exhibited significant improvements in pulmonary artery pressures, pulmonary capillary wedge pressures, and cardiac index. When compared with baseline, significantly more patients received angiotensin-converting enzyme (ACE) inhibitors after 24 hours of milrinone and at the end of milrinone therapy (67% vs 86%, p <0.01). Likewise, significantly more patients also received oral hydralazine and/or nitrates at the end of milrinone therapy (38% vs 65%, p <0.01) when compared with baseline. The mean doses of most oral medications at the 3 time periods were similar. The ACE inhibitor dose was significantly higher at the end of milrinone therapy when compared with baseline, and hydralazine dose was significantly higher at the end of therapy when compared with 24 hours. Few adverse effects were noted, with only 10% of patients experiencing symptomatic ventricular tachycardia and 2 patients with significant hypotension requiring discontinuation of the drug. The adverse events were similar in the group of patients who received milrinone for > or =7 days compared with the entire cohort. Milrinone was well tolerated over the long term in a controlled inpatient setting, and allowed uptitration of oral vasodilator therapy.

Comparison of the effects of cilostazol and milrinone on intracellular cAMP levels and cellular function in platelets and cardiac cells

Cilostazol is a potent cyclic nucleotide phosphodiesterase (PDE) type 3 (PDE3) inhibitor that was recently approved by the Food and Drug Administration (FDA) for the treatment of intermittent claudication. Its efficacy is presumed to be due to its vasodilatory and platelet activation inhibitory activities. Compared with those treated with placebo, patients treated with cilostazol showed a minimal increase in cardiac adverse events. Because of its PDE3 inhibitory activity, however, the possibility that cilostazol exerts positive cardiac inotropic effects is a safety concern. Therefore we compared the effects of cilostazol with those of milrinone, a selective PDE3 inhibitor, on intracellular cyclic adenosine monophosphate (cAMP) levels in platelets, cardiac ventricular myocytes, and coronary smooth muscle cells. We also compared the corresponding functional changes in these cells. Cilostazol and milrinone both caused a concentration-dependent increase in the cAMP level in rabbit and human platelets with similar potency. Furthermore, cilostazol and milrinone were equally effective in inhibiting human platelet aggregation with a median inhibitory concentration (IC50) of 0.9 and 2 microM, respectively. In rabbit ventricular myocytes, however, cilostazol elevated cAMP levels to a significantly lesser extent (p < 0.05 vs. milrinone). By using isolated rabbit hearts with a Langendorff preparation, we showed that milrinone is a very potent cardiotonic agent; it concentration-dependently increased left ventricular developed pressure (LVDP) and contractility. Cilostazol was less effective in increasing LVDP and contractility (p < 0.05 vs. milrinone), which is consistent with the cardiac cAMP levels. The cardiac effect of OPC-13015, a metabolite of cilostazol with about sevenfold higher PDE3 inhibition, was similar to cilostazol. Whereas milrinone concentration-dependently increased cAMP in rabbit coronary smooth muscle cells, cilostazol did not have such an effect. However, both compounds increased coronary flow equally in rabbit hearts. Our results show that although cilostazol and milrinone both inhibit PDE3, cilostazol preferentially acts on vascular elements (platelets and flow). This unique profile of cilostazol is consistent with its beneficial and safe clinical outcomes in patients with intermittent claudication.

Parenteral inotropic support for advanced congestive heart failure

Parenterally administered positive inotropic agents remain an important component of the therapeutics of cardiac dysfunction and failure. Dobutamine, a catechol, remains the prototype of this drug group, but recently has been joined by the phosphodiesterase III inhibitor, milrinone. Compared with dobutamine, milrinone has greater vasodilating-unloading properties. The catecholamine, dopamine, is often used as a parenteral positive inotrope; but at moderate to high dose, it evokes considerable systemic vasoconstriction. At lower doses, dopamine appears to augment renal function. Levosimendan and toborinone, new compounds with several mechanisms of action, are under active clinical investigation and review for approval. Parenteral positive inotropic therapy is indicated for short-term (hours to days) treatment of cardiovascular decompensation secondary to ventricular systolic dysfunction, low-output heart failure. More prolonged or continuous infusion of one of these agents may be necessary as a "pharmacologic bridge" to cardiac transplantation, another definitive intervention, or more advanced, intense medical therapy. An occasional patient will require a continuous infusion via indwelling venous catheter and portable pump, simply to be able to be discharged from the hospital setting and function in the home environment. Intermittent parenteral inotropic therapy for chronic heart failure has provoked considerable controversy and passion among cardiologists and heart failure specialists; an attempt is made to present this topic in an objective manner.