Separation of the direct myocardial and vasodilator actions of milrinone administered by an intracoronary infusion technique

Intraoperative milrinone versus dobutamine in cardiac surgery patients: a retrospective cohort study on mortality

Background

Several choices of inotropic therapy are available and used in relation to cardiac surgery. Comparisons are necessary to select optimal therapy. In Denmark, dobutamine and milrinone are the two inotropic agents most commonly used to treat post-bypass low cardiac output syndrome. This study compares all-cause mortality with these drugs.

Methods

In a retrospective observational study we investigated 10,700 consecutive patients undergoing cardiac surgery from 1 April 2006 to 31 December 2013 at Aarhus and Aalborg University Hospitals in the Central and Northern Denmark Region. Prospectively entered data in the Western Danish Heart Registry on intraoperative use of inotropes were used to identify 952 patients treated with milrinone, 418 patients treated with dobutamine, and 82 patients receiving a combination of the two inotropes. All-cause mortality among patients receiving dobutamine was compared to all-cause mortality among milrinone receivers.

Multiple logistic regression analyses including preoperative and intraoperative variables along with g-formula analyses were used to model 30-day and 1-year mortality risks. Reported were standardized mortality risk differences between the treatment groups.

Results

Among patients receiving intraoperative dobutamine, 18 (4.3%) died within 30 days and 49 (11.7%) within 1 year. Corresponding 30-day and 1-year mortality for milrinone receivers were 81 (8.5%) and 170 (17.9%). Risk of death within 30 days and 1 year was increased for intraoperative milrinone compared to dobutamine with a standardized risk difference of 4.06% (confidence interval (CI) 1.23; 6.89, p = 0.005) and 4.77% (CI 0.39; 9.15, p = 0.033), respectively. Sensitivity analyses including adjustment for milrinone preference, hemodynamic instability prior to cardiopulmonary bypass, and separate analyses on hospital level all confirmed a sign toward increased mortality among milrinone receivers.

Conclusions

Intraoperative use of milrinone in cardiac surgery may be associated with an increase in all-cause mortality compared to use of dobutamine.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-1969-1) contains supplementary material, which is available to authorized users.

Novel selective PDE type 1 inhibitors cause vasodilatation and lower blood pressure in rats

BACKGROUND AND PURPOSE

The PDE enzymes (PDE1-11) hydrolyse and thus inactivate cyclic nucleotides and are important in the regulation of the cardiovascular system. Here,we have investigated the effects on the cardiovascular system, of two novel selective PDE1 inhibitors, Lu AF41228 and Lu AF58027.

EXPERIMENTAL APPROACH

We used rat mesenteric small arteries (internal diameters of 200-300 μm), RT-PCR and measured isometric wall tension. Effects of Lu AF41228 and Lu AF58027 on heart rate and BP were assessed in both anaesthetized and conscious male rats.

KEY RESULTS

Nanomolar concentrations of Lu AF41228 and Lu AF58027 inhibited PDE1A, PDE1B and PDE1C enzyme activity, while micromolar concentrations were required to observe inhibitory effects at other PDEs. RT-PCR revealed expression of PDE1A, PDE1B and PDE1C in rat brain, heart and aorta, but only PDE1A and PDE1B in mesenteric arteries. In rat isolated mesenteric arteries contracted with phenylephrine or U46619, Lu AF41228 and Lu AF58027 induced concentration-dependent relaxations which were markedly reduced by inhibitors of guanylate cyclase, ODQ, and adenylate cyclase, SQ22536, and in preparations without endothelium. In anaesthetized rats, Lu AF41228 and Lu AF58027 dose-dependently lowered mean BP and increased heart rate. In conscious rats with telemetric pressure transducers, repeated dosing with Lu AF41228 lowered mean arterial BP 10-15 mmHg and increased heart rate.

CONCLUSIONS AND IMPLICATIONS

These novel PDE1 inhibitors induce vasodilation and lower BP, suggesting a potential use of these vasodilators in the treatment of hypertension and vasospasm.

Effects of commonly used inotropes on myocardial function and oxygen consumption under constant ventricular loading conditions

Inotropic medications are routinely used to increase cardiac output and arterial blood pressure during critical illness. However, few comparative data exist between these medications, particularly independent of their effects on venous capacitance and systemic vascular resistance. We hypothesized that an isolated working heart model that maintained constant left atrial pressure and aortic blood pressure could identify load-independent differences between inotropic medications. In an isolated heart preparation, the aorta and left atrium of Sprague Dawley rats were cannulated and placed in working mode with fixed left atrial and aortic pressure. Hearts were then exposed to common doses of a catecholamine (dopamine, epinephrine, norepinephrine, or dobutamine), milrinone, or triiodothyronine (n = 10 per dose per combination). Cardiac output, contractility (dP/dtmax), diastolic performance (dP/dtmin and tau), stroke work, heart rate, and myocardial oxygen consumption were compared during each 10-min infusion to an immediately preceding baseline. Of the catecholamines, dobutamine increased cardiac output, contractility, and diastolic performance more than clinically equivalent doses of norepinephrine (second most potent), dopamine, or epinephrine (P < 0.001). The use of triiodothyronine and milrinone was not associated with significant changes in cardiac output, contractility or diastolic function, either alone or added to a baseline catecholamine infusion. Myocardial oxygen consumption was closely related to dP/dtmax (r(2) = 0.72), dP/dtmin (r(2) = 0.70), and stroke work (r(2) = 0.53). In uninjured, isolated working rodent hearts under constant ventricular loading conditions, dobutamine increased contractility and cardiac output more than clinically equivalent doses of norepinephrine, dopamine, and epinephrine; milrinone and triiodothyronine did not have significant effects on contractility.

Effects of milrinone and epinephrine or dopamine on biventricular function and hemodynamics in an animal model with right ventricular failure after pulmonary artery banding

Right ventricular (RV) failure due to chronic pressure overload is a main determinant of outcome in congenital heart disease. Medical management is challenging because not only contractility but also the interventricular relationship is important for increasing cardiac output. This study evaluated the effect of milrinone alone and in combination with epinephrine or dopamine on hemodynamics, ventricular performance, and the interventricular relationship. RV failure was induced in 21 Danish landrace pigs by pulmonary artery banding. After 10 wk, animals were reexamined using biventricular pressure-volume conductance catheters. The maximum pressure in the RV increased by 113% ( P < 0.0001) and end-diastolic volume by 43% ( P < 0.002), while left ventricular (LV) pressure simultaneously decreased ( P = 0.006). Concomitantly, mean arterial pressure (MAP; −16%, P = 0.01), cardiac index (CI; −23%, P < 0.0001), and mixed venous oxygen saturation (SvO2; −40%, P < 0.0001) decreased. Milrinone increased CI (11%, P = 0.008) and heart rate (HR; 21%, P < 0.0001). Stroke volume index (SVI) decreased (7%, P = 0.03), although RV contractility was improved. The addition of either epinephrine or dopamine further increased CI and HR in a dose-dependent manner but without any significant differences between the two interventions. A more pronounced increase in biventricular contractility was observed in the dopamine-treated animals. LV volume was reduced in both the dopamine and epinephrine groups with increasing doses In the failing pressure overloaded RV, milrinone improved CI and increased contractility. Albeit additional dose-dependent effects of both epinephrine and dopamine on CI and contractility, neither of the interventions improved SVI due to reduced filling of the LV.

Use of inotropes and vasopressor agents in critically ill patients

Inotropes and vasopressors are biologically and clinically important compounds that originate from different pharmacological groups and act at some of the most fundamental receptor and signal transduction systems in the body. More than 20 such agents are in common clinical use, yet few reviews of their pharmacology exist outside of physiology and pharmacology textbooks. Despite widespread use in critically ill patients, understanding of the clinical effects of these drugs in pathological states is poor. The purpose of this article is to describe the pharmacology and clinical applications of inotropic and vasopressor agents in critically ill patients.

Reversal of oxidant-mediated biochemical injury and prompt functional recovery after prolonged single-dose crystalloid cardioplegic arrest in the infantile piglet heart by terminal warm-blood cardioplegia supplemented with phosphodiesterase III inhibitor

PURPOSE

The benefit of terminal blood cardioplegia (TWBCP) is insufficient after prolonged ischemia associated with inevitable oxidant-mediated injury by this modality alone. We tested the effects of TWBCP supplemented with high-dose olprinone, which is a phosphodiesterase III inhibitor, a clinically available compound with the potential to reduce oxidant stress and calcium overload. We evaluated the effects with respect to avoiding oxidant-mediated myocardial reperfusion injury and prompt functional recovery after prolonged single-dose crystalloid cardioplegic arrest in a infantile piglet cardiopulmonary bypass (CPB) model.

METHODS

Fifteen piglets were subjected to 90 min of cardioplegic arrest on CPB, followed by 30 min of reperfusion. In group I, uncontrolled reperfusion was applied without receiving TWBCP; in group II, TWBCP was given; in group III, TWBCP was supplemented with olprinone (3 μg/ml). Myocardial performance was evaluated before and after CPB by a left ventricular (LV) function curve and pressure-volume loop analyses. Biochemical injury was determined by measurements of troponin-T and lipid peroxide (LPO) in coronary sinus blood.

RESULTS

Group III showed significant LV performance recovery (group I, 26.5% ± 5.1%; group II, 42.9% ± 10.8%; group III, 81.9% ± 24.5%, P < 0.01 vs. groups I and II), associated with significant reduction of troponin-T and LPO at the reperfusion phase. No piglets in group III needed electrical cardioversion.

CONCLUSION

We concluded that TWBCP with olprinone reduces myocardial reperfusion injury by reducing oxidant-mediated lipid peroxidation, and it accelerates prompt and persistent LV functional recovery with suppression of reperfusion arrhythmia.

Unmasking of neonatal renovascular hypertension by milrinone used for cardiac dysfunction

A neonate initially presented with heart failure, with severe cardiac dysfunction confirmed by echocardiography, at 3 days of age. Blood pressure at presentation was in the high normal range. It was not until there was a rapid improvement of left-ventricular function on intravenous milrinone that the infant was noted to be hypertensive on day of life 7. It is noteworthy that milrinone, a drug with vasodilator and inotropic properties, paradoxically unmasked hypertension by rapidly improving left-ventricular function. Subsequent work-up showed the etiology of hypertension to be left renal artery stenosis. We present this case to alert clinicians to the rarer causes of left-ventricular dysfunction and to point out that its etiology, i.e., hypertension, may not be apparent until there is improvement in the systolic function of the left ventricle.

Differential pharmacologic sensitivities of phosphodiesterase-3 inhibitors among human isolated gastroepiploic, internal mammary, and radial arteries

Systematic investigations of the actions of phosphodiesterase (PDE)-3 inhibitors on different human vascular tissues have not been performed. We investigated the effects of specific PDE-3 inhibitors (olprinone, milrinone, and amrinone) on contracted human gastroepiploic arteries (n = 70), internal mammary arteries (n = 72), and radial arteries (n = 70) harvested from a total of 134 patients, all of whom were undergoing coronary artery bypass surgery. Each of these PDE-3 inhibitors dose-dependently diminished the contractile responses to 10(-6) mol/L norepinephrine and to either 10(-9) or 10(-8) mol/L of the thromboxane A2 analog U46619. In inducing vasorelaxations, these inhibitors were significantly more potent in norepinephrine-contracted rings than in those contracted with U46619. Further, at concentrations similar to the maximum therapeutic plasma concentrations (10(-7) mol/L olprinone; 10(-6) mol/L milrinone; 10(-5) mol/L amrinone) olprinone and milrinone were more potent at inducing relaxations than amrinone in gastroepiploic arteries and radial arteries, whereas in internal mammary arteries milrinone was more potent than the others. These results suggest different activities for the three PDE-3 inhibitors among human arteries located in different regions and may be informative about the effectiveness of these inhibitors in preventing spasms in the various arterial grafts used in revascularization.

IMPLICATIONS

Because three phosphodiesterase-3 inhibitors (milrinone, olprinone, and amrinone) differed in their vasodilator potencies (against the contractile response to either norepinephrine or a thromboxane A2 analog) among human arteries removed from different parts of the body, their vascular relaxation profiles should be considered before they are used clinically.

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.

The calcium sensitizer levosimendan improves the function of stunned myocardium after percutaneous transluminal coronary angioplasty in acute myocardial ischemia

OBJECTIVES

We assessed the effects of levosimendan on left ventricular (LV) function in patients with acute myocardial ischemia and after coronary angioplasty.

BACKGROUND

The calcium sensitizer levosimendan improves the function of myocardium in experimental stunning.

METHODS

Twenty-four patients with an acute coronary syndrome underwent angioplasty followed by double-blinded, randomized treatment with 24 microg/kg of levosimendan (n = 16) or placebo (n = 8). Left ventricular pressures and volumes were recorded by cineventriculography and micromanometer-tipped catheters 10 min after angioplasty before drug administration (baseline) and 20 min after drug administration. Left ventricular function was assessed by the pressure-volume loop, and regional function analysis by the Slager method.

RESULTS

The number of hypokinetic segments decreased with levosimendan, from 8.9 +/- 0.9 to 6.5 +/- 1.1 (mean +/- SEM), as compared with an increase from 7.8 +/- 1.0 to 8.5 +/- 1.1 with placebo (p = 0.016). A leftward and/or upward shift of the systolic part of the pressure-volume loop, indicating improved systolic function, was observed in eight of 16 of the levosimendan-treated and one of eight of the placebo patients (p = 0.178). In addition, the single-beat elastance was increased by levosimendan (p = 0.045). The pressure-volume area (p = 0.001), end-systolic pressure (p = 0.002), and volume index (p < 0.001) were decreased by levosimendan, but there was no change in the end-systolic pressure-volume ratio. End-diastolic pressure remained unchanged, whereas the end-diastolic volume index was decreased by levosimendan (p = 0.002). The time constant of isovolumic LV pressure fall decreased with levosimendan (p = 0.001).

CONCLUSIONS

Levosimendan improved the function of stunned myocardium without obvious impairment of diastolic function.

Cardiac and vascular effects of diltiazem, dobutamine and amrinone, drugs used after myocardial revascularization

Hemodynamic care during postoperative management of myocardial revascularization should include vasorelaxing drugs to insure adequate graft and coronary flow, and stimulation of stroke volume to maintain vascular perfusion pressure. We tested the cardiac (inotropic and lusitropic) and vascular (relaxant) effects of diltiazem (0.1 nM to 0.1 mM), dobutamine (10 microM to 10 mM) and amrinone (10 microM to 1 mM) on isolated rat atria and thoracic aorta, and also on isolated human saphenous vein (HSV) and human mammary artery (HMA). Dobutamine produced a maximal positive inotropic effect (+dF/dt max = 29 +/- 7%) at its ED50 for aortic relaxation (88 +/- 7 microM). Conversely, at their ED50 for aortic relaxation diltiazem depressed myocardial contractility and amrinone did not exhibit myocardial effects. In HSV and HMA contracted with 80 mM potassium, diltiazem and dobutamine (but not amrinone) had a vasorelaxant activity similar to that in rat aorta. Norepinephrine-contracted human vessels were significantly more sensitive than potassium-contracted vessels to the relaxant effect of amrinone (ED50 HMA = 15 +/- 5 microM, ED50 HSV = 72 +/- 31 microM, P < 0.05). We conclude that at concentrations still devoid of myocardial effects dobutamine and amrinone are effective dilators in graft segment vessels and rat aorta contracted by membrane depolarization. If the difference between aortic and myocardial tissue still holds in human tissues, at the appropriate concentrations these drugs should be expected to improve cardiac performance while still contributing to the maintenance of graft patency.

Milrinone Reduces Cerebral Vasospasm After Subarachnoid Hemorrhage of WFNS Grade IV or V

The preventative effect of cisternal irrigation with milrinone against vasospasm was evaluated in 12 patients with subarachnoid hemorrhage (SAH) of World Federation of Neurosurgical Societies grade IV or V treated between September 1999 and September 2000. All aneurysms were clipped or embolized within 72 hours of the onset of SAH. Inlet and outlet tubes were placed in either the supratentorial cisternal space, lateral ventricle, or spinal subarachnoid space. Lactated Ringer solution containing urokinase (120 IU/ml), ascorbic acid (3.5 mg/ml), and milrinone (3.6 microg/ml) was continuously infused at 30 ml/hr for as long as 2 weeks. Angiographical vasospasm was detected in only two of the 11 patients who received milrinone irrigation and underwent postoperative angiography. Vasospasm may have resulted from irrigation obstruction associated with pneumocephalus in one patient and clot in the sylvian fissure in the other patient. The outcome of the milrinone irrigation therapy was significantly better than that of the conventional therapy. This study suggests that cisternal irrigation with milrinone is safe and effective, and reduces the occurrence of vasospasm in patients with poor grade aneurysmal SAH.

Olprinone: a phosphodiesterase III inhibitor with positive inotropic and vasodilator effects

Olprinone is a newly developed phosphodiesterase III inhibitor characterized by several properties. First, olprinone has positive inotropic and vasodilator actions and improves myocardial mechanical efficiency. Second, olprinone augments cerebral blood flow by a direct vasodilatory effect on cerebral arteries. The cerebrovascular reactivity to olprinone is marked in patients with impaired cerebral circulation. Third, olprinone selectively improves carotid artery distensibility, which may be attributable to differences in the arterial structural components or the reactivity of smooth muscle cells to olprinone. Fourth, olprinone improves inadequate redistribution of brain perfusion and may prevent cerebral metabolic abnormalities in heart failure.

Comparison of dobutamine-based and milrinone-based therapy for advanced decompensated congestive heart failure: Hemodynamic efficacy, clinical outcome, and economic impact

BACKGROUND

The use of parenteral positive inotropic agents still remains a major component of therapy for patients with advanced decompensated congestive heart failure (CHF). However, no consensus guidelines have been developed for the appropriate selection of a first-line inotropic therapy. We sought to compare the clinical outcome and economic cost of dobutamine-based and milrinone-based therapy in patients with acute exacerbation of CHF.

METHODS AND RESULTS

We retrospectively analyzed the outcome of 329 patients admitted to the heart failure unit with acute exacerbation of CHF. More patients were treated with dobutamine-based therapy (269/329, 81.7%) than with milrinone-based therapy (60/329, 18.3%). Both groups had similar baseline characteristics and similar hemodynamic profiles at baseline, with the exception of higher mean pulmonary arterial pressure in the milrinone group (47 mm Hg vs 42 mm Hg, P <.001). One hundred nine patients (40%) of the dobutamine group required parenteral nitroprusside for hemodynamic optimization compared with 11 patients (18%) in the milrinone group (P <.001). The use of parenteral nitroglycerin and dopamine was similar in both groups. There was no significant difference in the in-hospital mortality rate (dobutamine 7.8% vs milrinone 10%) or clinical outcome between the 2 groups. However, the average direct drug cost per patient was significantly reduced in the dobutamine group compared with the milrinone group ($45 +/- $10 vs $1855 +/- $350, P <.0001).

CONCLUSION

Dobutamine-based therapy is an attractive approach for the treatment of decompensated advanced heart failure, achieving comparable clinical efficacy to milrinone with a significantly reduced economic cost.

Inhibition of phosphodiesterase type III before aortic cross-clamping preserves intramyocardial cyclic adenosine monophosphate during cardiopulmonary bypass

Inotropes are often used to treat myocardial dysfunction shortly after cardiopulmonary bypass (CPB). beta-Adrenergic agonists improve contractility, in part by increasing cyclic adenosine monophosphate (cAMP) production, whereas phosphodiesterase type III inhibitors prevent its breakdown. CPB is associated with abnormalities at the beta-receptor level and diminished adenyl cyclase activity, both of which tend to decrease cAMP. These effects may be increased in the presence of preexisting myocardial dysfunction. We tested the hypothesis that inhibition of phosphodiesterase type III before global myocardial ischemia and pharmacologic arrest results in the preservation of intramyocardial cAMP concentration during CPB. Twenty adult patients undergoing coronary artery bypass grafting with CPB were studied. After CPB was instituted, a myocardial biopsy was obtained from the apex of the left ventricle. Patients were randomized to receive either placebo or milrinone (50 micro/kg) through the bypass pump 10 min before aortic cross-clamping. Another myocardial biopsy was performed adjacent to the left ventricular apex just before weaning from CPB. Myocardial cAMP concentration was determined by radioimmunoassay. Myocyte protein content was determined by the Bradford method by using a commercial kit. There were no significant demographic differences between the groups; however, patients in the Milrinone group had a lower left ventricular ejection fraction than placebo (41% +/- 13% vs 53% +/- 7%; P < 0.05). Patients who received milrinone had larger cAMP concentrations at the end of CPB compared with placebo (21 +/- 12.5 pmol/mg protein versus 12.8 +/- 2.2 pmol/mg protein; P < 0.05). The administration of milrinone before aortic cross-clamping is associated with increased intramyocardial cAMP concentration at the end of CPB.

IMPLICATIONS

The administration of a single dose of milrinone before aortic cross-clamping resulted in significantly larger intramyocardial cyclic adenosine monophosphate concentration in myocardial biopsy specimens compared with controls.

Low-level inotropic stimulation with type III phosphodiesterase inhibitors in patients with advanced symptomatic chronic heart failure receiving beta-blocking agents

beta-blocking agents are now well established as a cornerstone therapy in mild to moderate heart failure. Patients with more advanced heart failure depend on adrenergic activation to maintain adequate myocardial function. This leads to significant difficulties in using beta-blockers in advanced or severe heart failure. In addition, recent data indicate that adrenergic withdrawal might be detrimental in some of these patients. In higher doses, positive inotropic agents have been shown to increase mortality when used alone in subsets with advanced heart failure. Preliminary data suggest that the combination of low-dose phosphodiesterase inhibitors and a beta-blocker may be better tolerated and does not appear to be associated with the adverse effects of either therapy used alone. We discuss the theoretic underpinning of this approach and the supportive clinical data.

Milrinone for the treatment of cerebral vasospasm after subarachnoid hemorrhage: report of seven cases

OBJECTIVE

The intra-arterial infusion of papaverine has been used for dilation of spastic cerebral vessels after aneurysmal subarachnoid hemorrhage, although its efficacy is controversial. Milrinone is an inotropic drug that dilates vessels by phosphodiesterase inhibition in a mechanism similar to that of papaverine. We examined the effects of intra-arterial and subsequent intravenous administration of milrinone on patients with symptomatic cerebral vasospasm.

METHODS

Seven patients with cerebral vasospasm were enrolled in this study. Milrinone was delivered intra-arterially via catheter at a rate of 0.25 mg/min. The total delivered dose was between 2.5 and 15 mg. Radiological measurement of the middle cerebral artery diameter and cerebral blood flow was carried out before and after arterial infusion. Intravenous treatment followed at 0.50 or 0.75 microg/kg/min for up to 2 weeks from the onset of subarachnoid hemorrhage.

RESULTS

Dilation of the vasospastic vessels occurred in all patients. The rate of cerebral blood flow was calculated in six patients and was increased in all. Subsequent intravenous infusion was effective in preventing a recurrence of symptomatic vasospasm in four of the seven patients.

CONCLUSION

It is suggested that milrinone was effective and safe for the treatment of cerebral vasospasm after subarachnoid hemorrhage in the patients in this series. Intra-arterial infusion with adjunctive intravenous infusion holds promise as a clinically advantageous treatment regimen.

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.

Effect of milrinone on left ventricular relaxation and Ca(2+) uptake function of cardiac sarcoplasmic reticulum

Milrinone, a phosphodiesterase 3 (PDE3) inhibitor, is known to enhance left ventricular (LV) contractility by an inhibition of the breakdown of cAMP through the mechanism inhibiting PDE3. However, it is unclear whether milrinone also exerts positive lusitropy, like dobutamine. Here, we assessed the effects of milrinone on in vivo LV relaxation, as well as the Ca(2+)-ATPase activity and the Ca(2+) uptake function of the cardiac sarcoplasmic reticulum (SR), compared with the effect of dobutamine on those functions. After dobutamine (3 microg x kg(-1) x min(-1)) was administered, the peak value of the first derivative of LV pressure (+dP/dt) increased by 46%, whereas the time constant (tau) of LV pressure decay decreased by 6.9%, respectively. After milrinone (10 microg/kg) was administered, the peak +dP/dt increased to a similar extent as dobutamine (46%), whereas tau decreased much more than dobutamine (19.9%; P < 0.05). In LV crude homogenate, the thapsigargin-sensitive, Ca(2+)-ATPase activity-cAMP relationships was significantly less increased by milrinone compared with dobutamine (P < 0.05), indicating the higher sensitivity of the SR Ca(2+)-ATPase activity on cAMP by milrinone than by dobutamine. In the SR vesicles purified from LV muscles, the addition of cAMP increased the SR Ca(2+) uptake in a dose-dependent fashion, and the PDE3 inhibitors (milrinone and cGMP) significantly augmented this response (P < 0.05). Hence, milrinone substantially improved LV relaxation in association with an acceleration of the SR Ca(2+)-ATPase activity and the SR Ca(2+) uptake. This acceleration might be due to an inhibition of the membrane-bound PDE3 in the SR, leading to a local elevation of cAMP.

Effect of olprinone, a phosphodiesterase III inhibitor, on arterial wall distensibility: differentiation between aorta and common carotid artery

Although the effects of phosphodiesterase III (PDE III) inhibitors as vasorelaxants have been well documented, there are only few data on the wall response of different arteries. We evaluated the artery-specific effect of olprinone (OP), one of the PDE III inhibitors, on the major branches of human arteries and peripheral circulation. In 14 healthy subjects (average age: 57.5 +/- 21.2 years), systolic and diastolic diameters (Ds and Dd, respectively) and the time velocity integral (VI) of flow velocity patterns were measured by M-mode and Doppler echocardiography in the carotid artery (CA), the ascending aorta (asAo), the abdominal aorta (abAo), and the left ventricular outflow tract. Blood pressure (BP) was simultaneously measured using a cuff sphygmomanometer. Measurements were taken before and 20min after a bolus injection of OP (0.2 microg/kg). Distensibility (Ds - Dd), stiffness parameter beta (In(systolic BP/diastolic BP)/(Ds/Dd - 1)), cardiac output (CO: (Flow Area) x VI x HR at left ventricular outflow), selective flow volume (FV: (Flow Area) x VI x HR at CA or abAo), and vascular resistance (VR: mean BP/(CO or FV)) were then calculated. The distensibility increased significantly after OP administration (P = 0.0015), but that of the asAo or abAo did not change. Although there was a significant increase in CO (P = 0.001) and a significant decrease in systemic VR (P = 0.001) following OP administration, the FV and VR of both CA and abAo did not change significantly. The selectiveness of the effect of OP was demonstrated in terms of the CA wall distensibility. This was thought to be attributable to the differences in the structural components or the reactivity of smooth muscle cells to OP.

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.

Clinical overview of the novel inotropic agent toborinone

Toborinone (OPC-18790, Otsuka Pharmaceutical Co. Ltd, 2(1H) -quinolone,6-[3-[ [3,4-dimethoxyphenyl)methyl] amino]-2-hydroxy prop oxyl]-,(.+-.)-) is a novel iv. inotropic agent. Positive inotropic effects are produced by PDE inhibition with the resulting increase in cAMP and intracellular calcium levels. Unlike other inotropic agents that increase cAMP, there is an absence of positive chronotropic effects, which are attributed to prolongation of the action potential due to blockade of delayed rectifier currents. There is also marked venous and arterial vasodilating properties. The absence of heart rate increases results in decreased myocardial oxygen consumption compared with conventional inotropes. Studies in human heart failure patients have been consistent with previous work in animal studies, confirming the effects of toborinone as being positive inotropy (relatively weak), marked arterial and venous vasodilatation and absence of increase in myocardial oxygen consumption. Data regarding safety in larger clinical trials, particularly regarding arrhythmias, is at present unavailable. This information will determine whether this agent becomes an accepted iv. therapeutic option for congestive heart failure.

Milrinone therapy in catecholamine-dependent critically ill patients with heart failure

BACKGROUND

Treatment with the PDE-III inhibitor milrinone improves hemodynamics in patients with heart failure. We examined whether therapy with milrinone is safe and effective in critically ill patients with catecholamine-dependent heart failure and whether treatment with milrinone facilitates weaning from prolonged catecholamine therapy.

METHODS

Twenty adult patients with reduced left ventricular function and prolonged (7+/-4 days) catecholamine therapy in whom attempts at catecholamine weaning had failed were examined. Patients were prospectively randomised either to group A (addition of a fixed dose of 0.5 microg x kg(-1) x min(-1) milrinone to catecholamine therapy) or to group B (continued catecholamine therapy without milrinone). Dobutamine and norepinephrine treatment and fluid intake were titrated according to predefined hemodynamic goals. Hemodynamic parameters, fluid requirements and catecholamine dose were monitored.

RESULTS

After 24 h of study treatment goup A showed a significant increase in cardiac index (2.2+/-0.4 1 min(-1) x m(-2) to 2.7+/-0.51 min(-1) x m(-2); P<0.005), a decrease in systemic vascular resistance (1,427+/-609 dyn x s x cm(-5) to 951+/-184 dyn x s x cm(-5); P<0.005), required lower doses of dobutamine (5.9+/-4.2 microg x kg(-1) x min(-1) to 2.2+/-3.3 microg x kg(-1) x min(-1); P<0.02), but showed a tendency for higher vasoconstrictor (0.14+/-0.16 microg x kg(-1) x min(-1) to 0.29+/-0.43 microg x kg(-1) x min(-1); P=n.s.) and fluid requirements (+1,404+/-2,257 ml/24 h to +2,508+/-1,873 ml/ 24 h; P=n.s.). No significant changes occurred in group B. Weaning from catecholamine therapy was more often achieved in group A and more milrinone treated patients were discharged alive from the ICU (80% vs. 30%; P<0.05).

CONCLUSIONS

Milrinone improves central hemodynamics and may facilitate weaning from prolonged catecholamine support in critically ill patients with heart failure. Its administration in this subset of critically ill patients is safe, but eventually is associated with additional vasoconstrictor and fluid requirements.

Vasopressin as an alternative to norepinephrine in the treatment of milrinone-induced hypotension

OBJECTIVE

To determine whether vasopressin could be effective in treating the hypotension associated with phosphodiesterase III inhibition. Phosphodiesterase III inhibitors are cardiotonic agents that increase myocardial contractility and decrease vascular smooth muscle tone. The vasodilatory effect can be profound, and the resulting hypotension frequently requires the administration of catecholamine pressors.

DESIGN

Retrospective analysis of existing data.

SETTING

The medical or surgical intensive care unit of Columbia-Presbyterian Medical Center.

PATIENTS

Three consecutive patients receiving milrinone and requiring catecholamine pressors to maintain systolic arterial pressure of > or =90 mm Hg.

INTERVENTIONS

Vasopressin was administered to the three patients.

MEASUREMENTS AND MAIN RESULTS

Vasopressin (0.03-0.07 units/min) increased systolic arterial pressure from 90+/-4.7 to 130+/-2.3 mm Hg while reducing the administration of catecholamine pressors.

CONCLUSIONS

Vasopressin at very low doses appears to be an effective vasopressor for milrinone-induced hypotension.

The use of milrinone in pre-transplant assessment of patients with congestive heart failure and pulmonary hypertension

BACKGROUND

Pulmonary hypertension in patients with congestive heart failure (CHF) is a risk factor for increased mortality after orthotopic cardiac transplantation. Reversibility of elevated pulmonary vascular resistance (PVR) by pharmacologic agents predicts improved outcomes. Milrinone, a phosphodiesterase inhibitor with vasodilating and positive inotropic properties, has been shown to lower PVR in one previous study. However, no study has documented outcomes after cardiac transplantation in patients in whom reversibility of pulmonary hypertension was demonstrated after administration of milrinone.

METHODS

We retrospectively reviewed 19 patients with CHF and pulmonary hypertension defined as PVR > or = 3 Wood units, PVRI (pulmonary vascular resistance index) > or = 4 resistance units, or TPG (transpulmonary gradient = mean pulmonary artery pressure--mean capillary wedge pressure) > or = 12 mmHg being assessed for cardiac transplantation. A sub-group of 14 patients with severe pulmonary hypertension defined as PVR > or = 4, PVRI > or = 6 and TPG > or = 15 was also examined. Milrinone was administered as a bolus (50 ug/kg) and hemodynamic parameters were measured at 5, 10 and 15 minutes. Six patients received cardiac transplants.

RESULTS

Administration of milrinone significantly lowered PVR, PVRI, mean pulmonary artery pressure (PAM)(all p = 0.002) and pulmonary capillary wedge pressure (PCWP)(p = 0.006). Cardiac output (CO) increased significantly (p = 0.001). TPG did not change (p = 0.33). In patients with severe pulmonary hypertension, the magnitude of these changes was greater. In addition, TPG was significantly lowered (p = 0.02).

CONCLUSION

Milrinone lowered PVR by decreasing PAM and increasing CO significantly. In addition, PCWP was significantly lowered. These finding confirm both vasodilatory and inotropic effects of milrinone. Patients with severe pulmonary hypertension had more pronounced effects. There were no deaths in the group of patients proceeding to cardiac transplantation. Our study demonstrates the efficacy of milrinone in lowering PVR as well as suggesting safety in use in patients undergoing cardiac transplantation.

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.

Relationship between myocardial milrinone content and its acute hemodynamic and electrophysiologic effects

One of the major determinants of the short-term effects of many cardioactive drugs is the concentration of the drug specifically within the myocardium. However, no information regarding the disposition of the phosphodiesterase inhibitor milrinone in the heart is available. We therefore determined the time course of short-term myocardial milrinone uptake from paired transcoronary sampling and simultaneous coronary sinus blood flow after a 1-mg intravenous bolus in patients undergoing diagnostic cardiac catheterization. In accordance with this intention, a sensitive, reproducible method for the determination of milrinone in human whole-blood samples was developed. The reverse-phase high-performance liquid chromatographic method described used a C18 column with UV-absorbance detection at 326 nm, with a limit of detection of 0.6 ng/ml, and was highly reproducible. The short-term hemodynamic and electrophysiologic effects of the drug also were determined. Significant increases in spontaneous heart rate and LV+dP/dtmax (at constant heart rate) were observed, accompanied by reductions in mean arterial pressure, systemic vascular resistance, and PR interval, without significant changes in atrioventricular nodal or ventricular effective refractory periods. Peak content (1.89 +/- 0.30% of injected dose) was rapidly attained, 0.56 +/- 0.06 min after milrinone injection. Time of peak effects was significantly delayed (7-10 min after injection) relative to time of peak myocardial milrinone content. Residual myocardial milrinone content was 69.1 +/- 5.7% of maximum 12.5 min after injection. It is concluded that both myocardial uptake and the onset of positive inotropic effects after intravenous injection of milrinone were very rapid. However, there was significant hysteresis between peak myocardial content and subsequent hemodynamic effects.

Beneficial effects of intermittent home administration of the inotrope/vasodilator milrinone in patients with end-stage congestive heart failure: a preliminary study

BACKGROUND

End-stage congestive heart failure (CHF) is associated with a high mortality rate and is often refractory to standard medical treatment. Although parenteral inotropes have been beneficial in hospitalized patients, their use in outpatients has been limited by toxicity and tachyphylaxis.

METHODS AND RESULTS

To determine whether patients with end-stage CHF could safely tolerate intermittent outpatient inotropic therapy and demonstrate both symptomatic and functional improvement with these agents, we studied the effects of low-dose, intermittent home infusions of the inotrope/vasodilator milrinone in 10 patients with end-stage CHF. After showing hemodynamic improvement with milrinone while hospitalized, central lines were placed and patients were given the drug at home with small portable infusion pumps, starting at 3 days a week for 6 hours at a time over a 3-month period. Patients tolerated the drug well, with no deaths and a fourfold decrease in hospitalizations during the study. Arrhythmias were minimal and angina decreased in two patients. Mean total, physical, and emotional scores on the Minnesota Living with Heart Failure Questionnaire reflected a general trend of symptomatic improvement throughout the infusion period. The mean number of reported hours of improvement after infusion progressively increased throughout the study, producing a mean of 25 hours of postinfusion improvement during the final week (p < 0.01). Repeat hemodynamic study at the end of the 3-month period showed trends toward improvement in cardiac function.

CONCLUSIONS

This is the first study to demonstrate safety, efficacy, hemodynamic, and functional improvement in patients receiving low-dose, intermittent outpatient milrinone therapy. We believe this improvement partly relates to a "training" effect on the heart or peripheral muscles and circulation. These promising results suggest that given appropriately, inotropes have an important therapeutic role in the outpatient treatment of end-stage CHF.

Effects of a new cardiotonic phosphodiesterase III inhibitor, olprinone, on cardiohemodynamics and plasma hormones in conscious pigs with heart failure

We examined the effects of a novel phosphodiesterase III inhibitor, olprinone, on the cardiohemodynamics and plasma hormones in conscious pigs with pacing-induced heart failure. After pacing for 5-10 days, cardiac output (CO) decreased from 2.25 +/- 0.17 to 1.67 +/- 0.13 L/min (n = 8, p < 0.01) and stroke volume (SV) decreased from 20.1 +/- 2.1 to 12.0 +/- 1.6 ml (n = 8, p < 0.01), whereas left arterial pressure (LAP) increased from 2.8 +/- 1.2 to 16.7 -/+ 0.9 mm Hg (n = 7, p < 0.001) and systemic vascular resistance (SVR) increased from 38.7 +/- 3.5 to 49.8 +/- 4.2 mm Hg/L/min (n = 8, p < 0.01). Sequential intravenous infusions of 0.03, 0.3, and 3.0 microg/kg/min of olprinone at 30-min intervals to eight pigs caused dose-dependent increases in the decreased CO, SV, and maximal rate of rise in left ventricular pressure (LV dP/dt(max)) and decreased the elevated LAP and SVR. Olprinone at 3.0 microg/kg/min maximally increased CO, SV, and LV dP/dt(max) by 40.0 +/- 10.8% (p < 0.05 vs. vehicle), 25.6 +/- 6.9% (p < 0.05), and 43.9 +/- 11.2% (p < 0.01), respectively, and brought about a slight increase in heart rate and decreases in LAP and SVR, by 35.9 +/- 7.3% (p < 0.001) and 27.9 +/- 4.8% (p < 0.01), respectively. Olprinone did not affect the rate-pressure product. In addition, olprinone produced significant decreases in the plasma levels of atrial natriuretic peptide and cyclic guanosine monophosphate, with no changes in the plasma levels of cyclic adenosine monophosphate and catecholamines or plasma renin activity. These findings indicate that the short-term intravenous infusions of olprinone ameliorated the decreased left ventricular function without affecting myocardial oxygen consumption or the sympathetic nervous system in conscious pigs with heart failure.

Mechanisms of positive inotropic action of flosequinan, hydralazine, and milrinone on mammalian myocardium

Flosequinan is an arterial and venous dilator that also has a positive inotropic effect at relatively higher doses. The purpose of this study was to determine the mechanism of this positive inotropic effect in ferret papillary muscles loaded with the Ca2+ indicator, aequorin. Over the range of doses from 10(-6) to 10(-3) M, flosequinan produced a 61 +/- 9% increase in peak tension that was accompanied by a corresponding increase in [Ca2+]i. This positive inotropic effect was not selectively blocked by addition to the perfusate of procaine 0.6 microM, tetrodotoxin 10(-6) M or by verapamil, 5 x 10(-8) M. In contrast, the positive inotropic effect of flosequinan, but not milrinone or hydralazine, was potentiated by prior addition of ouabain 3 nM to enhance intracellular Ca2+ via reduction of the Na+/Ca2+ exchange. Moreover, antagonists of Na+/Ca2+ exchange, including cadmium 10 microM, amiloride 600 microM and choline substitution for 1/3 Na+ in the perfusate, blocked the response to flosequinan but not hydralazine or milrinone. These results indicate that flosequinan produces a positive inotropic effect by reduction of Na+/Ca2+ exchange in mammalian myocardium. Moreover, flosequinan has the potential to interact synergistically with other positive inotropic agents such as digoxin that affect Na+/Ca2+ exchange by direct or indirect actions.

Effect of bolus milrinone on hemodynamic variables and pulmonary vascular resistance in patients with severe left ventricular dysfunction: a rapid test for reversibility of pulmonary hypertension

OBJECTIVES

To examine the feasibility of using milrinone to test pulmonary vascular reactivity in patients before heart transplantation, we tested the hypothesis that milrinone would lower pulmonary vascular resistance (PVR) in patients with severe heart failure.

BACKGROUND

Fixed pulmonary hypertension is a risk factor for right heart failure and death after orthotopic heart transplantation. Sodium nitroprusside, the agent used most commonly to test for reversibility of pulmonary hypertension before transplantation, requires dose titration and is frequently limited by hypotension. Milrinone is an intravenously active phosphodiesterase inhibitor that acts rapidly and exerts both positive inotropic and direct vasodilator effects in patients with heart failure. The ability of milrinone to lower PVR in patients with heart failure has not been tested.

METHODS

In 27 patients with New York Heart Association functional class III or IV heart failure referred for heart transplantation with a PVR > or = 200 dynes-s-cm-5, we measured the hemodynamic response to a single intravenous bolus of milrinone (50 micrograms/kg body weight) infused over 1 min.

RESULTS

Milrinone decreased PVR in all patients. The effect was maximal 5 to 10 min after the bolus and persisted for at least 20 min. The reduction in PVR at 5 min ([mean +/- SEM] 31 +/- 4%) was associated with a 42 +/- 4% increase in cardiac output and decreases of 12 +/- 4% and 16 +/- 5% in mean pulmonary artery and pulmonary artery wedge pressures, respectively, but no change in transpulmonary pressure gradient. Milrinone had no effect on heart rate or systemic arterial pressure. The magnitude of the decrease in PVR correlated inversely with the milrinone-induced increase in cardiac output.

CONCLUSIONS

Bolus milrinone consistently decreases PVR in patients with pulmonary hypertension secondary to severe heart failure. This effect is rapid in onset and well tolerated, even by patients with low systemic arterial pressure. An intravenous bolus of milrinone can be used to test for the reversibility of pulmonary hypertension in patients with heart failure undergoing evaluation for heart transplantation.

Cardiovascular responses to experimental infra-renal aortic cross-clamping. Modulating effects of isoflurane, sodium nitroprusside and milrinone

BACKGROUND

Pharmacological control of blood pressure is usually indicated during aortic cross-clamping (AXC). The aim of this study was to analyze the modulation by isoflurane (ISO), sodium nitroprusside (SNP) and milrinone (MIL) of the systemic circulatory responses to a standardized infra-renal AXC.

METHODS

Chloralose-anaesthetized pigs were exposed to AXC at control (no vasoactive drugs) and during the administration of each of the drugs.

RESULTS

During control, AXC increased mean arterial pressure (MAP, 17 +/- 4%) and systemic vascular resistance (SVR, 27 +/- 7%), but induced no significant changes in cardiac output (CO), heart rate (HR), pulmonary arterial pressures, pulmonary vascular resistance or central venous pressure. Low-dose ISO (0.7%) and investigated doses of SNP and MIL did not significantly alter this response. High-dose ISO (1.4%, attenuated the AXC-induced increase in SVR, but not in MAP. All drugs decreased non-clamp MAP levels. Therefore, with low-dose ISO and with SNP or MIL, peak MAP during AXC was not significantly different from control non-clamp levels (i.e. prior to pharmacological or surgical interventions). High-dose ISO was associated with a MAP during AXC that was below control non-clamp levels.

CONCLUSIONS

The objective that during AXC MAP should not exceed control non-clamp levels was achieveable by ISO, SNP or MIL. The modulating actions of the drugs on MAP during AXC were exerted mainly through reductions in non-clamp levels. This systemic hypotension was associated with decreased CO and SVR during ISO, and with decreased SVR and increased HR during SNP and MIL. Attenuation of the AXC-induced increase in SVR was produced only by 1.4% ISO.

Comparative efficacy of short-term intravenous infusions of milrinone and dobutamine in acute congestive heart failure following acute myocardial infarction. Milrinone-Dobutamine Study Group

The purpose of this study was to compare the hemodynamic and clinical effects of milrinone, a vasodilating and positive inotropic agent, with those of dobutamine in patients with congestive heart failure (CHF) following acute myocardial infarction (AMI). Thirty-three patients in Killip classification II or III within 12 h to 5 days after AMI were randomized in a multicenter, open-label clinical trial to receive a 24-h infusion of milrinone or dobutamine. Drugs were titrated to achieve at least a 30% increase in cardiac index (CI) from mean baseline or at least a 25% decrease in mean pulmonary capillary wedge pressure (MPCWP) from baseline. Both drugs improved CI, MPCWP, and other hemodynamic parameters. Criteria for decrease in MPCWP were met by 94% (15/16) of the milrinone-treated patients and 57% (8/14) of dobutamine-treated patients (p = 0.03). Both groups met the minimum efficacy criterion for CI. Maximal reduction in MPCWP over 0-3 h was greater in the milrinone group (-53.2%) than in the dobutamine group (-31.0%; p < or = 0.01); reductions were sustained over 24 h. Both drugs improved echocardiographic global ejection fraction and were generally well tolerated. The short-term infusion of milrinone may have a role in the management of CHF following AMI, especially when the aim is the rapid reduction of pulmonary congestion.

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.

Effects of intracoronary infusion of an inotropic agent, E-1020 (loprinone hydrochloride), on cardiac function: evaluation of left ventricular contractile performance using the end-systolic pressure-volume relationship

The phosphodiesterase (PDE) III inhibitor, E-1020 (loprinone hydrochloride), has positive inotropic and vasodilating effects. This study evaluated the positive inotropic effect of intracoronary E-1020 in eight patients with coronary artery disease and hypertensive heart disease. A direct intracoronary infusion of the PDE III inhibitor minimizes its vasodilating effect. After baseline hemodynamic measurements and coronary arteriography, a micromanometer-tipped 8F conductance catheter was introduced into the left ventricle to determine the hemodynamic effects of E-1020. Saline and vehicle were infused into the left main coronary artery at a rate of 2 ml/min. The dose of intracoronary E-1020 increased from 2.5 to 5.0 and 7.5 micrograms/min. The inotropic effect of E-1020 was defined as the change in the slope of the end-systolic pressure-volume relationship (Emax), which was independent of afterload and preload. Emax significantly increased at infusion rates of 7.5 micrograms/min from control. Peak +dP/dt increased at an infusion rate of 5.0 micrograms/min or higher, while left-ventricular end-diastolic pressure (LVEDP) decreased significantly at a rate of 5.0 and 7.5 micrograms/min. Intracoronary infusion of E-1020 at a rate of 2.5 micrograms/min produced a plasma concentration of 20 ng/ml, which was identical to the minimum effective plasma concentration seen in previous study by intra venous infusion. However, at a plasma concentration of 20 ng/ml, E-1020 has more vasodilating effects than inotropic effects. Clinically, E-1020 appears to have a positive inotropic effect that depends on the extent of myocardial perfusion.

Distinctive anatomical patterns of gene expression for cGMP-inhibited cyclic nucleotide phosphodiesterases

Type III cGMP-inhibited phosphodiesterases (PDE3s) play important roles in hormonal regulation of lipolysis, platelet aggregation, myocardial contractility, and smooth muscle relaxation. We have recently characterized two PDE3 subtypes (PDE3A and PDE3B) as products of distinct but related genes. To elucidate their biological roles, in this study we compare cellular patterns of gene expression for these two enzymes during rat embryonic and postnatal development using in situ hybridization. PDE3B [corrected] mRNA is abundant in adipose tissue and is also expressed in hepatocytes throughout development. This mRNA is also highly abundant in embryonic neuroepithelium including the neural retina, but expression is greatly reduced in the mature nervous system. Finally, PDE3B [corrected] mRNA is localized in spermatocytes and renal collecting duct epithelium in adult rats. PDE3B mRNA is highly expressed in the cardiovascular system, including myocardium and arterial and venous smooth muscle, throughout development. It is also abundant in bronchial, genitourinary and gastrointestinal smooth muscle and epithelium, megakaryocytes, and oocytes. PDE3A [corrected] mRNA demonstrates a complex, developmentally regulated pattern of gene expression in the central nervous system. In summary, the two different PDE3s show distinctive tissue-specific patterns of gene expression suggesting that PDE3B [corrected] is involved in hormonal regulation of lipolysis and glycogenolysis, while regulation of myocardial and smooth muscle contractility appears to be a function of PDE3A [corrected]. In addition, the present findings suggest previously unsuspected roles for these enzymes in gametogenesis and neural development.

Effects of pimobendan, its active metabolite UD-CG 212, and milrinone on isolated blood vessels

The effects of pimobendan, 2-(4-hydroxy-phenyl)-5-(5-methyl-3-oxo-4,5-dihydo-2H-6-pyridazinyl ) benzimidazole (UD-CG 212), and milrinone were investigated on isometric contraction of vascular preparations in rats and guinea-pigs. The drugs dose dependently relaxed aortic, carotid and femoral arterial and mesenteric venous preparations precontracted with KCl or norepinephrine. The rank order of potency (negative log EC50 value) for these drugs was dependent upon the sources of the preparations and stimulants used. The relaxation response to milrinone was reversible, that to UD-CG 212 was poorly reversible, and that to pimobendan was intermediate. Relaxation responses to cromakalim were inhibited by 0.1 microM glibenclamide, whereas those to pimobendan, UD-CG 212 and milrinone were inhibited by glibenclamide only at doses as high as 10-30 microM. The drugs potentiated the relaxation response to isoproterenol but not glyceryl trinitrate, and noncompetitively inhibited arterial contractions accompanied by voltage-dependent Ca2+ influxes. It is suggested that the drugs are potent vasorelaxants, acting directly on vascular smooth muscle and that the vasorelaxant effects are mediated through cyclic AMP-dependent mechanisms.

The effects of chronic oral milrinone therapy on early postinfarction left ventricular remodeling

Left ventricular remodeling following acute transmural myocardial infarction may result in early left ventricular enlargement. To characterize the effects of milrinone on components of early left ventricular dilation, rats (n = 120) underwent left coronary artery ligation or sham surgery. In the immediate postoperative period, rats received either no treatment or milrinone (3.17 +/- 0.08 mg/kg/day) dissolved in drinking water for 20 days. Twenty-one days after the initial surgery, hemodynamic measurements were made. The rats were then put to death and the hearts arrested in diastole were excised and fixed at a constant pressure for morphometric analysis. To examine the effects of milrinone on the relative contribution of infarcted and noninfarcted segments to early left ventricular dilation after acute myocardial infarction, a subgroup of infarcted rats chosen randomly was put to death 3 days after the initial surgery for morphometric analysis. Compared with infarcted untreated rats, infarcted milrinone-treated rats had a lower left ventricular volume (1.41 +/- 0.07 ml/kg vs 2.16 +/- 0.19 ml/kg, p < 0.001), lower left ventricular wall stress (0.64 +/- 0.03 vs 0.91 +/- 0.06, p < 0.001), and a lower expansion index (1.61 +/- 0.12 vs 2.61 +/- 0.22, p < 0.001). Morphometric analysis revealed that the noninfarcted segment length did not differ between the two infarcted groups either 3 days or 21 days after left coronary artery ligation. Infarct segment length also did not differ between the two infarcted groups at 3 days, but at 21 days infarct segment was shorter in the milrinone-treated group compared with the untreated group (p < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of phosphodiesterase inhibitors in heart failure

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

Effects of intravenous milrinone on left ventricular function in ischemic and idiopathic dilated cardiomyopathy

M-mode echocardiography and Doppler were used to assess the effects of phosphodiesterase inhibition on subendocardial function in dilated cardiomyopathy, and in particular, to study interactions with both systolic and diastolic left ventricular function. Twelve adult patients with dilated cardiomyopathy were studied (6 ischemic in origin and 6 idiopathic), 7 of whom were being considered for cardiac transplantation. Cardiac index increased without significant change in heart rate or blood pressure. Longitudinal mitral ring motion, which had been uniformly reduced, increased markedly after intravenous milrinone. Left ventricular cavity size decreased, and shortening fraction, posterior wall thickness, and rates of posterior wall thickening and thinning increased markedly. Left atrial pressure decreased, and isovolumic relaxation time increased. However, the peak velocity and duration of the transmitral E wave increased, with no change in the A wave. Improved longitudinal (subendocardial) function was reflected by improved posterior wall dynamics, and early filling, possibly by augmentation of restoring forces. Thus, severely reduced subendocardial function in dilated cardiomyopathy is potentially reversible, with marked effects on systolic and diastolic function. These previously unrecognized actions of milrinone provide further evidence to justify its short-term use in supporting the severely depressed myocardium.

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.

Intravenous milrinone following cardiac surgery: I. Effects of bolus infusion followed by variable dose maintenance infusion. The European Milrinone Multicentre Trial Group

The hemodynamic and adverse effects of intravenous milrinone were studied in 99 adult patients (66 men) following elective myocardial revascularization, mitral and/or aortic valve surgery. All patients had a low cardiac output (cardiac index [CI] mean 1.93, range, 1.11 to 2.5 L/min/m2) despite adequate cardiac filling pressure (mean pulmonary capillary wedge pressure [PCWP] 11.5 mmHg, range, 8 to 20 mmHg). Following a period of baseline stability (mean 17.8 minutes, range, 10 to 50 minutes), patients received a bolus infusion of 50 micrograms/kg over 10 minutes. A continuous maintenance infusion of 0.375 (low), 0.5 (mid) or 0.75 (high) micrograms/kg/min was administered for a minimum of 12 hours. Patients were allocated to each dosage group sequentially, not randomly. Hemodynamic measurements were made before the start of milrinone and 15 minutes after the bolus infusion. Further measurements were made at 30, 45, and 60 minutes, and at 3, 6, and 12 hours after the start of treatment. Measurements were also made at 2 and 4 hours after treatment was stopped. The bolus infusion caused significant increases in CI, heart rate (HR), and stroke index (SI), (P < 0.001), and significant falls in PCWP, right atrial pressure (RAP), mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR), mean arterial pressure (MAP), and systemic vascular resistance (SVR) (P < 0.001). These effects were maintained to a significant degree by each of the three maintenance infusion regimens, although the pulmonary vasodilator effects appeared less predictable and more dose dependent. Eighteen patients (19%) had arrhythmias; 16 of these were judged not to be serious events. Two were deemed serious; these were both episodes of fast atrial fibrillation (AF).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of intravenous phosphodiesterase inhibition in chronic heart failure: simultaneous pre- and afterload reduction with a single agent

Intravenous phosphodiesterase inhibition with milrinone is known to have a beneficial effect on haemodynamics in chronic heart failure. Its effect on lower limb capacitance vessels has not been previously investigated. We have studied the effect of intravenous milrinone in 10 patients with severe chronic heart failure. Thirty minutes after commencement of treatment mean cardiac index had risen by 26% and pulmonary artery wedge pressure, systemic vascular resistance and right atrial pressure had fallen by 51, 24 and 89%, respectively (p less than 0.05 for all changes). These changes were maintained for the 2 h observation period with no evidence of tolerance and were accompanied by a 17% increase in venous volume (p less than 0.01) and a 42% increase in ejection fraction (p less than 0.001) at 30 min; at 120 min the improvement in ejection fraction had been maintained and a further increase in venous volume to 38% above baseline was evident. The increase in venous volume was strongly correlated with the decrease in mean pulmonary artery wedge pressure and mean right atrial pressure at 30 min and 2 h (r = -0.80 and -0.69 for mean pulmonary artery wedge pressure, r = -0.88 and -0.56 for mean right atrial pressure). Milrinone therefore has clinically important venodilating properties, in addition to its known effects as an arterial vasodilator and a positive inotrope.

Purification and properties of the cGMP-inhibited cAMP phosphodiesterase from bovine aortic smooth muscle

Pure cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) in micrograms quantities was isolated from bovine aortic smooth muscle after more than 5000-fold purification using DEAE ion-exchange and affinity chromatography with a derivative of the specific cGI-PDE inhibitor cilostamide conjugated as a ligand to aminoethyl agarose (CIT-agarose). The cGI-PDE, which constituted about half of the high affinity cAMP-PDE activity of a tissue homogenate, was identified with a 105-kDa protein on SDS-PAGE through use of antibodies towards the human platelet, bovine cardiac and bovine adipose tissue cGI-PDE in Western blot and immunoprecipitation/immunoinactivation analysis. As observed during purification of the enzyme from other tissues the enzyme protein was exquisitely sensitive to proteolytic nicking during purification, resulting in several 30-77-kDa polypeptide fragments. Rapid immunoprecipitation from fresh tissue extracts was the only was found to partially prevent the proteolysis. The native enzyme had apparent molecular sizes of approx. 100,000 or, mainly approx. 220,000 by gel chromatography, presumably indicating the presence of monomeric and dimeric forms. The enzyme hydrolyzed cAMP and cGMP with normal Michaelis-Menten kinetics with Km of 0.16 and 0.09 microM, respectively, with Vmax for hydrolysis of cAMP of 0.3 compared to 3.1 mumol/min per mg protein for cAMP. The enzyme was potently and selectively inhibited by cGMP (IC50 approximately 0.25 microM) and the cardiotonic/vasodilatory drugs OPC-3911 (a cilostamide derivative), milrinone and CI-930 (IC50 approximately 0.05, 0.40 and 0.25 microM, respectively). The cGI-PDE was phosphorylated by cAMP-dependent protein kinase as has been reported for the analogous enzymes in heart, adipose tissue and platelets. The identification of a cGI-PDE in the aortic smooth muscle and its inhibitor specificity is consistent with the hypothesis that inhibition of this enzyme is important in the mechanism through which these drugs produce vasorelaxation.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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