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

BACKGROUND

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

METHODS

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

RESULTS

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 Patients treated with milrinone had more hospitalizations (44 vs. 39 percent, P = 0.041), were withdrawn from double-blind therapy more frequently (12.7 vs. 8.7 percent, P = 0.041), and had serious adverse cardiovascular reactions, including hypotension (P =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

CONCLUSIONS

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

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

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

Deficient production of cyclic AMP: pharmacologic evidence of an important cause of contractile dysfunction in patients with end-stage heart failure

We studied the effects of different classes of inotropic drugs on human working myocardium in vitro that was isolated from the hearts of patients with end-stage heart failure, and compared the responses to these drugs with those noted in muscles from nonfailing control hearts. Although peak isometric force generated in response to increased extracellular calcium reached control levels in the muscles from patients with heart failure, the time course of contraction and rate of relaxation were greatly prolonged. The inotropic effectiveness of the beta-adrenergic agonist isoproterenol and the phosphodiesterase inhibitors milrinone, caffeine, and isobutylmethylxanthine was markedly reduced in muscles from the patients with heart failure. In contrast, the effectiveness of inotropic stimulation with acetylstrophanthidin and the adenylate cyclase activator forskolin was preserved. After a minimally effective dose of forskolin was given to elevate intracellular cyclic AMP levels, the inotropic responses of muscles from the failing hearts to phosphodiesterase inhibitors were markedly potentiated. These data indicate that an abnormality in cyclic AMP production may be a fundamental defect present in patients with end-stage heart failure that can markedly diminish the effectiveness of agents that depend on generation of this nucleotide for production of a positive inotropic effect.

Evaluation of a new bipyridine inotropic agent--milrinone--in patients with severe congestive heart failure

Milrinone, a derivative of amrinone, has nearly 20 times the inotropic potency of the parent compound and does not cause fever or thrombocytopenia in normal volunteers or in animals sensitive to amrinone. In 20 patients with severe congestive heart failure, intravenous milrinone resulted in significant decreases in left ventricular end-diastolic pressure (from 27 +/- 2 to 18 +/- 2 mm Hg), pulmonary wedge pressure, right atrial pressure, and systemic vascular resistance, as well as a slight reduction in mean arterial pressure. Significant increases occurred in cardiac index (from 1.9 +/- 0.1 to 2.9 +/- 0.2 liters per minute per square meter) and the peak positive first derivative of left ventricular pressure, with a slight increase in heart rate. Hemodynamic improvement was sustained during a 24-hour continuous infusion. Nineteen of the 20 patients subsequently received oral milrinone (29 +/- 2 mg per day) for up to 11 months (mean, 6.0 +/- 0.8), with sustained improvement in symptoms of heart failure. In 10 patients receiving long-term oral milrinone (greater than or equal to 6 months) radionuclide ventriculography showed continued responsiveness, with a 27 per cent increase in left ventricular ejection fraction after 7.5 mg of the drug. Four patients died after a mean of 4.8 months of therapy, and three patients with severe underlying coronary-artery disease and angina pectoris required additional antianginal therapy. No patient had fever, thrombocytopenia, gastrointestinal intolerance, or aggravation of ventricular ectopy. We conclude that milrinone shows promise for the longterm treatment of congestive heart failure.

Impaired chronotropic response to exercise in patients with congestive heart failure. Role of postsynaptic beta-adrenergic desensitization

The mechanism responsible for the attenuated heart rate (HR) response to exercise in patients with congestive heart failure (CHF) was investigated in 46 normal subjects and 59 patients with CHF stratified by peak exercise oxygen consumption (VO2). The peak exercise HR and the increment in HR from rest to peak exercise were decreased in CHF patients, and both correlated strongly with peak VO2 (r = 0.810, p less than 0.0001; r = 0.863, p less than 0.0001, respectively). Peak exercise norepinephrine level (NE) and the increment in NE from rest to peak exercise were not attenuated in CHF patients. Resting NE was elevated in CHF patients and correlated inversely with peak VO2 (r = -0.595, p less than 0.001). However, no significant correlation occurred between peak VO2 and either peak exercise NE or the exercise increment in NE. The ratio of the exercise increments in HR and NE, and indirect index of sinoatrial node sympathetic responsiveness, was markedly reduced in CHF patients and was inversely related to the severity of exercise impairment. Likewise, the HR response to a graded isoproterenol infusion was markedly reduced in CHF patients. Age-matching of normal subjects and CHF patients did not affect the foregoing observations. Infusion of CHF patients with the phosphodiesterase inhibitor milrinone caused a significant increase in the ratio of the exercise increments in HR and NE. These data strongly suggest that the attenuated HR response to exercise in CHF patients is due, at least in part, to postsynaptic desensitization of the beta-adrenergic receptor pathway.

Oocyte maturation involves compartmentalization and opposing changes of cAMP levels in follicular somatic and germ cells: studies using selective phosphodiesterase inhibitors

The second messenger cAMP has been implicated in the regulation of mammalian and amphibian oocyte maturation. Although a decrease in intraoocyte levels of cAMP precedes germinal vesicle breakdown (GVBD), the gonadotropin induction of ovulation and oocyte maturation is associated with major increases of cAMP in ovarian follicles. In the mammalian system, isolated oocytes undergo spontaneous maturation in vitro but this process is blocked by treatment with a phosphodiesterase (PDE) inhibitor, IBMX, which increases intraoocyte cAMP levels. In contrast, the same inhibitor, when added to cultured follicles for a brief time, increases follicle cAMP levels, followed by the induction of GVBD. To resolve the paradoxical actions of this PDE inhibitor on the maturation of isolated and follicle-enclosed oocytes, we hypothesized that meiotic maturation requires opposing fluctuations of cAMP levels in the somatic granulosa and germ cells. Such opposing fluctuations may result from selective expression and regulation of PDEs in the somatic and germ cell compartments of the follicle. To test this hypothesis, PDE activity was manipulated in different follicular cells using type-specific inhibitors. The impact of the ensuing changes in cAMP levels in the two compartments was monitored by the induction of GVBD. In isolated oocytes, spontaneous GVBD was blocked by two inhibitors of type 3 PDE (cGMP-inhibited: CGI-PDE), milrinone and cilostamide. In contrast, treatment with an inhibitor for type 4 PDE (cAMP-specific), rolipram, was ineffective. These findings suggest that the oocyte expresses type 3 but not type 4 PDE and that increases in intraoocyte cAMP suppress GVBD. This hypothesis was confirmed by in situ hybridization studies with PDE3 and PDE4 probes. PDE3B mRNA was concentrated in oocytes while PDE4D was mainly expressed in granulosa cells. In cultured follicles, LH treatment induced oocyte maturation but the gonadotropin action was blocked by inhibitors of type 3 but not the type 4 PDE inhibitors. Furthermore, treatment with the type 4, but not the type 3, PDE inhibitor mimics the action of LH and induces oocyte maturation, presumably by increasing cAMP levels in granulosa cells. Our findings indicate that PDE subtypes 4 and 3 are located in follicle somatic and germ cells, respectively. Preferential inhibition of PDE 3 in the oocyte may lead to a delay in oocyte maturation without affecting the cAMP-induced ovulatory process in the somatic cells. Conversely, selective suppression of granulosa cell cAMP-PDE may enhance the gonadotropin induction of ovulation and oocyte maturation. Thus, in addition to the well-recognized differential expression and regulation of adenylate cyclase in the somatic and germ cell compartments of the follicle, we suggest that selective regulation and expression of PDEs may be involved in the regulation of cAMP levels and control of oocyte maturation in the preovulatory mammalian follicle.

Positive inotropic and vasodilator actions of milrinone in patients with severe congestive heart failure. Dose-response relationships and comparison to nitroprusside

Milrinone is a potent positive inotropic and vascular smooth muscle-relaxing agent in vitro, and therefore, it is not known to what extent each of these actions contributes to the drug's hemodynamic effects in patients with heart failure. In 11 patients with New York Heart Association class III or IV congestive heart failure, incremental intravenous doses of milrinone were administered to determine the dose-response relationships for heart rate, systemic vascular resistance, and inotropic state, the latter measured by peak positive left ventricular derivative of pressure with respect to time (dP/dt). To clarify further the role of a positive inotropic action, the relative effects of milrinone and nitroprusside on left ventricular stroke work and dP/dt were compared in each patient at doses matched to cause equivalent reductions in mean arterial pressure or systemic vascular resistance, indices of left ventricular afterload. Milrinone caused heart rate, stroke volume, and dP/dt to increase, and systemic vascular resistance to decrease in a concentration-related manner. At the two lowest milrinone doses resulting in serum concentrations of 63 +/- 4 and 156 +/- 5 ng/ml, respectively, milrinone caused significant increases in stroke volume and dP/dt, but no changes in systemic vascular resistance or heart rate. At the maximum milrinone dose administered (mean serum concentration, 427 +/- 11 ng/ml), heart rate increased from 92 +/- 4 to 99 +/- 4 bpm (P less than 0.01), mean aortic pressure fell from 82 +/- 3 to 71 +/- 3 mmHg (P less than 0.01), right atrial pressure fell from 15 +/- 2 to 7 +/- 1 mmHg (P less than 0.005), left ventricular end-diastolic pressure fell from 26 +/- 3 to 18 +/- 3 (P less than 0.005), stroke volume index increased from 20 +/- 2 to 30 +/- 2 ml/m2 (P less than 0.005), stroke work index increased from 14 +/- 2 to 21 +/- 2 g X m/m2 (P less than 0.01), and dP/dt increased from 858 +/- 54 to 1,130 +/- 108 mmHg/s (P less than 0.005). When compared with nitroprusside for a matched reduction in mean aortic pressure or systemic vascular resistance, milrinone caused a significantly greater increase in stroke work index at the same or lower left ventricular end-diastolic pressure. Milrinone caused a concentration-related increase in dP/dt (32% increase at maximum milrinone dose), whereas nitroprusside had no effect. These data in patients with severe heart failure indicate that in addition to a vasodilating effect, milrinone exerts a concentration-related positive inotropic action that contributes significantly to the drug's overall hemodynamic effects. The positive inotropic action occurs at drug levels that do not exert significant chronotropic or vasodilator effects.

Cardiotonic activity of milrinone, a new and potent cardiac bipyridine, on the normal and failing heart of experimental animals

Milrinone (Win 47203) is a potent cardiac bipyridine with inotropic and vasodilator properties. Its effects were studied in anesthetized and unanesthetized dogs and in isolated cardiac tissues from guinea pigs. In the anesthetized dog, the intravenous injection of milrinone (0.01-0.1 mg/kg) increased cardiac contractile force (CF) (23 +/- 6.1 to 87 +/- 8.9%), maximum left ventricular pressure development (24 +/- 5.8 to 119 +/- 16.1%), and cardiac output (16 +/- 4.5 to 33 +/- 8.9%), with less than a 30% increase in heart rate (HR). Significant decreases in systolic and diastolic blood pressures were seen at 0.3-3 mg/kg i.v. Oral doses of milrinone (0.1-1.0 mg/kg), in unanesthetized dogs, increased cardiac CF by 35 +/- 7.0 to 99 +/- 17.0%, with a maximum increase in HR of 40 +/- 7.1% and no significant change in blood pressure. Milrinone was effective in the presence of ouabain and dopamine without enhancing their arrhythmogenic properties. It was also effective in reversing propranolol-, verapamil-, or pentobarbital-induced heart failure. The inotropic response does not seem to involve the stimulation of the autonomic receptors, the release of endogenous catecholamines, histamine, or prostaglandins, or the inhibition of Na+,K+-adenosine triphosphatase. Milrinone is an inhibitor or cardiac adenosine 3',5'-monophosphate (cAMP) phosphodiesterase, with resultant increases in cardiac cAMP levels. However, the time course for this increase does not seem to correspond to the increase in muscle developed tension, and, therefore, it is unlikely to be responsible for the initiation of the inotropic response. Milrinone is a potent cardioactive agent which should be beneficial in the treatment of acute and chronic congestive heart failure.

Increase of Gi alpha in human hearts with dilated but not ischemic cardiomyopathy

In myocardial membranes from hearts with dilated cardiomyopathy (DCM), there was a 37% increase of the Gi alpha-protein as measured by 32P-ADP-ribosylation of a approximately 40 kDa pertussis toxin substrate. Immunoblotting techniques also showed increased amounts of Gi alpha in DCM. In hearts with ischemic cardiomyopathy (ICM), Gi alpha was not altered compared with nonfailing myocardium (NF). Basal and Gpp(NH)p-stimulated adenylate cyclase activity was reduced in DCM but not in ICM. The number of beta-adrenoceptors was similarly reduced both in DCM and ICM compared with NF. Alterations of m-cholinoceptors or A1-adenosine receptors did not occur. Consistently, "indirect" negative inotropic effects of the m-cholinoceptor agonist carbachol and the A1-adenosine receptor agonist R-PIA were not different in ICM, DCM, and nonfailing myocardium. In ICM and DCM, there was a marked reduction of the positive inotropic responses to isoprenaline and milrinone. However, there was a further reduction in DCM compared with ICM. It is concluded that the increase of Gi alpha is accompanied by a reduction of basal and guanine-nucleotide-stimulated adenylate cyclase activity. Alterations of m-cholinoceptors and A1-adenosine receptors do not appear to be involved. The further decrease of the positive inotropic effects of isoprenaline and milrinone in DCM provides evidence that the increase of Gi alpha is functionally relevant in DCM but not ICM and hence might contribute to the reduced effects of endogenous catecholamines and exogenous cAMP-dependent positive inotropic agents in the former but not the latter condition.

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.

Nitric oxide regulates the calcium current in isolated human atrial myocytes

Cardiac Ca2+ current (ICa) was shown to be regulated by cGMP in a number of different species. Recently, we found that the NO-donor SIN-1 (3-morpholino-sydnonimine) exerts a dual regulation of ICa in frog ventricular myocytes via an accumulation of cGMP. To examine whether NO also regulates Ca2+ channels in human heart, we investigated the effects of SIN-1 on ICa in isolated human atrial myocytes. An extracellular application of SIN-1 produced a profound stimulatory effect on basal ICa at concentrations > 1 pM. Indeed, 10 pM SIN-1 induced a approximately 35% increase in ICa. The stimulatory effect of SIN-1 was maximal at 1 nM (approximately 2-fold increase in ICa) and was comparable with the effect of a saturating concentration (1 microM) of isoprenaline, a beta-adrenergic agonist. Increasing the concentration of SIN-1 to 1-100 microM reduced the stimulatory effect in two thirds of the cells. The stimulatory effect of SIN-1 was not mimicked by SIN-1C, the cleavage product of SIN-1 produced after liberation of NO. This suggests that NO mediates the effects of SIN-1 on ICa. Because, in frog heart, the stimulatory effect of SIN-1 on ICa was found to be due to cGMP-induced inhibition of cGMP-inhibited phosphodiesterase (cGI-PDE), we compared the effects of SIN-1 and milrinone, a cGI-PDE selective inhibitor, on ICa in human. Milrinone (10 microM) induced a strong stimulation of ICa (approximately 150%), demonstrating that cGI-PDE controls the amplitude of basal ICa in this tissue. In the presence of milrinone, SIN-1 (0.1-1 nM) had no stimulatory effect on ICa, suggesting that the effects of SIN-1 and MIL were not additive. We conclude that NO may stimulate ICa in human atrial myocytes via inhibition of the cGI-PDE.

Improvement in indexes of diastolic performance in patients with congestive heart failure treated with milrinone

To elucidate the mechanisms by which the new bipyridine inotropic agent milrinone improves cardiac function, we examined multiple indexes of left ventricular diastolic function before and after administration of milrinone to patients with advanced (NYHA class III or IV) congestive heart failure. In 13 patients left ventricular pressure measurements were made with a micromanometer to permit assessment of peak negative dP/dt and the time constant of left ventricular isovolumic relaxation, T, before and after milrinone. In nine patients radionuclide ventriculographic studies were performed during left heart catheterization, allowing calculation of left ventricular peak filling rate, volumes, and the diastolic pressure-volume relationship before and after milrinone. After intravenous administration of milrinone, peak negative dP/dt increased (+ 18%; p less than .01) and T decreased (-30%; p less than .01), while heart rate increased by only 8% (87 +/- 12 to 94 +/- 15 beats/min; p less than .01), left ventricular systolic pressure did not change, and mean aortic pressure fell by 11% (p less than .01). Left ventricular peak filling rate increased (1.2 +/- 0.6 to 1.7 +/- 0.7 end-diastolic volumes/sec; p less than or equal to .02) despite a decrease in left ventricular filling pressure (mean pulmonary wedge pressure 27 +/- 7 to 18 +/- 9 mm Hg; p less than .01). There was a fall in left ventricular end-diastolic pressure (28.6 +/- 6 to 19 +/- 7 mm Hg; p less than or equal to .01), with no significant change in left ventricular end-diastolic volume. This was associated with a downward shift in the left ventricular diastolic pressure-volume relationship in most cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of milrinone on coronary hemodynamics and myocardial energetics in patients with congestive heart failure

To examine the effect of milrinone on myocardial energetics in patients with congestive heart failure, we measured systemic, pulmonary, and coronary hemodynamics in 18 patients before and after intravenous administration of milrinone (125 +/- 36 micrograms/kg). There was a 45% increase in cardiac index (2.1 +/- 0.5 to 3.0 +/- 0.6 liters/min/m2; p = .0001), a 39% fall in the pulmonary capillary wedge pressure (28 +/- 8 to 17 +/- 8 mm Hg; p = .0001), and a 42% increase in left ventricular external work (3758 +/- 1419 to 5340 +/- 1598 g-m/min; p = .0001). Both the heart rate-blood pressure product (9624 +/- 2272 to 9380 +/- 2428 mm Hg-beats/min; p = NS) and regional left ventricular myocardial oxygen consumption (7.6 +/- 2.9 to 8.1 +/- 3.1 ml O2/min; p = NS) were unchanged after milrinone, resulting in a 45% increase in calculated left ventricular external efficiency (p = .004). Although myocardial oxygen consumption did not change, regional great cardiac venous blood flow increased significantly (73 +/- 32 to 85 +/- 34 ml/min; p = .02) as a result of a 30% reduction in regional coronary vascular resistance (1.32 +/- 0.99 to 0.93 +/- 0.54 mm Hg-min/ml; p = .004), a decrease comparable to the concurrent 37% and 38% falls seen in systemic and pulmonary vascular resistance, respectively. These changes were associated with an 11% fall in the transcoronary arterial-venous oxygen difference (111 +/- 24 to 99 +/- 21 ml/O2/liter; p = .0001), which is consistent with a primary coronary vasodilator effect of milrinone.(ABSTRACT TRUNCATED AT 250 WORDS)

Sustained hemodynamic and clinical effects of a new cardiotonic agent, WIN 47203, in patients with severe congestive heart failure

The hemodynamic and clinical effects of WIN 47203, a newly synthesized noncatecholamine, nonglycosidic inotropic agent, were studied in 11 patients with severe chronic congestive heart failure. Intravenous WIN 47203 increased cardiac index from 1.93 +/- 0.36 to 2.87 +/- 0.45 l/min/m2 (p less than 0.001) and reduced pulmonary capillary wedge pressure from 27.0 +/- 8.4 to 16.3 +/- 6.1 mm Hg (p less than 0.001). Mean systemic arterial pressure decreased from 75.2 +/- 6.7 to 72.4 +/- 6.3 mm Hg (p less than 0.01) and systemic vascular resistance from 1591 +/- 397 to 1071 +/- 293 dyn-sec-cm5 (p less than 0.001); heart rate was unchanged. Oral WIN 47203 produced similar hemodynamic improvement. Hemodynamic monitoring of six consecutive doses did not demonstrate evidence for attenuation of effectiveness. Chronic therapy with WIN 47203 produced substantial symptomatic improvement and increased maximal oxygen uptake at 1 week. Patients were further improved after 4 weeks of WIN 47203, and maximal oxygen uptake increased from 9.0 +/- 1.9 to 11.6 +/- 2.5 ml/kg/min (p less than 0.01 vs control). No overt clinical or laboratory manifestations of toxicity were observed. Withdrawal of WIN 47203 in two patients in whom clinical benefit was not sustained resulted in clinical and hemodynamic deterioration, which was reversed by reinstitution of the drug. Therefore, this study demonstrates the acute and sustained cardiotonic efficacy of WIN 47203 in man. If long-term administration remains well tolerated and without side effects, this drug appears to be very promising for treatment of chronic severe congestive heart failure.

Survival of patients with severe congestive heart failure treated with oral milrinone

The safety and efficacy of long-term oral milrinone therapy were evaluated over a 2 1/2 year period in 100 patients who had severe congestive heart failure despite conventional therapy. Long-term oral milrinone therapy (27 +/- 8 mg/day initial dose) was well tolerated; drug-related side effects occurred in only 11% of patients and led to drug withdrawal in only 4% of patients. Of 94 patients evaluated after 1 month of therapy, 51% had improved by at least one New York Heart Association functional class. Despite hemodynamic and clinical improvements, life table analysis showed a 39% mortality rate at 6 months and a 63% mortality rate at 1 year of therapy. Characteristics at study entry that predicted death within 6 months included more advanced functional class, impaired renal function, lower right ventricular ejection fraction, presence of nonsustained ventricular tachycardia on 24 hour ambulatory electrocardiography, more impaired baseline hemodynamic function and absence of clinical improvement after 1 month of milrinone therapy. Multivariate analysis selected lower baseline cardiac index and aortic systolic pressure as the most significant variables in predicting death; patients who died of progressive heart failure had less frequent use of antiarrhythmic drugs and greater increases in furosemide and milrinone doses during long-term follow-up than did those who died suddenly. Thus, although milrinone is well tolerated and produces early symptomatic benefits in approximately half of patients with congestive heart failure refractory to conventional therapy, there is no evidence that it improves the high baseline mortality in this disorder.

Characterization of the cardiotonic effects of milrinone, a new and potent cardiac bipyridine, on isolated tissues from several animal species

The cardiotonic activity of milrinone (Win 47203), a potent analogue of amrinone, was demonstrated in isolated guinea pig, cat, rabbit, rat, and hamster atria and papillary muscles. Milrinone, in concentrations of 0.1-300 micrograms/ml, caused concentration-dependent increases in guinea pig papillary muscle and atrial developed tension with minimal increases in atrial rate. Compared with the in vitro inotropic activity of amrinone, milrinone was approximately 30 times more potent. The inotropic and chronotropic effects of milrinone do not appear to be mediated by the release of endogenous norepinephrine, by the direct stimulation of beta-adrenergic or histaminergic receptors, or through the stimulation of prostaglandin synthesis. The inotropic response of the guinea pig papillary muscles to isoproterenol was potentiated when isoproterenol was given at the peak effect of a minimally effective concentration of milrinone or after prolonged incubation with milrinone. No potentiation was observed when isoproterenol was administered at the peak effect of a high concentration of milrinone, which suggests that the positive inotropic action of milrinone may not be solely attributable to cyclic AMP phosphodiesterase inhibition.

Sensitization of dog and guinea pig heart myofilaments to Ca2+ activation and the inotropic effect of pimobendan: comparison with milrinone

We compared the effects of the newer inotropic drugs, pimobendan (UD-CG 115 BS) and milrinone (Win 47203), on the electrical, mechanical and biochemical activity of intact and detergent-skinned preparations of cardiac muscle. Both of these agents increased contractile force of guinea pig papillary muscle preparations bathed under physiological conditions or depolarized with 25 mM K+o. The positive inotropic action was associated with potentiation of the Ca2+-dependent slow action potentials (APS). Contractile force developed in the presence of 25 mM [K]o and 1 microM isoproterenol was increased further by addition of 50 microM pimobendan with no effect on the slow action potential. Milrinone (50 microM) did not produce a further increase in the force or potentiate the slow APs. Pimobendan, in a dose-dependent manner, increased active tension developed by chemically-skinned dog heart muscle fibers at submaximally activating concentrations of Ca2+, whereas milrinone did not. At pCa 6.25, the half-maximal concentration of pimobendan for stimulation of force development was about 40 microM. At maximally activating levels of Ca2+ (pCa 4.5), pimobendan had little or no effect on force development. The effect of pimobendan on force was paralleled by changes in the Ca2+-activated Mg-ATPase activity of the isometric skinned fiber preparations. Moreover, the tension-cost (unit increase in ATPase rate/unit increase in force) was unchanged in the presence of pimobendan. Milrinone did not affect ATP hydrolysis by the skinned fiber preparations. Force-pCa and ATPase-pCa relations of skinned fiber preparations contracting isometrically were shifted to the left by 0.15-0.20 pCa units in the presence of 50 microM pimobendan. In contrast, there was no effect of pimobendan on the ATPase activity of unloaded myofibrillar preparations. The stimulation of force and ATPase activity of the skinned heart muscle fibers could be accounted for by an effect of pimobendan on the affinity of the regulatory (low affinity, Ca2+-specific) binding sites of cardiac troponin C. Ca2+ binding to the "structural" high affinity sites of troponin C was slightly inhibited. The results indicate that the positive inotropic actions of pimobendan, but not milrinone, may involve activation of the cardiac myofilaments by a direct effect involving an increased affinity of the regulatory site on troponin C for Ca2+.

Systemic and coronary effects of intravenous milrinone and dobutamine in congestive heart failure

The effects of dobutamine and intravenous milrinone on systemic hemodynamics, coronary blood flow and myocardial metabolism were studied in 11 patients with severe congestive heart failure. Although milrinone and dobutamine similarly increased cardiac index from 1.9 +/- 0.4 to 2.5 +/- 0.4 liters/min per m2 (p less than 0.001) and from 1.9 +/- 0.4 to 2.8 +/- 0.8 liters/min per m2 (p less than 0.001), respectively, milrinone decreased left ventricular end-diastolic pressure to a greater extent than dobutamine, that is, from 26 +/- 6 to 12 +/- 8 mm Hg (p less than 0.001) versus 26 +/- 8 to 20 +/- 8 mm Hg (p less than 0.001). In contrast to dobutamine, milrinone significantly reduced mean systemic arterial and right atrial pressures. Dobutamine increased the first derivative of left ventricular pressure (dP/dt) from 1,013 +/- 309 to 1,360 +/- 538 mm Hg/s (p less than 0.01) but milrinone did not. Similarly, blood flow and myocardial oxygen consumption were increased by dobutamine from 152 +/- 87 to 187 +/- 118 ml/min (p less than 0.05) and from 17.7 +/- 10.9 to 21.5 +/- 14.9 ml O2/min (p less than 0.05), respectively, but were unchanged by milrinone. Both drugs significantly decreased coronary vascular resistance and myocardial oxygen extraction but did not change myocardial lactate extraction. Thus, dobutamine and milrinone produce similar improvement in cardiac index. However, dobutamine increases myocardial oxygen consumption, whereas milrinone does not. This difference can probably be explained by the substantial vasodilating properties of milrinone.

Hemodynamic effects of i.v. milrinone lactate in pediatric patients with septic shock. A prospective, double-blinded, randomized, placebo-controlled, interventional study

STUDY OBJECTIVE

To determine the hemodynamic effects of i.v. milrinone lactate in pediatric patients with nonhyperdynamic septic shock. Specifically we tested the hypothesis that i.v. milrinone would increase cardiac index by 20% and decrease systemic vascular resistance index by 20% during a 2-h study period.

DESIGN

Prospective, double-blinded, randomized, placebo-controlled, descriptive, interventional study.

SETTING

Twenty-six-bed pediatric ICU at Children's Medical Center of Dallas and a 10-bed pediatric trauma ICU at Parkland Memorial Hospital.

PATIENTS/PARTICIPANTS

Twelve patients (age range, 9 months to 15 years) with nonhyperdynamic septic shock despite administration of catecholamines (cardiac index [CI] normal [3.5 to 5.5 L/min/m2] or low [< or =3.5 L/min/m2]; systemic vascular resistance index [SVRI] normal [800 to 1,600 dyne.s.cm5/m2] or high [> or =1,600 dyne.s.cm5/m2]; and pulmonary capillary wedge pressure [PCWP] normal [8 to 12 mm Hg] or higher) with clinical signs of poor perfusion were enrolled, randomized, and treated in a blinded fashion with i.v. milrinone and placebo.

INTERVENTIONS

Patients were randomized into two groups. Group A received a loading dose of 50 micrograms/kg i.v. of milrinone followed by a continuous i.v. infusion of 0.5 microgram/kg/min while group B received an equal volume loading dose and continuous infusion of placebo. After 2 h, group A received an equal-volume loading dose followed by a continuous infusion of placebo while the milrinone infusion continued, while group B received a 50 micrograms/kg loading dose of milrinone followed by a continuous infusion of 0.5 microgram/kg/min while the placebo infusion remained. Outcome variable were measured at baseline, 0.5, 1.0, 2.0, 2.5, 3.0, and 4.0 h. Echocardiographic measurements were taken at baseline, hour 2, and hour 4 in all subjects. No changes in other inotropic or mechanical ventilatory support were allowed during the study period.

MEASUREMENTS AND MAIN RESULTS

Milrinone significantly increased CI, stroke volume index (SVI), right and left ventricular stroke work index, and oxygen delivery (Do2) at 0.5, 1.0, and 2.0 h postloading dose (p < 0.05) while significantly decreasing SVRI, pulmonary vascular resistance index, and mean pulmonary arterial pressure at 0.5, 1.0, and 2.0 h postloading dose (p < 0.05). No clinically or statistically significant changes in heart rate, systolic and diastolic BP, mean systemic arterial pressure, or PCWP were observed during milrinone treatment compared to placebo.

CONCLUSIONS

CI, SVI, and Do2 significantly increased while SVRI significantly decreased when compared to placebo after i.v. administration of milrinone to pediatric patients with nonhyperdynamic septic shock. No adverse effects were observed. In a volume-resuscitated pediatric patient with septic shock, when administered in addition to catecholamines, milrinone will improve cardiovascular function.

Intracoronary infusion of dobutamine to patients with and without severe congestive heart failure. Dose-response relationships, correlation with circulating catecholamines, and effect of phosphodiesterase inhibition

We infused dobutamine into the left main coronary artery of 24 patients with severe congestive heart failure (CHF) and 8 normal subjects without hemodynamic dysfunction. The maximal +dP/dt response to intracoronary (IC) dobutamine in CHF patients was only 37% of that in normals. This decrease in maximal response was not associated with a rightshift in the EC50 for dobutamine's effect on +dP/dt, or a decrease in the affinity of myocardial beta adrenergic receptors for dobutamine determined in vitro. In nine of the CHF patients, IC dobutamine infusion was followed by IC infusion of the phosphodiesterase inhibitor milrinone, and subsequently, by a second IC infusion of dobutamine. After IC milrinone, the increase in +dP/dt caused by IC dobutamine (74 +/- 10%) was significantly greater than that caused by the first infusion of dobutamine (52 +/- 11%; P less than 0.003) or milrinone (42 +/- 6%; P less than 0.001). Resting plasma norepinephrine was markedly elevated in CHF patients (837 +/- 208 ng/liter), but not in normal subjects (142 +/- 32 ng/liter); and the increase in +dP/dt caused by IC dobutamine was inversely related to resting plasma norepinephrine levels (r = -0.653; P less than 0.001). IC dobutamine caused a dose-related decrease in plasma norepinephrine (maximal effect, -160 +/- 31 ng/liter; P less than 0.001). Thus, (a) the maximal inotropic response to dobutamine is markedly depressed in patients with severe CHF, and is significantly greater after pretreatment with the phosphodiesterase inhibitor milrinone; (b) the impairment in inotropic response to dobutamine is inversely related to circulating norepinephrine levels; and (c) myocardial stimulation by dobutamine results in withdrawal of sympathetic tone.

Phosphodiesterase 3 inhibitors suppress oocyte maturation and consequent pregnancy without affecting ovulation and cyclicity in rodents

During each reproductive cycle, a preovulatory surge of gonadotropins induces meiotic maturation of the oocyte in the preovulatory follicle followed by ovulation. Although gonadotropins stimulate cAMP production in somatic cells of the follicle, a decrease in intra-oocyte cAMP levels is required for resumption of meiosis in oocytes. Based on the observed compartmentalization of the cAMP-degrading enzyme, phosphodiesterase, in follicular somatic and germ cells, inhibitors of phosphodiesterase 3 were used to block meiosis in ovulating oocytes in rodents. By this strategy, we demonstrated that fertilization and pregnancy could be prevented without disturbing follicle rupture and normal estrous cyclicity. In contrast to conventional contraceptive pills that disrupt ovarian steroidogenesis and reproductive cycles, the present strategy achieves effective contraception by selective blockage of oocyte maturation and development without alterations in ovulation and reproductive cyclicity.

The role of cAMP- and cGMP-dependent protein kinases in the cardiac actions of the new calcium sensitizer, levosimendan

OBJECTIVE

The role of phosphodiesterase III inhibition and calcium sensitization in the cardiac actions of levosimendan, (R)-[[4-(1,4,5, 6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl)phenyl]hydrazono]propane dinitrile, was studied.

METHODS

Various heart preparations were used to investigate positive inotropy, chromotropy, coronary flow and calcium sensitivity of contractile proteins. The cAMP- and cGMP-dependent protein kinases (PKA and PKG) were inhibited by KT5720 and KT5823, respectively. Furthermore, the synthesis of cAMP was stimulated by forskolin and increased phosphorylation of troponin I was induced by isoprenaline.

RESULTS

In Langendorff guinea-pig heart, levosimendan (0.01-1 microM) and milrinone (0.1-10 microM) increased the left ventricular systolic peak pressure almost to the same extent. In the presence of KT5720 (1 microM) milrinone was devoid of positive inotropic activity. In contrast, KT5720 did not antagonize the inotropic effect of levosimendan at < or = 0.03 microM (-up to the EC50 of levosimendan). The effects of levosimendan and milrinone on heart rate and coronary flow were not affected by KT5720. The PKG inhibitor, KT5823 (1 microM), on the other hand, potentiated the levosimendan-induced increase in coronary flow while it had no effect on the increase induced by milrinone. The mechanical parameters were not affected by KT5823. In the papillary muscle, the positive inotropic effect of milrinone but not that of levosimendan was potentiated by forskolin (0.1 microM). In contrast to milrinone, the positive inotropy by levosimendan was decreased by isoprenaline pretreatment (0.1 microM; 3 min). In line with this, the calcium-sensitizing effect of levosimendan was decreased in skinned fibers prepared from isoprenaline-treated hearts.

CONCLUSIONS

Our results indicate that the cardiac effects of levosimendan at its therapeutically relevant concentrations were not mediated through PKA or PKG and its positive inotropy is therefore most probably due to the previously reported troponin-C-mediated calcium sensitization of contractile proteins.

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

To determine the relative contributions of milrinone's positive inotropic and vasodilator actions in patients with severe congestive heart failure, the drug was administered by constant infusion directly into the left main coronary artery of 11 patients with New York Heart Association functional class III or IV heart failure. Intracoronary infusion of milrinone at rates up to 50 micrograms/min had no effect on mean arterial pressure or systemic vascular resistance but resulted in dose-related increases in peak positive dP/dt (+21%), stroke volume index (+18%), and stroke work index (+21%) and decreases in heart rate (-3%), mean right atrial pressure (-25%), and left ventricular end-diastolic pressure (-17%). In eight patients, intravenous administration (75 micrograms/kg) after the intracoronary infusion resulted in significant decreases in mean arterial pressure (-14%) and systemic vascular resistance (-40%), further increase in stroke volume index compared with intracoronary administration, and further decreases in mean right atrial and left ventricular end-diastolic pressures compared with intracoronary administration. These data indicate that milrinone exerts both positive inotropic and vasodilator actions that contribute significantly to the drug's overall hemodynamic effect.

Influence of levosimendan, pimobendan, and milrinone on the regional distribution of cardiac output in anaesthetized dogs

1. The distribution of cardiac output during administration of levosimendan, a new myofilament calcium sensitizer, is unknown. We examined and compared the effects of levosimendan, pimobendan, and milrinone on regional tissue perfusion by use of the radioactive microsphere technique in barbiturate-anaesthetized dogs. 2. Haemodynamics and regional blood flow were determined before and during infusions of levosimendan (0.75, 1.5, and 3.0 micrograms kg-1 min-1), pimobendan (10, 20, and 40 micrograms kg-1 min-1), or milrinone (1.0, 2.0, and 4.0 micrograms kg-1 min-1). 3. All three drugs caused similar increases in heart rate, cardiac output, and left ventricular +dP/dt and decreases in end-diastolic pressure and systemic vascular resistance. No changes in subendocardial, midmyocardial, and subepicardial blood flow occurred during administration of levosimendan. However, a redistribution of blood flow from subendocardium to subepicardium was observed. Pimobendan increased midmyocardial and subepicardial blood flow and reduced the endo/epi ratio to a greater degree than levosimendan. Milrinone did not affect myocardial perfusion. 4. Levosimendan increased blood flow to the renal medulla and decreased renal medullary and cortical vascular resistance. Levosimendan increased blood flow to the small intestine and liver and reduced vascular resistance in these organs. Pimobendan increased hepatic blood flow to a greater degree than levosimendan but did not alter small intestinal perfusion. All three drugs decreased splenic blood flow to similar degrees. Levosimendan and pimobendan reduced cerebral vascular resistance. Levosimendan and milrinone reduced skeletal muscle vascular resistance. 5. The results indicate that levosimendan, pimobendan, and milrinone cause subtlety different alterations in regional tissue perfusion while producing similar haemodynamic effects.