Comparison of the effects of amrinone and sodium nitroprusside on haemodynamics, contractility, and myocardial metabolism in patients with cardiac failure due to coronary artery disease and dilated cardiomyopathy

Davids versus Goliaths: Pharma and academia threats to individual scientists and clinicians

Background

We previously described experiences of clinicians who published adverse drug reaction reports. We now report on threats and intimidations leveled against clinicians and scientists who received publicly documented threats after communicating safety, efficacy, or data integrity findings contrary to corporate interests.

Methods

Data on threats and intimidations were obtained from transcripts of governmental hearings or agencies, university-affiliated reports, media interviews, and investigative journalism articles. Content and timing of threats and intimidation, subsequent harms, numbers of persons seriously injured or who died from individual toxicities, financial payments from sponsors related to safety, efficacy, or data integrity concerns, and civil settlements and criminal findings were evaluated.

Findings

Twenty-six individuals who communicated safety, efficacy, or data integrity concerns were targets of threats and intimidation from corporate employees (twenty-three individuals) or regulatory personnel (three). Seventeen individuals identified instances where pharmaceutical sponsors submitted fraudulent data in support of regulatory approval of a drug or device. Scientist and clinician communications were followed by drug/device withdrawals (fourteen drugs/devices), black box warnings (six drugs), withdrawal of a sponsor’s application for regulatory approval (one device), and delay of approval of a sponsor’s application for regulatory approval (one drug). Actions mainly occurred after persons communicated with pharmaceutical employees (fourteen). Intimidation efforts by corporate personnel included threats of lawsuits (eighteen individuals), hiring private investigators (nine), and public disparagement at conferences (eleven). Related intimidation efforts carried out by academia or regulatory agency superiors included threats of: loss of positions (six), loss of grant funding (two), delays in decisions regarding tenure (two); or reassignment to a low-level position (one). Academic harms included lost: hospital or university appointments (nine and six, respectively), grant funding (two), chairperson title of an international clinical trial group (one), and journal editorial board position (one). Corporate harms included payment of $1 million to defense attorneys in three cases filed against clinicians.

Interpretation

Threats and intimidation carried out by corporate employees and/or academic supervisors followed public communication of concerns regarding patient safety, drug efficacy, or data integrity, including instances where sponsors were identified as having submitted fraudulent data to regulatory or government agencies. Consideration should be given to filing criminal charges against pharmaceutical executives who are discovered by scientists or clinicians to have knowingly submitted fraudulent data to regulatory or governmental agencies, rather than causing the scientists and clinicians who submit such reports to risk losing their reputations and occupations.

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.

The role of cyclic nucleotide phosphodiesterases in the regulation of adipocyte lipolysis

This study assessed the effects of selective inhibitors of 3',5'-cyclic nucleotide phosphodiesterases (PDEs) on adipocyte lipolysis. IC224, a selective inhibitor of type 1 phosphodiesterase (PDE1), suppressed lipolysis in murine 3T3-L1 adipocytes (69.6 +/- 5.4% of vehicle control) but had no effect in human adipocytes. IC933, a selective inhibitor of PDE2, had no effect on lipolysis in either cultured murine 3T3-L1 adipocytes or human adipocytes. Inhibition of PDE3 with cilostamide moderately stimulated lipolysis in murine 3T3-L1 and rat adipocytes (397 +/- 25% and 235 +/- 26% of control, respectively) and markedly stimulated lipolysis in human adipocytes (932 +/- 7.6% of control). Inhibition of PDE4 with rolipram moderately stimulated lipolysis in murine 3T3-L1 adipocytes (291 +/- 13% of control) and weakly stimulated lipolysis in rat adipocytes (149 +/- 7.0% of control) but had no effect on lipolysis in human adipocytes. Cultured adipocytes also responded differently to a combination of PDE3 and PDE4 inhibitors. Simultaneous exposure to cilostamide and rolipram had a synergistic effect on lipolysis in murine 3T3-L1 and rat adipocytes but not in human adipocytes. Hence, the relative importance of PDE3 and PDE4 in regulating lipolysis differed in cultured murine, rat, and human adipocytes.

Intravenous vasodilator therapy in congestive heart failure

The prevalence of congestive heart failure (CHF) is increasing in the US and worldwide, partly because patients are living longer. Treatment of CHF is mostly on an outpatient basis, but inpatient care is required for decompensated CHF, acute CHF or poor response to outpatient treatment. Control of symptoms is usually achieved by diuresis. Intravenous (IV) vasodilators are an important adjunct to the inpatient treatment of CHF. They work mainly by reducing the afterload on the myocardium although preload reduction also occurs. After clinical stabilisation, the goal is to switch to a maintenance oral regimen to be continued as outpatient therapy. The range of IV vasodilators available for inpatient treatment of CHF includes nitrates, phosphodiesterase inhibitors, dobutamine, morphine, ACE inhibitors, B-type natriuretic peptides and endothelin receptor antagonists. As each agent may have a different mechanism or site of action, each agent may affect preload, contractility or afterload to a different extent and it may be desirable to choose one over the other in a particular clinical setting. Examples of standard therapy include dobutamine, milrinone and nitroglycerin. Nesiritide, a B-type natriuretic peptide, is a newer vasodilator and US FDA approved for use in acute CHF. However, most studies with this agent have been in small numbers of patients with anecdotal findings. Larger studies are warranted to pinpoint the efficacy and adverse effects of this agent. It is primarily used to reduce the acuity of decompensated CHF on admission to hospital.Endothelin receptor antagonists show promise in the management of acute CHF, but continue to be investigational. Long-term data on their efficacy and safety are limited. None of the endothelin receptor antagonists are FDA approved for use in patients with CHF.

Perindopril effect on uncoupling protein and energy metabolism in failing rat hearts

Uncoupling proteins, inner mitochondrial membrane proton transporters, are important for regulating myocardial energy efficiency. We investigated the effects of the ACE inhibitor perindopril on cardiac performance, myocardial energy efficiency, and uncoupling protein expression in an aortic regurgitation rat model. Twenty male Sprague-Dawley rats, in which aortic regurgitation was produced, were divided into untreated and perindopril-treated (5 mg x kg(-1) x d(-1)) rats. The treatments were initiated 3 days after operation. Ten control rats were sham-operated. Measurements of blood pressure and echocardiography were repeated before and 100 days after operation (endpoint). Left ventricular uncoupling protein-2 expression, creatine phosphate, and adenosine triphosphate were measured at endpoint. In perindopril-treated rats, systolic and diastolic blood pressure decreased after treatment (92+/-4/65+/-2 mm Hg). At endpoint, left ventricular end-diastolic dimension in untreated (10.7+/-0.2 mm) and treated rats (9.2+/-0.2 mm) was increased, and fractional shortening was reduced in untreated rats (28+/-1%) but did not change in treated rats (36+/-2%). Uncoupling protein-2 mRNA expression increased in untreated rats (3.7-fold) and was suppressed by perindopril (1.5-fold). The creatine phosphate was reduced in untreated rats (10.6+/-0.7 micro mol/g) but not in treated rats (15.9+/-2.0 micro mol/g). In the chronic stage of aortic regurgitation, perindopril improved cardiac performance and myocardial energy efficiency, in which the suppression of uncoupling protein-2 may play an important role.

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.

Effects of amrinone on cardiac contraction and relaxation in isolated, perfused rat heart

The effects of amrinone on cardiac contraction and relaxation were assessed in isolated, perfused rat hearts. It was found that the left ventricular developed pressure (LVDP), dp/dtmax and -da/dtmax did not significantly increase, and the time constant (tau) did not markedly shorten with perfusion of low concentration (1 nmol/L, 100 nmol/L) of amrinone. The perfusion with higher concentration (1000 nmol/L) of amrinone reduced LVDP (P < 0.01), dp/dtmax (P < 0.01), -dp/dtmax (P < 0.01), and prolonged tau (P < 0.05) significantly. It was assumed that amrinone has no direct positive inotropic effect, and can not improve cardiac relaxation. On the contrary, the cardiac contraction and relaxation will be inhibited at higher concentration of amrinone.

The effects of afterload reduction on myocardial carbon 11-labeled acetate kinetics and noninvasively estimated mechanical efficiency in patients with dilated cardiomyopathy

METHODS AND RESULTS

With echocardiography and dynamic carbon 11-labeled acetate (C-11 acetate) positron emission tomographic imaging, C-11 acetate kinetics and a parameter that estimates mechanical ventricular efficiency (the work metabolic index) were defined in eight patients with dilated cardiomyopathy. The effect of afterload reduction with nitroprusside on these parameters was evaluated in six of these patients. Nitroprusside increased stroke work index but decreased the C-11 clearance rate. The work metabolic index determined noninvasively increased and correlated well with an invasive approach. The work metabolic index was inversely correlated with systemic vascular resistance. Nitroprusside shifted this relationship upward and to the left.

CONCLUSION

This method of estimating efficiency is feasible and may represent a unique noninvasive approach for the evaluation of cardiac performance and responses to therapy.

Acute effects of dobutamine on myocardial oxygen consumption and cardiac efficiency measured using carbon-11 acetate kinetics in patients with dilated cardiomyopathy

OBJECTIVES

The aim of this study was to use positron emission tomography (PET)-derived carbon (C)-11 acetate kinetics to determine the effects of dobutamine on oxidative metabolism and its effects on myocardial efficiency in a group of patients with dilated cardiomyopathy.

BACKGROUND

Dobutamine is known to improve myocardial function but may do so at the expense of myocardial oxygen consumption, which could be a potential deleterious effect. Carbon-11 acetate kinetics correlate with myocardial oxygen consumption as shown in animal models. Combining these scintigraphic measurements of oxygen consumption with estimates of cardiac work results in a work-metabolic index, which reflects cardiac efficiency.

METHODS

Eight patients with nonischemic dilated cardiomyopathy underwent dynamic PET imaging, echocardiography and hemodynamic measurements. Seven of these patients were also studied while receiving dobutamine. Direct measurements of myocardial oxygen consumption using coronary sinus catheterization were obtained with eight of the PET studies to validate C-11 acetate in patients with cardiomyopathy.

RESULTS

The mean (+/- SD) C-11 clearance rate significantly increased with dobutamine from 0.105 +/- 0.027 to 0.155 +/- 0.023 min-1 (p = 0.001). Directly measured myocardial oxygen consumption had a linear relation to the mean C-11 clearance rate (r = 0.8, p = 0.018). Dobutamine was noted to significantly reduce systemic vascular resistance as well as the severity of mitral regurgitation. The work-metabolic index determined using hemodynamic variables and PET data increased from 2 +/- 0.7 x 10(4) to 2.6 +/- 0.6 x 10(4) (p = 0.04). Efficiency, estimated by employing the oxygen consumption to k2 relation, also increased from 13 +/- 4.5% to 16.9 +/- 6.4% (p = 0.04).

CONCLUSIONS

Despite an increase in myocardial oxygen consumption, dobutamine led to an increase in work-metabolic index in patients with dilated nonischemic cardiomyopathy. Dobutamine reduced systemic vascular resistance and mitral regurgitation, suggesting that in this group of patients, it had important vasodilatory action in addition to its inotropic effects. The use of the C-11 acetate PET for determining myocardial oxygen consumption and estimating efficiency could potentially complement existing clinical measures of ventricular performance and may allow improved and objective evaluation of therapy in patients with heart failure.

Inotropic support of the critically ill patient. A review of the agents

Intensive care patients often require inotropic support to stabilise circulation and to optimise oxygen supply. In this context, the catecholamines norepinephrine (noradrenaline), epinephrine (adrenaline), dopamine and dobutamine are still the mainstay of therapy. They provide, to different extents, a variety of adrenoceptor-mediated actions comprising vasoconstriction (via alpha-receptors) as well as vasodilatation (via beta 1-receptors), and an increase in cardiac output by enhancing inotropy and heart rate (again via beta 1-receptors). Because of their favourable pharmacokinetic profile (plasma half-lives of about 2 minutes) their actions can easily be controlled. Combinations of different catecholamines with each other or with other drugs such as phosphodiesterase inhibitors or nitrates lead to a broad spectrum of possible haemodynamic actions. However, the use of catecholamines is limited by side effects like tachycardia, hypertension and disturbances of organ perfusion caused by vasoconstriction. Furthermore, as a result of receptor downregulation during long term therapy, the efficacy of catecholamine treatment decreases. These shortfalls stimulated the search for alternatives to catecholamine treatment. Among these, phosphodiesterase inhibitors (e.g. enoximone and amrinone) appear to be the most promising drugs which have been introduced into acute clinical practice up to now. They act via inhibition of the phosphodiesterase isoenzyme III, leading to higher intracellular calcium levels by increasing cyclic adenosine monophosphate (cAMP) levels. These agents improve cardiac performance by enhancing contractility, reducing left ventricular afterload and improve diastolic relaxation. In cases of failing catecholamine therapy due to receptor downregulation, treatment with phosphodiesterase inhibitors may still be effective since their action is not receptor-mediated. Inhibition of the phosphodiesterase enzyme in vascular smooth muscle leads to vasodilatation. Therefore, in low cardiac output states combined with increased total peripheral or pulmonary vascular resistance, phosphodiesterase inhibitor therapy is particularly effective. Depending on the dosage and the speed of intravenous administration, the use of phosphodiesterase inhibitors sometimes results in pronounced decrease of blood pressure which may require vasopressor therapy. Other drugs including histamine H2-agonists are currently under investigation. Their value in the treatment of intensive care patients has still to be evaluated.

Intravenous fenoldopam infusion in severe heart failure

Fenoldopam, a selective DA1-receptor agonist, infused intravenously for 24 hours (0.6 +/- 0.3 microgram/kg/min, range 0.1-1.5) in 25 patients with NYHA functional class III or IV heart failure, produced a prompt and sustained hemodynamic response. Cardiac index rose from an average preinfusion baseline value of 1.8 to 2.6/l min. Stroke volume index increased from 19 to 26 ml/m2 and stroke work index increased from 18 to 25 g M/m2. These changes were accompanied by a reduction in systemic vascular resistance from an average of 2400 to 1500 dynes sec/cm5. There was no change in the heart rate or right atrial pressure. There was a transient reduction in the left ventricular filling pressure from 25 to 20 mmHg. Urinary sodium excretion did not change significantly. Transient asymptomatic thrombocytopenia developed in four patients. The drug was well tolerated by all patients. These results suggest that continuous intravenous infusion of fenoldopam is safe and produces favorable hemodynamic responses in severe heart failure. However, unlike its effects in patients with hypertension, it failed to produce sustained natriuresis in these patients.

Current status of phosphodiesterase inhibitors in the treatment of congestive heart failure

The phosphodiesterase inhibitors have been recognised as potent inotropic and vasodilating drugs. In acute congestive heart failure they increase cardiac output, decrease left pulmonary capillary wedge pressure, and reduce total peripheral resistance with an improvement in loading conditions of the failing heart. Their potency in reversal of symptoms of acute congestive heart failure is quite similar to, or even better than, treatment with intravenous catecholamines and sodium nitroprusside. In chronic congestive heart failure, however, these agents increase mortality and have deleterious effects in the outcome of patients with severe left ventricular dysfunction.

Current status of non-digitalis positive inotropic drugs

Considerable effort and resources have been directed at the development and study of positive inotropic drugs over the past 10-15 years. Much has been learned about the physiology and pharmacology of myocardial contraction, the application of agents to augment contractility, and, importantly, the general and specific limitations of positive inotropic therapy. Studies on acute inotropic intervention have now shown that a drug's ability to augment overall cardiac performance is heavily dependent on its effects on vasculature, vascular control, and ventricular-vascular coupling. The clinical research on new agents has served to remind us how difficult it is to formulate the "ideal" positive inotropic or cardiovascular support drug for the critical care setting. The vast effort to develop a chronically and orally administrable drug to replace or even supplement digitalis has generally been disappointing. The dopaminergic agents (e.g., ibopamine, levodopa) act primarily via vasodilation and their effectiveness and role in managing heart failure remain unresolved. The initial excitement about the phosphodiesterase III inhibitors (e.g., amrinone, milrinone, enoximone) has been tempered by the results of large well-designed trials indicating variable effectiveness and a prominent adverse effect profile. During long-term oral administration none of these agents has been shown to improve clinical status or exercise capacity beyond that achieved by digoxin, when administered either separately or in combination with digoxin. The Prospective Randomized Milrinone Survival Evaluation (PROMISE) trial, showing that repeated oral administration of milrinone can increase mortality in heart failure, is having a devastating effect on the further development of this class of drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute positive inotropic intervention: the phosphodiesterase inhibitors

Phosphodiesterase inhibitors that are selective for cAMP-specific cardiac and vascular PDE III comprise a new group of agents for the treatment of heart failure, which at present are limited to clinical shortterm intravenous use and research uses only. Although both intravenous amrinone and milrinone are FDA approved, only amrinone is available for general clinical use. Selective phosphodiesterase inhibition produces beneficial actions of positive inotropy and peripheral vasodilation that result from increased cardiac and vascular muscle concentrations of intracellular cAMP and ionic calcium. In addition, a positive lusitropic action (enhancement of cardiac relaxation) has been observed. Neither beta-adrenergic agonist activity nor inhibition of the sodium-potassium ATPase is produced by these agents. The magnitude of hemodynamic improvement generally exceeds that of the cardiac glycosides and is comparable with that of intravenous catecholamines such as dobutamine. The different pharmacodynamic profile of the PDE inhibitors is additive to the effects of cardiac glycosides, complementary and synergistic to the actions of catecholamines, and has been shown to have favorable effects on coronary hemodynamics. As a result there is continued enthusiasm for the short-term intravenous use of amrinone and potentially milrinone in the setting of acute heart failure resulting from systolic dysfunction (after myocardial infarction, open heart surgery, or infectious or toxic myocarditis), heart failure resulting from right ventricular systolic dysfunction, and when patients with severe heart failure await cardiac transplantation. Initiation of treatment with an intravenous bolus followed by a maintenance infusion provides prompt increases in stroke volume and cardiac output and simultaneous reductions in right and left ventricular filling pressures and systemic vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive assessment of the inodilator action of amrinone in healthy man

The effects of a single dose of 2 mg/kg amrinone (60 min constant rate IV infusion) have been assessed in a double-blind, placebo-controlled, within-subject cross-over study in six healthy volunteers. Combined impedance cardiography, phonocardiography and electrocardiography revealed a protracted drop in mean ventricular ejection time and electromechanical systole together, with a protracted rise in the "contractility" indices dZ/dtmax and the Heather index HI. The profile is compatible with combined venous vasodilation and positive inotropic action. In spite of the methodological constraints, endpoints were reached that were both detectable and relevant. The profiling permitted a better distinction to be made between the possible levels of action than systolic time intervals alone could have done. Therefore, these methods may be of value in the early development of "inodilator" drugs.

Haemodynamic profile of an inhibitor of phosphodiesterase III, adibendan (BM 14.478): comparison with nitroprusside and dobutamine in conscious dogs

1. This study was performed to investigate whether cardiac positive inotropic as well as peripheral vasodilator properties of adibendan contribute to its overall haemodynamic profile in conscious dogs. 2. Haemodynamic measurements were carried out in conscious chronically instrumented dogs after administration of adibendan, sodium nitroprusside or dobutamine. 3. The cardiovascular changes induced by adibendan (0.01 and 0.03 mg kg-1) resembled those of dobutamine (1.0-4.0 micrograms kg-1 min-1): left ventricular dP/dt60 (LV dP/dt60), stroke volume (SV) and cardiac output (CO) increased to a similar extent, but mean arterial pressure (MAP) and heart rate (HR) remained unchanged. 4. In contrast to dobutamine, higher doses of adibendan (0.1-1.0 mg kg-1) decreased MAP and LVEDP. These effects were of a similar magnitude to those observed following nitroprusside administration (0.5-12.5 micrograms kg-1 min-1). In contrast to nitroprusside, adibendan still showed additional effects on LV dP/dt60 and CO. 5. From these results, it is concluded that both the peripheral vasodilator and the cardiac positive inotropic action of adibendan contribute to its overall haemodynamic profile.

Enoximone: true inotropic effects? Do they cause ischemia? Analysis of end-systolic pressure-volume relations using the conductance (volume) catheter technique

True positive inotropy of enoximone is hard to prove clinically. It could increase the risk of myocardial ischemia when used in coronary artery disease (CAD). The analysis of the end-systolic pressure-volume relationship (ESPVR) as a load-independent parameter of the contractile left ventricular function (LVF) allows for differentiation of enoximone's unloading effects. Therefore, we analyzed ESPVR and LVF in 12 of 18 CAD patients before and after enoximone, 0.75 mg/kg intravenously. The slope k increased (seven patients) and loops of the ESPVR (12 patients) moved leftward with the enoximone an average of 32% and downward 19%, in the diastolic portion. The delta percent changes in enoximone versus control (18 patients) indicated an improved LVF via load changes: LV filling pressure fell by 50% and end-systolic volume by 28%, while dp/dt max rose by 25%, LV work by 10%, and ejection fraction by 11%. Lastly, the pacing-induced myocardial ischemia threshold increased from an average of 58 +/- 18 sec to 89 +/- 12 sec after eximone, while ischemic postpacing LV filling pressure and ST-segment changes normalized under the drug's influence. Thus, enoximone improved LVF, both by unloading and by true positive inotropy. Lack of enoximone-induced angina and an increased anginal threshold indicate that the drug can be used safely in CAD patients as well.

Pressure-volume analysis as a method for quantifying simultaneous drug (amrinone) effects on arterial load and contractile state in vivo

Pressure-volume relation analysis was used to independently quantify changes in ventricular contractile performance and vascular loading in intact anesthetized dogs before and after a single bolus of intravenous amrinone. Ventricular systolic property changes were characterized by the end-systolic elastance (Ees = slope of the end-systolic pressure-volume relation) and arterial properties by the effective arterial elastance (Ea = end-systolic pressure/stroke volume ratio). Pressure-volume data were obtained by the conductance catheter technique with loading varied by transient inferior vena cava occlusion. Amrinone induced a 27% increase in ejection fraction at 10 min (from 44% to 56%) as a result of both a significant rise in contractility (mean Ees 4 +/- 2 to 6 +/- 3 mm Hg/ml, p less than 0.001) and simultaneous reduction in arterial loading (Ea reduction from 6 +/- 2 mm Hg/ml to 5 mm Hg/ml, p less than 0.001). Over the subsequent 30 min, Ea revealed a significant recovery toward baseline, whereas Ees was less altered. Mean percent changes (% delta) in both variables were linearly correlated: % delta Ea = -1.6 x % delta Ees + 3.1, r = 0.96, p less than 0.001. In addition to separating ventricular from vascular property changes, the pressure-volume coupling framework was used to predict net pump performance (ejection fraction). Model predictions showed good agreement with experimental data. Thus, pressure-volume relations can be used to separately quantitate simultaneous changes in ventricular and vascular loading properties in vivo produced by pharmacologic agents with complex actions. Use of this approach in drug testing in humans should simplify data interpretation regarding mechanisms of action in specific clinical settings.

Amrinone: is it the inotrope of choice?

In the treatment of acute heart failure, conventional therapy with epinephrine, norepinephrine, dopamine, and dobutamine may be used effectively to treat inotropic abnormalities. However, the addition of a vasodilator to catecholamine therapy may be needed to help improve lusitropic function. Because it seems to exert positive inotropic and lusitropic effects, the phosphodiesterase inhibitor amrinone may be a valuable addition to the anesthesiologist's armamentarium for the treatment of acute heart failure. When used as adjunctive therapy with catecholamines, amrinone has been shown to exert a significant additive and synergistic effect. Amrinone may also be the inotrope of choice in patients who are refractory to therapy with conventional inotropes, due to its positive inotropic and lusitropic effects, combined with its vasodilating effects. Because of its broad pharmacodynamic spectrum, amrinone may effectively control all of the major elements involved in myocardial performance--preload, afterload, contractility, and heart rate.

Cardiovascular effects of forskolin and phosphodiesterase-III inhibitors

In the first part of this presentation, data is reported on the hemodynamic effects of forskolin given to patients with dilated cardiomyopathy in a concentration of 3 micrograms/kg/min and 4 micrograms/kg/min. At the lower dosage, forskolin had no effect on dP/dtmax, cardiac index, ejection fraction, or myocardial oxygen consumption. With small dosages of dobutamine, however, an increase of all four parameters has been observed in the same group of patients. Systemic vascular resistance and left ventricular enddiastolic pressure fell with forskolin given at the lower concentration. Forskolin administered at a dosage of 4 micrograms/kg/min induced an increase in dP/dtmax by 19% and a 16% rise in heart rate. However, these changes were associated with symptomatic flush syndromes. Therefore, forskolin may serve as a vasodilating substance in lower concentrations, but cannot be used as a positive inotropic compound because of the subjective symptoms. In the second part, a study is reported in which an anti-ischemic effect of the phosphodiesterase inhibitor enoximone was observed in patients with proven significant coronary heart disease. With respect to the hemodynamic parameters, the most striking findings were the decreases in left ventricular enddiastolic pressure and systemic vascular resistance. Furthermore, when left ventricular stroke work index was plotted as a function of the left ventricular enddiastolic pressure, enoximone shifted the left ventricular function curve to the left. Therefore, the anti-ischemic effect of enoximone may not only be due to a reduction in preload and afterload but may rather reflect an effect on diastolic compliance. Studies with intracoronary injections of enoximone and animal experiments support this hypothesis.

Historical perspectives and update of amrinone

The pathophysiological understanding and management of acute and chronic heart failure have changed dramatically in the past decade. Since the early 1980s, a major effort has been made to develop nonglycosidic, noncatecholamine agents that combine inotropic and vasodilating properties, in order to treat myocardial dysfunction unresponsive to current therapy. Within this context, increasing attention has been paid to the role of intracellular cyclic adenosine monophosphate (cAMP) in myocardial contractility. The pharmacologic use of catecholamines to stimulate beta-receptors activates adenylate cyclase, which in turn leads to an increase in intracellular levels of cAMP. In addition, phosphodiesterase 3 (PDE 3) inhibition may prevent the degradation of cAMP, thus maintaining high intracellular levels of the substance. Intravenous amrinone has been shown clinically to improve hemodynamic status remarkably in the patient experiencing a low cardiac output syndrome, by increasing CO while decreasing filling pressures and pulmonary arterial pressures, without increasing myocardial O2 demand. This report will review several studies of different types of patients and explain the effects of amrinone alone and in combination with the more traditionally used catecholamines. It must be stressed that amrinone, in spite of its dual action of inotropy and vasodilation, should not be considered a rival to catecholamines but rather an enhancer of them, which clinicians should consider using in the early stages of therapy in many different settings.

Hemodynamic, antiischemic, and neurohumoral effects of enoximone in patients with coronary artery disease

To evaluate the risk of ischemia in 17 patients with significant coronary artery disease, the influence of enoximone was analyzed under the following conditions: (1) at rest (RC) and during exercise (ExC) under control conditions and (2) at rest (RE) and during exercise (ExE) after administration of enoximone (0.75 mg/kg, intravenously). During ExC all patients had ischemia (angina, and ST segment alterations); metabolic markers of ischemia (MMI) increased, as did the mean pulmonary artery pressure, from 19 to 41 mm Hg. However, during ExE ischemia was abolished (no angina, decrease in mean pulmonary artery pressure to 24 mm Hg, and improvement in MMI) and there was some improvement in left ventricular pump function, whereas pre- and afterload decreased (pulmonary artery pressure by 40%, systemic vascular resistance by 10%), and heart rate, arterial pressure, and myocardial oxygen consumption (MVO2) were all unchanged (p greater than 0.05). Comparative hemodynamics at RE vs RC showed a decrease in pulmonary artery pressure (by 25%) and pulmonary vascular resistance (by 19%) and an increase in heart rate (by 11%), whereas arterial pressure and MVO2 were unchanged (p greater than 0.05). Enoximone did not induce changes in plasma catecholamine, prostaglandin, or thromboxane levels (p greater than 0.05), whereas the atrial natriuretic factor decreased (by 15%), probably because of unloading of the atria during exercise. We concluded that enoximone induces beneficial hemodynamic effects in coronary artery disease without causing ischemia, probably by enhancing myocardial contractility, vasodilation, and improved diastolic properties.

Effect of oral milrinone on end-systolic relations in patients with severe congestive heart failure

The new inotropic agent milrinone has both vasodilator and inotropic cardiovascular effects, but the importance of these effects in patients with severe congestive heart failure (CHF) is controversial. The left ventricular (LV) end-systolic pressure-diameter relation was used to determine the independent inotropic effect of milrinone. Seven patients with New York Heart Association class III CHF were invasively monitored with right-sided heart catheters and radial arterial lines. M-mode echocardiography was used to measure LV dimensions. The effect of a 10-mg oral dose of milrinone on hemodynamic, echocardiographic and end-systolic variables was determined. End-systolic pressure was measured at the dicrotic notch of the arterial pressure tracing and end-systolic LV dimensions at the time of aortic valve closure. Methoxamine (n = 6) or nitroprusside (n = 1) was used to alter afterload so that the end-systolic pressure-diameter relation could be determined. Arterial vasodilation from milrinone was evidenced by a decrease in mean arterial blood pressure (88 +/- 5 to 77 +/- 2 mm Hg, p less than 0.025) and an increase in cardiac index (from 2.7 +/- 0.2 to 3.2 +/- 0.2 liters/min/m2, p less than 0.025), with no change in heart rate (80 +/- 5 beats/min). Milrinone decreased preload as assessed by the pulmonary artery wedge pressure (from 17 +/- 2 to 10 +/- 2 mm Hg, p less than 0.01) and end-diastolic LV diameter (from 7.4 +/- 0.4 to 7.0 +/- 0.4 cm, p less than 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)

Combined hemodynamic and scintigraphic assessment of piroximone (MDL 19,205) and comparison with dobutamine and nitroprusside

The acute hemodynamic responses to intravenous infusion of piroximone (MDL 19,205), a nonglycoside, noncatecholamine agent with positive inotropic activity in vitro, were compared with those of intravenous dobutamine and sodium nitroprusside, respectively, in 2 groups of patients with New York Heart Association class III or IV symptoms. Each drug was titrated to optimal dosage (dobutamine, 12.5 +/- 3.9 micrograms/kg/min; nitroprusside, 2.5 +/- 0.6 micrograms/kg/min; piroximone 1.4 +/- 0.6 mg/kg) and simultaneous hemodynamic and scintigraphic values were measured. In group 1, the increase in cardiac index was slightly greater with piroximone than with dobutamine (from 1.6 +/- 0.5 to 2.7 +/- 0.6 vs 2.4 +/- 0.6 liters/min/m2, p less than 0.025) and only piroximone significantly decreased left ventricular (LV) filling pressure (from 29 +/- 7 to 22 +/- 8 mm Hg, p less than 0.05). Both agents increased heart rate and systolic blood pressure. In group 2, cardiac index increased similarly with nitroprusside and piroximone (1.5 +/- 0.6 to 2.6 +/- 0.8 and 1.6 +/- 0.5 to 2.6 +/- 0.5 liters/min/m2, difference not significant), whereas LV filling pressure decreased slightly less with piroximone (29 +/- 7 to 24 +/- 10 vs 30 +/- 7 to 20 +/- 11 mm Hg, difference not significant). Only nitroprusside reduced mean arterial pressure (88 +/- 13 to 72 +/- 12 mm Hg, p less than 0.001 between drugs). In group 1, systolic blood pressure to end-systolic volume ratio increased in 9 of 10 patients taking both piroximone and dobutamine, whereas in group 2, this ratio increased in 7 of 8 patients taking piroximone and declined in 7 of 8 taking nitroprusside.(ABSTRACT TRUNCATED AT 250 WORDS)

The rational selection of inotropic drugs in cardiac surgery

Despite improvements in surgical technique and intraoperative myocardial protection, certain patients have need for inotropic drug support after cardiac surgery. This review examines drugs that are currently in use for inotropic support of the heart, including calcium, epinephrine, dopamine, dobutamine, isoproterenol, and amrinone. Patient factors that may have an impact on the selection of appropriate drugs are also examined. Application of these data to specific patients must be guided by the particular hemodynamic derangements present. Careful analysis of the specific hemodynamic disorder and tailoring of inotropic therapy to these abnormalities are crucial. Such a rational approach to the selection of inotropic agents requires continuous hemodynamic assessment and recognition that the patient's condition and needs may change rapidly early after heart surgery dictating adjustment of subsequent therapy.

Inotropic effect of enoximone in patients with severe heart failure: demonstration by left ventricular end-systolic pressure-volume analysis

Left ventricular end-systolic pressure-volume analysis was employed to assess the inotropic effect of the phosphodiesterase inhibitor enoximone (formerly MDL-17,043) in nine patients with severe heart failure (New York Heart Association class IV symptoms, mean ejection fraction = 0.22). Left ventricular pressure-volume loops were constructed using high fidelity left ventricular pressure measured with micromanometer-tipped catheters and simultaneous left ventricular volume obtained by gated blood pool imaging. Afterload was reduced with the vasodilator nitroprusside to generate the baseline left ventricular end-systolic pressure-volume relation, a relatively load-independent measure of contractile function. The intravenous administration of enoximone (mean dose 75 mg) shifted the end-systolic pressure-volume point upward and leftward from the baseline pressure-volume relation in eight of the nine patients, demonstrating a positive inotropic effect of this agent. The maximal rate of left ventricular pressure development (peak positive dP/dt) increased from 1,030 +/- 142 to 1,381 +/- 219 mm Hg/s (p less than 0.01) on enoximone despite a significant decrease in preload (as assessed by left ventricular end-diastolic pressure and volume) and a small, insignificant decrease in mean arterial pressure. Two patients developed angina after enoximone administration; both patients had coronary artery disease and experienced a greater than 30% increase in heart rate-systolic blood pressure product. Thus, enoximone has a significant inotropic effect in patients with severe heart failure. Like other inotropic drugs, it has the potential to increase myocardial oxygen demand and thereby precipitate ischemia.

[Hemodynamic effects of intravenous perfusion of amrinone in increasing doses in 12 patients with severe heart decompensation]

Twelve patients with severe heart failure were given amrinone by intravenous infusion in doses rising from 1 to 2, 3 and 4 mg X min-1, the interval between each dose being 30 min. The total cumulative dose was 300 mg over 120 min. Haemodynamic measurements were started the day before treatment to take into account nycthemeral fluctuations in haemodynamics and the possible effects of maintenance treatments and meals, all factors which might influence the baseline values. When given at a rate of more than 2 mg X min-1, amrinone significantly improved cardiac function (p less than 0.001). The mean pulmonary capillary pressure fell from 24.1 +/- 5.3 to 13.7 +/- 8.6 mmHg, and the cardiac index rose from 1.75 +/- 0.40 to 2.51 +/- 0.32 1 X min-1 X m-2. Heart rate and blood pressure were not significantly modified. No adverse reaction was observed during the infusion and the following 24 hours. Thus, intravenous amrinone proved effective in patients with severe heart failure, with maximal effects being obtained in doses of 3 mg X min-1.

Comparative study of cardiovascular profiles of milrinone and amrinone by use of isolated, blood-perfused dog heart preparations

The cardiac and coronary vasodilator effects of milrinone and amrinone were compared in isolated, blood-perfused papillary muscle and sinoatrial (SA) node and atrioventricular (AV) node preparations of dogs. Milrinone (0.3-100 nmol) and amrinone (0.01-3 mumol) were administered intra-arterially. Both drugs increased the force of contraction of paced and unpaced papillary muscles and the rate of automaticity of the latter; they increased sinus rate and accelerated AV nodal conduction. However, both drugs were not homogeneously effective on cardiac variables but affected them in the following order: The force of contraction of the ventricular muscle greater than SA nodal automaticity divided by AV nodal conduction greater than ventricular automaticity. In producing these cardiac effects, milrinone was 30-60 times more potent than amrinone. Both drugs increased (coronary) blood flow in all preparations. In this respect milrinone was about ten times more potent than amrinone. As a result, milrinone can be characterized as having almost equal cardiotonic and coronary vasodilatory effects, whereas amrinone is more coronary vasodilatory than cardiotonic. These differences in cardiovascular profile may contribute to their differential salutary mechanisms in the treatment of heart failure. Both drugs induced neither AV nodal tachycardia nor ventricular arrhythmia.

The positive inotropic response to milrinone in isolated human and guinea pig myocardium

The bipyridine derivative, milrinone, produced positive inotropic effects in isolated, contracting right ventricular papillary muscles and left atria from guinea pigs as well as in human papillary muscle strips. The inotropic effect was biphasic in guinea pig papillary muscles (EC50, high affinity, 1.5 X 10(-6) mol/l, about 35% of maximal effect; apparent EC50, 3 X 10(-5) mol/l with a maximal effect at 2 X 10(-4) mol/l) but monophasic in guinea pig left atria (EC50, 6 X 10(-5) mol/l) and in human papillary muscle strips (EC50, 5.8 X 10(-5) mol/l). In guinea pig papillary muscles, reserpine pretreatment or l-practolol preincubation reduced the low concentration effect only. In the presence of l-practolol, carbachol reduced the low concentration effect only. In the presence of l-practolol, carbachol reduced but not abolished the inotropic effects of milrinone (3 X 10(-6) mol/l, 1 X 10(-4) mol/l) in both guinea pig and human myocardium. This antagonism was prevented by atropine preincubation. The maximum inotropic effect of milrinone was similar to that of ouabain and calcium in guinea pig myocardium but markedly less than either calcium or ouabain in human myocardium. Milrinone inhibited crude guinea pig and human cardiac phosphodiesterase activity in vitro but did not inhibit 3H-ouabain binding to partially purified human cardiac (Na+ + K+)-ATPase-containing membranes. We conclude that the primary mode of action of milrinone in both guinea pig and human myocardium is through inhibition of phosphodiesterase.(ABSTRACT TRUNCATED AT 250 WORDS)

Additive effects of dobutamine and amrinone on myocardial contractility and ventricular performance in patients with severe heart failure

The effects of amrinone, dobutamine, and a combination of the two drugs on peak positive left ventricular dP/dt and left ventricular performance were evaluated in 11 patients with chronic congestive heart failure. When administered alone, both dobutamine (10.9 micrograms/kg/min) and intravenous amrinone (1.9 mg/kg/min) significantly increased left ventricular dP/dt and performance. When compared with dobutamine alone, the addition of amrinone resulted in further increases in left ventricular dP/dt and cardiac index (to 1319 +/- 419 from 1202 +/- 376 mm Hg/sec, p less than .002, and to 3.56 +/- 0.78 from 3.04 +/- 0.67 liters/min/m2, p less than .01, respectively). The combination also induced a further reduction in left ventricular end-diastolic pressure (to 15.3 +/- 11.3 from 18.2 +/- 10.3 mm Hg, p less than .05) when compared with amrinone alone. The combination of dobutamine and amrinone increased heart rate slightly when compared with either drug alone, but did not further reduce systemic arterial pressure when compared with amrinone alone. The dose-response curve of left ventricular dP/dt and performance during titration of dobutamine with and without the addition of intravenous amrinone was evaluated in seven patients. The addition of amrinone to any dose of dobutamine produced higher cardiac index and lower systemic vascular resistance than dobutamine or amrinone alone. Thus, when compared with dobutamine alone in patients with chronic congestive heart failure, the addition of intravenous amrinone to dobutamine results in an additive improvement in left ventricular performance throughout the dose range.

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.

Evaluation of intravenous amrinone: the first of a new class of positive inotropic agents with vasodilator properties

Amrinone is the first noncatecholamine inotropic agent with substantial vasodilating properties to be approved by the Food and Drug Administration. Its use in acute congestive heart failure (CHF) is associated with significant increases in cardiac index, reductions in pulmonary capillary wedge pressure and systemic vascular resistance and little or no change in mean arterial pressure. Pharmacokinetic studies of amrinone report an elimination half-life of 2.6-8.3 hours, with slower elimination more likely in patients with compromised renal or hepatic function. Intravenous bolus doses of 0.75-3.5 mg/kg followed by infusions of 5-20 micrograms/kg/min produce hemodynamic improvements similar to those with dobutamine. Side effects with amrinone therapy are usually mild, but thrombocytopenia occurs in 2.4% of patients. Amrinone appears equally as efficacious as dobutamine in the management of acute CHF, but its role in therapy depends on efficacy and side effect data in greater numbers of patients.

Effects of intracoronary and intravenous amrinone infusions in patients with cardiac failure and patients with near normal cardiac function

The effects of intracoronary and intravenous infusions of amrinone were studied to distinguish the drug's direct cardiac actions from its peripheral vascular and neuroendocrine properties. Intracoronary infusions of amrinone were found to have no haemodynamic effect other than producing a slight reduction in the left ventricular ejection fraction and some suggestion of coronary vasodilatation in patients with impaired left ventricular function. They did not improve contractility, cardiac output, or filling pressures and had no significant effect on myocardial metabolism, although therapeutic concentrations of the drug were detected in coronary sinus blood. Intravenously administered amrinone reduced filling pressures and improved the cardiac index in all patients, but haemodynamic improvements were most pronounced in the patients with the worst cardiac function. These changes were accompanied by improvements in the indices of contractility only in patients in whom alterations in concentrations of free fatty acid, glycerol, and glucose suggested peripheral catecholamine release. In the patients with the best basal cardiac function intravenously administered amrinone produced a reduction in myocardial work and evidence of myocardial ischaemia, as a result of excessive reduction of coronary perfusion pressure and increased heart rate, without any appreciable increase in cardiac index. It is concluded that, at the concentrations of the drug that can be achieved in man without adverse effects, amrinone has no direct positive inotropic effect. Haemodynamic changes are predominantly the result of vasodilatation, although catecholamines may be released in some patients.