Newer cardiotonic agents: implications for patients with heart failure and ischemic heart disease

Cardiopulmonary effects of enoximone or dobutamine and nitroglycerin on mitral valve regurgitation and pulmonary venous hypertension

OBJECTIVE

To compare the cardiovascular and pulmonary effects of the phosphodiesterase III inhibitor enoximone (EN) or a combination of dobutamine (DOB) and nitroglycerin (NTG) before and after mitral valve repair or replacement.

DESIGN

Prospective, randomized, controlled clinical study.

SETTING

University hospital.

PARTICIPANTS

Twenty patients with mitral regurgitation and pulmonary venous hypertension scheduled for elective mitral valve surgery.

INTERVENTIONS

Patients fulfilling the inclusion criteria of the study were randomly allocated into a group treated with EN (group 1, n = 10) or DOB and NTG (group 2, n = 10). A cardiopulmonary status was obtained after induction of anesthesia and mechanical ventilation during stable hemodynamic conditions (control). Then the patients received either EN (bolus dose 1.0 mg/kg followed by a continuous infusion of 10 micrograms/kg/min) or DOB (8.0 micrograms/kg/min) and NTG (1.0 microgram/kg/min) according to the randomization. After a period of 20 minutes, all parameters were measured again. The study drugs were stopped, and cardiac surgery was performed. Infusions of EN (without additional loading dose) or DOB and NTG were started again in the above-described doses 10 minutes before separation from cardiopulmonary bypass (CPB). Respiratory and hemodynamic measurements were made 20 minutes after weaning from CPB and 60 minutes after admission of the patient to the intensive care unit.

MEASUREMENTS AND MAIN RESULTS

Both groups were comparable regarding preoperative and control data. Before mitral valve surgery, cardiac output (CO) and heart rate (HR) increased by 46% (p < 0.05) and 31% (p < 0.01) during infusion of EN with minor changes of mean systemic arterial pressure (PSA) and gas exchange. Mean pulmonary arterial pressure (PPA) decreased from 32 +/- 11 mmHg to 23 +/- 11 mmHg (p < 0.05). Similar alterations were observed in group 2 (delta CO + 26%, p < 0.05, delta HR + 39%, p < 0.01); however, PPA and calculated pulmonary vascular resistance remained unchanged. After separation from CPB, EN and DOB-NTG achieved comparable effects on CO, HR, and PSA, but PPA was significantly lower in group 1. In addition, venous admixture and alveolo-arterial oxygen tension gradient were lower in EN-treated patients.

CONCLUSION

Enoximone or DOB and NTG have comparable effects on CO, PSA, and HR in mitral regurgitation and pulmonary hypertension, but EN is more effective in reducing PPA without deterioration of gas exchange.

Refractory Heart Failure: A Therapeutic Approach

Optimal “triple therapy” for patients with chronic congestive heart failure (CHF) includes diuretics, digoxin, and either angiotensin-converting enzyme inhibitors or hydralazine plus nitrates. Refractory CHF is defined as symptoms of CHF at rest or repeated exacerbations of CHF despite “optimal” triple-drug therapy. Most patients with refractory CHF require hemodynamic monitoring and treatment in the intensive care unit. If easily reversible causes of refractory CHF cannot be identified, then more aggressive medical and surgical interventions are necessary. The primary goal of intervention is to improve hemodynamics to palliate CHF symptoms and signs (i.e., dyspnea, fatigue, edema). Secondary goals include improved vital organ and tissue perfusion, discharge from the intensive care unit, and, in appropriate patients, bridge to cardiac transplantation. Medical interventions include inotropic resuscitation (e.g., adrenergic agents, phosphodiesterase inhibitors, allied nonglycoside inodilators), load resuscitation (e.g., afterload and preload reduction with nitroprusside or nitroglycerin; preload reduction with diuretics and diuretic facilitators, such as dopaminergic agents or ultrafiltration), and electrical resuscitation (e.g., prevention of sudden death, correction of new or rapid atrial fibrillation, or dual chamber pacing in the setting of relative prolongation of the PR interval and diastolic mitral/tricuspid regurgitation). Surgical interventions are temporizing (e.g., intra-aortic balloon pump and other mechanical assist devices) or definitive (e.g., coronary artery revascularization, valvular surgery, and cardiac transplantation). Although these interventions may improve immediate survival in the short term, only coronary artery revascularization and cardiac transplantation have been shown to improve long-term survival.

Comparative vasoactive effects of amrinone on systemic and pulmonary arteries in rabbits

Amrinone has been increasingly used in management of low cardiac output syndrome during anesthesia, particularly when associated with right heart failure and pulmonary hypertension. This in vitro study was performed to determine and compare the direct vasoactive effects of amrinone on isolated rabbit systemic and pulmonary arteries. Responses of aortic and pulmonary artery rings from New Zealand white rabbits were assessed in the presence and absence of intact endothelium and with or without precontraction by norepinephrine (NE, 3 x 10(-6)M) or potassium chloride (KCl, 3 x 10(-2)M). Using a tissue bath preparation, cumulative concentration response curves of amrinone were obtained at different concentrations after a period of stabilization. Amrinone caused a dose-related vasodilation of NE-precontracted aortic and pulmonary arteries. It elicited about 65% and 90% relaxation, respectively, at a concentration of 300 mumol/L. Amrinone also induced a dose-related vasodilation of KCl-precontracted aortic and pulmonary arteries but to a lesser degree. All these effects were endothelium independent. By comparison, amrinone caused more relaxation in both NE- and KCl-precontracted pulmonary artery than aortic rings. In conclusion, amrinone has significant endothelium-independent, direct vasodilatory effects on isolated rabbit systemic and pulmonary arteries, more pronounced in the latter, particularly NE-precontracted vessels. Amrinone may have some calcium channel-blocking effect.

Amrinone loading during cardiopulmonary bypass in neonates, infants, and children

OBJECTIVES

To determine whether amrinone is bound to cardiopulmonary bypass circuits. When amrinone is administered to children during cardiopulmonary bypass, determine whether measured amrinone concentrations differ from those predicted based on a reported volume of distribution of 1.6 L/kg.

DESIGN

In vitro study: Uptake of amrinone by cardiopulmonary bypass circuits was determined. Clinical study: Prospective, open label investigation.

SETTING

University-affiliated tertiary children's hospital.

PARTICIPANTS

Clinical study: 27 children participated, including 5 neonates and 9 infants.

INTERVENTIONS

In vitro study: Waste blood was circulated within seven pediatric cardiopulmonary circuits. Amrinone was administered, and blood was serially assayed for amrinone levels. Clinical study: Amrinone (mean dose 4.9 mg/kg) was loaded during cardiopulmonary bypass and amrinone concentrations in pump blood were determined at termination of bypass. Amrinone measured by high-performance liquid chromatography.

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary bypass circuit uptake reduced amrinone concentrations to 79% of predicted. After correcting for circuit uptake, serum amrinone levels in patients were significantly higher than predicted. The levels, expressed in the ratio of measured: predicted amrinone concentration, did not differ among neonates, infants, and children older than 1 year of age.

CONCLUSIONS

When amrinone is administered to children during cardiopulmonary bypass, about 20% of the dose becomes bound to the circuit. Available drug is distributed within a smaller volume than predicted. This may be the consequence of the physiologic perturbations of hypothermic cardiopulmonary bypass.

Haemodynamic effects of R 80122 immediately after cardiopulmonary bypass; preliminary results

R 80122 is a new short-acting phosphodiesterase type III inhibitor. In a preliminary investigation, three patients, scheduled for coronary artery bypass surgery, were given R 80122 after weaning from cardiopulmonary bypass. Two patients received 10 micrograms.kg-1.min-1 for 10 min as a loading infusion followed by a 5 micrograms.kg-1.min-1 maintenance dose. One patient received a 20 micrograms.kg-1.min-1 for 10 min loading infusion followed by a 10 micrograms.kg-1.min-1 maintenance infusion. After weaning from cardiopulmonary bypass and during the administration period, no arrhythmias or cardiac ischaemia were detected. The administration of R 80122 improved the haemodynamic profile with an increase in cardiac output, a decrease in systemic vascular resistance and a stable heart rate and mean arterial blood pressure. These preliminary results indicate that R 80122 possesses positive inotropic activity in combination with vasodilating properties.

Hemodynamic effects of amrinone and colloid administration in children following cardiac surgery

Amrinone was used as the sole vasoactive medication in 9 of 14 children (aged 5 months to 8.25 years) given the drug following open repair of congenital cardiac lesions. Four children received a concomitant dopamine infusion and one infant had the infusion stopped after 5 hours for low mean arterial pressure (49 mmHg). In the 10 children receiving only amrinone, cardiac index increased 21% (range, 0 to 94%) after a total loading dose of 4.5 mg/kg given over 1 hour. Four of 14 patients (29%) required dopamine infusions to maintain mean arterial pressure over 55 mmHg and in these children cardiac index increased from baseline and was maintained during the amrinone infusion. Preload was held constant by administration of whole blood or plasmanate during amrinone loading; a decrease in systemic vascular resistance index was seen resulting in a stable arterial blood pressure. Minimal chronotropic effect was seen and no arrhythmias occurred. The sole child with postoperative pulmonary hypertension had a beneficial decrease in pulmonary artery pressure, increase in cardiac index, and stable systemic blood pressure during amrinone use. Cardiac index changes during amrinone loading in these children were variable and less clearly related to serum levels than reported in adults. Pharmacokinetic analysis in 12 children showed a clearance of 3.4 mL/min/kg, a volume of distribution of 1.65 L/kg, and an elimination half-life of 5.75 hours. Decreases in platelet counts were seen in 6 children and platelet transfusion was needed in 1; thus, serial platelet counts should be monitored.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulatory effects of the PDE-inhibitors piroximone and enoximone

1. The isolated circulatory response to intravenous application of the phosphodiesterase (PDE) inhibitors piroximone and enoximone was studied. 2. In a randomized sequence of 30 male patients undergoing elective aortocoronary bypass grafting either piroximone (0.5 mg kg(-1); n = 10) or enoximone (0.5 mg kg(-1); n = 10) were given during steady state of cardiopulmonary bypass (CPB). A group in which NaCl was given as a placebo served as a control (n = 10). 3. MAP was reduced by piroximone (maximum -23 mm Hg) and enoximone (maximum -18 mm Hg), whereas it increased in the control (+20 mm Hg). Volume of the extracorporeal circuit indicating venous pooling decreased more pronouncedly in the enoximone patients (-440 ml) than in the piroximone group (-300 ml). 4. Laser Doppler flows (LDFs) increased in both PDE-III inhibitor groups with the higher and longer increase in the enoximone-treated patients (LDF-forehead maximum +44%, LDF-forearm maximum +33%). Piroximone-induced increase in both LDFs was less pronounced with respect to both time and degree (LDF-forehead maximum +30%, LDF-forearm +12%). 5. Oxygen consumption (VO2) was significantly higher in the PDE-III inhibitor-treated than in the control patients. 6. Piroximone and enoximone showed significant vasodilatory properties at the arterial and venous side (= 'venous pooling'), from which patients with heart failure would profit. 7. Vasodilation could be observed for a longer period and was more pronounced in the enoximone-treated than in the piroximone patients. Alterations in capillary skin blood flow measured by laser Doppler technique gave evidence for an improvement in nutritive microcirculation, which was slightly more pronounced in the enoximone patients.

Interaction between inhalational anaesthetics and enoximone on isolated heart muscle

1. The present study describes the effects of halothane or isoflurane on enoximone activity in the isolated left atria of the rat. 2. Concentration-response curves were obtained for the positive inotropic effects of enoximone on electrically stimulated left atria. 3. Enoximone significantly (P < 0.01) increased the contractile force (56% maximum) with all the concentrations tested (10(-9) -10(-3) M). 4. When halothane (1.5% v/v) was present in the organ bath, the maximum effect obtained with enoximone (9%) was significantly lower than that obtained with enoximone alone. 5. Similar results were obtained with enoximone in the presence of halothane plus diltiazem. Isoflurane (1.5% v/v) did not significantly modify the maximum effect obtained with enoximone alone. 6. The administration of diltiazem antagonized the positive inotropic effects of enoximone in the presence of isoflurane or halothane. 7. These results shows that halothane, but not isoflurane, decreased the potency of enoximone on the isolated left atria and suggests that this effect may be mediated by the blocking of the influx of extracellular calcium through voltage-dependent calcium channels inhibited by diltiazem.

Phosphodiesterase-inhibitors enoximone and piroximone in cardiac surgery: influence on platelet count and function

OBJECTIVE

Some phosphodiesterase (PDE)-inhibitors are believed to alter platelet count and function due to changes in intracellular cAMP. Whether newly developed (specific) PDE-inhibitors negatively influence platelet function in cardiac surgery should be investigated in a randomized study.

METHODS

Eighty patients undergoing aorto-coronary bypass grafting were divided into 4 groups and received either the new PDE-III-inhibitor piroximone (group 1), the PDE-III-inhibitor enoximone (group 2), epinephrine (group 3) or no inotropic support (control). PDE-III-inhibitors were given as a bolus followed by infusion until starting of cardiopulmonary bypass (CPB). In addition to platelet count and a thrombelastogram, platelet function was assessed by aggregometry (ADP, epinephrine, collagen). Measurements were done before, during and after CPB until the 1st postoperative day.

RESULTS

Platelet count and postoperative blood loss did not differ between the groups within the entire investigation period. Maximum aggregation and maximum gradient of platelet aggregation to all stimuli were not changed by either PDE-inhibitor enoximone or piroximone. CPB resulted in a significant decrease of all aggregation variables which was without differences due to treatment. Platelet aggregation recovered in the post-bypass period and exceeded baseline values on the 1st postoperative day.

CONCLUSION

It is concluded that enoximone and the new PDE-III-inhibitor piroximone do not affect platelet function and can be used before CPB without risking platelet-related bleeding in cardiosurgical patients in the perioperative period.

Enoximone treatment of impaired myocardial function during cardiac surgery: combined effects with epinephrine

Enoximone belongs to a new class of noncatecholamine-positive inotropes, which selectively inhibit phosphodiesterase type III and increase cyclic AMP (cAMP). This study was performed in 30 coronary artery surgery patients with impaired myocardial function (ejection fraction [EF] less than 50%). The study's two purposes were to investigate the hemodynamic effects of enoximone, 0.5 mg/kg, administered following induction of anesthesia (phase I), and to assess whether enoximone can potentiate the actions of sympathomimetic agents during weaning from cardiopulmonary bypass (CPB) (phase II). Starting with already reduced hemodynamics, induction of anesthesia led to a further deterioration of blood pressure and cardiac output (CO). Administration of enoximone produced a significant increase in cardiac index (CI) (+47%), whereas pulmonary capillary wedge pressure (PCWP) (-37%), pulmonary artery pressure (PAP) (-17%), and systemic vascular resistance (SVR) (-17%) were significantly reduced. Heart rate (HR) was not increased, and no dysrhythmias occurred during the investigation. The hemodynamic effects were maintained for 30 minutes until the start of the operation. In phase II, where weaning from CPB was not possible without pharmacological support, either enoximone (0.5 mg/kg) + epinephrine (0.1 micrograms/kg/min) or only epinephrine (same dosage) was randomly selected. Weaning was successful in both groups, but the combined therapy produced a larger increase in cl and a more pronounced decrease of the elevated filling pressure (PCWP). PAP was not changed in the combined therapy group, but increased in the patients receiving epinephrine alone. It is concluded that enoximone has beneficial hemodynamic effects in the perioperative period, and that potentiation of the effects of epinephrine in severe heart failure may be one of the drug's most useful features.

Comparison of dobutamine and enoximone for low output states following cardiac surgery

Low output syndrome sometimes complicates early postoperative states following cardiac surgery. A comparative study of haemodynamic responses to enoximone and dobutamine was carried out in two groups of 20 patients each, during a 24-hour postoperative observation period. Parameters in addition to routine measurements were determined using a pulmonary artery catheter. Enoximone, 1 mg/kg i.v. in total, was given in the first 20 minutes. The infusion was then reduced to 3-20 micrograms/kg/minute for the next 24 hours. Dobutamine was administered in a continuous dose of 5-7 micrograms/kg/minute over the same period. After 15 minutes' therapy with enoximone, cardiac index increased from 2.31 +/- 0.34 litres/minute/m2 to 3.30 +/- 0.38 litres/minute/m2; after 120 minutes to 3.83 +/- 0.60 litres/minute/m2 and after 24 hours to 4.34 +/- 0.50 litres/minute/m2. Pulmonary capillary wedge pressure at the same intervals decreased from 15.21 +/- 1.65 mm Hg initially to 12.11 +/- 2.83, 11.2 +/- 4.50 and 8.77 +/- 2.98 mm Hg. After dobutamine, cardiac index rose from 2.33 +/- 0.60 litres/minute/m2 to 2.90 +/- 0.81 (15 minutes), 3.52 +/- 0.74 (120 minutes) and 4.12 +/- 1.07 litres/minute/m2 (24 hours). The pulmonary wedge pressure values decreased in this group, from 15.20 +/- 3.14 mm Hg at the beginning to 13.74 +/- 3.02 (15 minutes), 12.17 +/- 5.25 (120 minutes) and 9.81 +/- 4.23 mm Hg (24 hours). The enoximone group showed a diminution of systolic arterial pressure of 14% in the first 120 minutes, with a return to initial values after 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

RETRACTED: Efficacy of the phosphodiesterase inhibitor enoximone in complicated cardiac surgery

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the request of the editor. In 2018, CHEST published a notice1 that all articles authored by Joachim Boldt be read with caution due to expressions of concern about falsified data. In 2020, CHEST received additional evidence of research misconduct and breaches of scientific integrity that were discovered following an investigation by the author's former institution, the University of Giessen2. In light of this new evidence, this article has been retracted by CHEST. 1. Irwin, R.S., MD, Master FCCP. Notice From the Editor in Chief. CHEST 153(3), p. 767. 2. Mukherjee, J. Statement on the scientific credibility of articles published by Joachim Boldt, formerly professor at Justus Liebig University (JLU), Giessen, Germany. https://ars.els-cdn.com/content/image/1-s2.0-S000709122030163X-mmc3.pdf.

Comparative effects of enoximone and theophylline on plasma catecholamines and haemodynamics in cardiosurgical patients

The release of endogenous catecholamines in aorto-coronary bypass graft patients receiving either 0.5 mg/kg enoximone (n = 10), 4.0 mg/kg theophylline (n = 10) or saline solution (control, n = 10) has been studied, as well as certain haemodynamic parameters. Adrenaline (A) and noradrenaline (NA) concentrations were not significantly changed by the administration of enoximone. Theophylline caused a small increase in NA (+40% in the 1st min) and a marked increase in A (approximately +7000% in the 1st min), which still remained elevated at the end of the investigation period (+220% in the 30th min). The major haemodynamic effects of enoximone were a significant increase in cardiac index (CI; +35%) and a decrease in pulmonary capillary wedge pressure (PCWP; -27%), pulmonary artery pressure (PAP; -21%), RVEDV and RVESV, while the heart rate (HR) remained almost unchanged. The dominant haemodynamic effects of theophylline were an increase in HR (+26%; arrhythmia in 3 patients), PAP (+22%), and RVEDV (+19%), while RVESV (+26%), MAP (-16%), CI (-14%), and RVEF (-15%) fell significantly. It is concluded that the haemodynamic actions of enoximone are not mediated by catecholamine release, whereas the adverse cardiovascular effects of theophylline might partly be explained by the significant increase in plasma adrenaline.

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.

[Indications for inotropic agents in cardiac surgery]

Inotropic drugs are widely used before, during and after cardiac surgery. Besides the old well known inotropic drugs, new sympathomimetic drugs and phosphodiesterase inhibitors are available. They can be used alone or in combination. The choice of drug is difficult to make and depends, for one part, on the side-effects of each drug. Before surgery, they are required for patients who present with cardiogenic shock while waiting for emergency repair of their lesion. During surgery, inotropic drugs are used before, during and after using cardiopulmonary bypass. After surgery, they are used to treat low cardiac output states. A decision algorithm is suggested, but it is modified by personal clinical experience, aetiological patterns and pharmacological data. Therapeutic doses must be adjusted according to haemodynamic data. Physiological controls are required, such as venous return and heart rate. Mechanical assistance devices must not be forgotten, especially after myocardial reperfusion and weaning from extracorporeal circulation.