Cardiotonic agents in the management of chronic cardiac failure

Role of the Phytochemical Compounds like Modulators in Gut Microbiota and Oxidative Stress

BACKGROUND

Currently, daily consumption of green herb functional food or medicinal herbs has increased as adopted by many people worldwide as a way of life or even as an alternative to the use of synthetic medicines. Phytochemicals, which are a series of compounds of relatively complex structures and restricted distribution in plants, usually perform the defensive functions for plants against insects, bacteria, fungi or other pathogenic factors. A series of studies have found their effectiveness in the treatment or prevention of systemic diseases such as autoimmune diseases, cancer, neurodegenerative diseases, Crohn's disease and so on.

OBJECTIVE

This review systematizes the literature on the mechanisms of the phytochemicals that react against unique free radicals and prevent the oxidative stress and also summarizes their role in gut microbiota inhibiting bacterial translocation and damage to the intestinal barrier and improving the intestinal membrane condition.

CONCLUSION

The gut microbiota modulation and antioxidant activities of the phytochemicals shall be emphasized on the research of the active principles of the phytochemicals.

For the love of paradox: from neurobiology to pharmacology

The acute and chronic effects of certain drugs can often be opposite. For example, in congestive heart failure acute administration of β-adrenoceptor agonists results in beneficial improvement in symptoms of the disease, but their chronic use increases mortality. Conversely, certain β-adrenoceptor antagonists/inverse agonists (β-blockers) initially cause a detrimental response by decreasing cardiac contractility in congestive heart failure, whereas chronic treatment with the same β-blockers improves contractility and survival. Furthermore, this time-dependent reversal of outcomes occurs in nonpharmacological interventions, such as exercise, and can even be observed in the response of plants to pruning or other stressors, with the results being a different short-term versus long-term effect. Here, we review some of these phenomena with a special emphasis on the temporal dissociation of pharmacological effects. Although Francis Colpaert used this knowledge to lead a drug discovery project for an analgesic compound that initially produced hyperalgesia, we focused on examples outside the central nervous system.

The safety and effects of the beta-blocker, nadolol, in mild asthma: an open-label pilot study

Beta-blockers are currently contraindicated in asthma because their acute administration may be associated with worsening bronchospasm. However, their effects and safety with their chronic administration are not well evaluated. The rationale for this pilot study was based on the paradigm shift that was observed with the use of beta-blockers in congestive heart failure, which once contraindicated because of their acute detrimental effects, have now been shown to reduce mortality with their chronic use. We hypothesized that certain beta-blockers may also be safe and useful in chronic asthma therapy. In this prospective, open-label, pilot study, we evaluated the safety and effects of escalating doses of the beta-blocker, nadolol, administered over 9 weeks to 10 subjects with mild asthma. Dose escalation was performed on a weekly basis based on pre-determined safety, lung function, asthma control and hemodynamic parameters. The primary objective was to evaluate safety and secondary objectives were to evaluate effects on airway hyperresponsiveness, and indices of respiratory function. The escalating administration of nadolol was well tolerated. In 8 out of the 10 subjects, 9 weeks of nadolol treatment produced a significant, dose-dependent increase in PC20 that reached 2.1 doubling doses at 40 mg (P<0.0042). However, there was also a dose-independent 5% reduction in mean FEV1 over the study period (P<0.01). We conclude that in most patients with mild asthma, the dose-escalating administration of the beta-blocker, nadolol, is well tolerated and may have beneficial effects on airway hyperresponsiveness. Our findings warrant further testing in future larger trials.

Getting to the heart of asthma: can "beta blockers" be useful to treat asthma?

beta(2)-adrenoceptor agonists are the mainstay for the acute symptomatic treatment of asthma and provide effective bronchoprotection to a wide range of bronchoconstrictor agents. However, over the past 4 decades there has been a continuing debate concerning whether regular chronic treatment with these drugs may be doing more harm than good. The FDA's recent decision to add black box warnings concerning the regular use of salmeterol- and formoterol-containing compounds, as well as their decision not to recommend agents containing long-acting beta(2)-adrenoceptor agonists as first-line therapy, seems to confirm the concerns regarding the regular use of the long-acting beta(2)-adrenoceptor agonists. A similar debate arose in the late 1980s concerning the use of beta-adrenoceptor agonists in the treatment of heart failure. In this disease, short-term use of beta agonists is associated with increased cardiac index and stroke volume, yet their long-term use is associated with increased morbidity and mortality. Moreover, certain beta blockers that are initially detrimental when used short term are now considered beneficial in the treatment of this disease when used chronically. Here, there is a parallel, as beta blockers are contraindicated in patients with asthma but the use of beta blockers chronically has never been evaluated. This begs the question of whether a similar paradigm shift is applicable in the treatment of asthma and whether under certain circumstances the long-term use of certain beta blockers may be useful in the treatment of this disease.

The temporal hormesis of drug therapies

Recent publications in the field of asthma therapeutics and studies performed over the last decade in the treatment of chronic heart failure suggest a phenomenon called 'temporal hormesis'. This phenomenon can be defined as the beneficial action of drug after chronic administration as opposed to its detrimental acute effects. Temporal hormesis may be related to the classification of the drug molecule as an agonist, antagonist or an inverse agonist. This phenomenon may be a more general principal applicable in the treatment of other diseases apart from asthma and chronic heart failure.

Long-term studies with xamoterol in heart failure

1. Xamoterol (Corwin, Carwin, Corwil, Xamtol, ICI 118,587) is a beta 1-adrenoceptor partial agonist which, unlike full beta-adrenoceptor agonists, does not down-regulate beta-adrenoceptors in the rat ventricle during chronic administration. 2. Improvements in myocardial performance have been demonstrated following acute administration of xamoterol to patients with mild or moderate heart failure, and these are sustained during at least 1 year of continued treatment. 3. Exercise duration is increased by xamoterol in patients with left ventricular dysfunction and benefit is still apparent after at least 1 year of therapy. 4. Despite sustained cardiac stimulation, xamoterol does not appear to affect adversely mortality in patients with mild or moderate heart failure. 5. Few adverse events directly attributable to xamoterol were reported during 3 month efficacy studies in more than 600 patients, and the laboratory safety profile over 1 year of treatment is good. 6. Xamoterol is a promising, well-tolerated addition to established therapies for chronic mild or moderate heart failure.

Long-term treatment with oral enoximone for chronic congestive heart failure: the European experience

The long-term safety and efficacy of the inotropic/vasodilatory agent enoximone (50 to 100 mg 3 times daily) were evaluated in 30 patients with chronic congestive heart failure (New York Heart Association classes II to IV). Nineteen patients had idiopathic dilated cardiomyopathy and 11 had ischemic heart disease. Patients were receiving maintenance therapy of digitalis and diuretics. Cardiac function was assessed at 12 week intervals (physical examination, exercise testing, chest x ray, echocardiography, radionuclide angiography, 24-hour Holter monitoring and blood chemistry). During a mean follow-up of 40 weeks, 6 patients died, due to noncardiac (n = 1) and sudden death (n = 1) and to cardiac failure (n = 4) within 36 weeks of drug treatment. In the remaining patients New York Heart Association class improved in 18, was stationary in 5 and deteriorated in 1. Exercise capacity increased during the first 26 weeks and was maintained improved thereafter. Clinical improvement appeared not to wane with time. No change in heart rate, blood pressure and cardiothoracic ratio was observed. Echocardiographic left ventricular dimensions did not change significantly; however, the fractional shortening increased from baseline (14%) to 19% after 12 weeks, 17% after 26 weeks and 21% after 52 weeks (p less than 0.05). The preejection period/left ventricular ejection time ratio decreased from 0.74 to 0.35, 0.44 and 0.43 (p less than 0.05), respectively. There was an increase in radionuclide ejection fraction from 23% to 27% (difference not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Intermittent, ambulatory dobutamine infusions in patients with severe congestive heart failure

Thirteen ambulatory patients with severe congestive heart failure were treated with weekly, outpatient 48-hour infusions of dobutamine. All 13 patients had at least a 25% increase in cardiac output during initial dobutamine titration, with a corresponding improvement in systemic vascular resistance. Improvement in functional class was achieved in only seven patients. Additionally, only three patients survived the 26-week study period. Although no change in ventricular ectopy was noted during the initial dobutamine infusions, six patients experienced sudden death; three other patients died of progressive heart failure and one died from pulmonary embolism. These data suggest that chronic intermittent ambulatory dobutamine infusions are only partly successful in improving symptoms and probably do not prolong survival in patients with severe congestive heart failure. Administration of this form of therapy on a clinical basis should be undertaken cautiously until safety and efficacy are demonstrated in prospective, controlled trials.

Enoximone (MDL 17,043) for stable, chronic heart failure secondary to ischemic or idiopathic cardiomyopathy

To examine the efficacy and safety of enoximone for treatment of patients with chronic, clinically stable cardiac failure secondary to ischemic or myopathic heart disease, 31 patients were enrolled into an early phase II trial. The hemodynamic response to intravenous and oral enoximone was assessed and compared with the response to dobutamine therapy (5 to 10 micrograms/kg/min). Maximal O2 uptake, an objective measure of effort tolerance, was serially monitored. Intravenous (1 to 2 mg/kg) and oral (1 to 2 mg/kg) enoximone improved (p less than 0.05) cardiac index while reducing right atrial and wedge pressures to a greater extent than dobutamine. The salutary hemodynamic response to oral enoximone was sustained for 6 to 8 hours and was not associated with subacute drug tolerance. Maximal O2 uptake was increased (p less than 0.05) at 2, 4, 8, 12, 24 and 52 weeks of oral enoximone therapy (1.4 +/- 0.5 mg/kg every 8 hours) while radionuclide ejection fraction at 65 weeks increased (p less than 0.05) from baseline (39 +/- 16% vs 30 +/- 9%). Nine patients, 8 of whom were in functional class III or IV on enrollment, died after a mean of 18 weeks: 4 from cardiac failure and 5 suddenly. Two patients had adverse gastrointestinal effects. Oral enoximone (1 to 2 mg/kg every 8 hours) appears to be useful in the short- and long-term management of clinically stable, chronic cardiac failure. Controlled phase III trials are warranted.

The future role of inotropic drugs

Inotropic drugs have not, as yet, been shown in double-blind, randomised and placebo-controlled trials to be of value in the treatment of heart failure. There are theoretical reasons why inotropic drugs may initiate arrhythmias, worsen ischaemia and possibly even increase mortality.

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.

Comparative vasoactive therapy for heart failure

Dopamine and dobutamine increase myocardial contractility by beta-adrenergic stimulation. Both agents provide significant support for decompensating congestive heart failure (CHF) patients. At the same time, both agents can have significant adverse effects. In 1981, it was reported that amrinone, a bipyridine derivative, produced hemodynamic changes similar to those of dobutamine. To confirm these results, the hemodynamic and clinical effects of amrinone were compared with those of dopamine and dobutamine in 15 consecutive patients with CHF. Although each drug improved maximal cardiac index to a similar extent, dopamine did not decrease pulmonary artery wedge pressure and caused a greater increase in heart rate. Dobutamine and amrinone conferred similar hemodynamic benefits: cardiac index improved from 2.4 +/- 0.2 to 3.4 +/- 0.2 liters/min/m2 with dobutamine and from 2.1 +/- 0.2 to 3.2 +/- 0.2 liters/min/m2 with amrinone. Pulmonary artery wedge pressure decreased similarly: from 19 +/- 2 to 13 +/- 1 mm Hg with dobutamine and from 18 +/- 2 to 12 +/- 1 mm Hg with amrinone. Dobutamine and amrinone produced similar modest decreases in mean arterial pressure and increments in heart rate. Dopamine was poorly tolerated; 5 patients developed such severe adverse reactions that this drug was discontinued prematurely. Dobutamine and amrinone were much better tolerated. Although amrinone caused asymptomatic tachycardia (heart rate increase greater than 20% over baseline) in 4 patients, no patient developed an adverse reaction warranting its premature termination.

Pathophysiology of cardiac failure

The pathophysiologic cycle of heart failure is initiated by myocardial failure that accompanies a reduction in myocardial contractility secondary to ischemic or myopathic heart disease. Reduction in cardiac output and oxygen delivery to the tissues is followed by vasoconstriction that raises systemic vascular resistance to preserve systemic arterial pressure while maintaining regional O2 availability. As a consequence, however, impedance to left ventricular ejection is increased, creating an additional hemodynamic burden for the failing heart. A vicious cycle ensues. Hemodynamic features of acute cardiac failure include decreases in cardiac output and mixed venous O2 saturation, together with increases in left ventricular filling pressure and systemic resistance. If hypotension is present with failure, there is a markedly decreased cardiac output or an inappropriate increase in systemic resistance. If acidosis is also present with hypotension and failure, cardiac output is severely decreased and lactic acid is increased. A major objective of medical therapy in acute heart failure is to enhance ventricular emptying, thereby increasing cardiac output and O2 delivery while decreasing left ventricular filling pressure, pulmonary venous pressure and vascular resistance. Potent intravenous drugs that have a positive inotropic effect on the myocardium, including amrinone and dobutamine, have been shown to increase ventricular emptying in patients with acute heart failure. Intravenous amrinone improves pump performance without adversely raising myocardial O2 consumption, thereby enhancing myocardial efficiency. These drugs also promote a degree of vasodilation through both direct and secondary effects on the systemic circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in left ventricular function, coronary hemodynamics and myocardial catecholamine balance with MDL 17043, a new inotropic vasodilator agent, in patients with severe heart failure

To evaluate changes in myocardial energetics and systemic and cardiac sympathetic activity associated with improved left ventricular function after MDL 17043, a new inotropic vasodilator agent, systemic and coronary hemodynamics and myocardial catecholamine balance were determined in 17 patients with severe heart failure. After the administration of MDL 17043, cardiac index increased by 67% and pulmonary capillary wedge pressure decreased (25 +/- 5 to 14 +/- 7 mm Hg, p less than 0.01), indicating improved left ventricular function. Coronary sinus blood flow (75 +/- 29 to 111 +/- 51 ml/min, p less than 0.01) and myocardial oxygen consumption (9.9 +/- 3.3 to 11.8 +/- 5.4 ml/min, p less than 0.05) increased despite decreased myocardial oxygen extraction (11.7 +/- 2 to 10.1 +/- 3.3 vol%, p less than 0.05) and a higher coronary sinus oxygen content. Although transmyocardial lactate extraction remained unchanged, increased myocardial oxygen consumption has potential deleterious effects on myocardial metabolic function. Arterial norepinephrine concentrations and transmyocardial norepinephrine release also remained unchanged. These findings suggest that MDL 17043 improves left ventricular pump function, but produces no detectable change in systemic and cardiac sympathetic activity. Improved left ventricular function is associated with increased myocardial oxygen consumption despite primary coronary vasodilation.

Pharmacologic therapy of low output syndromes after cardiac surgery

With the advancement of surgical techniques and myocardial protection we can expect that patients previously felt to be inoperable because of poor ventricular function will be surgical candidates. This group of patients will on occasion develop severe left ventricular dysfunction in the peri-operative period. Optimum management in this setting will require acquisition of haemodynamic data, assessment of ventricular loading conditions and inotropic state and the selection of appropriate drug therapy. Drugs are available with specific haemodynamic profiles and therapy is enhanced by matching the abnormal haemodynamics of patients with an appropriate therapeutic agent. If the patient fails to respond quickly to pharmacotherapy, consideration should be directed toward use of an intra-aortic balloon pump.

Mechanisms of improved left ventricular function following intravenous MDL 17,043 in patients with severe chronic heart failure

To evaluate the mechanisms for improved left ventricular function with MDL 17,043 in patients with severe chronic heart failure, 24 patients were evaluated by simultaneous determination of hemodynamics by right heart catheterization and ejection fraction by computerized nuclear probe before and following intravenous administration of MDL 17,043 (mean cumulative dose 3.6 mg/kg). Following MDL 17,043, there was an increase in cardiac index (+62%), stroke volume index (+42%), and stroke work index (+68%), together with a decrease in pulmonary capillary wedge pressure (-46%), indicating improved left ventricular pump function. There was a marked reduction in systemic vascular resistance (-40%) and a modest reduction in arterial pressure, indicating decreased left ventricular outflow resistance. The ratio of peak systolic blood pressure to calculated left ventricular end-systolic volume tended to increase, but the change was not statistically significant. Despite a marked increment in stroke volume index, left ventricular ejection time corrected for heart rate was shortened, suggesting enhanced contractility. In the group as a whole, the calculated left ventricular end-diastolic volume remained unchanged, but it increased in 14 patients. Since pulmonary capillary wedge pressure fell in each patient, this suggests improved overall left ventricular distensibility. Thus, decreased left ventricular outflow resistance, and possibly increased contractile function, and improved left ventricular diastolic compliance may all contribute to improved left ventricular pump function with MDL 17,043 in patients with severe heart failure.

Oral amrinone for the treatment of chronic congestive heart failure: results of a multicenter randomized double-blind and placebo-controlled withdrawal study

A placebo-controlled study was employed to evaluate the effects of oral amrinone in patients with congestive heart failure. After a baseline period of at least 4 weeks of standard treatment for refractory congestive heart failure, oral amrinone was added to the treatment regimen of 173 patients. Patients were predominantly male (89%), aged 24 to 76 years (mean 54), with ischemic (52%) or idiopathic (37%) dilated cardiomyopathy, in New York Heart Association functional class II (40%), III (59%) and IV (1%) and having a mean (+/- standard deviation) left ventricular ejection fraction of 25 +/- 15%. Phase 1: After the addition of amrinone (113 +/- 33 mg three times daily), 52 patients (30%) showed a maximal increase in treadmill exercise time exceeding 2 minutes (Naughton protocol), 72 (42%) had a lesser increase, 24 (14%) developed limiting adverse reactions, 20 (12%) died and 5 dropped out of the study. Fifty-two "responders" (30%) who were free of limiting side effects and had a greater than 2 minute increase in exercise time were randomized in double-blind fashion to continued amrinone or switched to placebo (each plus standard treatment) for an additional 12 weeks. Phase 2: Comparison of 31 of these 52 responders who continued to receive amrinone with the remaining 21 randomized to placebo revealed no significant differences in vital signs, indexes of left ventricular size and function, systolic time intervals or maximal exercise time. Continued follow-up study of patients receiving either amrinone or placebo revealed decreases in exercise times of 7 and 10%, respectively (both p less than 0.05 compared with before randomization). Episodes of worsened congestive heart failure severe enough to mandate termination of double-blind treatment were as frequent in patients taking placebo (4[18%] of 21) as in those taking amrinone (4[13%] of 31; p = NS). The average symptom score and functional class of each treatment group remained comparable. Adverse effects such as gastrointestinal and central nervous system complaints were more common with amrinone treatment as were elevations of serum liver enzymes and reduced platelet counts. This large multicenter, randomized double-blind withdrawal study revealed no change in estimates of cardiac performance after the discontinuation of amrinone. These findings suggest that amrinone, in the dosages tested, does not importantly improve cardiac function beyond that provided by standard treatment with digoxin, diuretic drugs and vasodilators.

Beta-adrenergic stimulation of the failing ventricle: a double-blind, randomized trial of sustained oral therapy with prenalterol

Eleven patients with severe left ventricular impairment (mean ejection fraction 24%) and moderate impairment of exercise tolerance underwent a double-blind, placebo-controlled, cross-over trial of the orally administered beta-agonist prenalterol. Exercise hemodynamics and tolerance were measured during bicycle and treadmill exercise after 2 weeks of therapy with placebo or prenalterol. Cardiac index, ejection fraction, and stroke work index were not improved and exercise duration and peak oxygen consumption were not significantly different during the two treatments. During prenalterol treatment heart rate during exercise was consistently reduced. These results show that prolonged therapy with prenalterol does not improve hemodynamics or exercise tolerance and is associated with a diminished heart rate response to exercise.

Old and new inotropic drugs

An ideal cardiotonic agent should improve cardiac contractility and increase the oxygen supply to various tissues without inducing tachycardia, arrhythmias, decrease in coronary blood flow or increment in oxygen requirements of the myocardium. It should also be safe and orally active and have a persistent action. The aim of this paper is to describe various positive inotropic drugs at our disposal. The hemodynamic effects and the indications of adrenaline, noradrenaline, isoprenaline, dopamine, dobutamine and cardiac glycosides are presented first. Then several new promising orally active compounds are discussed.

Pirbuterol hydrochloride: evaluation of beta adrenergic agonist activity in reversible obstructive pulmonary disease and congestive heart failure

Pirbuterol hydrochloride is a beta 2 adrenergic agonist with a structure similar to that of albuterol, except for the substitution of a pyridine ring for the benzene ring. It is comparable in duration of action to albuterol when given by inhalation, but it is threefold less potent by weight. In man, pirbuterol and albuterol have similar beta 2 selectivity. In the acute therapy of chronic obstructive pulmonary disease, pirbuterol is most effective in oral doses of 15-20 mg, and by aerosol in doses of 400 micrograms or greater. Long-term studies of oral pirbuterol in doses between 30-60 mg/day are promising, but further research is warranted. The combination of pirbuterol's beta 2 and lesser beta1 activity has proven helpful in the therapy of refractory congestive heart failure. Improvement of function of both right and left ventricles and systemic and pulmonic circulations has been demonstrated acutely. Drug effect wanes, as with other beta adrenergic agonists, due to the development of tolerance; however, long-term benefit appears to persist in both pulmonary and cardiac patients. Pirbuterol will be marketed in the United States as 10 and 15 mg tablets and as a 200 micrograms per actuation metered dose aerosol for use in pulmonary patients only; it will not be approved for use in congestive heart failure. In terms of beta 2 selectivity, duration of action, potency and frequency of side effects, pirbuterol is comparable to the two beta 2 agonists already available in the United States, albuterol and terbutaline.

Pirbuterol, an oral beta-adrenergic receptor agonist, in the treatment of chronic cardiac failure

Pirbuterol (PB), an oral beta-adrenergic-receptor agonist, has the pharmacologic effects of vasodilation and positive inotropy. The present studies were undertaken to determine the value of PB in the long-term therapy of chronic cardiac failure. A double-blind, randomized, 7-week trial comparing PB (20 mg three times daily) with placebo in 12 patients was followed by 12 weeks of open PB therapy. Dose-dependent nervousness and tremulousness limited the unit PB dose to less than 20 mg in six patients. In all patients, clinical status, exercise tolerance and maximal oxygen uptake, left ventricular echocardiographic dimension and cardiothoracic ratio were unchanged from control after 7 weeks of placebo or PB or after 12--19 weeks of PB. To assess the adequacy of 20 mg of PB, the dose-response relations of cardiocirculatory effects to 10, 15, 20 and 30 mg of PB were compared in seven of the above patients and nine other patients. Cardiac output was significantly elevated and wedge pressure reduced after all four doses, but these changes were sustained from 6 hours after 20- and 30-mg doses only. Thus, the role of PB in the management of chronic cardiac failure appears limited; judgment of its utility must await the results of additional controlled trials.

Reduction of Lethal Toxicity of Doxorubicin by Amrinone

Administration of attirinone, a new inotropic agent, markedly reduced acute lethal toxicity in normal female Swiss and male BALB/c mice given lethal doses of doxorubicin. Because attirinone abolished the negative inotropic effect of doxorubicin in isolated guinea pig atria, it was suggested that partial protection from acute toxicity of the antitumor antibiotic is directly related to protection of cardiac function.