Acute effects of oral pirbuterol on myocardial oxygen metabolism and systemic hemodynamics in chronic congestive heart failure

Should acute treatment with inhaled beta agonists be withheld from patients with dyspnea who may have heart failure?

In patients with dyspnea, prehospital and emergency providers make therapeutic decisions before a diagnosis is established. Inhaled beta-2 agonists are frontline treatment for patients with dyspnea due to asthma or chronic obstructive pulmonary disease (COPD) exacerbations. However, these agents have been associated with increased adverse events when administered chronically to heart failure patients. Our goal was to determine the safety and efficacy of acute administration of inhaled beta-2 agonists to patients with heart failure. MEDLINE and EMBASE searches were performed using the terms "beta agonists," "albuterol," "congestive heart failure," and "pulmonary edema." Bibliographies of relevant articles were searched. Only studies addressing acute effects of beta-2 agonists were included for analysis. Twenty-four studies comprising 434 patients were identified that addressed the acute delivery of beta-2 agonists in subjects with heart failure--five studies with inhaled administration and 19 with systemic administration. No study directly evaluated the effects of inhaled beta-2 agonists to patients with acutely decompensated heart failure. Treatment of heart failure patients with beta-2 agonists resulted in transient improvements in pulmonary function and cardiovascular hemodynamics. Only one investigation reported an association between beta-2 agonist use and an increase in malignant dysrhythmias. Investigations in animal models of heart failure and acute lung injury demonstrated resolution of pulmonary edema with beta agonist administration. There is insufficient evidence to suggest that acute treatment with inhaled beta-2 agonists should be avoided in patients with dyspnea who may have heart failure. Based on small studies and indirect evidence, administration of beta-2 agonists to patients with heart failure seems to improve pulmonary function, cardiovascular hemodynamics, and resorption of pulmonary edema. Although an increase in adverse effects with the use of beta-2 agonists cannot be ruled out based on these data, there was no evidence of an increase in clinically significant dysrhythmias, especially when administered by inhalation. Based on these findings, further study should focus on the clinical outcomes of patients with acutely decompensated heart failure who are treated with inhaled beta-2 agonist therapy.

Pathophysiology and current therapy of congestive heart failure

Congestive heart failure is a common clinical syndrome, with a relatively poor prognosis in its advanced stages. During the development of heart failure, there is a decline in myocardial contractility and activation of neurohormonal systems. An overshoot of some of these compensatory mechanisms sets the stage for therapeutic interventions. Any of the three therapeutic classes of drugs (inotropic drugs, diuretics or vasodilators) can be used as first-line therapy. Other classes can be added to produce additive effects on ventricular function. Because vasodilators have been shown to prolong life, they should be used routinely in patients with heart failure. Arrhythmias and sudden death are relatively common in heart failure, although the value of antiarrhythmic therapy is less certain. Although current therapy is very helpful in patients with heart failure, it is clear that preventive approaches will be more effective in decreasing morbidity and mortality.

Newer positive inotropic agents in the treatment of chronic cardiac failure. Current status and future directions

Heart failure is a serious worldwide health problem of major proportions. For many physicians, digitalis (an inotropic agent of limited proportions) and diuretics have proven the standard of treatment for heart failure. Vasodilators have also gained acceptance in recent years. Nevertheless, many patients remain symptomatic and therefore attention has been given to the development of pharmacological agents with mechanisms of action targeted to cardiac and vascular smooth muscle. The newer generation of inotropic agents have clearly been shown to improve the pumping function of the failing heart in patients who remain symptomatic despite digitalis, diuretics and vasodilators, while myocardial oxygen consumption is not enhanced. Several uncontrolled trials with the phosphodiesterase inhibitors enoximone, milrinone and piroximone have concluded that these agents improve exercise capacity and thereby hold promise to enhance quality of life. Large scale controlled trials currently in progress will determine the ultimate efficacy, as well as safety, of these agents. Results to date with several orally active beta-adrenoceptor agonists suggest that their efficacy may be limited by the induction of ventricular arrhythmias.

Pirbuterol. A preliminary review of its pharmacological properties and therapeutic efficacy in reversible bronchospastic disease

Pirbuterol is a beta-adrenoceptor agonist which differs structurally from salbutamol in the substitution of a pyridine ring for the benzene ring. In common with salbutamol, pirbuterol demonstrates both bronchodilatory and cardiovascular effects. Generally, improvements of up to 25% are noted in forced expiratory volume in 1 second (FEV1) [versus baseline or placebo] in asthmatic patients treated with pirbuterol for several months. In individual 12-week double-blind comparative studies, pirbuterol aerosol appeared similar to orciprenaline (metaproterenol) aerosol, and orally administered pirbuterol appeared similar to orally administered salbutamol in bronchodilator efficacy. However, well-designed long term comparative studies are needed to more clearly define the comparative efficacy of pirbuterol and alternative beta-adrenoceptor agonists.

RO13-6438, a new inotrope-vasodilator: systemic and coronary hemodynamic effects in congestive heart failure

Systemic and coronary hemodynamics and transmyocardial norepinephrine release were determined before and after oral administration of RO13-6438, a new inotrope-vasodilator agent, in 12 patients with severe chronic heart failure unresponsive to conventional and vasodilator therapy. Improvement in left ventricular (LV) function was evident from a marked increase in cardiac index (from 2.09 +/- 0.45 to 3.30 +/- 0.73 liters/min/m2, p less than 0.01), stroke volume index (from 23 +/- 7 to 36 +/- 11 ml/m2, p less than 0.01), and stroke work index (from 23 +/- 11 to 36 +/- 14 g-m/m2, p less than 0.01), and concomitant fall in pulmonary capillary wedge pressure (from 26 +/- 7 to 16 +/- 8 mm Hg, p less than 0.01). Myocardial oxygen consumption did not change significantly (from 15.3 +/- 6.8 to 14.9 +/- 6.8 ml/min), but the ratio of minute work/myocardial oxygen consumption, an index of LV efficiency, increased significantly (p less than 0.05). Although average coronary sinus flow did not change, coronary sinus oxygen increased (from 3.2 +/- 0.8 to 4.2 +/- 1.5 vol%, p less than 0.05), and arterial-coronary sinus oxygen difference decreased (from 11.8 +/- 2.1 to 10.4 +/- 1.9 vol%, p less than 0.05), suggesting a primary vasodilating effect of RO13-6438 on the coronary vascular bed. Net transmyocardial norepinephrine release did not change despite the marked hemodynamic improvement. These findings suggest that RO13-6438 has the potential to cause marked improvement in LV function and LV efficiency in patients with severe, refractory congestive heart failure.

Comparative acute hemodynamic effects of intravenous sodium nitroprusside and MDL-17,043, a new inotropic drug with vasodilator effects, in refractory congestive heart failure

We compared the acute hemodynamic effects of intravenous nitroprusside (NTP), a pure vasodilator, to those of intravenous MDL-17,043 (MDL), a phosphodiesterase inhibitor with inotropic and vasodilator effects, in 12 patients with chronic refractory congestive heart failure (CHF). Intravenous NTP was infused and titrated to achieve optimal hemodynamic effects, whereas MDL was given intravenously in 0.5 mg/kg increments every 10 to 15 minutes until no further increase occurred in cardiac output or until a maximum cumulative dose of 4.5 mg/kg had been given. Both NTP and MDL reduced pulmonary capillary wedge pressure (27 +/- 5 to 15 +/- 6 and 29 +/- 3 to 15 +/- 7 mm Hg, respectively; both p less than 0.0001), systemic vascular resistance (2173 +/- 1137 to 1118 +/- 306 and 1805 +/- 425 to 956 +/- 235 dynes-sec-cm-5, respectively; both p less than 0.0002), mean arterial pressure (85 +/- 18 to 69 +/- 14 and 83 +/- 15 to 75 +/- 16 mm Hg respectively; both p less than 0.05), and increased cardiac index (1.7 +/- 0.4 to 2.6 +/- 0.4 and 1.8 +/- 0.2 to 3.3 +/- 0.5 L/minute/m2, respectively; both p less than 0.05) without an overall significant change in heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic and clinical effects of a new inotropic agent TA-064 in patients with refractory heart failure due to cardiomyopathy with special reference to dose-response effects

A new hydroxybenzyl alcohol derivative TA-064 exerts a positive inotropic action in experimental preparations. To assess the acute effects in man, we made a cardiac catheterization study of the hemodynamic responses to TA-064 (20 mg and/or 40 mg given orally) in eleven patients with refractory heart failure due to cardiomyopathy (nine patients with dilated cardiomyopathy and one with amyloidosis). All patients were already receiving full digitalis and diuretics therapy. The following statistically significant (P less than 0.05-0.01) effects were noted: Upon administration of 20 mg of the drug, the cardiac index (CI) increased from a mean +/- 1 SD of 1.6 +/- 0.4 to 2.1 +/- 0.6 l/min/m2; pulmonary capillary wedge pressure (PCW) fell from 25 +/- 5 to 21 +/- 5 mm Hg; right atrial pressure (RA) fell from 12 +/- 3 to 10 +/- 4 mm Hg. In contrast, when 40 mg TA-064 were administered orally, the CI increased from 1.7 +/- 0.4 to 2.4 +/- 0.9 l/min/m2; PCW fell from 25 +/- 8 to 20 +/- 6 mm Hg; pulmonary arterial mean pressure fell from 35 +/- 11 to 29 +/- 9 mm Hg. Neither systemic arterial mean pressure nor heart rate increased. No toxicity was observed. The plasma concentration of TA-064 increased dose-dependently and reached a peak value 0.5-1.5 h after oral administration. Plasma catecholamine levels revealed no significant changes before and after use of the drug; therefore, the mechanism of action may not have been mediated by catecholamine.

Comparative hemodynamic effects of intravenous dobutamine and MDL-17,043, a new cardioactive drug, in severe congestive heart failure

In 14 patients with severe congestive heart failure (CHF) due to ischemic heart disease or idiopathic dilated cardiomyopathy, the hemodynamic response to intravenous infusion of dobutamine (D) was compared to that of a new non-catechol, non-glycoside, inotropic and vasodilator agent, MDL-17,043 (MDL) administered in incremental intravenous doses. D and MDL produced comparable increases in cardiac index (L/min/m2) (1.8 +/- 0.4 to 2.9 +/- 0.8 and 1.7 +/- 0.3 to 3.3 +/- 0.6, respectively; both p = 0.001) and stroke volume index (ml/beat/m2) (24 +/- 8 to 35 +/- 9 and 22 +/- 7 to 39 +/- 11, respectively; both p = 0.001). Both D and MDL reduced left ventricular filling pressure (29 +/- 5 to 24 +/- 5 and 29 +/- 6 to 17 +2- 6 mm Hg, respectively; both p less than 0.05), and mean right atrial pressure (11 +/- 4 to 8 +/- 4 and 13 +/- 5 to 6 +/- 4 mm Hg, respectively; both p = 0.001). The overall changes in heart rate and mean arterial pressure were small with both D and MDL. However, MDL in comparison to D resulted in a significantly lower left ventricular filling pressure (p = 0.001), mean pulmonary arterial pressure (p = 0.001), and mean arterial pressure (p less than 0.05). The salutary hemodynamic effects of MDL on cardiac index and left ventricular filling pressure were sustained for an average of 9.6 hours, whereas the effects of D dissipated within 30 minutes of stopping the infusion. No serious adverse effects were noted during acute administration with either drug. Therefore, intravenous MDL may be a useful substitute for D in the acute therapy of severe CHF.

Potential value of oral beta 2-adrenoceptor agonists in congestive heart failure: a haemodynamic and metabolic study

This study was designed to investigate and compare the haemodynamic and metabolic responses to pirbuterol and salbutamol in patients with congestive heart failure and coronary artery disease. Attention was directed towards the effects these beta 2-adrenoceptor agonists have on left ventricular systolic function, systemic and coronary haemodynamics and myocardial substrate metabolism. Sixteen patients were randomly allocated to treatment with either pirbuterol 20 mg or salbutamol 6 mg. Since no statistically significant differences between the responses to these drugs were observed, combined data for both agents are presented. Ninety minutes after the drug intervention cardiac index increased from 2.2 +/- 0.1 to 2.9 +/- 0.2 1/min per m2 (P less than 0.001) in association with marked reductions in systemic vascular resistance (from 22 +/- 1 to 15 +/- 1 units, P less than 0.001) and increments in left ventricular dp/dtmax (from 1074 +/- 85 to 1422 +/- 133 mm Hg/sec, P less than 0.05). Modest reductions in left ventricular end-diastolic pressure (from 21 +/- 1 to 15 +/- 1 mm Hg, P less than 0.01) were observed. Heart rate increased from 82 +/- 5 to 91 +/- 4 beats/min (P less than 0.01) but the small fall in mean arterial pressure (from 86 +/- 3 to 78 +/- 3 mm Hg) was not significant. Drug-induced coronary vasodilatation reduced coronary coronary vascular resistance from 0.65 +/- 0.06 to 0.47 +/- 0.04 units (P less than 0.01) and led to a marked increase in coronary sinus blood flow (from 124 +/- 9 to 155 +/- 9 ml/min, P less than 0.05). Arterial levels of free fatty acids increased from 0.78 +/- 0.13 to 1.05 +/- 0.18 mmol/l (P less than 0.05) resulting in the preferential utilization of this substrate as a myocardial energy source. Despite the substantial haemodynamic improvement, however, no significant increase in myocardial oxygen uptake or lactate production was observed. Thus, in patients with coronary artery disease and congestive heart failure pirbuterol and salbutamol improve left ventricular function by a combination of afterload reduction and positive inotropism such that no appreciable deterioration in myocardial energetics occurs.

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.

Acute and long-term hemodynamic effects of oral pirbuterol in patients with chronic severe congestive heart failure: randomized double-blind trial

In 20 patients with severe congestive heart failure (CHF), we studied the effects of the beta-adrenergic agonist pirbuterol compared to placebo in both an acute double-blind randomized trial and after long-term treatment. Acutely, pirbuterol patients (n = 10) demonstrated a significant rise in cardiac index (2.2 +/- 0.14 to 3.2 +/- 0.32 L/min/m2), stroke index (26 +/- 2.6 to 35 +/- 2.9 ml/beat/m2), stroke work index (22 +/- 2.4 to 30 +/- 2.7 gm X m/m2), and ejection fraction (22 +/- 4 to 30 +/- 5%). These hemodynamic variables did not significantly change in placebo patients (n = 10). After 3 weeks of pirbuterol therapy, 14 patients (70%) were symptomatically improved and were continued on the drug for another 3 weeks; 13 of 14 patients who were symptomatically improved underwent restudy. Compared to pretreatment baseline, there was continued improvement in cardiac index (2.5 +/- 0.16 to 3.2 +/- 0.24 L/min/m2), stroke index (30 +/- 2.5 to 38 +/- 2.9 ml/beat/m2), stroke work index (26 +/- 2.3 to 35 +/- 3.1 gm X m/m2), and ejection fraction (24 +/- 1 to 28 +/- 4%). Patients more frequently improved were those with nonischemic cardiomyopathy and those with higher initial ejection fractions. These results demonstrate the acute beneficial effects of oral pirbuterol versus placebo in a double-blind randomized trial. Improvement was maintained during long-term therapy in the majority of CHF patients.

Effects of pirbuterol and sodium nitroprusside on pulmonary haemodynamics in hypoxic cor pulmonale

The acute haemodynamic effects of oral pirbuterol (a beta-agonist) were contrasted with those of sodium nitroprusside, a vasodilator, in six patients with hypoxic chronic bronchitis and emphysema. Sodium nitroprusside (1-5 mg/kg intravenously) reduced mean pulmonary arterial pressure and total pulmonary vascular resistance significantly (p less than 0.01) without change in cardiac output or right ventricular ejection fraction, measured by radionuclide ventriculography. Oral pirbuterol (22.5 mg) produced a greater reduction in total pulmonary vascular resistance than sodium nitroprusside, largely as a result of increasing cardiac output. Right ventricular ejection fraction also increased significantly after pirbuterol (p less than 0.01). Pirbuterol in a lower dosage (15 mg by mouth) in six further patients with hypoxic chronic bronchitis and emphysema produced similar changes in total pulmonary vascular resistance and right ventricular ejection fraction. Nine of the patients who were studied acutely thereafter received pirbuterol 15 mg thrice daily for six weeks, which produced a significant fall in systolic pulmonary arterial pressure and a rise in right ventricular ejection fraction (p less than 0.01), without a significant fall in arterial oxygen tension. Pirbuterol acts as a vasodilator on the pulmonary circulation in these patients and may in addition improve right ventricular performance by an inotropic action.

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

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

Symptoms, haemodynamics, and exercise capacity during long term treatment of chronic heart failure. Experience with pirbuterol

An open study of long term treatment with an oral beta 2 agonist (pirbuterol 20 mg three times daily) was undertaken in 63 patients with severe chronic heart failure. During three months of treatment 20 (32%) patients died, of whom 16 were taking the drug at the time of death. Mortality was related to initial functional class (New York Heart Association classification: 23% in grade III and 75% in grade IV). Concomitant treatment with digoxin did not affect mortality. The drug was well tolerated by most patients but unwanted side effects necessitated withdrawal of the drug in six (10%). Thirty-five patients were continuing to take the drug after three months, of whom 22 reported symptomatic improvement and only four deterioration. There was a relation between symptomatic improvement and increase in exercise capacity. At initial haemodynamic assessment a single dose of pirbuterol increased the cardiac index by 34% and the stroke index by 21%. Left ventricular filling pressure fell by 23% and systemic vascular resistance by 22%. Haemodynamic reassessment after three months of continuous treatment in 29 patients showed maintained improvement in the group as a whole, although individual variation was considerable. There was no apparent relation between haemodynamic improvement and improvement in exercise duration and symptoms. Severe heart failure has a poor prognosis. Identification of those patients who may derive benefit from treatment with a particular drug is not yet possible.

Cardiovascular effects of a newly synthesized cardiotonic agent (TA-064) on normal and diseased hearts

A new inotropic agent, TA-064, (-)-alpha-(3,4-dimethoxyphenethylaminomethyl)-4-hydroxybenzylalcohol, was shown to have strong effects in experimental animals. Its effectiveness and associated adverse effects were tested in humans invasively (n = 6) and noninvasively (n = 17). Increasing doses of intravenous infusion (1, 2, and 4 micrograms/kg/min) increased plasma levels to 15, 35, and 82 ng/ml, respectively, resulting in marked increases in the peak rate of left ventricular pressure rise (dP/dt) (1,450 +/- 63 to 3,042 +/- 349 mm Hg/s) (mean +/- standard error of the mean [SEM], p less than 0.01) and the ratio of dP/dt to left ventricular pressure at a developed pressure of 40 mm Hg (25 +/- 3 to 39 +/- 2 s-1) (p less than 0.01), with a reduction in left ventricular end-diastolic pressure (12 +/- 2 to 4 +/- 1 mm Hg) (p less than 0.01). Minimal or no changes were seen in heart rate and left ventricular systolic pressure. After a single oral dose (10 mg), the plasma level reached its peak at 90 minutes (16 +/- 9 ng/ml, n = 17). A positive inotropic effect was confirmed echocardiographically in both healthy volunteers (n = 8) and patients with congestive heart failure (CHF) (n = 9) who were maximally treated with conventional regimens: increase in mean velocity of circumferential fiber shortening (healthy volunteers: 1.29 +/- 0.05 to 1.60 +/- 0.11 circ/s [p less than 0.05]; patients with CHF: 0.69 +/- 0.08 to 0.93 +/- 0.09 circ/s [p less than 0.01]), ejection fraction (healthy volunteers: 68 +/- 2 to 75 +/- 2% [p less than 0.05], patients with CHF: 37 +/- 4 to 45 +/- 5% [p less than 0.01]) without change in heart rate. The cardiac index was increased only in the CHF group (2.71 +/- 0.22 to 3.21 +/- 0.24 liters/min/m2) (p less than 0.05). No significant untoward effects were observed. Thus TA-064 is a potent inotropic agent and can be used either parenterally or orally. Salutary effects can be expected in patients with congestive heart failure who are treated with digitalis and diuretic agents.

Acute haemodynamic comparison of amrinone and pirbuterol in chronic heart failure. Additional effects of isosorbide dinitrate

A randomised, within patient comparison was made in patients with severe chronic heart failure, to study the acute haemodynamic effects of oral agents which have inotropic and vasodilator properties. A non-glycosidic non-adrenergic positive inotropic agent with vasodilator properties (amrinone) was compared with a beta-agonist which has vasodilator and positive inotropic effects (pirbuterol). To assess whether combined treatment with a venodilator might be advantageous, the effect of adding isosorbide dinitrate was studied. Oral amrinone or pirbuterol were given in random order to each of 13 patients, on successive days, and oral isosorbide dinitrate was added after two-and-a-half hours. Control values before amrinone or pirbuterol were similar, and both drugs increased cardiac index while reducing left ventricular filling pressure, right atrial pressure, and systemic vascular resistance. Heart rate and blood pressure were unchanged. The magnitude of the changes caused by amrinone and pirbuterol were not significantly different. The addition of isosorbide dinitrate caused further falls in left ventricular filling pressure and right atrial pressures, and a fall in heart rate with each drug. Other measurements remained unchanged. Although amrinone and pirbuterol have different pharmacological properties, their acute haemodynamic effects in patients with chronic heart failure are indistinguishable.

Aspects of the pharmacology of beta-adrenoceptor agonists and antagonists

A short review is given of the distribution of and effects mediated through beta-receptors. The pharmacodynamic profiles of some beta-receptor agonists and antagonists are briefly outlined and the clinical advantages and disadvantages of different pharmacodynamic properties are discussed.

Myocardial metabolic alterations after contrast angiography

Contrast media used during angiography are known to produce transient alterations in cardiovascular physiology. However, little information is available concerning what alterations, if any, occur in myocardial metabolism after contrast angiography. Sixteen patients with symptoms of ischemic heart disease undergoing elective left ventriculography were studied. Coronary sinus and arterial blood samples were obtained for free fatty acids, glucose and lactate before and after performing left ventriculography with Renografin-76. Coronary blood flow was determined by the thermodilution technique. Five minutes after ventriculography, the arterial level of free fatty acids had decreased by 18.0 +/- 4.9 percent (mean +/- standard deviation) from the baseline (before angiography) samples (probability [p] less than 0.001). Associated with this decrease in arterial free fatty acids was an increase in the myocardial uptake of this substrate. At 5 minutes after left ventriculography, the free fatty acid uptake had increased 48.5 +/- 33.0 percent compared with the baseline value (p less than 0.001). After the injection of contrast medium, there was no significant change in the arterial levels of glucose or lactate. However, significant decreases in the myocardial uptake of glucose and lactate were demonstrated (-72.5 +/- 44.5 percent [p less than 0.001] and -43.2 +/- 22.9 percent [p less than 0.001], respectively) at 5 minutes. The changes in arterial free fatty acids and in the myocardial uptake of the various substrates persisted throughout the sampling period of 20 minutes after ventriculography. These results demonstrate that contrast medium significantly alters myocardial metabolism. These metabolic alterations persist longer than the hemodynamic changes induced by contrast angiography.

New hope for the failing heart

One sixth of this nation's citizens have disease of the heart and blood vessels; an estimated 3.5 to 4 million Americans have chronic cardiac failure. The individual and collective losses associated with heart failure are enormous. Standard medical therapy with digitalis and diuretics is frequently inadequate to control and morbidity associated with this often times malignant process. More effective medical therapy is therefore needed. The recent development of potent, orally active cardiotonic agents may make this objective a reality. At the present time, the new cardiotonic agents are still in the experimental stages of investigation. Phase II and III clinical trials must be either initiated or completed before the efficacy and safety of these agents will be known. It must be emphasized that objective parameters of ventricular function and the patients's quality of life must be monitored if meaningful verdicts are to be rendered. Information must be gathered that indicates whether prolonged therapy with these agents is detrimental to the myocardium. Despite this caveat, the availability of compounds having potent inotropic properties had generated much anticipation and excitement in clinical cardiology. Our ability to more effectively manage patients with chronic cardiac failure may now be on the horizon. There is, indeed, new hope for the failing heart.

Comparative pharmacology and clinical efficacy of newer agents in treatment of heart failure

The animal and human pharmacology of several new drugs (prazosin, trimazosin, pirbuterol, and carbazeran) useful in the treatment of congestive heart failure (CHF) is delineated in relation to the pharmacology of other agents employed for CHF management. Prazosin and trimazosin are selective alpha 1-blockers that cause a balanced increase in cardiac output (CO) and reduction in left ventricular filling pressure (LVFP); the reduction in diastolic blood pressure with these drugs is significantly related to increase in treadmill exercise, fall in LVFP, and increase in CO. Pirbuterol is a relatively selective beta 2-agonist with somewhat greater effects on CO than on LVFP. Early promise in CHF therapy is being shown by a novel series of cyclic adenosine monophosphate (cAMP) phosphodiesterase inhibitors with combined direct inotropic and vasodilator effects. Double-blind long-term studies demonstrate persistent efficacy of prazosin and trimazosin in CHF as measured by improvement in New York Heart Association functional class, treadmill exercise performance, and noninvasive measures of cardiac function; these data are supported by studies in which repeat cardiac catheterization has been performed after several months of therapy. Double-blind studies of other CHF drugs are in progress.

Problems in assessment of new pharmacologic agents for the heart failure patient

Modern management of congestive heart failure (CHF) employs inotropic drugs, vasodilators, and diuretics. Although pharmacologic classification of drugs is possible in animals, identification of predominant hemodynamic mechanisms in humans is more complex, because many effects of vasodilators and inotropic drugs are similar. We compared the effects of a vasodilator, prazosin, and two agents with both inotropic and vasodilatory properties, amrinone and pirbuterol, on cardiac index (CI), mean aortic pressure, left ventricular stroke work index (LVSWI), LV filling pressure (LVFP), systemic vascular resistance, LV ejection fraction (LVEF), and myocardial O2 consumption (MVO2) in 34 patients with advanced CHF. We concluded that (1) a rise in CI and LVEF, together with a fall in LVFP, does not necessarily indicate an inotropic effect; (2)both CI and LVEF may be increased by an inotropic mechanism in advanced CHF without a rise in MVO2; and (3) a drug-induced rise in LVSWI with stable or lower LVFP suggests an inotropic mechanism of action.