Safety and efficacy of esmolol (ASL-8052: an ultrashort-acting beta-adrenergic blocking agent) for control of ventricular rate in supraventricular tachycardias

Conversion of Atrial Fibrillation to Sinus Rhythm During Treatment With Intravenous Esmolol or Diltiazem: A Prospective, Randomized Comparison

Prior studies have suggested that intravenous diltiazem reduces the probability of spontaneous conversion of atrial fibrillation (AF) to sinus rhythm in the electrophysiology laboratory and in patients with postoperative AF. Whether diltiazem exerts the same effect in patients presenting to the emergency department (ED) with spontaneous AF is unclear. Fifty patients presenting to the ED with new-onset or paroxysmal AF and a rapid ventricular rate (>100 beats per minute) were randomly assigned to receive intravenous diltiazem or esmolol during the first 24 hours of presentation. Conversion to sinus rhythm occurred in 10 patients (42%) in the diltiazem group compared with 10 patients (39%) in the esmolol group ( P = 1.0). Diltiazem does not decrease the likelihood of spontaneous conversion of AF to sinus rhythm in the ED setting.

Intravenous diltiazem is superior to intravenous amiodarone or digoxin for achieving ventricular rate control in patients with acute uncomplicated atrial fibrillation

OBJECTIVES

To compare the clinical efficacy of intravenous diltiazem, digoxin, and amiodarone for acute ventricular rate (VR) control in patients with acute symptomatic atrial fibrillation (AF) necessitating hospitalization.

DESIGN

Randomized control trial.

SETTING

Acute emergency medical admission unit in a regional teaching hospital in Hong Kong.

PATIENTS

One hundred fifty adult patients with acute AF and rapid VR (>120 bpm).

INTERVENTIONS

Patients were randomly assigned in 1:1:1 ratio to receive intravenous diltiazem, digoxin, or amiodarone for VR control.

MEASUREMENTS AND MAIN RESULTS

The primary end point was sustained VR control (<90 bpm) within 24 hours; the secondary end points included AF symptom improvement and length of hospitalization. At 24 hours, VR control was achieved in 119 of 150 patients (79%). The time to VR control was significantly shorter among patients in the diltiazem group (log-rank test, p < 0.0001) with the percentage of patients who achieved VR control being higher in the diltiazem group (90%) than the digoxin group (74%) and the amiodarone group (74%). The median time to VR control was significantly shorter in the diltiazem group (3 hours, 1-21 hours) compared with the digoxin (6 hours, 3-15 hours, p < 0.001) and amiodarone groups (7 hours, 1-18 hours, p = 0.003). Furthermore, patients in the diltiazem group persistently had the lowest mean VR after the first hour of drug administration compared with the other two groups (p < 0.05). The diltiazem group had the largest reduction in AF symptom frequency score and severity score (p < 0.0001). In addition, length of hospital stay was significantly shorter in the diltiazem group (3.9 +/- 1.6 days) compared with digoxin (4.7 +/- 2.1 days, p = 0.023) and amiodarone groups (4.7 +/- 2.2 days, p = 0.038).

CONCLUSIONS

As compared with digoxin and amiodarone, intravenous diltiazem was safe and effective in achieving VR control to improve symptoms and to reduce hospital stay in patients with acute AF.

Beta-blockade at low doses restoring the physiological balance in myocytic antagonism

OBJECTIVE

The ventricular mass is organized in the form of meshwork, with populations of myocytes aggregated in a supporting matrix of fibrous tissue, with some myocytes aligned obliquely across the wall so as to work in an antagonistic fashion compared to the majority of myocytes, which are aggregated together in tangential alignment. Prompted by results from animal experiments, which showed a disparate response of the two populations of aggregated myocytes to negative inotropic medication, we sought to establish whether those myocytes that aggregated so as to extend obliquely across the thickness of the ventricular walls are more sensitive to beta-blockade than the prevailing population in which the myocytes are aggregated together with tangential alignment. If the two populations respond in similar differing fashion in the clinical situation, we hypothesize that this might help to explain why drugs blocking the beta-receptors improve function of the ventricular pump in the setting of congestive cardiac failure.

METHODS

We implanted needle probes in 13 patients studied during open heart surgery, measuring the forces generated in the ventricular wall and seeking to couple the probes either to myocytes aggregated together with tangential alignment or to those aggregated in oblique fashion across the ventricular walls. In a first series of patients, we injected probatory doses intravenously, amounting to a total bolus of 40-100mg Esmolol, while in a second series, we gave fixed yet rising doses of 5, 10, and 20mg Esmolol in three separate boluses.

RESULTS

Forces recorded in the aggregated myocytes with tangential alignment decreased insignificantly upon administration of low doses (57.1+/-12.4 mN-->56.6+/-7.6 mN), while forces recorded in the myocytes aggregated obliquely across the ventricular wall showed a significant decrease in the mean (59.3+/-11.6 mN-->47.4+/-6.4 mN).

CONCLUSIONS

The markedly disparate action of drugs blocking beta-receptors at low dosage seems to be related to the heterogeneous extent, and time course, of systolic loading of the myocytes. This, in turn, depends on whether the myocytes themselves are aggregated together with tangential or oblique alignments relative to the thickness of the ventricular walls.

Acute ventricular rate control in atrial fibrillation and atrial flutter

Atrioventricular node blocking agents including beta-adrenergic blockers, non-dihydropyridine calcium channel blockers and digoxin are usually effective in controlling ventricular rate in atrial fibrillation and flutter. Intravenous beta-blockers and non-dihydropyridine calcium channel blockers are equally effective in rapidly controlling the ventricular rate. The addition of digoxin to the regimen causes a favorable outcome but digoxin as a single agent is generally less effective in slowing the ventricular rate in acute setting. Clonidine, magnesium, and amiodarone have also been used for acute ventricular rate control in atrial fibrillation. Limited data suggest that combination regimens provide better ventricular rate control than any agent alone. The agent of first choice is usually individualized depending upon the clinical situation. Beta-blockers are preferable in patients with myocardial ischemia, myocardial infarction and hyperthyroidism and in post-operative state, but should be avoided in patients with bronchial asthma and chronic obstructive pulmonary disease where non-dihydropyridine calcium channel blockers are preferred. Beta-blockers are preferred drugs used for acute ventricular rate control in atrial fibrillation during pregnancy. In atrial fibrillation with Wolff-Parkinson-White syndrome, beta-blockers, calcium channel blockers and digoxin should be avoided, as these drugs are selective atrioventricular node blockers without slowing conduction through the accessory pathway, which can lead to increased transmission of impulses preferentially through the accessory pathway and precipitate ventricular fibrillation. The drug of choice for atrial fibrillation in pre-excitation syndrome is procainamide but propafenone, flecainide and disopyramide have also been used. When clinical condition is unstable or patient is hemodynamically compromised, immediate electrical cardioversion is the treatment of choice, as the best measure to control ventricular rate is by conversion to sinus rhythm. Factors precipitating rapid ventricular rate should be treated as well.

Pharmacologic management of atrial fibrillation in the elderly: rate control, rhythm control, and anticoagulation

Atrial fibrillation (AF) is the most prevalent major arrhythmia in the elderly. It may lead to significant morbidity and mortality through both primary cardiac effects and thromboembolic complications. It is controversial how aggressive physicians should be in their efforts to maintain normal sinus rhythm. Clearly, elderly patients with hemodynamic impairment or other symptoms of AF should undergo attempts to convert AF and maintain normal sinus rhythm, by means of cardioversion and initiation of antiarrhythmic medications. In patients left in AF, rate control with atrioventricular nodal-slowing agents is appropriate. The use of anticoagulation in the elderly is often complicated by concerns about excessive bleeding or falls in this population; however, evidence strongly supports the need for anticoagulation with close monitoring even in the extreme elderly. Because of the high prevalence of asymptomatic AF and the high burden of thromboembolism in the elderly, even patients ostensibly maintained in normal sinus rhythm should continue systemic anticoagulation in the absence of contraindications.

The Management of Atrial Fibrillation in the ICU

Atrial tachyarrhythmias are the most frequent arrhythmias occurring in ICU patients, being particularly common in patients with cardiovascular and respiratory failure. Unlike ambulatory patients in whom atrial fibrillation/flutter (AF) is likely to be short lived, in the critically ill these arrhythmias are unlikely to resolve until the underlying disease process has improved. Urgent cardioversion is indicated for hemodynamic instability. Treatment in hemodynamically stable patients includes correction of treatable precipitating factors, control of the ventricular response rate, conversion to sinus rhythm, and prophylaxis against thromboembolic events in those patients who remain in AF. Diltiazem is the preferred agent for rate control, while procainamide and amiodarone are generally considered to be the antiarrhythmic agents of choice.

Multifocal atrial tachycardia

Multifocal atrial tachycardia is typically seen in elderly patients with severe illnesses, most commonly COPD. The mechanism of the arrhythmia may be delayed afterdepolarizations leading to triggered activity, but this has not been firmly established. The initial treatment of multifocal atrial tachycardia should include supportive measures and aggressive reversal of precipitating causes. Since multifocal atrial tachycardia is commonly a secondary phenomenon, the role for antiarrhythmic therapy is unclear. Metoprolol, magnesium, and verapamil have been evaluated in a few treatment studies, and may have a role in the treatment of multifocal atrial tachycardia.

Indications and limitations of class II and III antiarrhythmic drugs in atrial fibrillation

In summary, the Class III antiarrhythmic agents amiodarone and sotalol are effective in restoring sinus rhythm in patients with chronic atrial fibrillation with a higher effectiveness of amiodarone. Both agents successfully prevent recurrent episodes of atrial fibrillation after electrical cardioversion and both can control heart rate in persistent atrial fibrillation. Amiodarone appears to be particularly suitable in patients with atrial fibrillation and concomitant congestive heart failure because it lacks clinically relevant negative inotropic activity. Both substances are also effective in controlling ventricular arrhythmias that are frequently present in patients with atrial fibrillation. Finally, both drugs possess antiadrenergic activity, which makes the substances particularly attractive in patients with coronary heart disease as the underlying cause of atrial fibrillation.

Esmolol in the Treatment of Multifocal Atrial Tachycardia

Multifocal atrial tachycardia (MAT) is a supraventricular tachydysrhythmia precipitated by a number of pharmacologic and physiologic disturbances. Corrections of these disturbances should take precedence in the treatment of MAT.

Esmolol prevents and suppresses arrhythmias during halothane anaesthesia in dogs

The antiarrhythmic effect of esmolol, a selective beta 1 adrenoreceptor blocker, was evaluated in the presence of epinephrine induced arrhythmias in dogs (n = 6). The arrhythmogenic dose of epinephrine (ADE) during 1.2 MAC halothane in dogs was increased from 3.23 +/- 0.25 (mean +/- SD) to 30.90 +/- 3.56 micrograms.kg-1.min-1 (P less than 0.001) by the prior administration of esmolol 0.5 microgram.kg-1 bolus followed by an infusion at the rate of 150 micrograms.kg-1.min-1. Higher esmolol infusion doses of 200 micrograms.kg-1.min-1 further increased ADE to 99.0 +/- 2.92 micrograms.kg-1.min-1 (P less than 0.001). After discontinuation of esmolol and during continued halothane anaesthesia, ventricular tachycardia was induced by increasing the infusion rate of the 100 micrograms.ml-1 solution of epinephrine. In all dogs ventricular tachycardia was restored to sinus rhythm by a bolus dose of esmolol (1 microgram.kg-1). We conclude that esmolol pretreatment increases the ADE during halothane anaesthesia in dogs. Our data suggest that esmolol may be useful as an antiarrhythmic agent in the management of epinephrine-related ventricular arrhythmias during anaesthesia in man.

Intravenous esmolol in acute aortic dissection

Acute aortic dissection is a devastating condition requiring prompt intensive pharmacologic management geared toward control of blood pressure and reduction in myocardial contractility (change in velocity/change in time). The treatment of choice currently is sodium nitroprusside and intravenous propranolol hydrochloride. During acute aortic dissection, hemorrhage may spread into the interatrial septum, extending to the atrioventricular junctional tissues, thus causing conduction abnormalities. Adverse effects of long-acting beta-blockers, including bradycardia, heart failure, and bronchospasm, may limit their usefulness because these effects persist for a long time after discontinuation. This may be detrimental, especially in patients with compromised cardiac function, bronchospastic disease, or both. We report a case of a 64-year-old woman with compromised cardiac function and aortic dissection who was successfully treated with esmolol hydrochloride (an ultrashort-acting beta-blocker) and sodium nitroprusside.

Emergencies in continuous dialysis patients: diagnosis and management

The number of patients undergoing long-term hemodialysis and peritoneal dialysis is growing in the United States. To provide adequate emergent care to these patients emergency physicians must understand the alterations in normal physiologies present in these patients and how this may affect care. Cardiovascular disease and infection (especially Staphylococcus aureus sepsis) are the leading causes of death among dialysis patients. These patients are also subject to a significantly higher incidence of life-threatening electrolyte disturbances, particularly hyperkalemia and hypercalcemia, than the general population. Suicide, cardiac tamponade, intracranial hemorrhage, bleeding disorders, and bowel infarction are also much more frequent. The inability of dialysis patients to excrete drugs, metabolites, toxins, and fluids significantly alters their responses to common emergencies and should directly influence their care. Failure to recognize these differences in physiology may result in the use of standard forms of emergency therapy that may compound, rather than treat, the underlying disorder. Although most dialysis patients who come into an emergency department have conditions that can, and should, be managed by their nephrologist, the presence of a life threatening emergency requires prompt, appropriate therapy by the emergency physician.

Multifocal atrial tachycardia: mechanisms, clinical correlates, and treatment

MAT is an uncommon arrhythmia most often seen in elderly patients with chronic pulmonary disease who are critically ill due to acute respiratory or cardiac decompensation. Its importance lies in the fact that it is commonly mistaken for AF, since both disorders are characterized by narrow ventricular complexes, irregular rates, and (depending on the ECG lead observed in MAT) by an apparent lack of P wave activity. This may lead to treatment with digoxin, a drug known to be ineffective in the therapy of MAT, with the potential for producing toxicity in patients who are predisposed. The incidence of MAT in hospitalized patients in various studies ranges from 0.13% to 0.40%. The mechanism of the arrhythmia is thought to be triggered activity arising from increased intracellular calcium stores that may be produced by hypokalemia, hypoxia, acidemia, and increased catecholamines, characteristics commonly found in patients with MAT. COPD, coronary artery disease, CHF, and infection (both pulmonary and nonpulmonary) are the most common clinical settings of MAT. Mortality is very high in all patients studied, ranging from 38% to 62%, and is due to their underlying disease processes and not to the arrhythmia. The need for intubation and mechanically assisted ventilation portends a particularly poor prognosis for survival. Treatment should initially consist of correction of the precipitating causes, as it is common for patients to convert to sinus rhythm both spontaneously and after these measures are taken.(ABSTRACT TRUNCATED AT 250 WORDS)

Nonthrombolytic intervention in acute myocardial infarction

Alternative interventions are available for patients in whom thrombolytic therapy is inappropriate after an acute myocardial infarction. Administration of a beta blocker within the first 24 hours of the patient's admission to the coronary care unit can reduce overall morbidity and mortality within the first 7 days by about 15%. Maintenance therapy with an oral beta blocker can reduce mortality within the succeeding 3 years by about 25%. Esmolol, a unique cardioselective beta 1-adrenergic receptor blocker with a half-life of 9 minutes, can enable some patients with relative contraindications to beta blockers to nevertheless benefit from early beta-blocking therapy. It also is useful in screening patients for subsequent therapy with beta blockers. Those who tolerate the esmolol infusion can be given a long-acting beta blocker. For patients who exhibit intolerance to esmolol, the infusion can be terminated with rapid return to baseline hemodynamics.

A randomized, double-blind, placebo-controlled study of verapamil and metoprolol in treatment of multifocal atrial tachycardia

PURPOSE

Multifocal atrial tachycardia is a difficult arrhythmia to treat. Patients not showing a response to the correction of predisposing conditions present a therapeutic dilemma. To assess the efficacy of two agents reported to be effective in this condition, verapamil, metoprolol, or placebo was given intravenously in a randomized, double-blind trial.

PATIENTS AND METHODS

Thirteen patients meeting inclusionary criteria were enrolled. Therapeutic response was defined as conversion to sinus rhythm, a decline in the ventricular rate of 15 percent or more [corrected], or a ventricular rate of less than 100 beats/minute. Four male and nine female patients having a mean age (+/- SD) of 81.9 +/- 14.2 years were enrolled. Automated serum chemistries, complete blood cell count with differential, arterial blood gas values, and serum digoxin and theophylline levels were determined and a 12-lead electrocardiogram was obtained at the start of the trial. Following the completion of each phase of the study, a repeat physical examination was performed, and arterial blood gas values and an electrocardiogram were obtained. The trial was designed to run for two days.

RESULTS

Two of 10 (20 percent), four of nine (44 percent), and eight of nine (89 percent) showed a response to placebo, verapamil, or metoprolol, respectively. Mean slowing of ventricular rate was 3.4, 7.3, and 24.5 percent for placebo, verapamil, and metoprolol, respectively (p less than 0.01 for metoprolol versus placebo). Five patients who showed a response to metoprolol had failed to have a response to verapamil.

CONCLUSION

We conclude that metoprolol appears to be more effective than verapamil in treating multifocal atrial tachycardia. However, careful patient selection is necessary in its use.

Dupont critical care lecture: Role of ultrashort-acting β-blockers in the perioperative period

beta-blockade can result in extreme bradycardia, significant conduction problems, bronchospasm, or left ventricular dysfunction. For this reason, the use of long-acting beta-blockers is of limited value in the perioperative period. Esmolol, due to its ultrashort action and cardioselective properties, has been shown to be safe and effective for use in treatment of tachycardia and hypertension. Doses of up to 300 microg/kg/min for up to seven hours have been used with a return to baseline parameters within 30 minutes of discontinuation of the infusion. It can also be safely used in treatment of the asthmatic patient with tachycardia or hypertension with no clinically significant increases in airway resistance. Studies using esmolol during general anesthesia have also demonstrated that it appears to have no significant interaction with various anesthetic agents.

Use of an ultrashort-acting beta-receptor blocker (esmolol) in patients with acute myocardial ischemia and relative contraindications to beta-blockade therapy

The hemodynamic responses to esmolol, an ultrashort-acting (t1/2 = 9 min) beta 1-adrenergic receptor antagonist, were examined in 16 patients with myocardial ischemia and compromised left ventricular function as evidenced by a mean pulmonary capillary wedge pressure of 15 to 25 mm Hg. Esmolol was infused intravenously to a maximal dose of 300 micrograms/kg body weight per min for less than or equal to 48 h in 16 patients: 9 with acute myocardial infarction, 6 with periinfarction angina and 1 with acute unstable angina. The sinus rate and systolic arterial pressure declined rapidly in all patients from baseline values of 99 +/- 12 beats/min and 126 +/- 19 mm Hg to 80 +/- 14 beats/min (p less than 0.05) and 107 +/- 20 mm Hg (p less than or equal to 0.05) during esmolol treatment. Rate-pressure product decreased by 33% and cardiac index by 14% during esmolol treatment, but pulmonary capillary wedge pressure was not significantly altered by drug infusion (19 +/- 3 mm Hg at baseline versus 19 +/- 5 during treatment, p = NS). In all patients there was a rapid return toward baseline hemodynamic measurements within 15 min of stopping administration of esmolol, and virtually complete resolution of drug effect was evident within approximately 30 min. During infusion of esmolol, four of nine patients receiving intravenous nitroglycerin required downward adjustment of nitroglycerin infusion rate to maintain systolic blood pressure greater than 90 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)

Esmolol: safety and efficacy in postoperative cardiothoracic patients with supraventricular tachyarrhythmias

Esmolol, an intravenous, ultrashort-acting beta-blocker, was studied for its ability to safely control supraventricular arrhythmias up to 24 hours in 15 postoperative cardiothoracic surgery patients with atrial fibrillation or flutter and rapid ventricular response. Esmolol obtained an initial therapeutic response in nine (60 percent) patients. Mean heart rate for the 15 patients was reduced from 139 +/- 12 beats/min before therapy to 106 +/- 21 beats/min during esmolol infusion (p less than 0.01). The mean time to a therapeutic response after initiation of therapy, using a multistep titration regimen (500 micrograms/kg/min loading infusions over one minute, prior to incremental titration steps from 50 to 300 micrograms/kg/min over 4 to 14 minutes), was 22 +/- 9 minutes, and therapy was continued for 17 +/- 9 hours in responders. Esmolol significantly lowered blood pressure in the group studied and resulted in mild supine or orthostatic hypotension in ten (67 percent) patients. Side effects, including hypotension (10/15 patients), gastrointestinal disturbances (2/15), and weakness or somnolence (6/15), were transient and were not associated with serious clinical sequelae. We conclude that esmolol is effective for rate control in a majority of postoperative cardiothoracic surgery patients with atrial fibrillation or flutter. Side effects, although mild, occur relatively frequently, limiting prolonged infusions and warranting close surveillance of patients.

Ultra-short-acting beta-adrenergic blockers

The ultra-short-acting beta-adrenergic blockers are parenteral agents that can be rapidly titrated in clinical situations where immediate beta-adrenergic blockade is warranted. The effects of those drugs rapidly dissipate after termination of treatment, providing an important safety feature. Esmolol, the prototype drug of this class, is approved for treatment of supraventricular tachyarrhythmias but also has potential use in treatment of patients with perioperative hypertension and acute myocardial ischemia.

Managing critically ill patients with esmolol. An ultra short-acting beta-adrenergic blocker

Esmolol is a new intravenous beta-adrenergic blocker with an ultrashort (nine-minute) elimination half-life, which has been studied predominantly for control of supraventricular tachycardia and management of certain types of hypertension. Clinical studies indicate that the efficacy of esmolol is equivalent to that of propranolol and verapamil for control of supraventricular tachycardia and to sodium nitroferricyanide (sodium nitroprusside) for control of postoperative hypertension. Esmolol also has been shown to control heart rate and blood pressure during episodes of acute myocardial ischemia. Cardioselectivity is similar to that of metoprolol, and the ability to titrate the effect of esmolol may provide additional assurance that beta-adrenergic blockade will remain within the cardioselective range. The most commonly observed adverse effect seen in clinical trials was asymptomatic hypotension. Hypotension may be minimized by titrating to the minimum effective dose and is readily reversed within 10 to 30 minutes of discontinuing the infusion of esmolol. These unique features represent advantages of great potential merit in critical care medicine.

The effects of esmolol on the hemodynamics of acute theophylline toxicity

The effects of esmolol, a beta 1-selective adrenergic receptor antagonist with a short duration of action, were studied in a canine model of the hemodynamics of theophylline toxicity. Animals were anesthetized, then given 50 mg/kg aminophylline IV over 20 minutes followed by a continuous infusion of 1.75 mg/kg/hr. Hemodynamic parameters, including heart rate, cardiac output, systemic blood pressure, pulmonary arterial pressure, and pulmonary artery wedge pressure, were measured every 30 minutes along with plasma catecholamines and theophylline levels. Marked tachycardia was seen in the intoxicated state, with heart rate rising from a baseline of 128.0 +/- 8.3 beats per minute (BPM) to 179.0 +/- 7.4 BPM (P = .012). This was associated with increases in catecholamines (baseline norepinephrine .04 +/- .04 ng/mL plasma rose to .42 +/- .21 ng/mL plasma after intoxication, P = .048). The average serum theophylline level during the experiment was 44.0 +/- 1.1 micrograms/mL serum. Esmolol then was given by IV infusion in these animals in doses of 25, 50, and 100 micrograms/kg/min. It returned the heart rate to the preintoxication baseline in a dose-related manner. Esmolol did not decrease cardiac output or lower blood pressure.

Esmolol: a titratable short-acting intravenous beta blocker for acute critical care settings

Esmolol (Brevibloc) is an intravenous, short-acting, titratable, cardioselective beta blocker with a very rapid onset and offset of action (t1/2 = 9.2 minutes). Esmolol-induced beta blockade can be maintained as long as infusion is continued. It exhibits neither intrinsic sympathomimetic activity nor significant membrane-stabilizing activity. It is rapidly metabolized by an esterase in the erythrocyte cytosol to an inactive acid metabolite. Its hemodynamic and electrophysiologic effects are similar to those of other beta blockers. Unlike the effects of other beta blockers, however, the effects of esmolol dissipate rapidly to baseline within 30 minutes after its discontinuation. Evidence obtained from clinical studies indicates that esmolol is effective and safe in reducing the ventricular rate in patients with supraventricular tachyarrhythmias, and in reducing the heart rate in patients with acute myocardial infarction and/or unstable angina. Esmolol has also been shown to be effective and safe in attenuating the tachycardia and hypertension seen during the intraoperative period. Data from postoperative patients indicate that esmolol is ideal as sole-agent therapy for the treatment of moderate postoperative hypertension associated with a hyperdynamic state. The short duration of action and titratability of esmolol make it an ideal drug for use in patients in whom the clinical need for beta blockade is limited in duration, and it offers additional safety in patients in whom beta blockade is beneficial; however, it might be precluded because of coexisting contraindications. To date, experience with esmolol in over 1200 patients has been gathered, and the adverse effect profile is basically similar to that reported here.

Safety and efficacy of flestolol, a new ultrashort-acting beta-adrenergic blocking agent, for supraventricular tachyarrhythmias

Flestolol, a new ultrashort-acting (half-life 6.9 minutes) beta-blocking drug, was administered by intravenous infusion to 18 patients with new-onset atrial fibrillation or flutter and rapid ventricular response (120 beats/min or more for at least 30 minutes). Drug dose of flestolol was progressively increased until at least 1 of 3 endpoints was achieved: at least a 20% reduction in heart rate from baseline, heart rate 100 beats/min or less, or conversion to normal sinus rhythm. Flestolol was then administered as a maintenance infusion up to 24 hours. When flestolol was discontinued, patients were monitored for 1 additional hour. The mean ventricular response at baseline of 133 +/- 12 beats/min decreased to 103 +/- 20 beats/min at the end of flestolol titration (p less than 0.0001). Fourteen patients (78%) achieved defined endpoints. All 14 patients who continued to receive maintenance infusion had a sustained response. When flestolol was discontinued, ventricular response increased 33 +/- 23% within 60 minutes. The only adverse effect seen was hypotension in 2 patients. Flestolol is effective in slowing ventricular response in new-onset atrial fibrillation and flutter, maintains a therapeutic effect during continuous infusion and rapidly loses therapeutic effect when discontinued.

Clinical electrophysiology of flestolol, a potent ultra short-acting beta blocker

We measured the electrophysiologic effects of flestolol, an ultra short-acting beta blocker, in 15 patients at two infusion rates: a 45 micrograms/kg loading dose followed by a 5 micrograms/kg/min infusion and a 60 micrograms/kg loading dose followed by a 10 micrograms/kg/min infusion. Electrophysiologic measurements were made after 15 minutes at each infusion rate (plasma concentrations 46 +/- 11 and 94 +/- 23 ng/ml). Flestolol produced dose-dependent effects on the sinus node, the atrioventricular (AV) node, and right ventricular refractoriness, whereas atrial refractoriness and infranodal conduction were unchanged. At the 10 micrograms/kg/min dose, flestolol prolonged sinus cycle length by a mean of 20% (p = 0.0001), corrected sinus node recovery time by 42% (p = 0.02), AH interval by 21% (p = 0.0001), AV node effective refractory period by 28%, AV node Wenckebach cycle length by 30% (0.0001), and right ventricular effective refractory period by 5% (p = 0.03). A significant concentration-effect relationship (p less than or equal to 0.03) was present for all variables which had significant dose-effect relationships. No patient developed hypotension, bradyarrhythmias, or other toxicity. Sinus cycle length decreased linearly with time in the post infusion period (r = 0.99); by 30 minutes post infusion, measured electrophysiologic variables had returned to control values and flestolol plasma concentration had decreased to 4 +/- 2 ng/ml. Flestolol's electrophysiologic effects are similar to those of other beta blockers. In doses up to 10 micrograms/kg/min, it is safe in selected patients, has rapid onset and offset of action, and does not cause acute rebound.

Efficacy and safety of esmolol vs propranolol in the treatment of supraventricular tachyarrhythmias: a multicenter double-blind clinical trial

The efficacy and safety of intravenous esmolol infusion was compared to that of intravenous propranolol injection in patients with supraventricular tachyarrhythmias (SVT) in a multicenter double-blind parallel study. A total of 127 patients were randomized to either the esmolol (n = 64) or propranolol (n = 63) group. Therapeutic response was achieved in 72% of esmolol and 69% of propranolol patients (p = NS). The average dose of esmolol in responders was 115 +/- 11 micrograms/kg/min. Therapeutic response was sustained in the 4-hour maintenance period in 67% of esmolol and 58% of propranolol patients (p = NS). Rate of conversion to normal sinus rhythm was similar in the two treatment groups. After discontinuation, rapid recovery from beta blockade (decrease in heart rate reduction) was observed in esmolol patients (within 10 minutes) compared to propranolol patients (no change in heart rate up to 4.3 hours). The principal adverse effect was hypotension, reported in 23 esmolol (asymptomatic in 19) and four propranolol (asymptomatic in three) patients. In the majority of esmolol patients, hypotension resolved quickly (within 30 minutes) after esmolol was discontinued. It was concluded that esmolol was comparable in efficacy and safety to propranolol in the treatment of patients with SVT. Unlike propranolol, because of the short half-life of esmolol, rapid control of beta blockade is possible with esmolol in clinical conditions when required.

Comparative efficacy and tolerance of esmolol to propranolol for control of supraventricular tachyarrhythmia

This multicenter, double-blind, randomized, parallel study compared the effectiveness and tolerance of intravenous esmolol with intravenous propranolol in patients with supraventricular tachyarrhythmia (heart rate [HR] greater than 120 beats/min). Efficacy was evaluated in 53 patients receiving esmolol and in 57 patients receiving propranolol. Patients randomized to esmolol received infusions of various doses of esmolol ranging from 50 to 300 micrograms/kg/min (each dose infused for 5 minutes) over a 30-minute titration period with intermittent placebo boluses of propranolol. Those randomized for propranolol received 1 mg/min for the first 3 minutes, and then another 3 mg from minutes 5 to 8 with continuous placebo esmolol infusion during the 30-minute titration period. A therapeutic response, defined by 20% or greater reduction in HR, HR less than 100 beats/min or conversion to normal sinus rhythm, was achieved in 72% of patients on esmolol compared with 69% of patients on propranolol (difference not significant). The therapeutic response was maintained in 67% of patients on esmolol and 58% of patients on propranolol (difference not significant) during a 4-hour maintenance period. Conversion to normal sinus rhythm occurred in 14% of esmolol patients and 16% of propranolol patients during titration and 10% of esmolol and 8% of propranolol patients during maintenance. After discontinuation of study drugs, a more rapid reversal of the reduction in HR was observed in esmolol patients compared with those patients receiving propranolol. Adverse reactions were seen in 29 (45%) patients on esmolol and 11 (18%) patients on propranolol. The principle adverse reaction was hypotension, which was predominantly asymptomatic and found in 23 patients receiving esmolol and 4 receiving propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of an ultra short-acting beta-blocker in patients with acute myocardial ischemia

Esmolol is a new ultra short-acting (half-life [t1/2] beta 9 min) beta 1-adrenergic-receptor antagonist reported to have no intrinsic sympathomimetic activity. The safety and efficacy of esmolol in lowering the ventricular rate and rate-pressure product in patients with acute myocardial infarction (n = 5), postmyocardial infarction angina (n = 10), or acute unstable angina (n = 4), and without cardiogenic shock were studied. After a 30 min observation period, esmolol was titrated to a maximum dose of 300 micrograms/kg/min and infused for up to 420 min. The ventricular rate fell from 92 +/- 11 (mean +/- SD) to 77 +/- 13 beats/min (p less than .01) and the systolic arterial pressure decreased from 120 +/- 13 to 97 +/- 11 mm Hg (p less than .01) during the initial 30 min titration period. There was no significant change during the maintenance phase, and both the ventricular rate and arterial pressure returned rapidly toward baseline values within 30 min of termination of the infusion. The cardiac index fell from 2.8 +/- 0.6 to 2.2 +/- 0.6 liters/min/m2 (p less than .01) during the same period, and also returned to the baseline level 30 min after termination of the infusion. There was no significant change in the pulmonary capillary wedge pressure, respiratory rate, or PR interval. Five patients required termination of infusion because of hypotension and all recovered uneventfully within 30 min of stopping the esmolol. One patient required a brief infusion of dopamine to restore hemodynamic stability.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-adrenergic blockers. Choosing among them

The six currently available beta-adrenergic blocking agents have significant and clinically important differences in their potency, selectivity, partial agonist effect, lipid solubility, and cost. These differences account for many of the observed variations in drug action and dosage scheduling as well as for some of the side effects. Careful choices within this group may lead to more effective treatment.