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

Open-Label Two-Dose Pilot Study of Landiolol for the Treatment of Atrial Fibrillation/Atrial Flutter in Caucasian Patients

BACKGROUND

We investigated for the first time the suitability of landiolol, an ultra-short-acting β1-specific β-blocker, for the treatment of atrial fibrillation/atrial flutter (AF/AFL) in Caucasian patients.Methods and Results:The 20 study patients received landiolol as a continuous infusion (starting dose 40 µg/kg/min) with (B+CI) or without (CI) a preceding bolus dose (100 µg/kg/min administered over 1 min) in a prospective open-label study. The primary endpoint was the proportion of patients with sustained heart rate (HR) reduction ≥20% or to <90 beats/min within 16 min of starting the CI. Secondary endpoints were the pharmacodynamics, pharmacokinetics, AF/AFL symptoms, safety and tolerability of landiolol. At 16 min, HR was reduced in all patients treated with landiolol. The primary endpoint was met by 60% of patients in the CI group and 40% in the B+CI group without a significant group difference. Overall reduction of AF/AFL symptoms at 16 min was 72%. Safety and local tolerability of landiolol were excellent, and no serious adverse events occurred.

CONCLUSIONS

Continuous infusion of landiolol with a starting dose of 40 µg/kg/min is suitable for the acute treatment of tachycardic AF/AFL in Caucasian patients. Administration of a preceding bolus seems unnecessary.

Atrial Fibrillation in the ICU

Atrial fibrillation (AF) is the most common arrhythmia encountered in the ICU. Preexisting AF is highly prevalent among older patients with chronic conditions who are at risk for critical illness, whereas new-onset AF can be triggered by accelerated atrial remodeling and arrhythmogenic triggers encountered during critical illness. The acute loss of atrial systole and onset of rapid ventricular rates that characterize new-onset AF often lead to decreased cardiac output and hemodynamic compromise. Thus, new-onset AF is both a marker of disease severity as well as a likely contributor to poor outcomes, similar to other manifestations of organ dysfunction during critical illness. Evaluating immediate hemodynamic effects of new-onset AF during critical illness is an important component of rapid clinical assessment aimed at identifying patients in need of urgent direct current cardioversion, treatment of reversible inciting factors, and identification of patients who may benefit from pharmacologic rate or rhythm control. In addition to acute hemodynamic effects, new-onset AF during critical illness is associated with both short- and long-term increases in the risk of stroke, heart failure, and death, with AF recurrence rates of approximately 50% within 1 year following hospital discharge. In the absence of a strong evidence base, there is substantial practice variation in the choice of strategies for management of new-onset AF during critical illness. We describe acute and long-term evaluation and management strategies based on current evidence and propose future avenues of investigation to fill large knowledge gaps in the management of patients with AF during critical illness.

New-onset atrial fibrillation in critically ill patients

New-onset atrial fibrillation is a common problem in critically ill patients, with reported incidence ranging from 5% to 46%. It is associated with significant morbidity and mortality. The present review summarizes studies investigating new-onset atrial fibrillation conducted in the critical care setting, focusing on the etiology, management of the hemodynamically unstable patient, rate versus rhythm control, ischemic stroke risk and anticoagulation. Recommendations for an approach to management in the intensive care unit are drawn from the results of these studies.

Automatically finding relevant citations for clinical guideline development

OBJECTIVE

Literature database search is a crucial step in the development of clinical practice guidelines and systematic reviews. In the age of information technology, the process of literature search is still conducted manually, therefore it is costly, slow and subject to human errors. In this research, we sought to improve the traditional search approach using innovative query expansion and citation ranking approaches.

METHODS

We developed a citation retrieval system composed of query expansion and citation ranking methods. The methods are unsupervised and easily integrated over the PubMed search engine. To validate the system, we developed a gold standard consisting of citations that were systematically searched and screened to support the development of cardiovascular clinical practice guidelines. The expansion and ranking methods were evaluated separately and compared with baseline approaches.

RESULTS

Compared with the baseline PubMed expansion, the query expansion algorithm improved recall (80.2% vs. 51.5%) with small loss on precision (0.4% vs. 0.6%). The algorithm could find all citations used to support a larger number of guideline recommendations than the baseline approach (64.5% vs. 37.2%, p<0.001). In addition, the citation ranking approach performed better than PubMed's "most recent" ranking (average precision +6.5%, recall@k +21.1%, p<0.001), PubMed's rank by "relevance" (average precision +6.1%, recall@k +14.8%, p<0.001), and the machine learning classifier that identifies scientifically sound studies from MEDLINE citations (average precision +4.9%, recall@k +4.2%, p<0.001).

CONCLUSIONS

Our unsupervised query expansion and ranking techniques are more flexible and effective than PubMed's default search engine behavior and the machine learning classifier. Automated citation finding is promising to augment the traditional literature search.

Early management of stroke patients in the emergency department

Stroke continues to be one of the leading causes of death and adult disability. Increasing public awareness of stroke has led to a rise in the number of patients presenting to emergency departments (EDs) who qualify for emergent and time-sensitive treatments such as t-PA, clot extraction, and surgery. Timely treatment and supportive care of the stroke patient in the ED is crucial for patient outcomes. Emergency medicine (EM) pharmacists are the medication experts and can have a significant impact on the care of a stroke patient. Thus, it is essential for EM pharmacists to have a solid knowledge of the current guidelines and evidence-based literature or lack there of. In this article, we describe the epidemiology of stroke, review the classifications of stroke, and discuss the present treatment strategies for emergent and supportive care.

Antiarrhythmic Drug Therapy of Supraventricular Tachycardia

Pharmacologic therapy is commonly used for the acute treatment and termination of paroxysmal supraventricular tachycardia (SVT) and continues to be an important long-term option for some patients. Drug choice depends on the correct diagnosis of the arrhythmia and an understanding of its mechanism. Pharmacologic agents commonly used in the acute and chronic treatment of SVT are reviewed along with their effect on the various types of SVT. Drugs that are well tolerated with minimal side effects are preferred over agents with perhaps more efficacy but higher risk of toxicity.

Atrial Fibrillation: The New Epidemic of the Ageing World

The prevalence of atrial fibrillation (AF) increases with age. As the population ages, the burden of AF increases. AF is associated with an increased incidence of mortality, stroke, and coronary events compared to sinus rhythm. AF with a rapid ventricular rate may cause a tachycardia-related cardiomyopathy. Immediate direct-current (DC) cardioversion should be performed in patients with AF and acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta blockers, diltiazem, or verapamil may be administered to reduce immediately a very rapid ventricular rate in AF. An oral beta blocker, verapamil, or diltiazem should be used in persons with AF if a fast ventricular rate occurs at rest or during exercise despite digoxin. Amiodarone may be used in selected patients with symptomatic life-threatening AF refractory to other drugs. Digoxin should not be used to treat patients with paroxysmal AF. Nondrug therapies should be performed in patients with symptomatic AF in whom a rapid ventricular rate cannot be slowed by drugs. Paroxysmal AF associated with the tachycardia-bradycardia syndrome should be treated with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in patients with AF and symptoms such as dizziness or syncope associated with ventricular pauses greater than 3 seconds which are not drug-induced. Elective DC cardioversion has a higher success rate and a lower incidence of cardiac adverse effects than does medical cardioversion in converting AF to sinus rhythm. Unless transesophageal echocardiography has shown no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective DC or drug cardioversion of AF and continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer, especially in elderly patients , ventricular rate control plus warfarin rather than maintaining sinus rhythm with antiarrhythmic drugs. Patients with chronic or paroxysmal AF at high risk for stroke should be treated with long-term warfarin to achieve an International Normalized Ratio of 2.0 to 3.0. Patients with AF at low risk for stroke or with contraindications to warfarin should be treated with aspirin 325 mg daily.

The pharmacokinetics of esmolol in pediatric subjects with supraventricular arrhythmias

Esmolol is often used in the acute management of children with arrhythmias and/or hypertension; however, pharmacokinetic studies of the drug in children have been limited. The objective of this study was to determine the pharmacokinetics of esmolol in children with a history of supraventricular arrhythmias (SVT) who were scheduled for diagnostic electrophysiology study or a catheter ablation procedure. Subjects were stratified into two age groups: 2-11 and 12-16 years. After an episode of stimulated or spontaneous SVT, esmolol was administered intravenously as a 1,000 microg/kg bolus followed by continuous infusion at 300 microg/kg/min. Blood samples were collected before, at 5, 10 and 15 min after the loading dose, and 3, 6, 9, 12, 15 and 20 min after the end of the infusion. Plasma concentration of esmolol was quantitated by a specific LC/MS assay. Pharmacokinetic data were available for 25 subjects. Arterial esmolol concentrations were approximately five times greater than venous concentrations. Esmolol had an extremely short distribution half-life (0.6 min), a rapid terminal elimination half-life (6.9 min), and a rapid clearance (119 +/- 51 mL/min/kg) which was not related to subject age or weight. Seventeen of the subjects (63%) converted to normal sinus rhythm in an average of 2 min (range 0-5 min). The pharmacokinetics of esmolol and its efficacy in terminating SVT in children is similar to that observed in adults.

Selection of drugs in pursuit of rate control strategy

Atrial fibrillation is the most common sustained arrhythmia. Based on multiple large randomized trials, rate control therapy has been shown to be safe and effective and is gaining greater acceptance as a frontline alternative to drugs to maintain sinus rhythm. Adequate rate control can be achieved by atrioventricular nodal blocking agents both in the acute and chronic settings. In refractory patients, other methods such as atrioventricular node ablation can be used to control rate.

Use of beta-blockers in atrial fibrillation

Atrial fibrillation is the most common arrhythmia in the general population and is frequently associated with organic heart disease. beta-adrenoceptor antagonists (b-blockers) are very effective in preventing atrial fibrillation after coronary artery bypass surgery. It has been shown recently that the beta-blocker metoprolol controlled release/extended release (CR/XL) is also effective in maintaining sinus rhythm after conversion of atrial fibrillation. There is concern that class I antiarrhythmic drugs, such as quinidine, disopyramide, and flecainide in particular, may increase mortality. The risk of proarrhythmia associated with beta-blocker treatment is very low. Therefore b-blockers, such as metoprolol CR/XL, may be the first line of treatment to maintain sinus rhythm, especially after myocardial infarction and in patients with chronic heart failure and in those with arterial hypertension. In patients with persistent atrial fibrillation, AV-nodal conduction-slowing drugs, such as calcium channel antagonists and beta-blockers are used to control the ventricular rate during atrial fibrillation. Several studies clearly show that beta-blockers alone, or in combination with digoxin are very effective in controlling the ventricular rate at rest and during exercise. beta-blockers are effective in maintaining sinus rhythm and controlling the ventricular rate during atrial fibrillation. Given these effects and their favorable effects on mortality, beta-blockers should be considered as first-line agents in the management of patients with atrial fibrillation.

Management of the older person with atrial fibrillation

Atrial fibrillation (AF) is associated with a higher incidence of mortality, stroke, and coronary events than is sinus rhythm. AF with a rapid ventricular rate may cause a tachycardia-related cardiomyopathy. Immediate direct-current (DC) cardioversion should be performed in patients with AF and acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta blockers, verapamil, or diltiazem may be given to slow immediately a very rapid ventricular rate in AF. An oral beta blocker, verapamil, or diltiazem should be used in persons with AF if a fast ventricular rate occurs at rest or during exercise despite digoxin. Amiodarone may be used in selected patients with symptomatic life-threatening AF refractory to other drugs. Nondrug therapies should be performed in patients with symptomatic AF in whom a rapid ventricular rate cannot be slowed by drugs. Paroxysmal AF associated with the tachycardia-bradycardia syndrome should be treated with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in patients with AF and with symptoms such as dizziness or syncope associated with ventricular pauses greater than 3 seconds that are not drug-induced. Elective DC cardioversion has a higher success rate and a lower incidence of cardiac adverse effects than does medical cardioversion in converting AF to sinus rhythm. Unless transesophageal echocardiography has shown no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective DC or drug cardioversion of AF and should be continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer, especially in older persons, ventricular rate control plus warfarin rather than maintaining sinus rhythm with antiarrhythmic drugs. Digoxin should not be used to treat patients with paroxysmal AF. Patients with chronic or paroxysmal AF at high risk for stroke should be treated with long-term warfarin to achieve an International Normalized Ratio of 2.0 to 3.0. Patients with AF at low risk for stroke or with contraindications to warfarin should receive 325 mg of aspirin daily.

Antidysrhythmic agents at the turn of the twenty-first century: a current review

The use of class IA agents is gradually on the decline, primarily as a result of its unfavorable risk-to-benefit ratio. Lidocaine, a class IB agent, has been widely used in the acute treatment of VT. However, alternate drugs are being considered increasingly as first-line agents in the acute treatment of VT. Class IC drugs are contraindicated in patients with structural cardiac abnormalities and have a limited usefulness in the management of dysrhythmias. Beta-blockers continue to increase their role in cardiology, and subsequently their use in managing dysrhythmias. Class III agents, including amiodarone, sotalol, ibutilide, and dofetilide, are among the most widely used antidysrhythmics. Class IV calcium channel blockers have a limited usefulness in tachydysrhythmias. Digoxin and adenosine have unique antidysrhythmic properties and will likely retain their roles as antidysrhythmic agents. In the wake of the effectiveness of amiodarone, the drug that crosses all classes, some now question the benefit of pure agents that block a single, specific ion channel in the heart. After CAST8 demonstrated that antidysrhythmics can increase mortality while seemingly suppressing dysrhythmias, new drugs will continue to undergo intense scrutiny with regard to their efficacy, safety, and usefulness in treating dysrhythmias.

Atrial fibrillation

The prevalence and incidence of atrial fibrillation increase with age. Atrial fibrillation is associated with a higher incidence of coronary events, stroke, and mortality than sinus rhythm. A fast ventricular rate associated with atrial fibrillation may cause tachycardia-related cardiomyopathy. Management of atrial fibrillation includes treatment of underlying causes and precipitating factors. Immediate direct-current cardioversion should be performed in persons with atrial fibrillation associated with acute myocardial infarction, chest pain due to myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous beta-blockers, verapamil, or diltiazem may be used to immediately slow a fast ventricular rate associated with atrial fibrillation. An oral beta-blocker, verapamil, or diltiazem should be given to persons with atrial fibrillation if a rapid ventricular rate occurs a rest or during exercise despite digoxin. Amiodarone may be used in selected persons with symptomatic life-threatening atrial fibrillation refractory to other drug therapy. Nondrug therapies should be performed in persons with symptomatic atrial fibrillation in whom a rapid ventricular rate cannot be slowed by drug therapy. Paroxysmal atrial fibrillation associated with the tachycardia-bradycardia syndrome should be managed with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in persons with atrial fibrillation in whom symptoms such as dizziness or syncope associated with non-drug-induced ventricular pauses longer than 3 seconds develop. Elective direct-current cardioversion has a higher success rate and a lower incidence of cardiac adverse effects than medical cardioversion in converting atrial fibrillation to sinus rhythm. Unless transesophageal echocardiography shows no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective direct-current or drug cardioversion of atrial fibrillation and continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer the treatment strategy of ventricular rate control plus warfarin rather than to maintain sinus rhythm with antiarrhythmic drugs, especially in older patients. Digoxin should not be used in persons with paroxysmal atrial fibrillation. Patients with chronic or paroxysmal atrial fibrillation who are at high risk for stroke should be treated with long-term warfarin to achieve an International Normalized Ratio (INR) of 2.0 to 3.0. Persons with atrial fibrillation who are at low risk for stroke or who have contraindications to warfarin should receive 325 mg aspirin daily.

Weathering the storm: beta-blockade and the potential for disaster in severe hyperthyroidism

Some patients with advanced thyrotoxicosis have occult cardiac dysfunction. The use of long-acting beta-blockers, traditional in the management of thyrotoxicosis, may have disastrous consequences in this setting. The following report documents the cardiovascular collapse and asystolic arrest of a patient with hyperthyroidism when treated with sotolol. Though the patient was successfully resuscitated, the long duration of action of sotolol necessitated prolonged inotropic and vasopressor support. A shorter acting beta-blocker, such as esmolol, theoretically may be a safer option.

Management of the older person with atrial fibrillation

OBJECTIVE

To review the management of the older person with atrial fibrillation (AF).

DATA SOURCES

A computer-assisted search of the English language literature (MEDLINE) database followed by a manual search of the bibliographies of pertinent articles.

STUDY SELECTION

Studies on the management of persons with AF were screened for review. Studies of persons older than age 60 and recent studies were emphasized.

DATA EXTRACTION

Pertinent data were extracted from the reviewed articles. Emphasis was placed on studies involving older persons. Relevant articles were reviewed in depth.

DATA SYNTHESIS

Available data about the management of persons with paroxysmal or chronic AF were summarized

CONCLUSIONS

Management of AF includes treatment of the underlying disease and precipitating factors. Immediate direct-current cardioversion should be performed in persons with AF associated with an acute myocardial infarction, chest pain caused by myocardial ischemia, hypotension, severe heart failure, or syncope. Intravenous verapamil, diltiazem, or beta-blockers should be used to slow a very rapid ventricular rate associated with AF immediately. Oral verapamil, diltiazem, or a beta-blocker should be given if a rapid ventricular rate occurs at rest or during exercise despite digoxin. Amiodarone may be used in selected persons with symptomatic life-threatening AF refractory to other drug therapy. Nondrug therapies should be performed in persons with symptomatic AF in whom a rapid ventricular rate cannot be slowed by drug therapy. Paroxysmal AF associated with the tachycardia-bradycardia syndrome should be treated with a permanent pacemaker in combination with drugs. A permanent pacemaker should be implanted in persons with AF who develop cerebral symptoms such as dizziness or syncope associated with ventricular pauses greater than 3 seconds that are not drug-induced. Elective cardioversion of AF should not be performed in asymptomatic older persons with chronic AF. Unless transesophageal echocardiography has shown no thrombus in the left atrial appendage before cardioversion, oral warfarin should be given for 3 weeks before elective direct-current or drug cardioversion of AF and continued for at least 4 weeks after maintenance of sinus rhythm. Many cardiologists prefer the treatment strategy, especially in older persons, of ventricular rate control plus warfarin rather than maintaining sinus rhythm with antiarrhythmic drugs. Digoxin should be avoided in persons with sinus rhythm who have a history of paroxysmal AF. Older persons with chronic or paroxysmal AF who are at high risk for stroke or who have a history of hypertension and no contraindications to warfarin should receive long-term warfarin to achieve an International Normalized Ratio of 2.0 to 3.0. Older persons with AF who are at low risk for stroke or who have contraindications to warfarin should receive 325 mg of aspirin daily.

The effects of a new ultra-short-acting beta-adrenergic blocker, ONO-1101, on cardiac function during and after cardiopulmonary bypass

The administration of an ultra-short-acting beta-adrenergic antagonist, esmolol, has been introduced as a novel method for beating-heart surgery. In the present study, a new ultra-short-acting beta-blocker, ONO-1101, was administered during cardiopulmonary bypass (CPB) to investigate its effects on cardiac function and hemodynamics. Nine adult mongrel dogs underwent 60 min of CPB during which they were given either ONO-1101 (ONO group; n = 4) or saline (control group; n = 5). In the ONO group, the hearts became flaccid enough for surgery to be performed without cardiac standstill within 10 min after the commencement of ONO-1101 with significant decreases in the heart rate, the preload recruitable stroke work (PRSW), and the slope of the end-systolic left ventricular pressure-volume relationship (Emax). The mean arterial pressure and systemic vascular resistance also decreased, but were maintained above 50 mmHg during CPB without catecholamine. These indices increased to the control group level 20 min after the discontinuation of ONO-1101. The serum concentration of ONO-1101 decreased from the maximum level of 121 +/- 15 microg/ml soon after infusion to 11 +/- 5 microg/ml within 30 min after discontinuation. These data suggest that ONO-1101 may be useful to enable beating-heart surgery to be performed without aortic cross-clamp as an ultra-short-acting beta-adrenergic blocker.

Pharmacologic control of heart rate in atrial fibrillation

Atrial fibrillation is associated with a resting heart rate in excess of age-matched subjects in sinus rhythm, and there is an additional steep rise in rate during exertion. This article reviews the factors responsible for this tachycardia, the pharmacologic agents commonly used for heart rate control, and the effects of atrial antiarrhythmic agents on the heart rate during paroxysmal atrial fibrillation.

Esmolol. A review of its therapeutic efficacy and pharmacokinetic characteristics

Esmolol is an ultra short-acting intravenous cardioselective beta-antagonist. It has an extremely short elimination half-life (mean: 9 minutes; range: 4 to 16 minutes) and a total body clearance [285 ml/min/kg (17.1 L/h/kg)] approaching 3 times cardiac output and 14 times hepatic blood flow. The alpha-distribution half-life is approximately 2 minutes. When esmolol is administered as a bolus followed by a continuous infusion, onset of activity occurs within 2 minutes, with 90% of steady-state beta-blockade occurring within 5 minutes. Full recovery from beta-blockade is observed 18 to 30 minutes after terminating the infusion. Esmolol blood concentrations are undetectable 20 to 30 minutes postinfusion. The elimination of esmolol is independent of renal or hepatic function as it is metabolised by red blood cell cytosol esterases to an acid metabolite and methanol. The acid metabolite, which is renally eliminated, has 1500-fold less activity than esmolol. Methanol concentrations remain within the range of normal endogenous levels. Clinically, esmolol is used for the following: (i) situations where a brief duration of adrenergic blockade is required, such as tracheal intubation and stressful surgical stimuli; and (ii) critically ill or unstable patients in whom the dosage of esmolol is easily titrated to response and adverse effects are rapidly managed by termination of the infusion. In adults, bolus doses of 100 to 200mg are effective in attenuating the adrenergic responses associated with tracheal intubation and surgical stimuli. For the control of supraventricular arrhythmias, acute postoperative hypertension and acute ischaemic heart disease, doses of < 300 micrograms/kg/min, administered by continuous intravenous infusion, are used. The principal adverse effect of esmolol is hypotension (incidence of 0 to 50%), which is frequently accompanied with diaphoresis. The incidence of hypotension appears to increase with doses exceeding 150 micrograms/kg/min and in patients with low baseline blood pressure. Hypotension infrequently requires any intervention other than decreasing the dose or discontinuing the infusion. Symptoms generally resolve within 30 minutes after discontinuing the drug. In surgical and critical care settings where clinical conditions are rapidly changing, the pharmacokinetic profile of esmolol allows the drug to provide rapid pharmacological control and minimises the potential for serious adverse effects.

Pharmacodynamics and pharmacokinetics of esmolol, a short-acting beta-blocking agent, in children

Esmolol, a short-acting intravenous cardioselective beta-blocking agent, was evaluated for age-dependent pharmacodynamic and pharmacokinetic features in 17 young patients (6 months to 14 years). A loading dose (500 micrograms/kg/min) alternating with a maintenance dose (25-200 micrograms/kg/min, titrating by 25 micrograms/kg/min every 4 min) was infused until the heart rate or mean arterial pressure decreased 10%. Cardiac index, left ventricular shortening fraction, and systemic vascular resistance were measured at baseline, peak esmolol effect, and recovery. Serum esmolol concentrations were obtained to determine the half-life and the elimination rate constant. Esmolol reduced the heart rate, blood pressure, shortening fraction, and cardiac index in all patients, but it did not change systemic vascular resistance. Maintenance esmolol dose was 118 +/- 49 micrograms/kg/min, and the half-life was 2.88 +/- 2.67 min. Blood pressure and heart rate returned to normal within 2-16 min, but cardiac index and shortening fraction took longer to recover. There were no statistically significant age-dependent pharmacodynamic effects, but blood pressure decreased prior to heart rate and cardiac index took longer to recovery in patients who weighed < or = 15 kg. The pharmacokinetic profile in young patients was similar to that of older patients, but the half-life was shorter. The only side effect was transient nausea and vomiting in one patient. Esmolol is a safe and efficacious beta-blocking agent in young patients.

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.

A new dosing regimen for esmolol to treat supraventricular tachyarrhythmia in Chinese patients

OBJECTIVES

The purpose of this study was to find a safe dosing regimen for esmolol infusion to rapidly control supraventricular tachyarrhythmia after cardiac surgery in Chinese patients.

BACKGROUND

Tachycardia increases cardiac work but reduces myocardial perfusion. Thus, in the critical period immediately after cardiac surgery, tachycardia itself warrants urgent intervention. Esmolol, an ultrashort-acting beta-adrenergic blocking agent, has been reported in western published reports to have good results and few side effects in the treatment of supraventricular tachyarrhythmia. However, its clinical application in Chinese patients has not yet been reported.

METHODS

When supraventricular tachyarrhythmia with a rapid ventricular response (> 110/min) was found early after cardiac surgery, esmolol infusion with a different dosing regimen was used to control the tachyarrhythmia.

RESULTS

With the dosing regimen recommended in western published reports (repeated loading infusion with stepwise increment), acute hypotension with systolic pressure < 80 mm Hg occurred in all six patients after 1 min of loading infusion of esmolol (500 micrograms/kg body weight per min). To avoid the aforementioned complications, a new dosing regimen was constructed. The initial infusion rate of esmolol was set at 150 or 100 micrograms/kg per min, depending on the patient's age and blood pressure. When the desired heart rate was achieved, the initial infusion rate was reduced to the maintenance infusion rate to maintain the therapeutic effect [Maintenance infusion rate = Initial infusion rate x (1 - e-0.077t), where t is the time period in minutes required by the initial infusion of esmolol to achieve the therapeutic effect]. With this new dosing regimen, tachycardia in most patients (9 of 11) could be controlled within 10 min, and no one experienced the side effect of hypotension. The maintenance infusion rate of esmolol needed to control supraventricular tachyarrhythmia in our patients was only 73 +/- 42 micrograms/kg per min (mean +/- SD), much less than that noted in western reports.

CONCLUSIONS

The dosing regimen for esmolol infusion recommended in western studies is not suitable for Chinese patients. In this report we propose a new dosing regimen for esmolol infusion that is both safe and rapid in the treatment of supraventricular tachyarrhythmia in Chinese patients.

A clinical study of intravenous cibenzoline in selected patients with recent-onset atrial tachyarrhythmia

Twenty-five adult patients with sustained atrial tachyarrhythmia (ATA) and without heart failure were treated by intravenous cibenzoline, 1 mg/kg, as a slow bolus infusion, followed by a 8 mg/kg/24 h continuous infusion. Sinus rhythm conversion was observed in 18 patients (72 percent success rate). Severe adverse cardiac events were observed in only one patient (4 percent occurrence rate), as a wide QRS complex tachycardia finally requiring a semiemergency direct-current cardioversion. Two minor side effects were additionally observed. A similar population of 21 patients was conventionally treated with amiodarone, either given intravenously, 15 to 20 mg/kg/24 h, or orally, 30 mg/kg/24 h as a single dose. An identical success rate (15/21; 71 percent) was observed. Our results indicate that in selected patients with ATA, cibenzoline and amiodarone are highly effective for producing sinus rhythm conversion. We suggest that the former drug may be used as a first-line treatment. In case of failure, the latter may constitute an alternative to transthoracic electrical countershock.

Adenosine and the treatment of supraventricular tachycardia

Adenosine has recently become widely available for the treatment of paroxysmal supraventricular tachycardia. In order to evaluate its role in the management of arrhythmias, we have reviewed the literature on the cellular mechanisms, metabolism, potential for adverse effects, and clinical experience of the efficacy and safety of intravenous adenosine. Adenosine produces transient atrioventricular nodal block when injected as an intravenous bolus. This is of therapeutic value in the conversion to sinus rhythm of the majority of paroxysmal supraventricular tachycardias, which involve the atrioventricular node in a re-entrant circuit. The mean success rate was 93% from over 600 reported episodes. Compared with other antiarrhythmic agents, adenosine is remarkable for its rapid metabolism and brevity of action, with a half-life of a few seconds. It commonly produces subjective symptoms, particularly chest discomfort, dyspnea, and flushing, which are of short duration only. No serious adverse effect has been reported. Arrhythmias may recur within minutes in a minority of patients. Comparative studies have shown that adenosine is as effective as verapamil in the treatment of supraventricular tachycardia, and has less potential for adverse effects. Patients with supraventricular tachycardia should initially be treated using vagotonic physical maneuvers. Immediate electrical cardioversion is indicated if the arrhythmia is associated with hemodynamic collapse. Adenosine is the preferred drug in those patients in whom verapamil has failed or may cause adverse effects, such as those with heart failure or wide-complex tachycardia. The safety profile of adenosine suggests that it should be the drug of first choice for the treatment of supraventricular tachycardia, but only limited comparative data to support this view are available at present.

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.

Around the beta-blockers, one more time

We review the pharmacology, pharmacokinetics, and relative costs of beta-blockers, as well as indications for and therapeutic controversies surrounding their use. It is hoped that this discussion will assist clinicians in making informed decisions when choosing a drug for a hospital formulary or a particular patient. Beta-blockers are indicated for a variety of noncardiovascular and cardiovascular conditions, including hypertension, ischemic heart disease, arrhythmias, and prophylaxis of myocardial infarction (MI). These agents compete with catecholamines at beta-adrenoreceptors. They have different ancillary properties, including intrinsic sympathomimetic activity (ISA), cardioselectivity, and membrane stabilizing-activity, and vary in their duration of action, route of elimination, and lipophilicity. Beta-blocking agents decrease oxygen demand by exerting a negative inotropic and chronotropic effect. They also reduce blood pressure and possess antiarrhythmic effects. Beta-blockers penetrate the central nervous system (CNS) to different degrees and can cause a wide variety of CNS adverse effects. Nonselective beta-blockers have been noted to slightly reduce renal blood flow. Nadolol is an exception in that either no change, or even a small increase in renal blood flow, is observed upon initiation of therapy. Beta-blockers also act on the pulmonary bed by preventing beta 2-mediated bronchodilation, thereby exacerbating bronchospastic disease in some patients. Beta-adrenergic blocking agents can potentiate both hypoglycemia and hyperglycemia in diabetic patients. Their effects on total peripheral resistance (TPR) are controversial. Initially it appears that beta-blockade increases TPR. After chronic therapy, however, TPR decreases to or below baseline values. These agents appear to be equally efficacious in the treatment of hypertension, arrhythmias, and ischemic heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular and antiarrhythmic effects of esmolol in children

This prospective study evaluated the cardiovascular and antiarrhythmic effects of esmolol, an intravenous beta-blocker with an extremely short half-life. Twenty patients (aged 2 to 16 years) underwent diagnostic electrophysiologic studies at rest and during beta-blockade induced with esmolol. An initial dose of 600 micrograms/kg was infused for 2 minutes and followed by an infusion of 200 micrograms/kg per minute. The dosage was increased by 50 to 100 micrograms/kg per minute every 5 to 10 minutes until a reduction of greater than 10% in either heart rate or mean blood pressure was seen. The dosage required to achieve beta-blockade ranged from 300 to 1000 micrograms/kg per minute (mean 550 micrograms/kg per minute). Electrophysiologic effects included a decrease in the rate of sinoatrial node discharge and delay in conduction through the atrioventricular node. There was no effect on His-Purkinje conduction. Atrial and ventricular effective refractory periods were unchanged. In six patients with supraventricular tachycardia, esmolol prevented induction of tachycardia in four and slowed the rate of the tachycardia in two. In four patients with ventricular tachycardia, clinical findings were improved in three and unchanged in one. Heart rate and blood pressure returned to near baseline values 10 minutes after the esmolol infusion was stopped. Adverse ventricular electrophysiologic effects were observed in two patients with biopsy evidence of myocarditis. No other adverse effects were seen. We conclude that the effects of esmolol in children are similar to those of other beta-blockers and that it is useful in the evaluation and management of pediatric tachyarrhythmias. The weight-adjusted dosage required to induce beta-blockade in children is larger than the adult dosage, and the effects of esmolol dissipate rapidly.

Acute theophylline toxicity and the use of esmolol to reverse cardiovascular instability

Theophylline overdoses are frequent conditions that may require emergency treatment. Clinical features common to severe theophylline toxicity include nausea and vomiting, tachydysrhythmias, metabolic disturbances, seizures, and cardiovascular collapse. Several reports have described these manifestations and their treatments. We report the case of a patient suffering from an acute, intentional theophylline overdose who exhibited the classic features of a toxic ingestion and describe the first reported use of IV esmolol in the treatment of accompanying cardiovascular manifestations.

Recent antiarrhythmic drugs

Clinical failure of antiarrhythmic drugs often occurs in practice. Therefore, there is a need for new, effective and long-acting drugs with a wide therapeutic range and a low level of toxicity. Most new class I compounds block the fast sodium ion inward current of myocardial cells. According to their effects on the recovery kinetics of the sodium ion channel, these drugs are classified into 3 groups: IA (intermediate--cibenzoline, pirmenol, hydroxy-3-S-dihydroquinidine, quinacainol); IB (fast--tocainide, moricizine); IC (slow--flecainide, encainide, propafenone, lorcainide, indecainide, recainam and penticainide). Class IC drugs greatly depress intracardiac conduction and are the most potent antiarrhythmic compounds able to suppress ventricular premature beats. However, it is doubtful that long-term suppression of ventricular arrhythmias will improve survival of the patients. Some new drugs have been developed belonging to other classes: class II, esmolol, a new ultrashort-acting beta blocker; class III, N-acetyl-procainamide and sotalol, which prolong duration of the action potential and increase ventricular refractoriness; class IV, the mixed sodium ion-calcium ion-potassium ion antagonist, bepridil. The pharmacologic properties and the clinical effects of these new antiarrhythmic drugs are reviewed. However, future therapeutic trends will depend on the results of large multicenter clinical secondary prevention trials such as the Cardiac Arrhythmia Suppression Trial. New antiarrhythmic drugs with original electrophysiologic profiles and minimal adverse effects must prove their ability not only to suppress arrhythmias but also to reduce sudden cardiac death rate.

Esmolol versus verapamil in the acute treatment of atrial fibrillation or atrial flutter

The effects of esmolol, an ultrashort-acting beta blocker, and verapamil were compared in controlling ventricular response in 45 patients with atrial fibrillation or atrial flutter, in a randomized, parallel, open-label study. Patients with either new onset (less than 48 hours, n = 31) or old onset (greater than 48 hours, n = 14) of atrial fibrillation or flutter with rapid ventricular rate were stratified to receive esmolol (n = 21) or verapamil (n = 24). Drug efficacy was measured by ventricular rate reduction and conversion to sinus rhythm. The heart rate declined with esmolol from 139 to 100 beats/min (p less than 0.001) and with verapamil from 142 to 97 beats/min (p less than 0.001). Fifty percent of esmolol-treated patients with new onset of arrhythmias converted to sinus rhythm, whereas only 12% of those who received verapamil converted (p less than 0.03). Mild hypotension was observed in both treatment groups. Esmolol compares favorably with verapamil with respect to both efficacy and safety in acutely decreasing ventricular response during atrial fibrillation or flutter. Moreover, conversion to sinus rhythm is significantly more likely with esmolol.

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)

Efficacy of esmolol in the treatment and transfer of patients with supraventricular tachyarrhythmias to alternate oral antiarrhythmic agents

The efficacy and safety of esmolol, a titratable intravenous beta-adrenergic blocking agent with a short elimination half-life (t 1/2 = 9.0 min) was evaluated in a multicenter open-label study for the treatment of supraventricular tachyarrhythmias (heart rate greater than 100 bpm). The study also investigated the feasibility of transferring patients from esmolol to alternate oral antiarrhythmic agents without loss of therapeutic response. Of the 113 patients studied, 95 (84%) achieved therapeutic response (reduction in heart rate of 15% or more or conversion to sinus rhythm). Most of these patients (93%) achieved the therapeutic response at esmolol doses of 200 micrograms/kg/min or lower. Transfer from esmolol to an oral antiarrhythmic agent(s) was studied in 76 patients. Alternate antiarrhythmic agents used in this study were digoxin (N = 25), propranolol (N = 21), verapamil (N = 10), metoprolol (N = 11), quinidine (N = 2), and a combination of two antiarrhythmic agents (N = 7). Sixty-seven (88%) patients were successfully transferred to oral antiarrhythmic agents without loss of the therapeutic response obtained with esmolol. The most frequent adverse effect observed during the study was hypotension, which resolved quickly (16 +/- 14 min) either by decreasing the dose or by discontinuation of esmolol infusion. This study supports previous observations concerning the safety and efficacy of esmolol in the treatment of supraventricular tachyarrhythmias. Furthermore, it demonstrates that the majority of patients successfully treated with esmolol can be safely and effectively transferred to oral therapy with alternate antiarrhythmic agents.

Controlled beta-receptor blockade with esmolol and flestolol

Beta-receptor-blocking agents are commonly used in the management of various cardiovascular diseases. Recently, esmolol, a pharmacokinetically novel cardioselective beta-receptor-blocking agent, has been introduced for use in the treatment of critically ill patients. It is devoid of intrinsic sympathomimetic activity and in doses used clinically, it has no direct depressant effect on the heart. Esmolol is an ester and is metabolized by choline-esterase to ASL 8123, an inactive molecule. Esmolol has an elimination half-life of nine minutes which accounts for its ultrashort duration of action. This unique pharmacokinetic property provides two advantages over other longer-acting beta-receptor-blocking agents. First, the magnitude of beta-receptor blockade can be titrated to a desired level. Second, if adverse effects are experienced, reducing the dosage or terminating the infusion results in rapid reversal of its pharmacological effects. Another ultrashort-acting, non-cardioselective beta-receptor blocking agent, flestolol is undergoing clinical evaluation. Esmolol has been approved for the management of supraventricular tachycardia. The clinical safety of these novel drugs will expand the use of beta-receptor-blocking agents in the management of cardiovascular diseases in critically ill patients.