Conversion of recent-onset atrial fibrillation with intravenous amiodarone: a meta-analysis of randomized controlled trials

Tedisamil: a new novel antiarrhythmic

Solvay Pharmaceuticals is currently developing tedisamil (KC-8857), a novel antiarrhythmic with additional anti-ischaemic properties, which acts via potassium channel blockade. This drug can be categorised as a class III antiarrhythmic agent due to its effects of action potential and QT interval prolongation in these patients. This agent was initially developed for its anti-ischaemic properties and Phase I trials have shown tedisamil to be an effective bradycardic agent, as well as causing a reverse rate-dependent QT interval prolongation. Subsequent Phase II results have confirmed that in patients with ischaemic heart disease, tedisamil had beneficial haemodynamic and anti-ischaemic effects. Phase III studies in patients with ischaemic heart disease indicated that tedisamil is an effective agent for the treatment of angina, resulting in a dose-dependent increase in anginal threshold (with a decrease in anginal attacks, increased exercise capacity during treadmill exercise and decreased electrocardiographic signs of exercise induced ischaemia) in comparison to placebo. Although tedisamil has been shown to be an effective anti-ischaemic agent, with Phase III trials for angina pectoris now completed, the company are now pursuing the use of tedisamil for the treatment of atrial fibrillation, for which tedisamil is still in Phase II/III clinical trials. Launch data are not yet known.

A benefit–risk assessment of class III antiarrhythmic agents

The prevalence of arrhythmia in the population is increasing as more people survive for longer with cardiovascular disease. It was once thought that antiarrhythmic therapy could save life, however, it is now evident that antiarrhythmic therapy should be administrated with the purpose of symptomatic relief. Since many patients experience a decrease in physical performance as well as a diminished quality of life during arrhythmia there is still a need for antiarrhythmic drug therapy. The development of new antiarrhythmic agents has changed the focus from class I to class III agents since it became evident that with class I drug therapy the prevalence of mortality is considerably higher. This review focuses on the benefits and risks of known and newer class III antiarrhythmic agents. The benefits discussed include the ability to maintain sinus rhythm in persistent atrial fibrillation patients, and reducing the need for implantable cardioverter defibrillator shock/antitachycardia therapy, since no class III antiarrhythmic agents have proven survival benefit. The risks discussed mainly focus on pro-arrhythmia as torsade de pointes ventricular tachycardia.

Intravenous amiodarone for conversion of atrial fibrillation: misled by meta-analysis?

Therapeutic goals for atrial fibrillation (AF) include ventricular rate control, stroke prevention, conversion to normal sinus rhythm, and maintenance of normal sinus rhythm. The optimal strategy of rate versus rhythm control for acute management of patients with AF is a continuing debate. However, selected patients may require acute treatment with antiarrhythmic agents for conversion of symptomatic AF episodes to normal sinus rhythm. Recently published randomized controlled trials, qualitative systematic reviews, meta-analyses, and evidence-based international consensus guidelines have addressed the controversy regarding acute conversion of AF using antiarrhythmic therapy. Although meta-analyses often provide the highest level of evidence, the validity and application of their results are based on the quality of their methodology and accuracy of reporting. Authors of the most recent meta-analysis of amiodarone for conversion of AF state that the drug is effective and relatively rapid acting in converting AF to normal sinus rhythm in a wide range of patients, and they recommend it as a first-line drug. We feel that these conclusions are overstated and potentially misleading due to methodologic limitations of the analysis. The results of this meta-analysis and others concerning acute conversion of AF should be viewed as hypothesis generating and not the definitive answer to this question. Ultimately, well-designed, adequately powered, randomized placebo- or rate-controlled trials are needed in specific patient populations with AF to determine the absolute benefit of intravenous amiodarone for conversion of AF to normal sinus rhythm. Until more data are available, intravenous amiodarone cannot be promoted as a first-line agent for this purpose.

Lack of a hypotensive effect with rapid administration of a new aqueous formulation of intravenous amiodarone

Hypotension is the most frequent adverse event reported with intravenous amiodarone. Hypotension has been attributed to the vasoactive solvents of the standard formulation (Cordarone IV) and is not dose related, but related to the rate of infusion. Drug labeling calls for intravenous amiodarone to be administered over 10 minutes. A new aqueous formulation of amiodarone (Amio-Aqueous) does not contain vasoactive excipients and may be administered safely by rapid administration without hypotension. This hypothesis was tested using combined data of 4 clinical trials; each assessed the development of hypotension prospectively. Hypotension was defined as a 25% decrease in systolic blood pressure (BP), with the development of a systolic BP of <90 mm Hg or a systolic BP that decreased to <80 mm Hg. In all, 358 Amio-Aqueous and 225 lidocaine boluses were administered to 278 patients; 246 had ventricular tachycardia (VT) during drug administration. Hypotension developed in 11% of patients on Amio-Aqueous versus 19% on lidocaine (p = NS), all during VT; most resolved spontaneously with VT termination. With both drugs, hypotension persisted after VT termination in 1% of patients; the incidence of drug-related hypotension occurred in 2% of patients (1% had hypotension requiring treatment). The Amio-Aqueous was discontinued in 1% of patients, and lidocaine was discontinued in 2% of patients because of hypotension. We conclude that Amio-Aqueous is at least as safe as lidocaine in terms of causing hypotension when administered rapidly. This is a significant advantage over the standard amiodarone formulation, because Cordarone cannot be administered by rapid bolus owing to excipient-related hypotension.

Advances in the acute pharmacologic management of cardiac arrhythmias

Safe and effective control of rapid ventricular rates in acute-onset atrial fibrillation (AF) can be accomplished with intravenous calcium antagonists, beta-blockers or amiodarone; digoxin is less effective. If pharmacologic cardioversion of AF is desired, single oral doses of propafenone or flecainide are safe and effective in patients without structural heart disease. Intravenous ibulitide is moderately effective in the conversion of persistent AF or atrial flutter, with a small risk of proarrhythmia. In wide QRS complex tachycardia of uncertain origin, adenosine and lidocaine are no longer recommended. Procainamide or amiodarone are the treatment options, but attempts should be made to define the origin of tachycardia. In the treatment of monomorphic ventricular tachycardia, lidocaine is no longer recommended; procainamide or amiodarone are the recommended therapies. In polymorphic ventricular tachycardia with a normal QT interval, beta-blockers are recommended. In shock-refractory ventricular fibrillation, lidocaine, and magnesium are ineffective; intravenous amiodarone should be the treatment of choice.

Role of amiodarone in the era of the implantable cardioverter defibrillator

Amiodarone is one of the most frequently used antiarrhythmic drugs in clinical practice. In patients with atrial fibrillation, in whom rhythm control is judged desirable, amiodarone is the most effective therapy. Amiodarone effectively prevents atrial fibrillation and may improve quality of life, but there is no evidence that it decreases mortality or severe morbidity in atrial fibrillation. In patients at risk for life-threatening ventricular arrhythmias, amiodarone may decrease mortality to a small degree, but the evidence for this benefit is incomplete. Patients with implantable cardioverter defibrillators frequently require antiarrhythmic drug therapy, especially to treat electrical storm. Amiodarone is useful in these patients; however, it may increase defibrillation thresholds in some patients. In patients with out-of-hospital DC shock-resistant VF, amiodarone is the most effective antiarrhythmic drug available to assist in resuscitation. Amiodarone is a complicated drug, and its optimal use requires careful patient surveillance with respect to potential adverse effects.

Pharmacologic and nonpharmacologic options to maintain sinus rhythm: guideline-based and new approaches

Atrial fibrillation is a common arrhythmia in patients with heart failure and is responsible for substantial morbidity and mortality. Restoration and preservation of sinus rhythm, therefore, has a premium. Of the numerous treatment options available, many must be avoided because of their potential for adverse effects or because of limited proof of efficacy in defined populations. Published guidelines provide help by synthesizing clinical trial data into a recommended approach. This article summarizes current information regarding the best methods applicable to patients with left ventricular dysfunction for rate control, sinus rhythm restoration and maintenance, and stroke prevention. New and evolving therapies and how they might fit into the evolving treatment paradigm are also briefly reviewed.