The role of oral 1C antiarrhythmic drugs in terminating atrial fibrillation

"Pill in the Pocket" Antiarrhythmic Drugs for Orally Administered Pharmacologic Cardioversion of Atrial Fibrillation

The therapy of atrial fibrillation often involves the use of a rhythm control strategy, in which 1 or more antiarrhythmic drugs (AAD), ablative procedures, and/or hybrid approaches involving both of these options are utilized in an attempt to restore and maintain sinus rhythm. For chronic therapy, an AAD is taken daily. However, for patients with symptomatic but infrequent, acute, but nondestabilizing episodes, the use of an AAD only at the time of an episode that can quickly restore sinus rhythm, generally as an out-patient, without the burden of a daily drug regimen, may be better. This is called "pill-in-the-pocket" therapy. This manuscript reviews the "pill-in-the-pocket" concept, traces its development from its origins using quinidine, to its expansion using class IC AADs, to the more recent investigation of ranolazine for this purpose. Who should get it, what it involves, its efficacy rates and concerns are all discussed.

Tissue velocity imaging of the left atrium predicts response to flecainide in patients with acute atrial fibrillation

BACKGROUND

Acute atrial fibrillation (AF) is often treated with the administration of intravenous flecainide; however, this treatment may not always be successful and is potentially hazardous. Previous studies suggest that electro-echocardiographic tissue velocity imaging (TVI) of the atrial wall may reflect atrial remodeling.

OBJECTIVE

To study whether atrial TVI can be used to identify nonresponders of flecainide administered intravenously in patients with acute AF.

METHODS

We used atrial TVI to measure atrial fibrillatory cycle length determined by using tissue velocity imaging (AFCL-TVI) and atrial fibrillatory wall motion velocity determined by using tissue velocity imaging (AFV-TVI) in the left atrium in 52 (55%) patients presenting with acute AF in the emergency department. These 2 parameters reflect electrical and structural remodeling, respectively. Standard baseline characteristics were recorded.

RESULTS

Patients were predominantly men (76%) and 64 ± 11 years old. Thirty-six (69%) patients had successful cardioversion after flecainide infusion. There were no significant differences in baseline characteristics between responders and nonresponders. Patients with a successful cardioversion had a longer mean AFCL-TVI and higher median (interquartile range) AFV-TVI compared with patients with failed cardioversion: 172 ± 29 ms vs 137 ± 35 ms (P < .001) and 4.2 (3.3-6.2) cm/s vs 2.3 (1.9-3.5) cm/s (P = .001).

CONCLUSIONS

Electro-echocardiographic atrial TVI measurement is a promising noninvasive tool for predicting outcome of pharmacological cardioversion. A short AFCL-TVI and a low AFV-TVI are related to failure of cardioversion of AF using flecainide.

Management of atrial fibrillation: translating clinical trial data into clinical practice

Atrial fibrillation is a supraventricular tachyarrhythmia with significant consequences in terms of morbidity and mortality. In light of the limitations of available pharmacologic treatment options (suboptimal efficacy plus safety and tolerability issues), atrial fibrillation management should be individualized based on patient characteristics and comorbidities that could influence response to specific management approaches. The importance of adequate anticoagulation should not be overlooked. This review provides a practical guide for primary care physicians, internists, and cardiologists on current management strategies for atrial fibrillation, based on recent guidelines and current clinical data.

Pharmacologic Conversion of Atrial Fibrillation and Atrial Flutter

Atrial fibrillation and atrial flutter are common arrhythmias in everyday clinical settings. Pharmacologic cardioversion (CV) is a simple and widely used strategy for the treatment of these arrhythmias, and many drugs are currently available. The choice of drug is strongly influenced by the time elapsed from atrial fibrillation onset and by a patient's clinical subset. Electrical direct-current CV is the treatment of choice in long-lasting forms; nevertheless, some agents also show efficacy in this setting. In addition, promising results come from studies on the efficacy and safety of new antiarrhythmic drugs and from therapeutic approaches that reduce the need for hospitalization and improve quality of life.

Atrial fibrillation: Choosing an antiarrhythmic drug

Atrial fibrillation is the most common arrhythmia encountered in clinical practice. The associated hemodynamic changes can lead to symptoms of palpitations, fatigue, light-headedness, or dyspnea. Extensive research in the use of antiarrhythmic drugs has been performed both to facilitate the conversion of atrial fibrillation to sinus rhythm and to maintain normal sinus rhythm. The relative merits of a rhythm control versus rate control strategy are briefly discussed. Efficacy of the available agents for pharmacologic cardioversion is reviewed in detail. Important drugs for maintenance of sinus rhythm include amiodarone, flecainide, propafenone, sotalol, and dofetilide. Selection of the appropriate antiarrhythmic drug must be individualized to the clinical situation, with Class IC drugs being first-line agents in the absence of structural heart disease. Regardless of agent selected, appropriate monitoring for development of adverse effects is of utmost importance.

Antiarrhythmic drug therapy of atrial fibrillation

In the post-AFFIRM era, treatment of AF has become the treatment of symptoms. In some patients, this will be simple rate control, but there remain a significant cohort of patients in whom rate control alone does not give acceptable symptom relief. In this group, antiarrhythmic therapy still has a role, and the AFFIRM trial indicates that this therapeutic strategy is without significant deleterious effect on mortality. The choice of antiarrhythmic agent must be individualized according to underlying cardiac pathologies and comorbidities, however. Most recently, the introduction of dofetilide has widened the therapeutic options in patients with severe heart disease, and the Canadian Trial of Atrial Fibrillation indicated the superior efficacy of amiodarone at low doses. The release/ development of newer Class III antiarrhythmic agents may offer hope for the benefits of amiodarone without the serious adverse effects with long-term therapy.

Reproducible efficacy of loading oral propafenone in restoring sinus rhythm in patients with paroxysmal atrial fibrillation

This is the first study to demonstrate the reproducibility of an oral propafenone loading dose in converting paroxysmal atrial fibrillation in patients without significant cardiac disease or hypertension. This finding may support the development of the "pill-in-the-pocket" treatment strategy in this group of patients.

Oral loading single dose flecainide for pharmacological cardioversion of recent-onset atrial fibrillation

The efficacy and safety of the single oral loading dose of flecainide for cardioversion of recent-onset atrial fibrillation was examined by reviewing the trials on the subject identified through a comprehensive literature search. Most of the trials used a single dose of 300 mg for oral loading. The success rate ranged from 57 to 68% at 2-4 h and 75 to 91% at 8 h after drug administration. The conversion time ranged from 110+/-82 to 190+/-147 min, depending on the duration of observation after drug administration, which in most trials was of 8 h. Single oral loading regimen of flecainide was significantly more efficacious than placebo, and was as efficacious as the single oral loading regimen of propafenone. Both the single oral loading and the intravenous loading regimens of flecainide were equally efficacious but the intravenous regimen resulted in an earlier conversion. Adverse effects reported were mild non-cardiac side effects, reversible QRS complex widening, transient arrhythmias and left ventricular decompensation. The transient arrhythmias were chiefly at the time of conversion and included appearance of atrial flutter and sinus pauses. No life-threatening ventricular arrhythmia or death was reported. The single dose oral loading regimen of flecainide appears to be effective for cardioversion of recent-onset atrial fibrillation with a relatively rapid effect within 2-4 h, and is free of serious complications in patients without structural heart disease. Patients with substantial structural heart disease were excluded from most of the trials.

Effect of a single oral dose of pilsicainide on pacing thresholds in pacemaker patients with and without paroxysmal atrial fibrillation

A single oral dose of pilsicainide, a class 1c antiarrhythmic drug, is effective in terminating acute-onset atrial fibrillation (AF), but its effect on pacing thresholds in pacemaker patients is unknown. The present study measured atrial and ventricular pacing thresholds after a single oral dose of pilsicainide in patients with and without AF. Twelve patients with dual-chamber pacemakers were evaluated. Pacing thresholds as well as plasma pilsicainide concentration were measured prior to and then at 30, 60, 90, 120 and 180 min and 24h following a single oral dose of pilsicainide (150 mg). Six patients had paroxysmal AF and the remaining 6 did not. Pacing thresholds increased significantly (134+/-8%) in the atrium (p<0.05) and in the ventricle (155+/-11%; p<0.001) following pilsicainide administration in all 12 patients. Plasma concentrations of pilsicainide showed a positive liner correlation with pacing thresholds (R=0.62, p<0.0001 in the atrium; R=0.74, p<0.0001 in the ventricle). Atrial pacing thresholds in the patients with AF showed a significant increase at 90, 120 and 180 min compared with the patients without AF (p<0.05). There was no significant difference in either the ventricular pacing threshold or the plasma pilsicainide concentration in the patients with and without AF. It was concluded that a single oral dose of pilsicainide increases the pacing thresholds in both the atrium and ventricle in a selected group of pacemaker-implanted patients; that is, those who are aged and with AF. Thus, careful attention should be paid to pacemaker-dependent patients, particularly those with paroxysmal AF, when administering pilsicainide.

Drug choices in the treatment of atrial fibrillation

When considering therapy for atrial fibrillation (AF), the dominant issues are rate control, anticoagulation, rhythm control, and treatment of any underlying disorder. Drug choices for rate control include beta-blockers, verapamil and diltiazem, and digitalis as first-line agents, with consideration of other sympatholytics, amiodarone, or nonpharmacologic approaches in resistant cases. Anticoagulation may be accomplished with aspirin or warfarin, with the latter preferred in all older or high-risk patients. Antiarrhythmic drug therapy may be used (1) to produce cardioversion (most effective with ibutilide or class IC agents in recent onset AF); (2) to facilitate electrical conversion (class III agents); (3) to prevent early reversion after cardioversion; (4) to maintain sinus rhythm during chronic therapy; and/or (5) to facilitate conversion of fibrillation to flutter, which may then be amenable to termination or prevention with antitachypacing or ablative techniques. Antiarrhythmic drug selection for AF is guided by efficacy considerations (most drugs are similar), by convenience, cost, and discontinuation considerations; and, most importantly, by safety considerations. When possible, agents with serious organ toxicity potential and proarrhythmic risk should be avoided as first-line choices. In structurally normal hearts, class IC antiarrhythmic drugs are least proarrhythmic and least organ toxic (when considered together). In normal hearts, sotalol, dofetilide, and potentially azimilide also appear to have attractive profiles. Amiodarone has low proarrhythmic risk but can produce bradyarrhythmias and toxicity. In hypertrophied hearts, the risk of torsade de pointes with class III/IA agents is enhanced, whereas in ischemia or conditions with impaired cell contact, whether functionally (as by ischemia) or anatomically (as by fibrosis, infiltration, etc), proarrhythmic risk with class I antiarrhythmic drugs (sustained ventricular fibrillation/flutter) is greatly increased. The class I drugs should be avoided in these circumstances. Additional issues to consider are where to initiate therapy (in- or outpatient), what follow-up protocols to use, and whether to limit therapy to proprietary drugs or to allow generic formulation substitution. Each of these considerations is detailed in this article.