Rhythm management in atrial fibrillation--with a primary emphasis on pharmacologic therapy: Part 3

Understanding Antiarrhythmic Drug Efficacy for the Clinical Practitioner: There Is More than Meets the Eye

Determining if a medication is effective should be easy: Either the condition is or is not improved. However, the truth is often more complex than that, including in the antiarrhythmic drug (AAD) management of atrial fibrillation. In clinical trials, AAD efficacy is usually determined by the time to first atrial fibrillation recurrence. Another AAD efficacy endpoint, in patients with cardiac implantable electrical devices, is a reduction of atrial fibrillation burden. Other cardiovascular outcomes have included hospitalization, heart failure, and cardiovascular or total mortality. In clinical practice AADs, for atrial fibrillation, are prescribed to reduce symptoms/improve quality of life, which usually correlate with reduced atrial fibrillation frequency, duration, and beneficial hemodynamic effects in certain patient subgroups. Time to first recurrence is not a reliable predictor of clinical efficacy endpoints in practice. This article presents a review for the practitioner of AAD efficacy endpoints in clinical trials versus those in clinical practice and why such differences are present.

Multicenter Analysis of Dosing Protocols for Sotalol Initiation

Sotalol, a Vaughan-Williams Class III antiarrhythmic medication, is used to manage atrial arrhythmias. Due to its QT-prolonging effect and subsequent increased risk of torsade de pointes, many centers admit patients during the initial dosing period. Despite its widespread use, little information is available regarding dosing protocols during this period. In this multicenter investigation, dosing protocols in patients initiating sotalol therapy were examined to identify predictors of successful sotalol initiation. Over a 4-year period, patients admitted to 5 hospitals in the United States for inpatient telemetry monitoring during initiation for nonresearch purposes were enrolled. A 3-day course of 5 of 6 doses of sotalol was considered successful completion of the loading protocol. Of the 213 enrolled patients, over 90% were successfully discharged on sotalol. Significant bradycardia, ineffectiveness, and excessive QT prolongation were reasons for failed completion. Absence of a dose adjustment was a strong predictor of successful initiation (odds ratio: 6.6, 95% confidence interval: 1.3-32.7, P = .02). Hypertension, use of a calcium channel blocker, use of a separate β-blocker, and presence of a pacemaker were predictors of dose adjustments. Marginal structural models (ie, inverse probability weighting based on probability of a dose adjustment) verified that these factors also predicted successful initiation via preventing any dose adjustment and suggests that considering these factors may result in a higher likelihood of successful initiation in future investigations. In conclusion, we found that the majority of patients admitted for sotalol initiation are successfully discharged on the medication. The study findings suggest that factors predicting need for dose adjustment can be used to identify patients who could undergo outpatient initiation. Prospective studies are needed to verify this approach.

The HARMONY Trial: Combined Ranolazine and Dronedarone in the Management of Paroxysmal Atrial Fibrillation: Mechanistic and Therapeutic Synergism

BACKGROUND

Atrial fibrillation (AF) requires arrhythmogenic changes in atrial ion channels/receptors and usually altered atrial structure. AF is commonly treated with antiarrhythmic drugs; the most effective block many ion channels/receptors. Modest efficacy, intolerance, and safety concerns limit current antiarrhythmic drugs. We hypothesized that combining agents with multiple anti-AF mechanisms at reduced individual drug doses might produce synergistic efficacy plus better tolerance/safety.

METHODS AND RESULTS

HARMONY tested midrange ranolazine (750 mg BID) combined with 2 reduced dronedarone doses (150 mg BID and 225 mg BID; chosen to reduce dronedarone's negative inotropic effect-see text below) over 12 weeks in 134 patients with paroxysmal AF and implanted pacemakers where AF burden (AFB) could be continuously assessed. Patients were randomized double-blind to placebo, ranolazine alone (750 mg BID), dronedarone alone (225 mg BID), or one of the combinations. Neither placebo nor either drugs alone significantly reduced AFB. Conversely, ranolazine 750 mg BID/dronedarone 225 mg BID reduced AFB by 59% versus placebo (P=0.008), whereas ranolazine 750 mg BID/dronedarone 150 mg BID reduced AFB by 43% (P=0.072). Both combinations were well tolerated.

CONCLUSIONS

HARMONY showed synergistic AFB reduction by moderate dose ranolazine plus reduced dose dronedarone, with good tolerance/safety, in the population enrolled.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; Unique identifier: NCT01522651.

Rate Versus Rhythm Control Pharmacotherapy For Atrial Fibrillation: Where are We in 2008?

Atrial fibrillation (AF) is the most common sustainedcardiac rhythm disturbance encountered by physicians. The management of AF isfocused on control of heart rate, correction of rhythm disturbance, andrisk-determined prophylaxis of thromboembolism. The goals of AF therapy are, aswith other serious disorders, to reduce mortality (if possible) and morbidity(improve quality of life, [QOL]). To this end, several large studies haveexamined rhythm-control versus rate-control strategies. Although a survivaladvantage to using rhythm control with currently available antiarrhythmic drugshas not been proven, neither has there been a significant excess risk versusrate control. Therefore, using our current therapies, the results have notsupported rate control or rhythm control as being a preferable first-linetherapy for AF as regards survival; importantly, neither do they disprove the hypothesis thatmaintenance of sinus rhythm is preferable to the continuation of AF,particularly if rate control fails to restore adequate QOL. Many post-hocanalyses and substudies have assessed QOL, functional status, and exercisetolerance, with the majority demonstrating important benefits associated withachievement of rhythm control. This review examines rate and rhythm controloptions, the clinical outcomes of several important AF trials, discusses thelimitations in applying the major morbidity/mortality findings to everydayclinical practice, and summarizes the lessons learned.

Pharmacological cardioversion of atrial fibrillation: current management and treatment options

Atrial fibrillation (AF) is the most common form of arrhythmia, carrying high social costs. It is usually first seen by general practitioners or in emergency departments. Despite the availability of consensus guidelines, considerable variations exist in treatment practice, especially outside specialised cardiological settings. Cardioversion to sinus rhythm aims to: (i) restore the atrial contribution to ventricular filling/output; (ii) regularise ventricular rate; and (iii) interrupt atrial remodelling. Cardioversion always requires careful assessment of potential proarrhythmic and thromboembolic risks, and this translates into the need to personalise treatment decisions. Among the many clinical variables that affect strategy selection, time from onset is crucial. In selected patients, pharmacological cardioversion of recent-onset AF can be a safely used, feasible and effective approach, even in internal medicine and emergency departments. In most cases of recent-onset AF, pharmacological cardioversion provides an important--and probably more cost effective--alternative to electrical cardioversion, which can then be employed as a second-line therapy for nonresponders. Class IC agents (flecainide or propafenone), which can be safely used in hospitalised patients with recent-onset AF without left ventricular dysfunction, can provide rapid conversion to sinus rhythm after either intravenous administration or oral loading. Although intravenous amiodarone requires longer conversion times, it is still the standard treatment for patients with heart failure. Ibutilide also provides good conversion rates and could be used for AF patients with left ventricular dysfunction (were it not for high costs). For long-lasting AF most pharmacological treatments have only limited efficacy and electrical cardioversion remains the gold standard in this setting. However, a widely used strategy involves pretreatment with amiodarone in the weeks before planned electrical cardioversion: this provides optimal prophylaxis and can sometimes even restore sinus rhythm. Dofetilide may also be capable of restoring sinus rhythm in up to 25-30% of patients and can be used in patients with heart failure. The potential risk of proarrhythmia increases the need for careful therapeutic decision making and management of pharmacological cardioversion. The results of recent trials (AFFIRM [Atrial Fibrillation Follow-up Investigation of Rhythm Management] and RACE [Rate Control versus Electrical Cardioversion for Persistent Atrial Fibrillation]) on rate versus rhythm control strategies in the long term have led to a generalised shift in interest towards rate control. Although carefully designed studies are required to better define the role of pharmacological rhythm control in specific AF settings, this alternative option remains a recommendable strategy for many patients, especially those in acute care.

Heart failure management in the elderly postoperative patient

As the population ages, the elderly will account for a significant portion of surgical cases. These patients have age-related cardiovascular changes and can suffer from multiple chronic disease conditions. Congestive heart failure is a chronic condition that afflicts nearly five million Americans. It is the most common diagnosis among patients 65 years or older, with 8% to 10% of senior citizens having this chronic disease. A comprehensive understanding of the pathophysiology, assessment, and management strategies of congestive heart failure will give the orthopaedic nurse the knowledge needed to help minimize the morbidity and mortality associated with this disease.

Atrial fibrillation in the elderly: facts and management

Although atrial fibrillation is not widely known by the general public, in developed countries it is the most common arrhythmia. The incidence increases markedly with advancing age. Thus, with the growing proportion of elderly individuals, atrial fibrillation will come to represent a significant medical and socioeconomic problem. The consequences of atrial fibrillation have the greatest impact. The risk of thromboembolism is well known; other outcomes of atrial fibrillation are less well recognised, such as its relationship with dementia, depression and death. Such consequences are responsible for diminished quality of life and considerable economic cost. Atrial fibrillation is characterised by rapid and disorganised atrial activity, with a frequency between 300 and 600 beats/minute. The ventricles react irregularly, and may contract rapidly or slowly depending on the health of the conduction system. Clinical symptoms are varied, including palpitations, syncope, dizziness or embolic events. Atrial fibrillation may be paroxysmal, persistent or chronic, and a number of attacks are asymptomatic. Suspicion or confirmation of atrial fibrillation necessitates investigation and, as far as possible, appropriate treatment of underlying causes such as hypertension, diabetes mellitus, hypoxia, hyperthyroidism and congestive heart failure. In the evaluation of atrial fibrillation, cardiac exploration is invaluable, including electrocardiogram (ECG) and echocardiography, with the aim of detecting cardiac abnormalities and directing management. In elderly patients (arbitrarily defined as aged >75 years), the management of atrial fibrillation varies; it requires an individual approach, which largely depends on comorbid conditions, underlying cardiac disease, and patient and physician preferences. This management is essentially based on pharmacological treatment, but there are also nonpharmacological options. Two alternatives are possible: restoration and maintenance of sinus rhythm, or control of ventricular rate, leaving the atria in arrhythmia. Pharmacological options include antiarrhythmic drugs, such as class III agents, beta-blockers and class IC agents. These drugs have some adverse effects, and careful monitoring is necessary. The nonpharmacological approach to atrial fibrillation includes external or internal direct-current cardioversion and new methods, such as catheter ablation of specific foci, an evolving science that has been shown to be successful in a very select group of atrial fibrillation patients. Another serious challenge in the management of chronic atrial fibrillation in older individuals is the prevention of stroke, its primary outcome, by choosing an appropriate antithrombotic treatment (aspirin or warfarin). Several risk-stratification schemes have been validated and may be helpful to determine the best antithrombotic choice in individual patients.

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.

Mechanisms of atrial fibrillation: is a cure at hand?

The mechanisms of atrial fibrillation relate to the presence of random reentry involving multiple interatrial circuits. Triggers for development of atrial fibrillation include rapidly discharging atrial foci (mainly from pulmonary veins) or degeneration of atrial flutter or atrial tachycardia into fibrillation. Therapy for control of atrial fibrillation includes drugs, atrial pacing for those with sinus node dysfunction, or ablation of the atrioventricular junction. Therapeutic maneuvers for cure of atrial fibrillation include surgical or radiofrequency catheter induced linear lesions to reduce the atrial tissue and prevent the requisite number of reentrant wavelets. We need a much better understanding of basic mechanisms before a true cure is at hand.

The importance of considering trial design when interpreting clinical trial results

BACKGROUND

In recent decades, clinical trials have played an increasingly important role in determining how we practice. Trial results proving that a clinical finding poses risk have led to interventions that try to reduce risk. Clinical trials proving that a particular therapy provides better outcome than another therapy have changed the therapies we now use. Unfortunately, the results of clinical trials are too often affected by biases or design issues that may overtly or covertly alter the results or the way they should really be used. In addition, these biases and design and analysis issues are rarely evident in the abstract sections or key figures and tables in the publications reporting the trials, which may be all the busy physician either reads or remembers.

METHODS AND MATERIALS

This manuscript discusses the issues involved in optimally understanding clinical trial design and interpretation so that practitioners can better understand how to intelligently read and apply trial results to clinical practice.

CONCLUSIONS

Clinical trial results can not be properly applied without consideration of trial design features and intertrial comparisons.

Atrial fibrillation in the elderly

Atrial fibrillation is the most common sustained arrhythmia seen in clinical practice. Although it occurs in any age patients, its frequency increases with age and is very common in the elderly. Atrial fibrillation causes substantial symptoms and morbidity and is an important cause of thromboembolism and stroke. The two approaches for therapy in those patients with intermittent or persistent atrial fibrillation are (1) maintenance of sinus rhythm with an antiarrhythmic drug or nonpharmacologic therapy, and (2) maintenance of atrial fibrillation with rate control. At the present time there are no data about the best approach and therapy must therefore be individualized.

Selecting an antiarrhythmic agent for atrial fibrillation should be a patient-specific, data-driven decision

Selecting an antiarrhythmic agent for atrial fibrillation (AF) should be a patient-specific decision. When possible, it should be based on sound rationale and available clinical data. This article details many of the thought processes that must go into this decision process and offers some suggested algorithmic starting points based on these considerations. With a patient's first episode of AF, termination is appropriate, but antiarrhythmic therapy should usually be withheld in order to assess the recurrence pattern. However, if severe hemodynamic or ischemic intolerance would make recurrence a serious risk, or if an early symptomatic recurrence is highly likely, antiarrhythmic therapy would be appropriate. Acute AF may terminate spontaneously or may be terminated iatrogenically. The latter may be achieved by direct current or pharmacologic approaches. The risks, benefits, and optimum utility of these approaches are addressed in the article. Infrequent recurrences may be treated with cardioversion; frequent or severely symptomatic episodes are best treated with attempts at suppression with chronic antiarrhythmic drug administration. Since the therapeutic efficacy of maintaining sinus rhythm is similar for the currently available agents, the drug selection process should be based in large part on safety and convenience considerations. The factors underlying this selection process and one suggested algorithm for drug choice are provided in this article.