The medical management of atrial fibrillation

Predictors of Atrial Fibrillation Recurrence in Hyperthyroid and Euthyroid Patients

BACKGROUND

Atrial fibrillation (AF) is the most common arrhythmia in adults, and is encountered in 10-15% of the patients with hyperthyroidism. Unless euthyroidism is restored, pharmacological or electrical cardioversion is controversial in patients with AF who remain hyperthyroid.

OBJECTIVE

The aim of this study was to assess the efficacy of electrical cardioversion and predictors of AF recurrence in hyperthyroid and euthyroid patients.

METHODS

The study included 33 hyperthyroid (21 males) and 48 euthyroid (17 males) patients with persistent AF. The patients were sedated with intravenous midazolam before undergoing electrical cardioversion delivered by synchronized biphasic shocks. Rates of AF recurrence were recorded.

RESULTS

Mean follow-up was 23.63 ± 3.74 months in the hyperthyroid group and 22.78 ± 3.15 months in the euthyroid group (p = 0.51). AF recurred in 14 (43.8%) and 21 (44.7%) patients in each group, respectively (p = 0.93). Multivariate regression analysis in each group showed that AF duration was the only predictor of AF recurrence, with odds ratios of 1.38 (95% confidence interval [CI] = 1.05 - 1.82, p = 0.02) in the hyperthyroid group and 1.42 (95% CI = 1.05 - 1.91, p= 0.02) in the euthyroid group.

CONCLUSION

Rates of long-term AF recurrence were similar in successfully cardioverted hyperthyroid and euthyroid patients. The only predictor of AF recurrence in both groups was AF duration.

Intravenous amiodarone for cardioversion of recent-onset atrial fibrillation

BACKGROUND

Atrial fibrillation (AF) is one of the most common causes of hospital admission, with a prevalence of up to 5% of the population, increasing with advancing age. Emergency direct current cardioversion is the therapy of choice when arrhythmia leads to hemodynamic compromise, but in patients who are hemodynamically stable, antiarrhythmic drugs are usually given to restore sinus rhythm.

HYPOTHESIS

The study was undertaken to assess the efficacy of intravenous amiodarone in cardioversion of recent-onset paroxysmal atrial fibrillation (AF). No standard antiarrhythmic therapy has been accepted for pharmacologic cardioversion of AF. Amiodarone seems to be a promising candidate, but only few randomized trials are available and the results are inconsistent.

METHODS

In all, 160 patients with AF lasting < 24 h were randomly assigned (2:1 fashion) to the amiodarone group (n = 106) receiving 5 mg/kg as a 30 min intravenous (i.v.) infusion, followed by i.v. infusion of 10 mg/kg during 20 h diluted in 1000 ml of 10% glucose with 20 IU of rapid-action insulin, 80 mEq of potassium chloride, and 8 g of magnesium sulphate (GIKM), or to the control group (n = 54) receiving 1000 ml of GIKM alone. Treatment was continued up to 20 h independent of sinus rhythm restoration.

RESULTS

Sinus rhythm was restored 20 h after initiation of therapy in 88 (83%) patients in the amiodarone group and in 24 (44%) patients in the control group (p < 0.0001). The difference between efficacy of the two treatment modalities became significant already after 8 h of therapy (53 vs. 14 patients with sinus rhythm, respectively, p < 0.05). The mean dose of amiodarone administered until sinus rhythm restoration was 740 +/- 296 mg. The presence and the type of underlying heart disease did not influence the conversion rate in either group. In two patients (1.8%) treated with amiodarone, the return of sinus rhythm was preceded by asystole.

CONCLUSION

Amiodarone is effective in the termination of AF lasting < 24 h. It may be particularly useful in patients with organic heart disease in whom class I antiarrhythmic agents may be contraindicated. During treatment, the heart rhythm should be monitored continuously.

Atrial Fibrillation

Our understanding of the pathophysiology and clinical consequences of atrial fibrillation has led to an evidence-based revolution in the management of atrial fibrillation over the last decade. As we improve in our ability to detect recurrent atrial fibrillation and treat it definitively, the patients who benefit from long-term anticoagulation may change. We can expect, however,that stroke prevention through systemic anticoagulation will be a cornerstone of atrial fibrillation management for decades to come. Innovations in anticoagulation therapy will make the use of these medications safer. Finally, as we further understand the underlying mechanisms of the development of atrial fibrillation, the pursuit of preventative therapy will be an investigational focus of great import.

Treating Atrial Fibrillation

Atrial fibrillation (AF), a rhythm characterized by disorganized depolarization of the atria, is frequently encountered in the clinical setting. This dysrhythmia significantly impacts hemodynamics, exercise tolerance, and quality of life. Many factors contribute to this complex dysrhythmia, ultimately leading to electrical and mechanical remodeling. Rhythm control has been the initial treatment choice for AF. However, until recently, differences in outcomes associated with rhythm control versus rate control for AF were unknown. Data from recent clinical trials suggest that rate control is equivalent to rhythm control in terms of mortality. In the rhythm-control group compared to the rate-control group, there was a tendency for increased hospitalizations and medication reactions (although these differences were not significant). Anticoagulation remains an important component of therapy when treating AF, but continues be to inadequately prescribed. Further, INRs commonly are not maintained in a therapeutic range. Finally, the results of the Atrial Fibrillation Follow-up Investigation of Rhythm Management (AFFIRM), Pharmacological Intervention in Atrial Fibrillation (PIAF), and the Comparison of Rate Control and Rhythm Control in Patients with Recurrent Persistent Atrial Fibrillation (RACE) trials provide guidance in treatment strategies for AF.

Management of patients with syncope and cardiac arrhythmias in an emergency department observation unit

Syncope is an ideal condition for the emergency observation setting because of its difficulty in diagnosis, many causes, high liability, and variable diagnostic approaches. Hospital admissions can be averted with appropriate patient selection for a short-term observation period. Atrial fibrillation is a common presenting condition in the emergency department. With aggressive management, the appropriately selected patient can have restoration of sinus rhythm and be safely discharged home.

Dofetilide, a new class III antiarrhythmic agent

Dofetilide is a new antiarrhythmic agent recently approved for conversion and maintenance of sinus rhythm in patients with atrial fibrillation (AF) and atrial flutter (AFl). It is a class III antiarrhythmic that works by selectively blocking the rapid component of the delayed rectifier outward potassium current. Dofetilide prolongs the effective refractory period in accessory pathways, both anterograde and retrograde. This can be seen on the electrocardiogram through a dose-dependent prolongation of the QT and QTc intervals, with parallel increases in ventricular refractoriness. Approximately 80% of drug is excreted in urine, so dosing must be based on creatinine clearance. The elimination half-life is approximately 10 hours. In clinical trials dofetilide was superior to flecainide in converting patients with AFl to normal sinus rhythm (NSR; 70% vs 9%, p<0.01). It also was more effective than sotalol in converting patients with both AF and AFl to NSR (29% vs 6%, p<0.05) and maintaining them in NSR for up to 1 year. Most patients converted within 24-36 hours. Dofetilide has a favorable risk:benefit profile. Torsades de pointes is the most serious side effect; it occurs in 0.3-10.5% of patients and is dose related. To minimize the risk of induced arrhythmia, patients who start or restart the drug should be hospitalized a minimum of 3 days for creatinine clearance measurements, continuous electrocardiographic monitoring, and cardiac resuscitation, if necessary.

The tachycardia-induced dog model of atrial fibrillation. clinical relevance and comparison with other models

In the past, investigators have relied extensively on acute in vivo models of atrial fibrillation (AF), in which AF was induced either pharmacologicly or by vagal stimulation. More recently, there is a need and desire for more clinically relevant models that can only be achieved with the use of chronically instrumented animals. One of these models is the atrial tachycardia-induced AF dog model, which is the main focus of this review. The model produces a persistent AF in 80% of animals paced at 400 beats/min for 6 weeks. Atrial tachycardia also induces various pathophysiologic and ultrastructural changes that often resemble electrical remodeling of atria in patients that have a high susceptibility to AF. This model can also be used to evaluate drug efficacy with respect to attenuation of AF duration or conversion of AF to sinus rhythm. The model may therefore be used to provide further insights into the discovery of new therapeutic approaches to modifying this atrial arrhythmic disorder in man.

Atrial fibrillation and its relationship to dental care

BACKGROUND

The number of Americans diagnosed with and treated for atrial fibrillation, or AF, continues to rise.

TYPES OF STUDIES REVIEWED

To determine how AF may affect the provision of dental care, the author conducted a literature search, using terms such as "atrial fibrillation" and "dental care." He found a lack of information on these combined topics. Therefore, the author extrapolated information from scientific peer-reviewed articles on AF, medical and surgical management of AF, and dental care to determine appropriate guidelines for dental treatment of patients with AF.

RESULTS

The author found that complications can arise from AF and that medical management of AF can affect the delivery of dental care. Dentists should determine the underlying cause of AF to decide if antibiotic prophylaxis is indicated. Patients who are receiving anticoagulation therapy may not need to alter their therapy schedules for minor oral surgery procedures. Anxiety as a result of AF may require use of anxiety-reducing protocols before dental treatment.

CLINICAL IMPLICATIONS

To reduce potential complications associated with dental care, dental practitioners should be familiar with AF and its treatment. Dental management of patients with AF may require treatment modifications, but generally will not deviate significantly from routine standards.