TOC | Cardiology    ATRIAL FIBRILLATION

Atrial fibrillation is the most common type of arrhythmia in adults. It is more common as patients age; the prevalence is 1% among those younger than age 60 years and increases to more than 8% in those older than age 80 years. When data are adjusted for age, men are affected more often than women. Cardiac conditions associated with the development of atrial fibrillation are hypertension, rheumatic mitral valve disease, coronary artery disease, and congestive heart failure. Noncardiac causes include hyperthyroidism, hypoxic pulmonary conditions, surgery, and alcohol intoxication. Patients with atrial fibrillation may have symptoms of hemodynamic compromise, such as irregular palpitations and lightheadedness, or more vague symptoms, such as malaise, but may be asymptomatic. Patients with atrial fibrillation are at increased risk for thromboembolic disease.

The Management of Atrial Fibrillation:
Reasons for restoration and maintenance of sinus rhythm in patients with AF include relief of symptoms, prevention of embolism, and avoidance of cardiomyopathy.

The management of AF can be divided into three areas  (In addition to treating underlying conditions) :

1.  Ventricular rate control
(Radiofrequency catheter ablation of AV junction followed by permanent pacemaker in refractory cases where the ventricular response cannot be controlled.)

Rate control is defined as a resting ventricular rate of atrial fibrillation < 100 beats/minute. Initial therapy with usual loading dose of digoxin 0.75-1 mg followed by maintenance digoxin should be used in patients with rapid atrial fibrillation. Additional rate control should be accomplished with either beta blockers (as atenolol, metoprolol) or calcium channel blockers (dilitiazem or verapamil). Digoxin should not be pushed to high doses. Digoxin is not a good drug for rate control in atrial fibrillation, particularly during enhanced sympathetic status such as physical activity, because the rate control of digoxin is solely from vagotonic action.

For rate control, clinicians generally choose among digoxin, beta-adrenergic antagonists, and/or calcium-channel-blockers, without a clear consensus about which agent is the most effective.  
Verapamil  (Calan) 5-10 mg IV (0.075 - 0.15 mg/kg)
Cardizem (Diltiazem) IV bolus for rate control of atrial fib/flutter.
- * Start 0.25 mg/kg IVP over 2 min (ave pt= 20mg dose), after 15 min if inadequate response, 0.35 mg/kg (ave pt = 25 mg dose) over 2 min;
      Infusion Rx start at 5 mg/h, range 10 - 15 mg/h.
- * Calcium blockers are contraindicated in atrial fib assoc. with  WPW Syndrome.
Atenolol (Tenormin) 5 mg IV, may repeat in 10 min  
Metoprolol (Lopressor) 2.5-5 mg IV, may repeat q2-5 min up to 15 mg  over 10-15 min
Propranolol 1-3 mg IV, start with 1 mg, then repeat with increment of 1 mg q5min
Esmolol IV 50-100 ug/kg/min for 4 min, then maintain at 50 ug/kg/min. (Max IV infusion rate 200 mcg/kg/min)
Digoxin 0.5-1 mg IV initial loading dose, then about 0.25 mg maintenance dose

2.  Cardioversion (Electrical  100-200 joules or Pharmacologic) of AF and subsequent maintenance of sinus rhythm , Medications: as
Amiodarone (Cordarone 150 mg IV bolus over 10 min, then 1 mg/min x 6 hrs, then 0.5 mg/min x 18 h;  Oral loading dose 800-1600 mg PO qd x 1-3 wks, reduc dose to 400-800 mg qd for 1 month when arrhytymia is controlled or adverse effects are prominent),
Flecainide (Tambocor 100,150 mg tab)  300 mg one dose for cardioversion
-  * contraindicated in 2nd & 3rd degree AV block, bifascicular blocks, heart failure.
Ibutilide (Corvert 1 mg IV over 10 min, may repeat after 10 min),
Dofetilide (Tikosyn 0.125, 0.25, or 0.5 mg cap),
Propafenone (Rythmol 150, 225, 300 mg tab or SR 225, 325, 425 mg cap)  , or the less effective Quinidine, Disopyramide, Sotalol.
In pooled analyses, we found strong evidence of efficacy for acute conversion of atrial fibrillation compared with controls for ibutilide, flecainide, dofetilide, propafenone, and amiodarone, with moderate evidence for quinidine. Insufficient evidence of efficacy was found for disopyramide and sotalol.

3.  Prevention of thromboembolism.
Risk-Based Antithrombotic Therapy in Patients With Atrial Fibrillation
* Risk factors for thromboembolism include heart failure, LV EF < 35%, history or hypertension  
Patient Features         Recommended Antithrombotic Therapy                                                                                                  
Age < 60, no heart disease (Lone AF)   Aspirin (325 mg per day) or no therapy
Age < 60, heart disease but no risk factors*   Aspirin (325 mg per day)
Age > 60 , no risk factors* Aspirin (325 mg per day)
Age > 60, with diabetes or CAD   Oral warfarin anticoagulation (INR 2.0-3.0), addition of aspirin (81-162 mg) per day is optional
Age > to 75 , especially women Oral warfarin anticoagulation (INR = 2.0)
Heart failure, LV ejection fraction < 35%,
thyrotoxicosis, and hypertension		 Oral warfarin anticoagulation (INR 2.0-3.0)
Rheumatic heart disease (mitral stenosis)
Prosthetic heart valves
Prior thromboembolism
Persistent atrial thrombus on TEE		 Oral warfarin anticoagulation (INR 2.5-3.5 or higher may be appropriate)

Contraindications for anticoagulation:

REF:  KP Clinical Guidelines 2004

New Onset Atrial Fibrillation

When atrial fibrillation duration has been less than 48 hours, no anticoagulation is required and cardioversion can be performed.
Rate control with beta blockers, calcium blockers, or digoxin is suggested to obtain a resting heart rate < 100 before attempted chemical cardioversion with antiarrhythmic medications such as 1A drugs (e.g., quinidine, procainamide, disopyramide), or 1C drugs (propafenone, flecainide).
Type 1C drugs should not be used in patients with prior myocardial infarction or with decreased left ventricular function.
Emergency direct current cardioversion for new onset atrial fibrillation should be considered in hemodynamically unstable patients or patients with congestive heart failure or myocardial infarction with rapid ventricular response.

After 48 hours, or if one is uncertain as to the duration of the new onset AF, the patient should be given warfarin therapy for at least 3 to 4 weeks at an INR of 2-3 and schedule for an elective cardioversion. During this period, rate control should be established with standard therapy including digoxin, calcium channel blockers, or beta blockers. Hospitalization is not required in these patients when starting warfarin therapy to establish therapeutic levels. This can be accomplished in an outpatient setting.

Recurrent Paroxysmal Atrial Fibrillation

For patients who experience brief or minimally symptomatic recurrences of paroxysmal AF, it is reasonable to avoid antiarrhythmic drugs unless troublesome symptoms occurs. Rate control and prevention of thromboembolism are appropriate in both situations.
When clinical indicated, in individuals with no or minimal structural heart disease, flecainide, propafenone, and sotalol are recommended as initial antiarrhythmic therapy. Second or third-line choices include amiodarone, dofetilide, disopyramide, procainamide, and quinidine, which all have greater potential for adverse reactions.

Recurrent Persistent Atrial Fibrillation

Defined as patient who have undergone at least 1 attempt to restore sinus rhythm and may remain in AF after its second occurrence with minimal or no symptoms. These patients should be treated with therapy for rate control and prevention of thromboembolism as needed. Alternatively, those with symptoms favoring sinus rhythm should be treated with an antiarrhythmic agent (in addition to medications for rate control and anticoagulation) before cardioversion.

Permanent Atrial Fibrillation

Permanent AF is given to patients in which sinus rhythm cannot be sustained after cardioversion of AF or when the patient and physician have decided to allow AF to continue without further efforts to restore sinus rhythm. It is important to maintain control of the ventricular rate and to use antithrombotic therapy .

     

Pharmacologic Agents:

Calcium Channel Blocking Agents

Diltiazem (Cardizem®)

Verapamil (Calan®, others)

Ca2+ gluconate may be given iv to decrease hypotensive effect of these calcium blocker agents

ß-Adrenergic Blocking Agents

Partial AV Nodal Ablation

Transesophageal Echocardiography (TEE)

       

12132004

Clinical Guideline: Management of Newly Detected Atrial Fibrillation:  AAFP & ACP  December 16, 2003

The recommendations are as follows:

Recommendation 1:
Rate control with chronic anticoagulation is the recommended strategy for the majority of patients with atrial fibrillation. Rhythm control has not been shown to be superior to rate control (with chronic anticoagulation) in reducing morbidity and mortality and may be inferior in some patient subgroups to rate control. Rhythm control is appropriate when based on other special considerations, such as patient symptoms, exercise tolerance, and patient preference. Grade: 2A

Recommendation 2:
Patients with atrial fibrillation should receive chronic anticoagulation with adjusted-dose warfarin, unless they are at low risk of stroke or have a specific contraindication to the use of warfarin (thrombocytopenia, recent trauma or surgery, alcoholism). Grade: 1A

Recommendation 3:
For patients with atrial fibrillation, the following drugs are recommended for their demonstrated efficacy in rate control during exercise and while at rest:
atenolol, metoprolol, diltiazem, and verapamil (drugs listed alphabetically by class). Digoxin is only effective for rate control at rest and therefore should only be used as a second-line agent for rate control in atrial fibrillation. Grade: 1B

Recommendation 4:
For those patients who elect to undergo acute cardioversion to achieve sinus rhythm in atrial fibrillation, both direct-current cardioversion (Grade: 1C+) and pharmacological conversion (Grade: 2A) are appropriate options.

Recommendation 5:
Both transesophageal echocardiography with short-term prior anticoagulation followed by early acute cardioversion (in the absence of intracardiac thrombus) with postcardioversion anticoagulation versus delayed cardioversion with pre- and postanticoagulation are appropriate management strategies for those patients who elect to undergo cardioversion. Grade: 2A

Recommendation 6:
Most patients converted to sinus rhythm from atrial fibrillation should not be placed on rhythm maintenance therapy since the risks outweigh the benefits. In a selected group of patients whose quality of life is compromised by atrial fibrillation, the recommended pharmacologic agents for rhythm maintenance are amiodarone, disopyramide, propafenone, and sotalol (drugs listed in alphabetical order). The choice of agent predominantly depends on specific risk of side effects based on patient characteristics. Grade: 2A

For pharmacologic cardioversion:

In pooled analyses, we found strong evidence of efficacy for acute conversion of atrial fibrillation compared with controls for ibutilide, flecainide, dofetilide, propafenone, and amiodarone, with moderate evidence for quinidine. Insufficient evidence of efficacy was found for disopyramide and sotalol.
The evidence showed greater efficacy for flecainide compared with propafenone, sotalol, and procainamide. Similarly, ibutilide was more efficacious than sotalol and procainamide. In other studies, propafenone was more efficacious than amiodarone , amiodarone was more efficacious than quinidine , and quinidine was more efficacious than sotalol.

The major concern with starting antiarrhythmic therapy for atrial fibrillation is the potential to induce polymorphic ventricular tachycardia, often called torsades de pointes.  The risk for torsades de pointes increases for patients with structural heart disease, hypokalemia, and bradycardia.  The greatest incidence of arrhythmia occurred within the first 24 hours or 3 days of therapy.  Most patients in these studies had structural heart disease.  Another study followed 172 patients, 82% of whom had normal ejection fractions; the researchers found no cases of significant arrhythmia in the first 4 days of therapy.   
Thus, current recommendations include a 1- to 3-day inpatient observation period after starting most antiarrhythmic agents for patients with atrial fibrillation.
Two exceptions were noted in a recent guideline: First, amiodarone can usually be given safely on an outpatient basis, and second, outpatient initiation of sotalol and disopyramide may be reasonable in patients without structural heart disease (left ventricular ejection fraction 0.45, coronary artery disease, valvular heart disease, or left ventricular hypertrophy), abnormal conduction system (sick sinus syndrome, atrioventricular conduction disturbances, or bundle-branch blocks), or long QT.
In our systematic review of RCTs, only 39 of the 60 clinical trials on the pharmacologic conversion of atrial fibrillation reported the incidence of ventricular arrhythmia, limiting the usefulness of these data. Of those reported, no ventricular arrhythmias occurred with amiodarone.  The incidence was 3% or less for flecainide, propafenone, and sotalol.

For direct electrical cardioversion:

The efficacy of traditional, external, monophasic direct-current cardioversion in consecutive patients has consistently been found to be 80% to 85% . Applying direct-current cardioversion directly in the right atrium through percutaneous catheter has been shown to increase the efficacy to more than 90%; however, the invasive nature of this procedure limits applicability. Biphasic defibrillators, which use less energy but apply both positive and negative currents, have also been shown to increase the efficacy of transthoracic cardioversion to more than 90%.

Conventional recommendations include treating patients experiencing atrial fibrillation with warfarin, with a goal international normalized ratio INR of 2.0 to 3.0, for 3 weeks before cardioversion and for 4 weeks after conversion.  Overall, the literature suggests that TEE-guided conversion using short-term preconversion anticoagulation (48 hours) and at least 3 weeks of appropriate postconversion anticoagulation may be an effective, safe alternative to the conventional approach.

What Is the Efficacy of Each Antiarrhythmic Agent for the Maintenance of Sinus Rhythm after Successful Conversion of Atrial Fibrillation to Sinus Rhythm?

In the 18 trials with a control arm, we found strong evidence of efficacy for amiodarone, propafenone, disopyramide, and sotalol. Moderate evidence was found for flecainide, quinidine, and azimilide.

Thus, safety and side effects are critical factors when considering whether to start or maintain antiarrhythmic therapy. Amiodarone appears to be relatively safe from a cardiac perspective but has a substantial profile of noncardiac side effects. The other antiarrhythmic agents require careful consideration in patients with structural heart disease because of the risk for proarrhythmia. In particular, flecainide is not indicated in patients with coronary artery disease.

REF:  ePocrate 10-2004

ACLS: Afib/flutter, Stable

1) Evaluate Cardiac Function [measure EF or assess clinical signs]  & Rule Out WPW  [evaluate EKG] &
    Determine Duration  [determine if afib/flutter < or > 48h]

    Warning Info: do not use adenosine, beta blockers, CCBs or digoxin to treat Afib/flutter w/WPW

2) Control Rate (any duration)

5a) Control Rhythm (duration <48h)

5b) Control Rhythm (duration >48h)

       

12132004