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Classification of Atrial Fibrillation

  •         Paroxysmal (ie, self-terminating or intermittent) AF – Paroxysmal AF is defined as recurrent AF (≥2 episodes) that terminates spontaneously in seven days or less, usually less than 24 hours.
  •         Persistent AF – Persistent AF is defined as AF that fails to self-terminate within seven days. Episodes often require pharmacologic or electrical cardioversion to restore sinus rhythm. While a patient who has had persistent AF can have later episodes of paroxysmal AF, AF is generally considered a progressive disease. In individuals with paroxysmal AF, progression to persistent and permanent AF occurs in >50% beyond 10 years despite antiarrhythmic therapy.
  •         Long-standing persistent AF – Long-standing persistent AF refers to persistent AF that has lasted for one year or more.
  •         Permanent AF – Permanent AF is a term used to identify individuals with persistent AF where a decision has been made to no longer pursue a rhythm control strategy.

** Definitions taken from UpToDate.

Management of atrial fibrillation (AF) is guided by 2 major principles: symptom control and prevention of thromboembolism.

These are typically managed through rhythm control or rate control.  Rhythm- and rate-control strategies are associated with similar rates of mortality and serious morbidity, such as embolic risk, which is best addressed using anticoagulation based on the CHADS2 or CHA2DS2-Vas criteria.

For asymptomatic or mildly symptomatic AF patients who are 65 years or older, it is suggested to use a rate-control as opposed to a rhythm-control strategy using medical therapy. This recommendation places a high priority on concerns about side effects of antiarrhythmic drug therapy or radiofrequency catheter ablation. Patients for whom a rhythm-control strategy may be reasonable include those who continue with clinically significant symptoms on a rate-control strategy.

For most patients with AF younger than age 65, particularly those who are symptomatic, rhythm controlmay be a better option. For younger, asymptomatic patients who are concerned about the potential side effects of antiarrhythmic drug therapy, and who are not inclined to undergo radiofrequency catheter ablation, a rate-control strategy is reasonable.

RATE CONTROL: Can be achieved with beta blockers, calcium channel blockers (verapamil, diltiazem), or digoxin.  Intravenous (IV) amiodarone may be needed for patients with poor left ventricular function. The drug selected and the route of administration (oral versus intravenous) are dictated by the clinical presentation. Overall, beta blockers or verapamil or diltiazem are the preferred therapeutic choices in the absence of heart failure. Digoxin is used mainly in heart failure as it is less likely to control the ventricular rate during exercise (when vagal tone is low and sympathetic tone is high), has little ability to terminate the arrhythmia, and often does not slow the heart rate in patients with recurrent atrial fibrillation (AF).  IV amiodarone may help control rate when the other drugs are ineffective or cannot be given.

RHYTHM CONTROL: For those patients in whom a rhythm control strategy is chosen, catheter ablation or antiarrhythmic drugs are the two principle therapeutic options.

For most patients with symptomatic paroxysmal atrial fibrillation (AF) who have chosen a rhythm rather than a rate control strategy antiarrhythmic drug (AAD) therapy rather than catheter ablation as first-line therapy is often attempted first. Patients who may reasonably prefer catheter ablation include younger individuals or those who are concerned about the potential complications of AAD.

Recommendations for Catheter ablation:

  •         For younger patients (age ≤70 years) with symptomatic paroxysmal AF with a left ventricular ejection fraction >40 percent who choose to not receive AAD therapy.
  •         Patients with symptomatic paroxysmal AF and who have failed or become intolerant to one or more AAD.
  •         For patients with symptomatic persistent or longstanding persistent AF who have failed or become intolerant of one or more AAD or who choose not to start antiarrhythmic therapy.

In an acute management setting for new onset Atrial Fibrillation, calcium channel blockers such as diltiazem 10mg every 10 minutes is a good first option.  If that does not break the arrhythmia, digoxin may be added. The third line is oftentimes Amiodarone.  Amiodarone can be effective as both an antiarrhythmic as well as for rate control.

 

The decision to pursue acute cardioversion is largely dictated by the severity of the patient’s symptoms. In patients with mild to moderate symptoms, concurrent with the initiation of the appropriate anticoagulation treatment, the initial therapy includes slowing the ventricular rate without an immediate strategy to restore sinus rhythm. Slowing the ventricular rate often results in significant improvement or even resolution of symptoms. Attempts to get the rate below 110 beats per minute should be the initial goal for rate.

Four circumstances for which urgent or emergent cardioversion may be needed. They include:

  1. Active ischemia (symptomatic or electrocardiographic evidence).
  2. Evidence of organ hypoperfusion.
  3. Severe manifestations of heart failure (HF) including pulmonary edema
  4. The presence of a preexcitation syndrome, which may lead to an extremely rapid ventricular rate due to the presence of an accessory pathway.

In a patient with any of these indications for urgent cardioversion, the need for restoration of normal sinus rhythm (NSR) takes precedence over the need for protection from thromboembolic risk. Intravenous anticoagulation with heparin should be started, but it should not cause a delay in emergent cardioversion. However, these four circumstances differ with regard to the urgency of cardioversion and in most cases rate control is possible as a temporizing measure.

Many patients begun on antiarrhythmic drug therapy should be hospitalized for continuous electrocardiographic monitoring due to a 10 to 15 percent incidence of adverse cardiac events during the initiation of therapy .

The two complications of greatest concern are bradycardia and proarrhythmia. Other adverse cardiac events can include significant QT prolongation, heart failure, rapid ventricular rate, conduction abnormalities, hypotension, and stroke. The risk is greatest in the first 24 hours and in patients with a prior myocardial infarction.

 

Outpatient initiation of antiarrhythmic drug therapy with the following agents may be considered:

  • Flecainide or propafenone in patients in sinus rhythm who have no underlying structural heart disease, normal baseline QT intervals, and no profound bradycardia or suspected sinus or atrioventricular (AV) node dysfunction.
  • Amiodarone or dronedarone in selected patients who have no other risk factors for torsades de pointes (eg, hypokalemia, hypomagnesemia) or sinus node dysfunction or AV conduction disease. Dronedarone and amiodarone are the only two drugs that can be initiated in outpatients while in atrial fibrillation.

 

Patients with an implantable cardioverter-defibrillator (ICD) represent another group in which outpatient initiation of therapy can be tried, since the ICD provides protection against the risks associated with bradyarrhythmias and tachyarrhythmias.


REFERENCES:
UPTODATE: ATRIAL FIBRILLATION MANAGEMENT.

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