Course:PostgradFamilyPractice/ExamPrep/99 Priority Topics/Atrial Fibrillation

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Atrial Fibrillation - Key Features

1. In a patient who presents with new onset atrial fibrillation, look for an underlying cause (e.g., ischemic heart disease, acute myocardial infarction, congestive heart failure, cardiomyopathy, pulmonary embolus, hyperthyroidism, alcohol, etc.)

2. In a patient presenting with atrial fibrillation,
a) Look for hemodynamic instability,
b) Intervene rapidly and appropriately to stabilize the patient.

3. In an individual presenting with chronic or paroxysmal atrial fibrillation,
a) Explore the need for anticoagulation based on the risk of stroke with the patient,
b) Periodically reassess the need for anticoagulation.

4. In patients with atrial fibrillation, when the decision has been made to use anticoagulation, institute the appropriate therapy and patient education, with a comprehensive follow-up plan.

5. In a stable patient with atrial fibrillation, identify the need for rate control.

6. In a stable patient with atrial fibrillation, arrange for rhythm correction when appropriate.

AF is the most common cardiac arrhythmia in adults; prevalence increases with age Pts with untreated AF are at a 5-fold increase for complications including: Thromboembolism, Stroke, Myocardial Ishcemia/Infarction, Heart Failure

Patients may be asymptomatic, have mild symptoms (e.g., palpitations, weariness, and reduced exercise capacity), or may have more severe symptoms (e.g., syncope, hear t failure or angina). Dyspnea, chest pain and palpitations are the most common presenting symptoms in emergency admissions.

AF can present with or without an associated underlying condition. A predisposing condition (both cardiac and non-cardiac) exists in > 90% of cases. Associated cardiac conditions are usually much more common (up to 80%).

Definitions:
Proxysmal AF – terminates spontaneously in <7 days
Persistent AF - >7days; not self-terminating
Permanent AF – cardioversion failed

Management:
Initial management strategies depend on the patient’s presentation
Acutely unwell patients (rapid AF with hypotension, syncope, chest pain, dyspnea, heart failure or neurological symptoms) require urgent rate control and possibly emergency cardioversion in a hospital setting. Stable patients require medication to slow heart rate and prevent emboli.

Long term management will include rate and/or rhythm control strategies. As well, all patients with AF should be stratified using a predictive index for stroke (e.g. CHADS) and for the risk of bleeding (e.g. HAS-BLED), and most patients should receive antithrombotic therapy.

Several RCTs and meta-analyses have concluded there are no differences between rate and rhythm control strategies in terms of mortality, cardiovascular events or stroke.

1. Rate Control:
Beta blocker is the preferred rate control drug, compared to a calcium channel blocker, in patients with angina, previous MI, or left ventricular systolic dysfunction. Digoxin, a second-line choice, is reserved for rate control in patients who are sedentary or who have left ventricular systolic dysfunction and it may be useful as an adjunct to beta blockers and calcium channel blockers in patients whose heart rate remains uncontrolled.

2010 Canadian guidelines recommend aiming for a “resting heart rate of less than 100 bpm”.

2. Rhythm Control:
Anit-arrhythmics are recommended for patients with AF who remain symptomatic with rate control therapy or in whom rate control therapy is unlikely to control symptoms. Anti-arrhythmic drugs should be avoided in patients with AF who have advanced sinus or AV nodal disease, unless the patient has a pacemaker/ implantable defibrillator.

3. Cardioversion:
Direct-current and pharmacologic cardioversion impose similar risk of thromboembolism, particularly if the arrhythmia has been present for more than 48 hours. Therefore, anticoagulation prophylaxis must be initiated before the procedure.

Pharmacologic cardioversion raises the risk of torsades de pointes and other serious arrhythmias. Pharmacologic cardioversion is most effective within seven days of AF onset.

Direct-current cardioversion is more effective than pharmacologic cardioversion when biphasic shocks are used.

When urgent cardioversion is needed, recommendations include a screening transesophageal echocardiograph and immediate anticoagulation with either unfractionated IV heparin or low-molecular- weight heparin, prior to cardioversion.

If no thrombus is seen on TEE, convert to oral anticoagulation after cardioversion and continue for at least four weeks — even if sinus rhythm is maintained.
If a thrombus is seen on TEE, cardioversion should be postponed and anticoagulation should be continued indefinitely.

For patients with AF of 48-hours or longer (or when the duration of AF is unknown), full anticoagulation is recommended for at least three weeks before and four weeks after cardioversion, regardless of the whether electrical or pharmacological cardioversion is used.

4. Rhythm Maintenance:
Sinus rhythm will be maintained in approximately 20–30% of patients without the need for long-term antiarrhythmic drug therapy. However, despite treatment, approximately 50–85% of patients relapse to AF by 12 months.

Choice of agent is based on left ventricular function. When function is normal, preferred agents are: dronedarone, flecainide, propafenone, or sotalol. However, flecainide and propafenone should not be used if CAD is present. When left ventricular function is abnormal (EF < 35%), amiodarone would be the preferred agent.

Overall, most patients converted to sinus rhythm from AF should not be placed on long-term rhythm maintenance therapy, as the risks of antiarrhythmic drugs outweigh the benefits.

5. Ablation Therapy:
Catheter ablation is recommended for AF in patients who remain symptomatic following adequate trials of anti-arrhythmic drug therapy. Catheter ablation is superior to antiarrhythmic drug therapy in preventing recurrences and reducing symptoms.

6. Antithrombotic Therapy:
Stroke is the major complication of AF, and the strokes related to AF tend to be more severe than strokes from other causes.

Decisions about antithrombotic therapy for individual patients are best informed by stratifying each patient with AF using a predictive index for risk of stroke (e.g. CHADS ) and for risk of bleeding (e.g. HAS-BLED).

Anticoagulation with dabigatran or warfarin reduces the risk of stroke by 50–68% Aspirin reduces the risk of stroke by about 22–36%.

It is recommended that most patients with a CHADS2of >1 receive anticoagulant therapy, either warfarin or dabigatran.

For patients who are at increased risk for stroke but cannot or will not take warfarin or dabigatran, the addition of clopidogrel to ASA may remain as an option.

Aspirin should not be added to an oral anticoagulant for AF patients without compelling indications for antiplatelet therapy (such as the presence of CAD), even for patients with AF who suffer an ischemic stroke or TIA despite therapeutic anticoagulation.

Study Guide

Atrial fibrillation

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