Atrial Fibrillation

Andreas Stein

Robert Smith, M.D.

August 11, 2003

Definition

Atrial fibrillation/flutter is a disorder of heart rhythm (arrhythmia) usually with rapid heart rate, in which the upper heart chambers (atria) are stimulated to contract in a very disorganized and abnormal manner.

Prevalence• Overall prevalence 1%• Increases with age• Higher in men than in women

Classification

• Paroxysmal AF: less than 7 days

• Persistent AF: longer than 7 days

• Permanent AF: longer than 1 year

• Lone AF: no structural heart disease

Etiology

• AF with Heart disease complicated by the following is most common (~80%):– Atrial enlargement– Elevation of atrial pressure– Infiltration or inflammation of atria

• Lone AF (~20%):– Electrophysiologic properties

Etiology (cont)

Common diseases underlying AF:

• Hypertension

• Coronary Heart disease / MI • Rheumatic heart disease

• Dilated cardiomyopathy

• Hypertrophic cardiomyopathy

• Congenital heart disease

• Hyperthyroidism

• Inflammation

Evaluation of AF

History and Physical Examination:– Define symptoms associated with AF – Clinical type or “pattern” (Classification)– Onset or date of discovery– Frequency and Duration – Precipitating causes and modes of termination– Response to drug therapy – Presence of heart disease or potentially

reversible causes

Evaluation of AF (cont)

• Electrocardiogram:– Presence of AF– Left ventricular hypertrophy– Preexcitation– Bundle branch block– Prior MI– Measure important intervals such as: RR,

QRS and QT

Evaluation of AF (cont)

• Echocardiogram– Transthoracic Echocardiogram:

• size and function of atria and ventricles• low sensitivity for thrombi

– Transesophageal Echocardiogram:• High sensitivity for atrial thrombi• Need of anticoagulation prior to cardioversion

• Assessment for Hyperthyroidism – TSH measurement

General Treatment Issues

• Rhythm control:– reversion to normal sinus rhythm

• Rate control:– administration of medications to control the ventricular

rate in chronic AF

• Choosing between rhythm and rate control • Prevention of systemic embolization

Rhythm Control

• Synchronized External DC Cardioversion– hemodynamically stable and unstable patients– ~80% overall success rate

• Pharmacologic Cardioversion– hemodynamically stable patients– Class IA ; IC ; III anti arrhythmic drugs– ~60% overall success rate

Rule out atrial thrombi by TEE or anticoagulation for 3 – 4 week

Drugs for AF <7 Days

Drugs for AF >7 Days

Maintenance of NSR

• ~20% maintain in NSR without chronic anti-arrhythmic therapy

• Class IA, IC, and III drugs:– Flecainide minimal heart disease– Amiodarone reduced EF– Sotalol coronary heart disease

• Alternative methods:– ablative procedures– pacing– insertion of an implantable atrial defibrillator

Maintenance of NSR

Rate control in chronic AF

Slowing AV nodal conduction:

• beta blocker

• calcium channel blocker

• digoxin

Rhythm Control vs. Rate Control

• Embolic events occur with equal frequency in rate control and rhythm control strategies

• Almost significant trend toward a lower incidence of the primary end point with rate control

Prevention of Systemic Embolization

• Anticoagulation during restoration of NSR – AF > 48 hours 3 to 4 weeks of warfarin prior to

and after cardioversion– recommended target INR is 2.5

• Anticoagulation in chronic AF – Aspirin: low risk patients (<65y; no risk factors)– Warfarin: other than low risk patients

~70% reduction of stroke