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KEY FEATURES

ESSENTIALS OF DIAGNOSIS

  • Irregularly irregular ventricular rhythm usually at rates > 100 bpm

  • Absence of distinct P waves on the ECG

GENERAL CONSIDERATIONS

  • The most common chronic arrhythmia

  • Prevalence increases with age from 0.1% for those < 55 years old to 9% in those > 80 years old. Nearly 70% of those with atrial fibrillation are > 65 years old

  • Common causes include:

    • – Hypertensive heart disease

    • – Coronary heart disease

    • – Rheumatic heart disease

    • – Systolic dysfunction of any cause

    • – Mitral valve disease

    • – Cardiac surgery

    • – Hyperthyroidism

    • – Idiopathic

  • Atrial fibrillation associated with Wolff-Parkinson-White syndrome may lead to very rapid ventricular rates and be life threatening

  • QRS complex is usually narrow (< 100 ms) but may be wide (> 120 ms) if there is aberrant conduction, a preexisting bundle branch block, or an accessory pathway

  • Long, short cycle length fluctuations are common

  • Faster ventricular rates may minimize cycle length fluctuation

  • Atrial fibrillation is classified as paroxysmal (self-terminating within 7 days), persistent (fails to terminate within 7 days and commonly requires cardioversion), long-standing persistent (episodes lasting longer than 12 months), or permanent, in which a decision has been made to not pursue rhythm control strategy. The term lone atrial fibrillation describes those with atrial fibrillation and no structural heart disease; however, this term is no longer commonly used

  • Paroxysmal, persistent, and permanent forms of atrial fibrillation all increase the risk of stroke

  • Atrial fibrillation is a leading cause of stroke; this risk is mitigated by anticoagulation therapy

  • Other causes of rapid regular ventricular rate include atrial flutter, junctional rhythm, and ventricular tachycardia

CLINICAL PRESENTATION

SYMPTOMS AND SIGNS

  • Palpitations, chest pain, shortness of breath, fatigue, and dizziness

  • Symptoms of precipitating or associated conditions may mask symptoms of atrial fibrillation

  • Alternatively, atrial fibrillation may produce symptoms in otherwise asymptomatic conditions

  • Syncope is uncommon

  • Atrial fibrillation may be an incidental finding in some patients (asymptomatic)

PHYSICAL EXAM FINDINGS

  • Variable S1, occasional S3, and absent S4

  • Absence of a waves in the jugular venous pulse

  • Pulse deficit (difference between the auscultated or palpated apical heart rate and palpated rate at the wrist) is common, particularly at fast heart rates

  • Irregularly irregular pulse

  • Signs of precipitating conditions like thyrotoxicosis, rheumatic mitral stenosis, and heart failure

DIFFERENTIAL DIAGNOSIS

  • Multifocal atrial tachycardia (P waves present but irregular)

  • Atrial flutter with variable atrioventricular (AV) block (P waves present but irregular)

  • Sinus rhythm with consecutive premature atrial contractions (P waves present but irregular)

  • Junctional rhythm (P waves absent but regular)

DIAGNOSTIC EVALUATION

LABORATORY TESTS

  • CBC, basic metabolic panel

  • Thyroid function (serum thyroid-stimulating hormone and free thyroxine)

  • Arterial blood gas analysis to assess for hypoxemia

ELECTROCARDIOGRAPHY

  • ECG to confirm atrial fibrillation (findings include fibrillatory wave, absence of p ...

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