Atrial Fibrillation
A chaotic, irregular heartbeat that causes poor blood flow and massively increases the risk of forming blood clots in the heart, leading to stroke.
Emergency Management: AFib with hemodynamic instability (hypotension, altered mental status, active angina). Requires immediate synchronized electrical cardioversion. DO NOT delay cardioversion for a TEE or anticoagulation in an unstable patient.
Atrial Fibrillation (AFib) is a supraventricular tachyarrhythmia characterized by uncoordinated atrial activation and consequent deterioration of atrial mechanical function. It is the most common sustained cardiac arrhythmia and significantly increases the risk of stroke, heart failure, and mortality.
Detailed Overview
AFib replaces normal sinus rhythm with chaotic electrical impulses originating most commonly from the pulmonary vein ostia. The atria quiver at 300-600 bpm rather than contracting. The AV node blocks most of these impulses, resulting in an irregularly irregular ventricular response. The lack of organized atrial contraction leads to blood stasis, particularly in the left atrial appendage (LAA), massively increasing the risk of thromboembolic stroke. Management hinges on three pillars: rate control, rhythm control, and most importantly, stroke prevention via anticoagulation.
Epidemiology & Demographics
Affects over 33 million people worldwide. Prevalence sharply increases with age, affecting >10% of individuals over 80. More common in men and individuals of European descent.
Etiological Mechanism
Cardiac causes: hypertensive heart disease, coronary artery disease, valvular heart disease (especially mitral stenosis). Non-cardiac causes: hyperthyroidism, sleep apnea, acute alcohol intoxication ('Holiday Heart Syndrome'), and pulmonary embolism.
Primary Causes
Structural remodeling (fibrosis, dilation) and electrical remodeling (shortened refractory periods) of the atria create an anatomical substrate capable of sustaining multiple wandering re-entry wavelets.
Trigger beats, typically premature atrial contractions firing from muscle sleeves extending into the pulmonary veins, hit an electrically vulnerable substrate (remodeled left atrium). Multiple micro-reentrant circuits form, wandering chaotically. This electrical chaos paralyzes the atrial muscle. Loss of the 'atrial kick' reduces cardiac output by up to 20%, triggering heart failure in borderline patients. Blood stagnates in the LAA, forming a fibrin-rich red clot that can embolize to the brain.
Diagnostic Criteria & Guidelines
A 12-lead ECG demonstrating: 1) Absence of distinct repeating P waves; 2) Irregularly irregular R-R intervals (when AV conduction is intact); 3) Fine or coarse fibrillatory waves.
Stroke Prevention: Calculate CHA2DS2-VASc score. If male >1 or female >2, initiate Direct Oral Anticoagulant (DOAC) like Apixaban 5 mg PO BID or Rivaroxaban 20 mg PO daily. Rate Control: Beta-blockers (Metoprolol succinate 25-100 mg daily) or non-dihydropyridine CCBs (Diltiazem 120-240 mg daily) to target a resting HR < 110 bpm.
Second-Line & Adjunctive Therapy
Rhythm Control (if symptomatic despite rate control or heart failure): Antiarrhythmics (Flecainide, Amiodarone, Sotalol) or Electrical Cardioversion (200 Joules synchronized shock). Catheter ablation (pulmonary vein isolation) is increasingly used first-line for symptomatic paroxysmal AFib.
Surgical & Procedural Management
Left Atrial Appendage Occlusion (LAAO) device (Watchman) for patients with high stroke risk who cannot tolerate long-term anticoagulation due to bleeding. Surgical Maze procedure performed concurrently during other open-heart surgeries.
Patient Counseling & Advice
Educate extensively on the critical importance of DOAC compliance; missing even one or two doses removes stroke protection. Educate on the signs of stroke (FAST: Face drooping, Arm weakness, Speech difficulty, Time to call 911).
Follow-Up & Monitoring Schedule
Annual ECG, checking renal function (creatinine) to adjust DOAC dosing (e.g., Apixaban requires a dose reduction to 2.5 mg BID if 2 of the following: Age > 80, Weight < 60 kg, Creatinine > 1.5).
Preventive Strategies
Strict blood pressure control, treating sleep apnea with CPAP, and maintaining normal body weight.
AFib independently increases the risk of mortality twofold and the risk of stroke fivefold. However, with strict adherence to DOACs and rate control, life expectancy approaches that of the general population.