Atrial Fibrillation (AF): Most common arrhythmia; characterized by an irregularly irregular ventricular rhythm and absence of discrete P waves.
Supraventricular Tachycardia: AF is classified as this type of arrhythmia.
Mechanism of AF
Atrial Activity: In AF, the atria quiver instead of contracting synchronously, leading to irregular and rapid beats.
Clot Formation: Most concerning complication is clot formation due to stasis, often in the left atrium, which can lead to embolism and stroke.
Heart Conduction System
Sinoatrial Node: The dominant pacemaker; sends impulses for synchronized atrial contraction (P wave on ECG).
Atrioventricular Node: Conducts impulses slower; acts as a gatekeeper to the ventricles.
Bundle of His and Purkinje Fibers: Impulses travel rapidly here, leading to ventricular contraction (QRS complex on ECG).
Triggers of AF
Ectopic Foci: Pacemaker cells located abnormally; commonly found in the left atrium near pulmonary veins.
Re-entry Circuit: Can result from ischemic heart disease, age, hypertension, leading to structural changes in atrial myocardium.
Types of Atrial Fibrillation
Paroxysmal AF: Lasts less than 7 days; often resolves spontaneously.
Persistent AF: Lasts longer than 7 days; may require intervention.
Permanent AF: Restoration to sinus rhythm is impossible; progressive remodeling occurs.
ECG Findings
Classic Characteristics: Absent P waves, irregularly irregular ventricular rate, F waves (fibrillatory waves), and varying heart rates (100-280 bpm).
Diagnosis
Paroxysmal AF: Diagnosed via Holter monitor or implantable loop recorder.
Persistent AF: Diagnosed with ECG.
Management Strategies
Acute Management
Unstable Patients: Require synchronized electrical cardioversion; followed by amiodarone infusion.
Stable Patients: Can use chemical cardioversion with antiarrhythmics (e.g., flecainide, sotalol).
Anticoagulation: Important if AF has been present for over 48 hours to rule out thrombus formation; transesophageal echocardiogram or four weeks of anticoagulation may be necessary prior to cardioversion.
Long-term Management
Rhythm Control vs. Rate Control: Depends on symptomatology, side effects, and contraindications.
Rate Control Medications: Beta blockers, calcium channel blockers, digoxin.
Rhythm Control Medications: Sotalol, amiodarone.
Anticoagulation: Assess using CHADS-VASc score to determine stroke risk; different anticoagulants for valvular vs. non-valvular AF.
Valvular AF: Warfarin is mainstay.
Non-Valvular AF: NOACs (e.g., rivaroxaban, apixaban) are preferred.
Catheter Ablation
Effective for paroxysmal AF; targets ectopic foci in pulmonary veins. More complex procedures needed for advanced AF.