artirial fibrillation

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"atrial fibrillation"[MeSH Terms] AND management

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Atrial Fibrillation (AF)

Definition and ECG Features

Atrial fibrillation is a supraventricular arrhythmia characterized electrocardiographically by:

Fibrillatory (f) waves: low-amplitude baseline oscillations, 300-600 beats/min, variable in amplitude, shape, and timing
Irregularly irregular ventricular rhythm
Ventricular rate during untreated AF is typically 100-160 beats/min

In some patients, f waves are very small and imperceptible; the diagnosis then rests on the irregularly irregular ventricular rhythm alone. In lead V1, f waves can occasionally mimic flutter waves. Atrial flutter, by contrast, produces waves at 250-350 beats/min that are constant in timing and morphology.

Braunwald's Heart Disease, p. 1272

Classification

Type	Definition
Paroxysmal	Terminates spontaneously within 7 days
Persistent	Present continuously for >7 days
Longstanding persistent	Persists for >1 year
Permanent	Patient and clinician jointly decide to abandon sinus rhythm restoration ("acceptance of AF" - a therapeutic attitude, not a pathophysiologic characteristic)

Note: The term "lone AF" (AF in patients <60 without hypertension or structural heart disease) has been abandoned due to inconsistent definitions.

Braunwald's Heart Disease, p. 1272

Epidemiology

AF occurs in about 12% of patients aged ≥75 years and 18% of patients aged ≥85 years. Approximately one-third of AF patients are ≥80 years. About 25% of AF cases can be classified by the autonomic setting in which they occur (vagal vs. adrenergic).

Risk factors and common comorbidities:

Hypertension (most common)
Coronary heart disease
Heart failure
Obesity
Sleep apnea
Hyperlipidemia
Hyperthyroidism
Braunwald's Heart Disease, p. 1272-1273

Mechanisms

Age-related changes in atrial tissue - including fibrosis and conduction abnormalities - provide the substrate for electrical disarray. Hypertension and structural heart disease add maladaptive atrial changes. This creates the conditions for multiple reentrant wavelets and/or focal triggers (commonly from the pulmonary vein ostia).

Clinical Features

Symptoms include:

Palpitations (less common in elderly)
Light-headedness
Chest discomfort
Shortness of breath
Fatigue
Decreased activity tolerance

In older adults, symptoms are frequently minimal or atypical. AF may first present as acute pulmonary edema (loss of atrial kick to a stiff LV), syncope, fall, or stroke.

Braunwald's Heart Disease, p. 1274

Diagnostic Evaluation

ECG: First-line; confirms irregular rhythm and f waves
Ambulatory monitoring: 24-hour Holter for daily symptoms; 2-4 weeks event monitor or mobile cardiac telemetry for sporadic symptoms; insertable loop recorder (battery life ~3 years) for cryptogenic stroke cases
Echocardiography: Assess atrial size, LV function, LVH, valvular disease
Labs: Thyroid, liver, renal function
Chest X-ray: If pulmonary disease suspected

Stroke Risk - CHA₂DS₂-VASc Score

The most important therapeutic goal is prevention of thromboembolic complications. The CHA₂DS₂-VASc score guides anticoagulation decisions:

Factor	Points
C - Congestive heart failure	1
H - Hypertension	1
A₂ - Age ≥75 years	2
D - Diabetes mellitus	1
S₂ - Stroke/TIA history	2
V - Vascular disease	1
A - Age 65-74 years	1
Sc - Sex category (female)	1

Score = 0: no anticoagulation
Score ≥2 (men) or ≥3 (women): oral anticoagulation recommended
All patients aged ≥75 have a score ≥2 and are candidates for anticoagulation regardless of AF type

Strongest individual predictors: prior stroke/TIA and mitral stenosis. With aspirin alone in AF + prior stroke, re-stroke risk is 10-12%/year.

Braunwald's Heart Disease, p. 1275

Anticoagulation

Anticoagulants are far more effective than antiplatelet agents (aspirin, clopidogrel) for thromboembolic prevention.

DOACs (Direct Oral Anticoagulants) are preferred over warfarin in nonvalvular AF:

Apixaban, rivaroxaban, dabigatran, edoxaban
No need for routine INR monitoring
Fewer food/drug interactions

Warfarin: Target INR 2.0-3.0 (2.0-2.5 in older patients). Dose typically 2-5 mg/day in seniors; significant drug interactions and dietary limitations are challenges.

Bleeding risk - HAS-BLED score: Counterbalances stroke risk assessment. Both risks increase with age. Recent evidence (reflected in the 2025 JACC meta-analysis, PMID 39918465) supports using only a P2Y12 inhibitor (avoiding aspirin) when anticoagulation is combined with antiplatelet therapy - this reduces bleeding compared to dual antiplatelet + anticoagulant.

Rate Control vs. Rhythm Control

Key principle: Stroke risk is the same in both strategies. Anticoagulation must continue regardless of approach based on the patient's CHA₂DS₂-VASc score.

Rate Control (first-line for most patients)

Target resting heart rate <110 bpm
Agents:
- Beta-blockers (first-line) or non-dihydropyridine CCBs (diltiazem, verapamil)
- Avoid verapamil + beta-blocker combination (risk of bradycardia/HF)
- Digoxin: second-line; useful in HFrEF; less effective during activity and in paroxysmal AF; should not be used as sole agent for paroxysmal AF
- Amiodarone: if other measures fail
- AV node ablation + pacemaker: when pharmacologic therapy fails

Avoid beta-blockers and non-dihydropyridine CCBs in decompensated heart failure.

Rhythm Control (selected patients)

Preferred when: first episode, significant symptoms, exercise intolerance, younger patients
Immediate cardioversion if hemodynamically unstable (ischemia, hypotension, severe HF)

Pharmacologic cardioversion (AF <7 days):

IV: ibutilide (~60-70% efficacy), amiodarone (~40-50%), procainamide (~30-40%)
Oral: propafenone 300-600 mg or flecainide 100-200 mg (in patients without structural heart disease)
"Pill-in-the-pocket" approach after supervised first dose

Electrical cardioversion: efficacy >95%; biphasic waveforms preferred; contraindicated in hypokalemia or digoxin toxicity.

Anticoagulation Around Cardioversion

AF Duration	Protocol
Unstable patient	Immediate cardioversion; IV heparin ASAP; then ≥4 weeks anticoagulation
Stable, <48 hours	Cardioversion with concurrent heparin/DOAC; then ≥4 weeks anticoagulation
Stable, ≥48 hours or unknown	3 weeks anticoagulation first, OR TEE to exclude thrombus then cardioversion; then ≥4 weeks anticoagulation

Symptom to Diagnosis: An Evidence-Based Guide, p. 301; Braunwald's Heart Disease, p. 1277-1279

Catheter Ablation

Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation for AF. It is particularly effective in paroxysmal AF and is considered when antiarrhythmic drugs fail or are not tolerated. The left atrial appendage (LAA) can also be occluded (e.g., LARIAT procedure or WATCHMAN device) in patients who cannot tolerate long-term anticoagulation.

Special Populations

WPW + AF: Can produce ventricular rates >250 bpm via the accessory pathway - AV nodal blockers (beta-blockers, CCBs, digoxin, adenosine) are contraindicated; use procainamide or electrical cardioversion
HFrEF: Rate control with digoxin or amiodarone; avoid negative inotropes
Pregnancy: Rate control with digoxin or beta-blockers; heparin for anticoagulation

Recent Evidence (2025-2026)

A 2025 JACC meta-analysis (PMID 39918465) confirms that in AF with stable coronary disease, anticoagulation alone (without aspirin) is preferred - reduces major bleeding without increasing ischemic events.
A 2026 systematic review in Heart (PMID 40962485) documents that AF is associated with significant long-term cardiovascular risks beyond stroke, including heart failure and cognitive decline, reinforcing aggressive risk factor management.

Sources: Braunwald's Heart Disease (11th ed.) | Symptom to Diagnosis: An Evidence-Based Guide (4th ed.) | Tintinalli's Emergency Medicine | Fuster and Hurst's The Heart (15th ed.) | PubMed PMID 39918465, 40962485

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