ATRIAL FIBRILLATION (AF)

Atrial fibrillation is a supraventricular tachyarrhythmia characterized by:

• • Irregularly irregular rhythm
  • No distinct P waves
  • Fibrillatory (f) waves
  • Variable R–R intervals

CLASSIFICATION 

 Also:

• Valvular AF → moderate–severe mitral stenosis / mechanical valve
• Non-valvular AF → all others

 TYPES OF AF BASED ON VENTRICULAR RESPONSE

PATHOPHYSIOLOGY

1. TRIGGERS

• Most commonly from pulmonary veins
• Focal ectopic activity
• Multiple re-entry circuits
• Electrical remodeling:
  • ↓ refractory period
  • “AF begets AF”

RISK FACTORS

CARDIAC

• Hypertension (most common)
• CAD
• Heart failure
• Valvular disease (esp. mitral stenosis)
• Cardiomyopathy

NON-CARDIAC

• Hyperthyroidism
• Obesity
• OSA
• Alcohol (“holiday heart”)
• Sepsis
• CKD

CLINICAL FEATURES

Symptoms

• Palpitations
• Dyspnea
• Fatigue
• Dizziness
• Syncope (rare)

Signs

• Irregularly irregular pulse
• Pulse deficit
• Variable S1

COMPLICATIONS

1. THROMBOEMBOLISM

• Stroke risk ↑ 5-fold
• Left atrial appendage thrombus

2. HEART FAILURE

• Loss of atrial kick
• Tachycardia-induced cardiomyopathy

3. MORTALITY ↑

DIAGNOSIS

Mandatory:

• ECG documentation ≥30 sec

Workup:

• Echocardiography
• Thyroid function tests
• Electrolytes
• Renal function
• Holter if paroxysmal

MANAGEMENT

1.  INITIAL APPROACH (ICU /EMERGENCY)

Step 1: Assess Stability

Hemodynamically unstable AF

• Hypotension
• Shock
• Pulmonary edema
• Ongoing ischemia
• Altered mental status

 Immediate treatment = synchronized cardioversion

 DC Cardioversion

• Biphasic: 120–200 J → escalate

Step 2: Stable Patient → Decide Strategy

 Rate control vs Rhythm control

2. RATE CONTROL (FIRST-LINE IN MOST)

 Target-Resting HR <110 bpm (lenient control acceptable per guidelines)

1.  Beta-blockers (FIRST LINE)

• Metoprolol
  • IV: 2.5–5 mg over 2 min (repeat q5 min, max 15 mg)
  • Oral: 25–100 mg BD
• Esmolol (ICU favorite)
  • Bolus: 500 mcg/kg
  • Infusion: 50–200 mcg/kg/min

 Preferred in:

• Post-MI
• Hyperadrenergic states

2.  Non-DHP Calcium Channel Blockers(Avoid in: HFrEF)

• Diltiazem
  • IV bolus: 0.25 mg/kg
  • Repeat: 0.35 mg/kg
  • Infusion: 5–15 mg/hr
• Verapamil
  • IV: 5–10 mg slow

3.  Digoxin

• Loading: 0.5 mg → 0.25 mg q6h (max 1–1.5 mg)
• Maintenance: 0.125–0.25 mg/day

 Best in:

• HF with low BP
• Sedentary patients

 Not effective in high sympathetic tone

4.  Amiodarone (when others fail or HF)

• IV: 150 mg over 10 min
• Then: 1 mg/min × 6 hr → 0.5 mg/min
• Oral: 200 mg BD → taper

 Preferred in:

• HFrEF
• ICU unstable rate

3.  RHYTHM CONTROL

Indications 

• Symptomatic AF despite rate control
• First episode
• AF <48 hr
• Younger patients
• Tachycardia-induced cardiomyopathy
• HF where AF worsens function

PHARMACOLOGICAL CARDIOVERSION

1. Amiodarone

• 150–300 mg IV over 10–30 min
• Conversion may take hours

2. Flecainide(Avoid in:Structural heart disease)

• Oral: 200–300 mg single dose
• IV: 2 mg/kg

3. Propafenone

• Oral: 450–600 mg

4. Ibutilide

• 1 mg IV over 10 min

 Risk: Torsades de pointes

ELECTRICAL CARDIOVERSION

• Biphasic: 120–200 J

4. ANTICOAGULATION 

Risk Assessment Stroke Risk → CHA₂DS₂-VASc

INTERPRETATION (ESC/AHA)

 HAS-BLED?

It estimates 1-year risk of major bleeding, especially:

• Intracranial hemorrhage
• GI bleeding
• Major extracranial bleeding

 Max score = 9

INTERPRETATION

HAS-BLED is NOT used to deny anticoagulation

According to ESC 2023 / AHA 2023:

• High HAS-BLED (≥3) →
  DO NOT stop anticoagulation
   Instead:
  • Correct risk factors
  • Monitor closely

ANTICOAGULATION OPTIONS

1.  DOACs (FIRST LINE)

• Apixaban
  • 5 mg BD
  • 2.5 mg BD if ≥2: age ≥80, wt ≤60, Cr ≥1.5
• Rivaroxaban
  • 20 mg OD
  • 15 mg if CKD
• Dabigatran
  • 150 mg BD
  • 110 mg BD (elderly/high bleeding risk)

2.  Vitamin K antagonist

• Warfarin
  • INR target: 2–3

Indications:

• Mechanical valves
• Moderate–severe mitral stenosis

ANTICOAGULATION AROUND CARDIOVERSION

AF → blood stasis in left atrium.Cardioversion → atrial contraction resumes.Restoring sinus rhythm  can dislodge a left atrial thrombus → stroke risk.

AF <48 hr

• Heparin/DOAC → cardioversion

AF >48 hr or unknown

• Anticoagulate ≥3 weeks
  OR
• TEE-guided cardioversion

Post cardioversion

• Continue ≥4 weeks

5.  SPECIAL SCENARIOS 

AF + WPW 

 Avoid AV node blockers:

• Beta-blocker
• Diltiazem
• Digoxin

 Use:

• Procainamide
• Electrical cardioversion

AF + SEPSIS / ICU

• First treat cause
• Amiodarone preferred
• Avoid aggressive beta-blockade in shock

Post-operative AF

• Beta-blockers first line
• Amiodarone if needed

6. LONG-TERM RHYTHM CONTROL

• Amiodarone
• Sotalol
• Flecainide
• Dronedarone

7. NON-PHARMACOLOGICAL MANAGEMENT

1.  CATHETER ABLATION (CORNERSTONE)

AF is most commonly triggered by ectopic foci from pulmonary veins (PVs) → isolate them electrically.

PROCEDURE: PULMONARY VEIN ISOLATION (PVI)

Techniques:

• Radiofrequency ablation (point-by-point lesions)
• Cryoballoon ablation (freezing PV ostia)

 INDICATIONS 

 Class I (STRONG RECOMMENDATION)

• Symptomatic paroxysmal AF refractory/intolerant to ≥1 antiarrhythmic drug
• Symptomatic persistent AF (selected cases)

 Class IIa 

• First-line therapy in:
  • Young patients
  • Symptomatic AF
  • Patient preference
• AF with heart failure (HFrEF) → improves:
  • EF
  • Symptoms
  • Mortality (CASTLE-AF evidence)

 COMPLICATIONS 

• Cardiac tamponade
• Stroke / TIA
• Pulmonary vein stenosis
• Atrio-esophageal fistula (rare but fatal)
• Phrenic nerve injury (cryoablation)

 GUIDELINE PEARLS

• Early rhythm control (including ablation) improves outcomes
• Preferred over drugs in selected patients
• Continue anticoagulation based on CHA₂DS₂-VASc (not rhythm success)

2. AV NODE ABLATION + PACEMAKER (“ABLATE & PACE”)

• Destroy AV node → eliminate rapid ventricular response
• Implant pacemaker → maintain heart rate

 INDICATIONS

• Refractory AF with uncontrolled rate
• Intolerance to drugs
• Tachycardia-induced cardiomyopathy

 TYPES OF PACING

• RV pacing (traditional)
• CRT (biventricular pacing) → preferred in HF
• His-bundle pacing (physiological pacing)

 LIMITATIONS

• Patient becomes pacemaker dependent
• AF persists (no rhythm control)
• Anticoagulation still required

4.  LEFT ATRIAL APPENDAGE (LAA) OCCLUSION

• Most thrombi in AF originate in left atrial appendage

 INDICATIONS

• AF + contraindication to long-term anticoagulation
• High bleeding risk

• Not first-line
• Short-term anticoagulation still needed post-procedure

5. SURGICAL MANAGEMENT

 MAZE PROCEDURE

• Create scar lines → block reentry circuits

INDICATIONS

• AF undergoing cardiac surgery (e.g., valve surgery)
• Failed catheter ablation

TRIALS 

REFERENCES

1.European Society of Cardiology (ESC)

• Hindricks G, et al.
• 2020 ESC Guidelines for the diagnosis and management of atrial fibrillation.

2.Oh’s Intensive Care Manual

3.Oxford handbook of internal medicine