Atrial fibrillation

Learning Objectives

  1. Understand the heart's electrical conduction.

  2. Define Atrial Fibrillation (AF).

  3. Recognize risk factors of AF.

  4. Learn rate and rhythm control options.

  5. Prevent AF-related strokes through anticoagulation.

Cardiac Arrhythmia

  • Atrial Fibrillation: A common heart arrhythmia where the heart's normal electrical rhythm is disrupted, leading to less effective blood pumping.

Heart's Electrical Function

  • Impulses start at the Sinoatrial (SA) node.

  • Blood flows from the atrium to the ventricle.

  • Atrioventricular (AV) node conducts impulses to the ventricles.

  • Right ventricle pumps blood to the lungs, and the left ventricle supplies the body.

Atrial Fibrillation Overview

  • Type: Supraventricular arrhythmia (originates in the atria).

  • Involves irregular and rapid atrial depolarization.

  • Atrial rates: 300-500 bpm; Ventricular rates: 120-180 bpm (regulated by the AV node).

Risk Factors

  • Unmodifiable: Age, congenital defects, genetic predispositions, previous heart disease, or surgery.

  • Modifiable: High blood pressure, sleep apnea, obesity, thyroid problems, diabetes, stimulant exposure, stress.

Consequences of AF

  • Thrombosis: Blood clots can form and cause strokes or embolism.

  • Reduced cardiac output can lead to heart failure.

Symptoms of AF

  • Palpitations, shortness of breath, fatigue, dizziness, irregular pulse.

  • Can be asymptomatic.

Diagnosis

  • ECG: Confirms AF and begins risk stratification.

Classification

  • By cause: Lone AF, related to hypertension or structural heart disease.

  • By occurrence: First detected, recurrent (paroxysmal, persistent, permanent).

Treatment Goals (NICE Guidelines)

  1. Prevent thromboembolic events.

  2. Relieve symptoms.

  3. Restore/maintain normal heart rhythm.

  4. Manage underlying causes.

AF Treatment Options

  1. Rate Control: First-line therapy using beta-blockers, calcium channel blockers, or digoxin.

  2. Rhythm Control: Cardioversion (either electrical or pharmacological) to re-establish sinus rhythm.

  3. Stroke Prevention: Anticoagulants to reduce the risk of stroke.

Rate Control vs Rhythm Control

  • Rate Control: Slows ventricular rate, relieves symptoms but doesn’t correct arrhythmia.

  • Rhythm Control: Aims to restore normal sinus rhythm and is suitable for specific cases, such as new-onset AF or heart failure.

Pharmacological Management

  • Beta-blockers: First-line for many patients. Atenolol and bisoprolol are commonly used.

  • Calcium Channel Blockers: Diltiazem and verapamil (not recommended for heart failure patients).

  • Digoxin: Used for sedentary patients or when other options are contraindicated.

Beta-Blockers and Other Rate-Control Drugs

  • Beta-blockers reduce heart rate and inhibit ectopic pacemaker activity.

  • Calcium channel blockers and digoxin help control heart rate but with different mechanisms and side effects.

Follow-up for Rate Control

  • Evaluate within 1 week of starting treatment to check drug tolerance, symptoms, heart rate, and blood pressure.

  • Adjust doses or combine therapies as needed.

Rhythm Control and Cardioversion

  • Cardioversion: Either pharmacological (using drugs like flecainide, propafenone, or amiodarone) or electrical (for more severe cases).

  • Drugs like amiodarone are effective but have serious side effects and require close monitoring.

Stroke Prevention

  • CHA2DS2-VASc score: Assesses stroke risk.

+ Score ≥ 2: High risk, requires anticoagulation.

  • HAS-BLED score: Assesses bleeding risk, guiding anticoagulation decisions.

Anticoagulation Therapy

  • Direct Oral Anticoagulants (DOACs) (e.g., apixaban, dabigatran) or Vitamin K antagonists are preferred.

  • Aspirin alone is no longer recommended for stroke prevention in AF.

Patient Counseling

  • Explain risks and benefits of anticoagulation.

  • Discuss lifestyle changes to reduce cardiovascular risk factors (e.g., stress, caffeine, and alcohol).

  • Provide resources for patient support groups.

AF Projections

  • AF prevalence is expected to double by 2060, making it a significant public health issue.