Makindo Medical Notes

Related Subjects: |Atrial Flutter |Atrial Fibrillation |AF and Anticoagulation |AF and Rate Control |AF and Rhythm Control and Cardioversion |AF ECG |DC cardioversion |Wolff-Parkinson White syndrome (WPW) |Supraventricular Tachycardia (SVT) |Ventricular Tachycardia |Ventricular Fibrillation |Resuscitation - Adult Tachycardia Algorithm |Resuscitation - Advanced Life Support

Quick Guide

About

• AF involves uncoordinated, chaotic atrial activation, leading to atrial mechanical dysfunction.
• Major risk of cardioembolism causing ischaemic stroke.
• Most patients need anticoagulation.

Aetiology

• Atrial fibrosis and loss of muscle mass, increased automaticity, or multiple re-entrant wavelets.
• Atrial rate in AF is 400-600/min, but ventricular response matters.
• Ventricular rate limited by AV node to about 200/min; accessory pathway (e.g., WPW) may allow faster rates, risking VF.

ECG

Physiology

• High heart rate shortens diastole, limiting LV filling and coronary perfusion.
• Impaired LV function or mitral stenosis worsens effects.

Clinical Presentation

• Asymptomatic, palpitations, dyspnea, chest discomfort, fatigue, stroke, syncope, low BP, irregular pulse.

Clinical Effects of AF

• Increased risk of death, stroke, hospital admissions, decreased quality of life, and LV dysfunction.

Causes of Atrial Fibrillation

• Ischemic, valvular, hypertensive heart disease, thyrotoxicosis, alcohol, sick sinus syndrome, pulmonary embolism, myocarditis, idiopathic AF.

Types of AF

Valvular vs. Non-Valvular AF

• Valvular AF often includes mitral stenosis, increasing thromboembolism risk.
• Non-Valvular AF excludes rheumatic mitral stenosis or valve repairs; CHA2DS2-VASc score is recommended for stroke risk assessment.

Investigations

• Bloods: FBC, U&E, Mg, Ca, K, TFT, LFT, alcohol, haemochromatosis.
• ECG: Absent p-waves, fibrillatory waves.
• Echocardiogram: Assess LV function, valve disease, LA size.
• TOE/TEE: Closer inspection of LA appendage for thrombus.

Rate Control

• Rate control aims to manage heart rate while allowing AF to persist. It is usually the initial approach, especially in older adults or those with minimal symptoms.
• The goal is to maintain a resting heart rate of <110 beats per minute in asymptomatic patients or a stricter target of <80 bpm in symptomatic patients.
• Beta-Blockers: Medications like metoprolol or bisoprolol are commonly used to control the heart rate by blocking adrenergic activity.
• Calcium Channel Blockers: Diltiazem and verapamil help slow conduction through the AV node, especially in patients who cannot tolerate beta-blockers.
• Digoxin: Often used in combination with other agents for rate control, particularly in patients with heart failure, as it increases vagal tone and slows AV nodal conduction.

Rhythm Control

Rhythm control aims to restore and maintain sinus rhythm, which may be preferred in symptomatic patients, younger individuals, or those who fail rate control. Rhythm control strategies include:

• Antiarrhythmic Drugs: Medications used to prevent recurrence of AF episodes.
  • Class Ic Agents (e.g., Flecainide, Propafenone): Effective in patients without significant structural heart disease.
  • Class III Agents (e.g., Amiodarone, Dronedarone, Sotalol): Suitable for patients with structural heart disease. Amiodarone is highly effective but associated with significant side effects, particularly with long-term use.
• Electrical Cardioversion: Direct current cardioversion (DCCV) is a procedure where a synchronized electric shock is administered to restore sinus rhythm, usually performed under sedation.
• Catheter Ablation: A more definitive approach where radiofrequency or cryotherapy is used to isolate the pulmonary veins, a common origin of AF triggers. Catheter ablation is indicated for symptomatic patients who do not respond to medications or as first-line therapy in some cases.

3. Anticoagulation for Stroke Prevention

AF increases the risk of thromboembolic events, especially stroke, as blood pools and clots in the left atrial appendage. Anticoagulation therapy is essential for stroke prevention, guided by the CHA₂DS₂-VASc score:

• Vitamin K Antagonists (e.g., Warfarin): Effective in reducing stroke risk with regular INR monitoring to maintain a target INR between 2.0 and 3.0.
• Direct Oral Anticoagulants (DOACs): Preferred over warfarin for most patients due to fewer dietary restrictions and no need for INR monitoring. Common DOACs include:
  • Apixaban
  • Rivaroxaban
  • Dabigatran
  • Edoxaban

Anticoagulation should be considered based on individual stroke and bleeding risk assessments, especially in patients with high CHA₂DS₂-VASc scores (≥2 for men, ≥3 for women).

Management of Underlying and Contributing Conditions

• Hypertension: Optimal blood pressure control is essential, as hypertension is a significant risk factor for AF.
• Heart Failure: Management of heart failure can reduce AF burden and improve outcomes.
• Obesity: Weight management is important, as obesity is associated with a higher AF incidence and recurrence rate.
• Sleep Apnea: Screening for and treating obstructive sleep apnea with continuous positive airway pressure (CPAP) can reduce AF recurrence.

Lifestyle Modifications and Patient Education

• Regular Exercise: Moderate exercise can improve cardiovascular fitness, though high-intensity exercise may exacerbate AF in some cases.
• Alcohol Moderation: Alcohol can increase the risk of AF episodes, so patients are advised to limit alcohol intake.
• Avoid Stimulants: Caffeine, nicotine, and other stimulants can increase heart rate and provoke AF episodes, so reduction or avoidance is recommended.
• Smoking Cessation: Smoking cessation reduces cardiovascular risk and may help decrease AF episodes.

Special Considerations in AF Management

• Age: Older adults may benefit more from rate control and anticoagulation due to higher thromboembolic risk and potential tolerance issues with antiarrhythmic drugs.
• Asymptomatic AF: Silent or asymptomatic AF is common and may require monitoring and anticoagulation if stroke risk is high, even without symptoms.
• Left Atrial Appendage Occlusion: For patients who cannot tolerate long-term anticoagulation, left atrial appendage occlusion (e.g., with a Watchman device) may provide an alternative stroke prevention method.