Atrial Fibrillation

• Effects of atrial fibrillation

  • Irregularly irregular ventricular contractions
  • Tachycardia (fast heart rate)
  • Heart failure due to impaired filling of the ventricles during diastole
  • Increased risk of stroke
• Common causes of atrial fibrillation

  • Sepsis
  • Mitral valve pathology (stenosis or regurgitation)
  • Ischaemic heart disease
  • Thyrotoxicosis
  • Hypertension
• Presentation of atrial fibrillation

  Patients are often asymptomatic, and atrial fibrillation is an incidental finding. It may be diagnosed after a stroke. Patients may present with palpitations, shortness of breath, dizziness or syncope (loss of consciousness), and symptoms of associated conditions (e.g., stroke, sepsis or thyrotoxicosis). The key examination finding is an irregularly irregular pulse. There are two differential diagnoses for an irregularly irregular pulse: Atrial fibrillation, Ventricular ectopics. Ventricular ectopics disappear when the heart rate gets above a certain threshold. Therefore, a regular heart rate during exercise suggests a diagnosis of ventricular ect
• Pathophysiology of atrial fibrillation

  The sinoatrial node produces organised electrical activity that coordinates the contraction of the atria. Atrial fibrillation occurs when this electrical activity is disorganised, causing the contraction of the atria to become uncoordinated, rapid and irregular. This chaotic electrical activity overrides the regular, organised activity from the sinoatrial node. It passes through to the ventricles, resulting in irregularly irregular ventricular contraction. Uncoordinated atrial activity means the blood can stagnate in the atria, forming a blood clot (thrombus). A thrombus formed in the left atrium may travel to the brain and block a cerebral artery, causing an ischaemic stroke. The risk of stroke is about 5 times higher than usual in patients with atrial fibrillation (depending on individual factors)
• Atrial fibrillation (AF) is a condition where the electrical activity in the atria of the heart becomes disorganised, leading to fibrillation (random muscle twitching) of the atria and an irregularly irregular pulse
• Alcohol and caffeine are lifestyle causes worth remembering
• Patients with a normal ECG and suspected paroxysmal atrial fibrillation

  Can have further investigations with 24-hour ambulatory ECG (Holter monitor), Cardiac event recorder lasting 1-2 weeks
• Investigations

  An ECG is required in all patients with an irregularly irregular pulse
• An echocardiogram

  May be required to investigate further in cases of valvular heart disease, heart failure, planned cardioversion, paroxysmal atrial fibrillation
• Ventricular ectopics disappear when the heart rate gets above a certain threshold
• Differential diagnoses for an irregularly irregular pulse

  • Atrial fibrillation
  • Ventricular ectopics
• Atrial fibrillation without valve pathology or with other valve pathologies, such as mitral regurgitation or aortic stenosis, is classed as non-valvular AF
• Rate control aims to get the heart rate below 100 and extend the time during diastole for the ventricles to fill with blood
• Options for rate control

  • Beta blocker first-line (e.g., atenolol or bisoprolol), Calcium-channel blocker (e.g., diltiazem or verapamil), Digoxin (only in sedentary people with persistent atrial fibrillation, requires monitoring and has a risk of toxicity)
• Rhythm control aims to return the patient to normal sinus rhythm and can be achieved through cardioversion or long-term rhythm control using medications
• Options for immediate cardioversion

  • Pharmacological cardioversion, Electrical cardioversion
• A regular heart rate during exercise

  Suggests a diagnosis of ventricular ectopics
• ECG findings in atrial fibrillation

  • Absent P waves
  • Narrow QRS complex tachycardia
  • Irregularly irregular ventricular rhythm
• Paroxysmal atrial fibrillation refers to episodes that reoccur and spontaneously resolve back to sinus rhythm, lasting between 30 seconds and 48 hours
• The NICE guidelines (2021) do not reference valvular atrial fibrillation. They recommend patients with valvular heart disease are referred to a cardiologist for further assessment and management
• Options for pharmacological cardioversion

  • Flecainide, Amiodarone (the drug of choice in patients with structural heart disease)
• Valvular atrial fibrillation is AF with significant mitral stenosis or a mechanical heart valve
• NICE guidelines (2021) suggest all patients with AF should have rate control as first-line, except with a reversible cause for their AF, new onset atrial fibrillation, heart failure caused by atrial fibrillation, symptoms despite being effectively rate controlled
• Principles to treating atrial fibrillation

  • Rate control
  • Rhythm control
  • Anticoagulation to prevent strokes
• Rhythm control may be offered to patients with a reversible cause for their AF, new onset atrial fibrillation, heart failure caused by atrial fibrillation, symptoms despite being effectively rate controlled
• Options for cardioversion

  • Immediate cardioversion, Delayed cardioversion
• Immediate cardioversion

  1. Pharmacological cardioversion

  2. Electrical cardioversion
• Electrical cardioversion

  Aims to shock the heart back into sinus rhythm using a cardiac defibrillator machine to deliver controlled shocks, usually done with sedation or general anaesthesia
• Transoesophageal echocardiography-guided cardioversion

  An option where available
• Ablation

  1. Left atrial ablation

  2. Atrioventricular node ablation and a permanent pacemaker
• Uncontrolled and unorganised activity in the atria leads to blood stagnating in the left atrium, particularly in the left atrial appendage, eventually causing a thrombus (clot) which can lead to an embolus and travel to the brain causing an ischaemic stroke
• Atrioventricular node ablation

  Involves destroying the connection between the atria and ventricles, a catheter procedure requiring a permanent pacemaker for ventricular contraction control
• Delayed cardioversion

  Used if atrial fibrillation has been present for more than 48 hours and the patient is stable, electrical cardioversion is recommended
• Options for pharmacological cardioversion

  • Flecainide
  • Amiodarone (the drug of choice in patients with structural heart disease)
• Left atrial ablation

  Performed in a catheter laboratory, involves general anaesthetic or sedation, radiofrequency ablation applied to burn abnormal areas of electrical activity to restore normal sinus rhythm
• Management of Paroxysmal Atrial Fibrillation

  Pill-in-the-pocket approach for patients with infrequent episodes without structural heart disease, using Flecainide as the usual treatment
• Anticoagulation

  Needed to prevent strokes
• With anticoagulation, patients with atrial fibrillation have around a 1-2% risk of stroke each year, depending on individual factors
• Anticoagulation treatment reduces coagulation (thrombus formation) by interfering with the clotting cascade
• Direct-Acting Oral Anticoagulants (DOACs) are oral anticoagulants that do not require INR monitoring, unlike warfarin