ATRIAL FIBRILLATION (AF): A HIGH-YIELD REVIEW FOR MEDICAL LICENSING EXAMS

Introduction

Welcome to today's episode. Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice. It is a frequent presentation in family medicine, emergency medicine, internal medicine, and cardiology, making it one of the highest-yield topics for Canadian medical licensing examinations including TDM, CCFP, and MCCQE1.

Definition

Atrial fibrillation (AF) is a supraventricular tachyarrhythmia characterized by chaotic atrial electrical activity resulting in:

• Absence of organized P waves
• Irregularly irregular ventricular rhythm
• Loss of effective atrial contraction
• Increased risk of thromboembolism and stroke

Causes

Cardiac Causes

• Hypertension (most common)
• Coronary artery disease
• Heart failure
• Valvular heart disease
• Cardiomyopathy
• Myocarditis
• Congenital heart disease

Non-Cardiac Causes

• Hyperthyroidism
• Pulmonary embolism
• Pneumonia
• Sepsis
• Chronic lung disease
• Obstructive sleep apnea
• Chronic kidney disease

Reversible Causes

• Alcohol ("Holiday Heart")
• Excess caffeine or stimulants
• Electrolyte abnormalities
• Recent surgery
• Acute infection
• Uncontrolled hypertension

Risk Factors

• Age ≥65 years
• Hypertension
• Diabetes mellitus
• Heart failure
• Coronary artery disease
• Obesity
• Sleep apnea
• Chronic kidney disease
• Smoking
• Excess alcohol
• Family history

Clinical Presentation

Many patients are asymptomatic.

Common symptoms include:

• Palpitations
• Rapid heartbeat
• Shortness of breath
• Fatigue
• Reduced exercise tolerance
• Chest discomfort
• Dizziness
• Syncope
• Stroke symptoms

SOAP Approach

Subjective

Ask about:

• Onset and duration
• Palpitations
• Chest pain
• Dyspnea
• Dizziness
• Syncope
• Previous AF episodes
• Medication history
• Alcohol use
• Thyroid disease
• Recent illness
• Stroke or TIA history
• Bleeding history

Objective

Vital Signs

• Heart rate
• Blood pressure
• Oxygen saturation
• Temperature

Physical Examination

Cardiovascular

• Irregularly irregular pulse
• Tachycardia
• Murmurs
• Signs of heart failure

Respiratory

• Pulmonary edema
• Infection

Neurological

• Evidence of stroke

Investigations

Essential

• 12-lead ECG
• CBC
• Electrolytes
• Creatinine/eGFR
• TSH
• Glucose or HbA1c

Additional

• Troponin if ischemia suspected
• BNP if heart failure suspected
• Chest X-ray
• Echocardiogram
• Holter monitor if intermittent symptoms

ECG Findings

• No distinct P waves
• Irregularly irregular rhythm
• Variable R-R intervals

Assessment

Determine:

1. Stable or unstable patient?
2. New-onset or recurrent AF?
3. Paroxysmal, persistent, or permanent AF?
4. Reversible cause present?
5. Need for anticoagulation using the Canadian CHAD-65 approach.

Management (Canadian Guidelines)

Step 1: Is the Patient Stable?

Unstable Features

• Hypotension
• Shock
• Acute pulmonary edema
• Ongoing ischemic chest pain
• Altered mental status
• Syncope

Management

Immediate referral to the Emergency Department for synchronized electrical cardioversion.

Step 2: Rate Control

Rate control is appropriate for most stable patients.

Metoprolol

• Start 25–50 mg orally twice daily
• Titrate gradually
• Typical maintenance: 50–100 mg twice daily

Bisoprolol

• 2.5–5 mg orally once daily
• Maximum: 10 mg daily

Diltiazem (avoid in HFrEF)

• Extended-release 120–180 mg once daily
• Maximum: 360 mg daily

Verapamil

• Extended-release 120–180 mg once daily
• Maximum: 480 mg daily

Digoxin

Useful mainly in:

• Heart failure
• Sedentary patients

Typical maintenance:

• 0.125 mg daily
• Lower doses in elderly patients and renal impairment

Step 3: Stroke Prevention (CHAD-65)

The Canadian CHAD-65 approach recommends anticoagulation if:

Age ≥65 years

OR

Any one of:

• Congestive heart failure
• Hypertension
• Diabetes mellitus
• Previous stroke or TIA

If CHAD-65 positive:

Start anticoagulation unless contraindicated.

Preferred DOACs:

Apixaban

• 5 mg twice daily
• Reduce to 2.5 mg twice daily in eligible patients

Rivaroxaban

• 20 mg once daily with food
• 15 mg once daily if renal function is reduced

Dabigatran

• 150 mg twice daily
• Lower dose may be appropriate in selected patients

Edoxaban

• 60 mg once daily
• Dose reduction when indicated

Warfarin

Indications:

• Mechanical heart valves
• Moderate or severe rheumatic mitral stenosis

Target INR:

2.0–3.0

Step 4: Rhythm Control

Consider rhythm control if:

• Significant symptoms
• Younger patients
• First episode
• Heart failure related to AF
• Patient preference
• Failure of rate control

Options:

• Electrical cardioversion
• Antiarrhythmic drugs
• Catheter ablation

Lifestyle Management

• Stop smoking
• Reduce alcohol intake
• Weight reduction
• Regular exercise
• Control blood pressure
• Manage diabetes
• Treat sleep apnea

Follow-Up in Family Medicine

Review within 1–4 weeks:

• Symptoms
• Heart rate
• Blood pressure
• Medication tolerance
• Renal function if taking a DOAC

Arrange:

• Echocardiogram if not already performed
• Cardiology referral if persistent symptoms, recurrent AF, uncertainty about rhythm control, or consideration of catheter ablation

Complications

• Ischemic stroke
• Systemic embolism
• Heart failure
• Tachycardia-induced cardiomyopathy
• Reduced quality of life

Red Flags

Urgent referral if:

• Hypotension
• Acute pulmonary edema
• Chest pain suggestive of myocardial infarction
• Syncope
• Acute stroke symptoms
• Altered mental status

Exam Pearls

• Always assess whether the patient is stable first.
• Confirm AF with a 12-lead ECG.
• Search for reversible causes such as hyperthyroidism, infection, and alcohol use.
• Use the Canadian CHAD-65 approach to determine the need for anticoagulation.
• DOACs are preferred for most patients with non-valvular AF.
• Immediate synchronized cardioversion is indicated for unstable patients.

Take-Home Message

Think systematically:

Recognize AF → Assess stability → Investigate reversible causes → Control the rate or rhythm → Apply CHAD-65 for stroke prevention → Arrange appropriate follow-up and referral when needed.