Doctors Revision

Cardiovascular System

Atrial Fibrillation

A common supraventricular tachyarrhythmia characterized by uncoordinated atrial activation leading to an irregular, often rapid, ventricular response. Can be paroxysmal, persistent, or permanent.

Also known as: AF, A-fib, Irregular Heartbeat

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Referral and warning signs

When to refer

Refer to cardiologist/specialist (H/RR) for: New diagnosis of AF for workup and management decisions (rate vs rhythm control, anticoagulation assessment). Haemodynamically unstable AF requiring urgent cardioversion. Consideration for rhythm control strategy (cardioversion, antiarrhythmic drugs, ablation). Difficult rate control. Assessment for anticoagulation if risk stratification unclear or contraindications present.

Red flags

  • Rapid ventricular rate causing haemodynamic instability (hypotension, shock, severe HF, syncope)
  • Signs/symptoms of acute stroke
  • AF associated with acute myocardial infarction
  • Severe bradycardia due to rate-controlling medications

Signs and symptoms

  • Often asymptomatic, discovered incidentally.
  • Palpitations (sensation of rapid, irregular heartbeat).
  • Fatigue, weakness.
  • Dizziness, lightheadedness, syncope (fainting).
  • Dyspnoea (shortness of breath).
  • Chest pain or discomfort (angina).
  • Irregularly irregular pulse (variable volume and timing).
  • Pulse deficit (apical heart rate > radial pulse rate).
  • May precipitate or worsen heart failure.

Risk factors

  • Increasing age
  • Hypertension
  • Valvular heart disease (especially mitral stenosis/regurgitation)
  • Ischaemic heart disease / Myocardial infarction
  • Heart failure
  • Cardiomyopathy
  • Congenital heart disease
  • Hyperthyroidism
  • Pulmonary disease (COPD, PE)
  • Obesity
  • Diabetes mellitus
  • Chronic kidney disease
  • Sleep apnoea
  • Excessive alcohol consumption ('holiday heart')
  • Post-cardiac surgery

Diagnosis

Clinical assessment

Suspected based on symptoms (palpitations, dizziness, dyspnoea) or finding an irregularly irregular pulse on examination. Assess haemodynamic stability.

Investigations

  • ECG (12-lead): Confirms diagnosis. Shows absent P waves, fibrillatory ('f') waves (often fine, irregular baseline oscillations), and irregularly irregular QRS complexes (variable R-R intervals).
  • Holter Monitor / Event Recorder: If AF is paroxysmal and not captured on routine ECG.
  • Echocardiogram: Assess cardiac structure, chamber size (especially left atrium), LV function, valve function; identify underlying heart disease.
  • Blood tests: Thyroid function tests (TSH, free T4), U&Es, Renal function, CBC.
  • Chest X-ray: Assess for cardiomegaly, pulmonary congestion.

Diagnostic criteria

ECG confirmation showing characteristic features (absent P waves, fibrillatory baseline, irregularly irregular R-R intervals).

Management

Non-pharmacological management

  • Management Goals: 1) Rate control, 2) Rhythm control (specialist), 3) Stroke prevention (anticoagulation), 4) Manage underlying cause/risk factors.
  • Acute Management (Rapid AF): Assess stability. If unstable (hypotension, severe HF, ongoing ischemia), requires urgent electrical cardioversion.
  • Rhythm Control Strategy (Cardioversion - electrical or pharmacological): Primarily for younger patients, first episode, symptomatic despite rate control, or if underlying cause reversible. Requires specialist assessment and often anticoagulation pre/post procedure.
  • Manage underlying conditions (hypertension, heart failure, thyroid disease, etc.).

Pharmacological treatment

  • Rate Control (Target resting HR <110 bpm, or lower if symptomatic):
  • - Beta-blockers: Preferred first-line. E.g., Atenolol 25-100mg OD, Bisoprolol 1.25-10mg OD, Metoprolol.
  • - Non-dihydropyridine Calcium Channel Blockers (CCBs): E.g., Verapamil, Diltiazem (use with caution if HF with reduced EF).
  • - Digoxin: Useful especially if concomitant heart failure or sedentary patient. Less effective for controlling exercise heart rate. Dose: Loading (optional), Maintenance 125-250 mcg OD.
  • - Combination therapy may be needed.
  • Stroke Prevention (Anticoagulation):
  • - Assess stroke risk using CHA2DS2-VASc score.
  • - Offer anticoagulation if score ≥2 (men) or ≥3 (women). Consider if score 1 (men) or 2 (women).
  • - Warfarin (target INR 2.0-3.0) OR Direct Oral Anticoagulants (DOACs - Dabigatran, Rivaroxaban, Apixaban, Edoxaban - preferred where available/affordable due to convenience/safety profile).
  • - Aspirin alone is generally NOT sufficient for stroke prevention in AF.
  • Rhythm Control (Pharmacological Cardioversion/Maintenance): Amiodarone, Flecainide, Propafenone, Sotalol (specialist initiation and monitoring required).

Monitoring

  • Monitor heart rate and rhythm.
  • Monitor symptoms.
  • Monitor INR regularly if on Warfarin.
  • Monitor for side effects of medications (bradycardia, hypotension with rate control agents; bleeding with anticoagulants; thyroid/lung/liver toxicity with Amiodarone).
  • Periodic review of stroke risk and need for anticoagulation.

Complications

  • Stroke / Systemic embolism
  • Heart failure (tachycardia-induced cardiomyopathy or exacerbation of underlying HF)
  • Reduced quality of life
  • Increased mortality
  • Bleeding (complication of anticoagulation)

Prevention

  • Management of underlying risk factors (hypertension, diabetes, obesity, thyroid disease, HF, IHD).
  • Limit alcohol consumption.
  • Smoking cessation.

Patient education

  • Explain atrial fibrillation, its irregular nature, and potential risks (stroke).
  • Explain management strategy (rate vs rhythm control, anticoagulation).
  • Importance of medication adherence (rate control, anticoagulation).
  • If on Warfarin: Need for regular INR monitoring, dietary consistency (Vit K), drug interaction awareness, signs of bleeding.
  • If on DOAC: Importance of taking as prescribed, signs of bleeding.
  • Recognizing symptoms of stroke (FAST - Face, Arms, Speech, Time) and seeking immediate help.
  • Lifestyle modifications (manage BP, weight, alcohol).
  • When to seek medical attention (e.g., severe palpitations, dizziness, syncope, signs of stroke/bleeding).

Uganda-specific notes

Valvular AF secondary to RHD is common. Rate control with beta-blockers or digoxin is feasible. Warfarin anticoagulation is possible but INR monitoring capacity is a major challenge. DOACs are often unavailable/unaffordable. Stroke risk assessment (CHA2DS2-VASc) should guide anticoagulation decisions where possible.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 4, Section 4.1.5

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