Arrhythmia

Aetiology/Causes

Cardiac Causes

• Ischaemic heart disease, cardiomyopathies, valvular disease, congenital heart abnormalities

• Structural heart disease (e.g., left ventricular dysfunction, previous MI)

Non-Cardiac Causes

• Electrolyte disturbances: Hyperkalaemia, hypokalaemia, hypomagnesaemia, hypocalcaemia

• Medications: Beta-blockers, digoxin, antiarrhythmics, QT-prolonging drugs

• Systemic: Thyrotoxicosis, infections, metabolic disorders

• Lifestyle: Excess caffeine, alcohol, smoking, stimulant use

Pathophysiology

• Impulse formation disorders: Altered automaticity (e.g., increased pacemaker activity), afterdepolarisations

• Impulse conduction disorders: Re-entry circuits (e.g., AV nodal re-entrant tachycardia), conduction blocks (e.g., AV block)

Clinical Assessment

Haemodynamic Compromise Indicators

• Hypotension, hypoperfusion

• Syncope, altered level of consciousness

• Chest pain, heart failure symptoms

Tachyarrhythmia Assessment

• Narrow vs Broad Complex:

  • Narrow: SVT, AF, Atrial Flutter

  • Broad: VT, VF, Torsades de Pointes

• If unstable: synchronised DC cardioversion

Bradyarrhythmia Assessment

• SA Node Dysfunction: Sick sinus syndrome, sinus bradycardia

• AV Node Dysfunction: Heart blocks (1st, 2nd, 3rd-degree)

• If unstable: transcutaneous pacing

Symptoms

• Palpitations, dizziness, syncope

• Chest pain, dyspnoea

• Fatigue, reduced exercise tolerance

Investigations

Initial Assessment

• ECG: Essential for diagnosis; identifies rhythm type and conduction abnormalities

• Blood tests: U&E, cardiac enzymes (if ACS suspected), TFTs

• Imaging: CXR (if structural disease suspected)

Further Testing

• Holter monitor: Intermittent arrhythmias

• Echocardiography: Structural heart disease assessment

• Electrophysiology Studies (EPS): For diagnosing complex arrhythmias

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Management

General Management Principles

• Maintain airway, assist breathing as needed

• Administer oxygen to maintain SpO2 >94%

• Continuous cardiac and BP monitoring

• Establish IV access

Bradyarrhythmias

• Atropine: 0.5mg IV every 3-5 min (max 3mg)

• Transcutaneous pacing if atropine ineffective

• IV adrenaline/isoprenaline while awaiting pacing

  • Adrenaline preferred if BP <80 mmHg (isoprenaline may reduce BP)

• Long-term: Permanent Pacemaker (PPM) for symptomatic bradycardia

Tachyarrhythmias

Narrow Complex (SVT, AF, Atrial Flutter)

• Vagal Manoeuvres: Valsalva, carotid massage (avoid in elderly)

• Adenosine: 6mg IV → 12mg → 18mg (caution in WPW)

• Beta-blockers or CCBs: If adenosine contraindicated

• Electric Cardioversion: If resistant to pharmacotherapy

Broad Complex (VT, VF, Torsades de Pointes)

• Antiarrhythmics: Amiodarone or Lidocaine

• Immediate defibrillation: VF or pulseless VT

• Magnesium sulphate: If Torsades suspected

Differential Diagnosis

Non-Cardiac Causes

• Anxiety/panic attacks, hyperventilation

• Thyrotoxicosis

• Electrolyte disturbances (hyperkalaemia, hypomagnesaemia)

• Drugs: Beta-agonists, digoxin toxicity, QT-prolonging medications

Structural Causes

• Cardiomyopathies, ischaemic heart disease, valvular pathology

Electrical Causes

• Long QT Syndrome, Brugada Syndrome, WPW

Prophylaxis & Long-Term Management

• Beta-blockers: Atenolol 25mg daily, Metoprolol 25mg BD

• Antiarrhythmics: Amiodarone, Sotalol for recurrent symptomatic arrhythmias

• Electrolyte optimisation: Maintain K+ 4–5 mmol/L, Mg2+ >1 mmol/L

• Lifestyle modification: Avoid stimulants (caffeine, alcohol), stress management

Complications

• Heart Failure: Due to persistent tachyarrhythmia or bradyarrhythmia

• Thromboembolism: AF → Stroke, systemic embolism

• Sudden Cardiac Death: VF, Torsades, VT progression

• Syncope & Falls: Especially in elderly with bradyarrhythmias

Risk Stratification: Identifying High-Risk Patients

• Structural heart disease: Previous MI, EF <35%

• Genetic syndromes: Long QT syndrome, Brugada, WPW

• ECG abnormalities: Prolonged QT, ventricular ectopics, non-sustained VT

• Symptoms: Syncope, exertional dizziness

• Family history: Sudden cardiac death

Device Therapy: Pacemakers & ICDs

Pacemaker (PPM) Indications

• Symptomatic bradycardia, heart block, sick sinus syndrome

Implantable Cardioverter Defibrillator (ICD) Indications

• Survivors of VF/VT arrest

• Severe LV dysfunction (EF <35%) for primary prevention

Notes:

• Unstable patients require urgent intervention (cardioversion/pacing/defibrillation)

• Adenosine first-line for SVT, but contraindicated in WPW with AF

• VF and pulseless VT require immediate defibrillation

• Long-term management includes rate/rhythm control, lifestyle modifications, and risk stratification