🚨 Tachyarrhythmias

Tachyarrhythmias are abnormally fast heart rhythms, typically >100 bpm, which can compromise cardiac output and lead to symptoms ranging from palpitations to cardiac arrest. They are broadly classified as narrow or broad complex, guiding immediate management. UK guidelines emphasise early recognition and treatment of haemodynamic instability.

Patients may present with palpitations, dizziness, syncope, dyspnoea, chest pain, or fatigue. Signs of haemodynamic instability include hypotension, altered mental status, signs of shock, or acute heart failure. A rapid, irregular or regular pulse is a key finding.

A: Ensure airway patency. B: Assess breathing rate, effort, and oxygen saturation; administer high-flow oxygen if hypoxic. C: Palpate pulse, measure blood pressure, assess capillary refill time, and obtain a 12-lead ECG immediately. D: Assess conscious level using AVPU/GCS, check pupillary response. E: Expose patient to look for signs of trauma or other pathology, check temperature.

Haemodynamic instability is paramount: systolic BP <90 mmHg, signs of shock (cool peripheries, prolonged capillary refill, altered mental status), acute heart failure (pulmonary oedema), or myocardial ischaemia (chest pain, ECG changes). These warrant immediate synchronised cardioversion.

Bedside: 12-lead ECG (crucial for diagnosis), continuous cardiac monitoring, pulse oximetry, blood pressure monitoring, blood glucose. Bloods: FBC, U&Es, LFTs, cardiac enzymes (troponin), thyroid function tests, toxicology screen if drug overdose suspected. Imaging: Chest X-ray if pulmonary oedema or other lung pathology is suspected.

If haemodynamically unstable, perform immediate synchronised direct current cardioversion. If stable, distinguish between narrow and broad complex tachycardias. For narrow complex, consider vagal manoeuvres, then intravenous adenosine. For broad complex, consider intravenous antiarrhythmics or expert review. Address reversible causes like hypoxia, electrolyte imbalances, and fever.

Immediate senior medical review (Registrar/Consultant) is required for any haemodynamically unstable tachyarrhythmia or if initial treatments are ineffective. Cardiology consultation is essential for complex or recurrent tachyarrhythmias. Consider ICU referral if requiring significant inotropic support or complex rhythm management.

Always check for a pulse; if pulseless, it's cardiac arrest and requires immediate defibrillation. Adenosine is contraindicated in asthma and Wolff-Parkinson-White syndrome. Broad complex tachycardia should be treated as ventricular tachycardia until proven otherwise. Remember the 'ABCD' approach for assessing instability.