Ventricular arrhythmias are abnormal rhythms arising from the ventricles. They are characterised by tachycardias with broad QRS complexes and no relation to P waves. Ventricular arrhythmias account for a significant proportion of sudden cardiac deaths.
Premature electrical discharge from a ventricular ectopic focus, producing an early and broad QRS. They are common and usually of no clinical importance.
An early broad QRS complex with no P wave.
Occasional ectopics are a normal finding in health patients and there is no treatment necessary.
In patients with heart disease (e.g. myocardial infarction), regular ectopics may be symptomatic and can lead to ventricular fibrillation, especially if they occur during a T wave (as partially repolarised tissue can depolarise and introduce a re-entry circuit). Treatment is not usually necessary, although electrolyte abnormalities should be investigated and treated. Catheter ablation or implantable cardioverter-defibrillator (ICD) devices can be considered if ectopics persistent and symptomatic.
Ventricular tachycardia (VT)
Ventricular beats at a rate >100 beats per minute. It usually occurs in diseased hearts, including myocardial infarction, cardiomyopathy and ventricular aneurysms. It is caused be either an increase in automacity or re-entry via scarred tissue.
VT may be monomorphic or polymorphic. Polymorphic VT (also known as torsades de pointes) develops in patients with long QT intervals (e.g. congenital long QT, hypocalcaemia). The polymorphism refers to the cardiac axis, whereby the axis of the QRS complexes varies over time as the depolarisation originates from multiple foci.
Monomorphic VT: Broad QRS complexes at a rate >100 bpm. No P waves present.
Polymorphic VT (torsades de pointes): Broad QRS complexes with varying axis. The QRS complexes oscillate smoothly between being upright and inverted. It can degenerate to ventricular fibrillation (VF).
Haemodynamically unstable (pulseless or hypotensive):
Treat as ventricular fibrillation with oxygen, defibrillation and correction of any electrolyte disturbances. Consider amiodarone if VT persists.
Provide oxygen and amiodarone (or lidocaine). Correct any electrolyte disturbances. If VT persists, consider further amiodarone doses or defibrillation.
Polymorphic VT should be treated with IV magnesium sulphate.
Very rapid and irregular ventricular contraction with no mechanical effect. Occurs when ventricular muscles contract independently from each other. Patients will be pulseless and unconscious.
Shapeless, rapid ECG oscillations. There will be no discernible P, QRS or T waves.
Manage as per life support guidelines – defibrillation is the only treatment. Also provide oxygen and correct any electrolyte disturbances.
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