Overview
Monomorphic VT is a focal or reentrant ventricular rhythm that requires rapid assessment and management, due to its risk of haemodynamic instability and collapse.
Classification
- Nonsustained VT - three or more ventricular beats at a rate of >100bpm, lasting less than 30 seconds, without haemodynamic instability
- Sustained VT - a ventricular rhythm at a rate of >100bpm, lasting at least 30 seconds or with haemodynamic instability
Pathogenesis
Mechanisms
- Monomorphic VT occurs most commonly in the context of a macro-reentrant pathway in a structurally abnormal heart. The rhythm may also be caused by a focal arrhythmogenic ventricular focus.
Causes of Monomorphic Ventricular Tachycardia
- Myocardial infarction
- Cardiomyopathy
- Congestive cardiac failure
Diagnosis
ECG Findings
- Heart rate >100bpm
- Regular rhythm (RR interval)
- Broad QRS complexes >120ms
A left bundle branch morphology classically suggests a right ventricular focus of VT, while a right bundle morphology pattern suggests a left ventricular focus. A septal focus may manifest as either a left or right bundle branch morphology.
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