Ventricular Tachycardia (VT)

VT is a type of broad complex tachycardia, and is characterised by 3 consecutive wide QRS complexes at a rate of >100bpm. This is an issue because, when the ventricles beat too fast, the heart isn't able to pump enough blood around the body. It then becomes life-threatening when sustained as it'll lower the BP, therefore resulting in light-headedness and syncope. Similar conditions to this include Torsades de Pointes (TdP) and Supraventricular tachycardia (SVT).

Main complications of VT are Ventricular fibrillation (VF), and Cardiac arrest.

Classification:

Classed based on its Morphology and Duration.

Morphology:

• Monomorphic VT - QRS complexes similar in all beats, indicating a single arrhythmogenic focus

  • Causes include MI, RV outflow tract

• Polymorphic VT (aka Torsades de Pointes) - QRS complexes vary in each beat, indicating multiple arrhythmogenic foci

  • Causes include those leading to a Prolonged QT

N.B. Polymorphic VT is when there's an unstable rhythm with a continuously varying QRS complex morphology (size). When this occurs with QT prolongation, it's called Torsades de Pointes. This is managed with IV Magnesium Sulphate (shortens QT interval).

Duration:

• Non-sustained VT (NSVT) - lasts < 30 secs w/spontaneous termination

• Sustained VT (VT) - lasts > 30secs, causing haemodynamic instability

The main causes of VT are:

• Structural heart disease e.g. post-MI

• Electrolyte imbalances e.g. hypokalaemia

• Prolonged QT syndrome e.g. drug-induced (e.g. erythromycin)

It's often asymptomatic, but may present with palpitations, light-headedness, SOB, or sudden cardiac arrest if complicated.

Main investigations to do are an ECG and Cardiac imaging (Echo, MRI, CT, Angio) to check for structural defects.

Management includes:

• Synchronised DC cardioversion if unstable

• IV Amiodarone if stable

• ICD - Used to terminate episodes of VT and prevent sudden cardiac arrest

• Ablation