Ventricular tachycardia

Definition

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This is a broad-complex tachycardia (QRS >120ms/3 small squares) which originates in the ventricles.

Epidemiology

Really common and dangerous, particularly in coronary artery disease.

Pathophysiology

There are three different types of VT:

• Fascicular - uncommon; associated with structural heart defects; from left bundle branch; short QRS complexes (0.11-0.14s); QRS complexes look like RBBB
• Right ventricular outflow tract - right axis deviation; LBBB pattern; provoked by catecholamine release, sudden changes in heart rate, exercise; responds to alpha-blockers and calcium antagonists.
• Polymorphic - looks like Torsades de pointes (QT interval normal in sinus rhythm); similar to AF; can lead to cardiogenic shock and VF.
• Torsades de pointes

Risk Factors

• Structural heart disease or coronary heart disease
• Electrolyte disturbances: hypokalaemia, hypocalcaemia and hyponatraemia