Ventricular tachycardia

Definition

Ventricular tachycardia (VT) consists of at least three consecutive ventricular beats at a rate of at least 120/min; some experts use a cut-off of 100/min. Slower repetitive ventricular rhythms are called accelerated idioventricular rhythm and are usually benign. VT may deteriorate into ventricular fibrillation.

Classification

• Monomorphic: a single focus or reentrant pathway, regular, identical-appearing QRS complexes
• Polymorphic: several foci or pathways, irregular, varying QRS complexes; a special form is torsades de pointes with a prolonged QT interval
• Nonsustained: duration under 30 seconds
• Sustained: duration of 30 seconds or more, or terminated earlier because of hemodynamic collapse
• Idiopathic VT without structural heart disease: outflow tract VT from the right or left ventricle (usually with exercise or emotional stress, left bundle branch block-like morphology with an inferior axis) and left fascicular VT (right bundle branch block-like morphology with left axis deviation)
• Bundle branch reentry VT: macro-reentry via the bundle branches in advanced cardiomyopathy or conduction system disease

Aetiopathogenesis

Most affected people have significant heart disease, especially prior myocardial infarction (scar reentry) or a cardiomyopathy. Contributing factors are electrolyte disorders (particularly hypokalemia and hypomagnesemia), acidemia, hypoxemia and adverse drug effects. Congenital or acquired long QT syndrome is associated with torsades de pointes; catecholaminergic polymorphic VT (CPVT) is a genetic disorder of intracellular calcium regulation with arrhythmias particularly during adrenergic activation.

Clinical features

Brief or slow VT may be asymptomatic. Sustained VT is almost always symptomatic: palpitations, light-headedness, chest pain, dyspnea, hypotension and syncope up to circulatory arrest and sudden cardiac death. Some patients tolerate VT surprisingly well; good tolerance therefore does not argue against VT.

Diagnosis

ECG

• Any wide QRS complex tachycardia (QRS at least 0.12 s) is considered VT until proven otherwise.
• Findings supporting VT: dissociated P waves (AV dissociation), fusion beats, capture beats (normally conducted sinus beats interrupting the tachycardia), concordance of QRS complexes in the precordial leads and a frontal axis in the "northwest" quadrant.
• Brugada criteria (modified): additional morphological criteria in V1 and V6 depending on right or left bundle branch block-like QRS morphology.

Search for the cause

• Resting ECG after the episode: infarct scar, QT interval, Brugada pattern, pre-excitation
• Laboratory tests: potassium, magnesium, blood gases (acidemia, hypoxemia), troponin
• Imaging and search for the cause: echocardiography, cardiac MRI (scar, cardiomyopathy), coronary angiography; electrophysiological study to clarify the mechanism

Keep learning in the app

Further reading (open access)

1. MSD Manual Professional: Ventricular Tachycardia (VT)
2. StatPearls: Ventricular Tachycardia

Cross-references