[Diagnostic criteria of ventricular tachycardia]

When ventricular tachycardia is very rapid or complicates cardiac disease it must be diagnosed as rapidly as possible so as not to delay treatment. A careful analysis of the surface electrocardiogramme is usually sufficient to distinguish ventricular tachycardia from other-wide QRS complex tachycardias when the widening is due to ventricular aberration. The diagnosis is easier when the start of the tachycardia is recorded or when the sinus rhythm is interspersed with ventricular extrasystoles of the same morphology as that of the tachycardia. Similarly, atrioventricular dissociation is diagnostic of ventricular tachycardia but its negative predictive value is weak. Extreme axial deviation of the QRS complexes, concording morphology in leads V1 or V2 and V6 and the analysis of the QRS complexes in the precordial leads nearly always enables identification of supraventricular tachycardia with aberration. On the other hand, the distinction between other causes of wide QRS complexes (supraventricular tachycardia with preexcitation or intraventricular conduction defects) remains difficult in the absence of a reference electrocardiogramme and the clinical context.