The diagnosis of wide complex tachycardia

Ventricular tachycardia is the diagnosis in approximately 80% of cases of WCT and in approximately 95% of cases with structural heart disease. The presence of atrioventricular dissociation, fusion beats, capture beats, and concordance are important findings strongly suggesting VT; whereas, QRS frontal axis and ventricular rate provide less definitive diagnostic information. A QRS width greater than 160 msec. for LBBB configuration WCT or greater than 140 msec. for RBBB configuration argues strongly for VT. The QRS morphology may be very helpful in selected cases. The duration of the arrhythmia does not discriminate between the etiologies of WCT, as all rhythms may be hemodynamically stable for prolonged periods. Finally, response to treatment may give diagnostic information in addition to therapeutic benefit.