Clinical differentiation of narrow QRS complex tachycardias.

Supraventricular tachycardias generally present with narrow QRS complexes and are quite commonly seen in the emergency department. Regular narrow QRS complex tachycardias occur in all age groups and may be associated with minimal symptoms, such as palpitations, or, present with hemodynamic compromise resulting in syncope. While history and physical examination are indispensable, they usually do not lead to a definitive diagnosis. The diagnosis is made by careful analysis of the 12-lead ECG. Therapy is based on hemodynamic assessment and understanding of the tachycardia mechanism.