ABSTRACT
Two main types of narrow-complex tachycardia–those caused by rapid atrial activity such as atrial tachycardia and those where an additional connection is present between the atria and ventricles, the atrioventricular re-entrant tachycardias. The re-entrant tachycardias can be further subdivided into those where the extra pathway is in the node–atrioventricular re-entrant tachycardiasthe–and those where there is an accessory pathway the atrioventricular re-entrant tachycardia. A narrow complex tachycardia with a ventricular rate that stays around 150 beats/min is highly sugggestive of the diagnosis of atrial flutter with two to one atrioventricular block. Atrial flutter is usually associated with coronary or hypertensive heart disease. Capture and fusion beats can be seen, confirming that the diagnosis is in fact a ventricular tachycardia. A capture beat looks like a normal QRS and occurs when an atrial impulse is conducted normally, activating the ventricle before the abnormal discharge from the ventricular focus.
