What is the QRS duration in narrow complex tachycardia?

In narrow complex tachycardia, the QRS duration is typically less than 0.12 seconds. This parameter is significant because it helps differentiate between different types of tachycardias. A narrow QRS complex indicates that the electrical impulse is originating from above the ventricles, which often implies a supraventricular origin, such as in atrial fibrillation with a rapid ventricular response or paroxysmal supraventricular tachycardia (PSVT).

If the QRS had been wider, particularly greater than 0.12 seconds, it might suggest a ventricular origin or other complications such as bundle branch blocks. Therefore, maintaining a QRS duration of less than 0.12 seconds is crucial for correctly identifying and managing narrow complex tachycardias.