What type of tachycardia was observed on the ECG for the 32-year-old male patient?

Narrow-complex supraventricular tachycardia is characterized by a rapid heart rate with a QRS complex duration of less than 120 milliseconds. This type often arises from reentrant circuits above the ventricles, such as those occurring in the atria or the AV node.

In this scenario, if the ECG shows a regular or slightly irregular rhythm with rapid rate, and the QRS complexes are narrow, it suggests a reentrant tachycardia mechanism, typically seen in conditions like atrioventricular nodal reentrant tachycardia (AVNRT) or atrioventricular reentrant tachycardia (AVRT) associated with atrial flutter or other mechanisms.

This classification is important clinically as narrow-complex tachycardias generally respond well to specific treatments such as vagal maneuvers or adenosine, whereas wide-complex tachycardia might indicate a more serious underlying pathology such as ventricular tachycardia or a conduction disturbance. In the context of the options provided, the ECG findings directly support the diagnosis of narrow-complex supraventricular tachycardia.