What ECG feature suggests a supraventricular origin of a tachycardia?

A normal R wave progression in the chest leads is indicative of proper conduction through the ventricles, which suggests that the electrical activity is originating from above the ventricles, thus supporting the diagnosis of a supraventricular tachycardia.

In the context of tachycardia, the presence of normal R wave progression indicates that the QRS complexes are narrow, which is typically seen with supraventricular origins such as atrial fibrillation or atrial flutter. Conversely, features like widened QRS complexes often suggest a ventricular origin of the tachycardia, while the absence of P waves can indicate both atrial fibrillation and certain types of junctional rhythms, not exclusively a supraventricular source. QT prolongation may indicate other underlying pathology or electrical instability but does not specifically indicate whether the tachycardia is supraventricular or ventricular in origin.

Thus, the identification of normal R wave progression serves as a reliable indicator of a supraventricular origin for tachycardia.