AVNRT accounts for approximately 60% of paroxysmal supraventricular tachycardias, defined as regular rapid narrow QRS tachycardias, and is more common than reentry associated with WPW. Usually a PAC provokes the arrhythmia. The rate range is 140-250 beats per minute and typically 150-200 beats per minute. The retrograde P wave is often hidden in the QRS, but when visualized it is usually 0.07 seconds or less after the QRS. The P wave following the QRS may simulate an extra S wave in the inferior leads or an R prime wave in lead V1. Both the S wave and or the R prime wave disappear when the arrhythmia terminates.
Successful treatment is usually dramatic: AV node blockade produced by carotid sinus massage or IV adenosine can usually abruptly convert the rhythm back to sinus. The following animation illustrates what we have just described.