A 59-year-old woman with a history of infrequent episodes of tachycardia (starting and ending abruptly) since her teens that are often terminated by Valsalva maneuver is presenting to the Emergency department during one of her typical episodes:

• AV Nodal Re-entrant Tachycardia
• Nonspecific ST abnormality

Vagal stimulation manoevers were not effective. Conversion to sinus rhythm was obtained after administration of an intravenous bolus of adenosine and the following ECG was recorded:

Notice that the pseudo-r’ is no longer present in V1.