Electrocardiogram showing SA nodal reentrant tachycardia. The first three beats are normal sinus beats at a rate of about 107 beats/min; the fourth beat is an atrial premature beat that is followed by a return to sinus rhythm. The eighth beat (arrow) represents the sudden onset of SA nodal reentrant tachycardia at a rate of about 145 beats/min. Since the P waves are similar to the sinus beats, the diagnosis is suggested only by the abrupt onset of the tachycardia.
Courtesy of Morton F Arnsdorf, MD.
Graphic 76364 Version 5.0
Normal rhythm strip
Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright.