File:E0007652.jpg The first tracing is clearly atrial flutter with an atrial rate of 270/min, and a ventricular rate of 135/min. The second recording shows much faster atrial activity (Note the distance between the turquoise arrows and the yellow arrows which mark out 3 atrial cycles). The second tracing is either atrial fibrillation (a know result of adenosine) or a faster atrial flutter (type II flutter) with variable block. Both of these effects could be seen as a result of the decrease in the atrial refractory period by the stimulation of the adenosine.