Today, you get THREE strips for your basic classes!  The first shows a PSVT - paroxysmal supraventricular tachycardia at a rate of about 220/minute.  The QRS complexes are narrow, and the rhythm is regular.  In the second strip, we see the moment of conversion after a dose of 6 mg. of adenosine was administered by rapid I.V. infusion.  The re-entry cycle is broken, and the patient experiences many PVCs, including groups of two, three, and even four in a row.  Soon, however, the rhythm settles into sinus rhythm with PACs, and later, just sinus rhythm (not shown).  For your more advanced students, the second strip shows the PVCs interacting with the underlying sinus rhythm.  There are several fusion beats with varying degrees of fusion, and one can sometimes see a sinus P wave just before a PVC.  None of this is clinically significant in this patient, because the ventricular ectopy was a side effect of the treatment, and was self-limited.  It is a great strip for teaching, though!