This is a nice example of sinus rhythm with ventricular bigeminy in a patient with intermittent chest pain and hypertension.  The underlying rhythm is most likely normal sinus rhythm, but every other sinus P wave is most likely hidden in the PVCs, and not conducted due to the refractory state of the ventricles after the PVCs.  Often, signs of the "hidden" P waves will show in some leads, but that is difficult to demonstrate here.

It may be difficult to be sure of an adequate underlying rate, so the PVCs should not be eliminated with antiarrhythmic drugs until there is some ECG sign of a normal underlying rate.

Remember, the fourth channel on this ECG is a Lead II rhythm strip.  So, if you teach rate and rhythm monitoring, and don't want to use a 12-Lead ECG for your students, simply crop the bottom strip for your class.