This ECG was taken from a 90-year-old woman. We have no other history, unfortunately. It is a good example of a sinus rhythm with complete AV block, also called third-degree AV block.
The defining characteristics of this rhythm include: 1) an underlying rhythm that is regular and with a physiological rate. In other words, the P waves are not so fast that they would not be expected to conduct one-to-one. 2) a second rhythm of regular QRS complexes that is unrelated to the P waves.