Atrial tachycardia with exit block and AV block

The ectopic P waves, easily seen in this example,occur in groups, separated by short pauses. This is likely due to an exit block just distal to the atrial pacemaker. Because not all of the P waves make it to the ventricles, there is also 2nd degree AV block. Therefore, two levels of block are present: one in the atria and one at the level of the AV junction.