A blocked or non-conducted P wave appearing without progressive lengthening of the PR interval is referred to as type II 2nd degree AV block. In this situation, the location of the block is distal to the AV node and indicates more advanced conducting system disease than that associated with type I block.
This ECG demonstrates type II 2nd degree AV block and left bundle branch block. It is from a 52 year old female with systemic lupus. There is sinus rhythm with a PR interval of 0.18 seconds and a single non-conducted P wave (arrow) that is not preceded by progressive lengthening of the PR interval. Note the absence of group beating and the fact that the RR interval encompassing the blocked P wave (1.40 seconds) is slightly greater than twice the preceding RR interval (2 x 0.64 =1.28 seconds).