Prolongation of the PR interval with maintenance of 1:1 AV conduction is referred to as 1st degree AV block. Higher degrees of block, in which not every P wave is transmitted to the ventricles, is referred to as 2nd or 3rd degree AV block and will be discussed in the bradycardia chapter (chapter 8). In the tracing shown here, every other P wave is blocked and does not activate the ventricles. This type of AV conduction disturbance, referred to as 2:1 AV block, is illustrated by the ladder diagram shown below the ECG strip
