Concealed conduction is tissue stimulation without direct effect, but leading to a change in conduction characteristics. A common example would be an interpolated PVC (a type of premature ventricular contraction) during normal sinus rhythm; the PVC does not cause an atrial contraction, because the retrograde impulse from the PVC does not completely penetrate the AV node. However, this AV node stimulation can cause a delay in subsequent AV conduction by modifying the AV node's subsequent conduction characteristics. Hence, the P-R interval after the PVC is longer than the baseline P-R interval.