How Can You Tell if You Have White Mold or Efflorescence? First, look at the type of material on which you see the white substance. If you see it on anything other than concrete or masonry, itâs mold. Second, spray the substance with a little water in a spray bottle and simply wipe it with a rag.
Thus, as shown in electrophysiologic studies, PR interval prolongation (ie, first-degree AV block) may be due to conduction delay within the right atrium, the AVN, the His-Purkinje system, or a combination of these. Overall, dysfunction at the AVN is much more common than dysfunction at the His-Purkinje system.
The PR interval is the time from the onset of the P wave to the start of the QRS complex. It reflects conduction through the AV node. The normal PR interval is between 120 â 200 ms duration (three to five small squares). If the PR interval is > 200 ms, first degree heart block is said to be present.