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.
PR interval. In electrocardiography, the PR interval is the period, measured in milliseconds, that extends from the beginning of the P wave (the onset of atrial depolarization) until the beginning of the QRS complex (the onset of ventricular depolarization); it is normally between 120 and 200ms in duration.