RN HESI Critical Care Cardiac Exam Dysrhythmia Management, Pacemakers, and Defibrillators Electrical impulses are generated from SA node (pacemaker of the heart). SA node is located on top of atrium.  Job of SA node to set heartrate.  SA node fires impulses rate at 60-100 beats per minute. AV node acts as secondary pacemaker. If SA node doesn’t fire, the AV node can initiate impulses. Problem is that AV node generates impulses 40-60 beats per minute. Signal starts at SA node  travels to AV node  travels to R and L bundle branches  Goes to purkinje fibers (PF).  The purkinje fibers can act as tertiary pacemakers. Problem is that they fire at rate of 20-40 beats per minute (not necessarily suitable with life). Dysrhythmia: something is wrong with conduction system.  When we interpret dysrhythmia, we use specific graph paper. Reason is bc graphs in little boxes represent something.  We look at 6 second strip; see hash marks at top of strip. Between two hash marks is 3 seconds. If you want 6 second strip, you have 3 hash marks.  Box: we look at vertical and horizontal. Vertically represents amplitude. Horizontally represents time (what we will focus on). One teeny small box = 0.04 seconds. There are 5 small boxes in one big box so 0.04 x 5 = 0.2 seconds. One ECG/EKG complex: P, PR interval, QRS, etc We read left to right for EKG complex  P wave: Atrial Depolarization. Round, uprigh