2017 RN HESI Critical Care Cardiac Exam.docx

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, upright, uniform, 1 for each QRS complex PR interval: Measure from beginning of P to beginning of QRS complex. Should be 0.12 – 0.2 seconds. Or 3-5 small boxes. QRS complex/interval: ventricular depolarization. Skinny or narrow. Measure QRS interval = 0.04 – 0.12 seconds. 1-3 small boxes. Measure beginning of Q to end of S. Most people do not have textbook QRS interval. ST segment: we do not measure, we look at it. If elevated (above baseline), signs of Myocardial Infarction. If depressed, sign of Myocardial Ischemia. If pt is having heart attack & ST segment is elevated = STEMI (ST elevation MI). If not elevated or hasn’t moved, called non-STEMI. Silent heart attack, if ST is depressed means they have had Myocardial Ischemia at some point in the past. If elevated, pt is probably having heart attack. -If it is elevated, probably having heart attack. If not elevated, can still be having heart attack. T wave: round, upright, commonly larger than P wave. U wave: some people have them, most people do not. If your pt has one, it is sign of hypokalemia. Don’t expect to see a U wave. QT interval: measured from beginning of Q to end of T. There is no normal, depends on pt. We don’t measure. There are some medications that can prolong QT interval which puts pt at risk for lethal dysrhythmias. Common drug is Amiodarone (prolongs QT interval so we watch closely). We will not measure intervals on exams but need to know what normal intervals are. Step 1: determine heart rate. Use 6 second method. Count QRS complex and multiply by 10. Step 2: determine if rhythm is regular or irregular. Measure R waves. Does the difference between the spaces match up with each space? Step 3: measure intervals. Measure PR interval. Look for a P wave starting on solid line. Measure beginning of P to beginning of QRS. Measure QR interval; beginning of Q to end of S. Step 4: look at shape of waveforms. Is p wave round, upright, & uniform? Is QRS skinny or narrow? Is T wave round and upright? Step 5: identify the rhythm. Ex. Normal sinus rhythm. With sinus, we do not tre