Summary Chapter 27 PDF

Summary Chapter 27 Electrical impulse travels from the sinus node to the AV node, these impulses are slowed down for a very short period, then continue down the conduction pathway via Bundle of HIS into the ventricles. The SA node serves as the pacemaker of the heart. The SA node continuously genera...

Summary Chapter 27 Electrical impulse travels from the sinus node to the AV node, these impulses are slowed down for a very short period, then continue down the conduction pathway via Bundle of HIS into the ventricles. The SA node serves as the pacemaker of the heart. The SA node continuously generates electrical impulses thus setting the normal rhythm and rate in a healthy heart. See the ECG GRAPH AND COMMONLY MEASURED COMPONENTS REVIEW SLIDE ON THE POWERPOINT. The P wave represents electrical depolarization of the atria. In healthy adults it originates in the SA node and disperses into both the left and right atria. Depolarization also corresponds to atrial contraction. PR interval- beginning of P wave to the beginning of the QRS. 0.12-0.20 seconds or 3-5 small boxes. In a normal rhythm. If you look at the small boxes, they represent 0.04 seconds. Membrane depolarization opens the voltage gated Na channels. QRS represents ventricular depolarization ST- segment- Interval between ventricular depolarization and ventricular repolarization- or the closing of the NA Channels and opening of the K+ channels. (Resting phase). In a normal rhythm there is always a p wave 0.12-0.20 sec and p wave is upright and round. QRS is narrow (0.08-0.10 seconds) And ST segment should be flat and then peaks with the t wave. Remember in STEMI the ST IS ELEVATED NOT FLAT (INFARCTION AND OCCLUSION) You also can look at the Rs and see if rate is regular or irregular. PACs ( atrial dysrhythmias ) Irregular and look at P wave morphology is abnormal and PVC is ventricular dysrhythmias. QRS is wide and bizarre and makes the rhythm irregular at that ectopic beat. See the powerpoint for the pictures of the rhythms and causes. SVT- SEE POWERPINT PICTURE- SUPRA (OR ABOVE THE VENTRICLES) Supra ventricular tachycardia. Faster rate beginning about the heart’s 2 lower chambers or ventricles. It is a rapid heartbeat that develops when normal electrical impulses of the heart are disrupted. SVT rates are usually 150-250 beats per minute. V tach – see picture you can see is wide bizarre and fast comes from ventricles, no p wave – QRS is wide and rate is 170 bpm or greater. If a patient has a pulse in this rhythm cardioversion with lower amount of joules 50-100 could be used and Lidocaine can be used look at Lidocaine’s MOA: decreases myocardial irritability in ventricles. Has little or no effect on the atrial tissue. Sustained V tach may lead to v fib where the heart is just quivering and there is no pulse and need CPR and defib. A pt in Vtach can be pulseless and if that is the case, CPR and defib. V tach and V fib are critical rhythms. So, you see what a normal rhythm looks like, a dysrhythmia is any deviation from the normal rhythm of the heart. Causes of dysrhythmias : ischemia, MI, CAD, heart failure, always have to watch patient closely after a MI they are at risk for dysrhythmias most common ones that could occur are Bradycardia, SVT, and VTACH. Another big cause could be electrolyte depletion K+ from for example n/v diarrhea, or diuretics etc. Need to replace K+ Never give K+ Iv PUSH, it will STOP THE HEART. Magnesium and Calcium as well. Many times, need to treat Magnesium first and then will help correct the K+ Level. Don’t overlook checking electrolytes as that could be the cause of a dysrhythmia. Look at Power Point Vaughan Williams Class- Look and think about depolarization and Na channels and repolarization K+ channels and will show you where the drug is aimed at with the electrophysiologic action potential. Class 1A- Sodium channel blockers- Decreases conduction (depolarization) in the atria and ventricles. Can be used for atrial and ventricular dysrhythmias. Quinidine Class 1B- Na channel blockers- decreases irritability in the ventricles. Lidocaine Used to treat ventricular dysrhythmias Class 2- Beta blockers Propranol Decreases SNS- Decreases excitability, workload and contributes to antidysrhythmic effects. Class 3- Amiodarone- Drugs that delay repolarization or block the K+ Channels. Class 4- Calcium Channel Blockers- Diltiazem- Slows AV node automaticity, Delay of AV node conduction, and reduction in myocardial contractility. Used to decrease heartrates in atrial fib, and SVT. Also review Adenosine, and Magnesium sulfate in powerpoints. I will NOT test you on analyzing the ECG rhythms. I just wanted you to see them and understand a little about them as the antidysrhythmics are used to treat those rhythms. If you understand the basic conduction and electrical physiology of the heart, then the drug class should make sense. As stated in powerpoints- nonpharmacological measures are usually tried first as all antidysrhythmics can cause dysrhythmias. Review the nursing implications on the powerpoints. I hope this helps