Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Principles of Electrocardiography Chapter 48
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 2 The Cardiac Cycle The cardiac cycle includes all of the events occurring in the heart during one single heartbeat. – Systole – Diastole The electrocardiograph records both the intensity and the actual time it takes for each part of the cardiac cycle to occur.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 3 Heartbeat Origin The heart beats in response to an electrical signal that originates in the sinoatrial (SA) node in the right atrium, spreads over the atria, and causes atrial contraction. SA node controls the rate of heart contraction by initiating electrical impulses every 60 to 100 times per minute.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 4 Ventricular Contraction This impulse continues to the atrioventricular (AV) node, through the bundle of His, and then through the right and left bundle branches, eventually causing ventricular contraction.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 5 Normal Sinus Rhythm Refers to a regular heart rate that falls within the average range of 60 to 80 beats/min
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 6 Normal Sinus Rhythm (cont’d)
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 7 The ECG machine Six-channel ECG machines Single channel ECG machines
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 8 The ECG machine (cont’d)
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 9 Electrocardiogram The horizontal lines on the ECG paper permit the determination of the intensity of the electrical activity or the relative strength of the heartbeat. The paper is pressure sensitive; it must be handled carefully to avoid making any additional markings that would blemish the tracing.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 10 Paper Record The stronger the beat, the greater the vertical deflection on the paper. The vertical lines represent time. The large squares each represent 0.2 seconds. Five of them equal 1 second.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 11 Paper Record (cont’d)
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 12 Electrodes and Leads Ten electrodes are placed on the patient’s arms, legs, and chest to pick up the electrical activity of the heart. Most offices use single-use, self-stick, disposable electrodes that are packaged with conductive jelly in the center. The leads carry the cardiac electrical impulses into the machine. The frontal leads include Leads I, II, III, aV R, aV L, and aV F. Horizontal plane leads include the six precordial or chest leads.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 13 Electrode Placement Taking an ECG requires knowledge of where to place the electrodes accurately and how to connect the leads to obtain the most accurate recording possible.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 14 Leads The 12-lead ECG consists of three limb leads – I – II – III Three augmented leads (aV R, aV L, and aV F ) Six precordial or chest leads (V 1, V 2, V 3, V 4, V 5, and V 6 )
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 15 Heart Function These leads record the electrical activity from different directions, giving the physician a picture of the function of different areas of the heart.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 16 Leads
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 17 ECG Electrode Placement
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 18 Chest Leads
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 19 Obtaining an ECG Preparation of the room and patient Applying leads to the patient
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 20 Obtaining an ECG Recording the ECG (see Procedure 48-1) Standardization, sensitivity, and speed Mounting an ECG tracing
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 21 Artifacts The medical assistant must recognize and correct the most common types of artifacts on the ECG recording. – Wandering baseline
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 22 Artifacts – Somatic tremor
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 23 Artifacts – Sixty-cycle interference
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 24 Artifacts – Interrupted baseline
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 25 Sensitivity Standards Most machines have 3 sensitivity standards that can be selected
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 26 Sensitivity Standards (cont’d)
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 27 Typical ECG Rhythm Abnormalities Sinus arrhythmias – Sinus bradycardia – Sinus tachycardia
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 28 Typical ECG Rhythm Abnormalities Atrial arrhythmias – Premature atrial contraction (PAC) – Atrial flutter Ventricular arrhythmias – Premature ventricular contraction – Ventricular fibrillation
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 29 Typical ECG Rhythm Abnormalities
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 30 Biochemical Arrhythmias Digitalis Potassium
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 31 Stress Test Conducted to observe and record the patient’s cardiovascular response to measured exercise challenges.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 32 Holter Monitor A portable system for recording the cardiac activity of a patient over a 24-hour period or longer. The patient must keep a journal of all stressful events and activities during the entire time the monitor is worn. A medical assistant is often responsible for instructing the patient in applying and removing the monitor.
Copyright © 2007 by Saunders, Inc., an imprint of Elsevier Inc. Slide 33 Patient Education Heart disease and stroke account for more than one third of all deaths. Talk to the patient about factors that could be modified, and give him or her encouragement for any attempt at complying with these suggestions. Include visual aids, posters, brochures.