copyright 2010 delmar, cengage learning. all rights reserved. chapter 37 electrocardiography
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Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Anatomy of the Heart Coronary arteries Click here to see an animationTRANSCRIPT
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Chapter 37
Electrocardiography
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Anatomy of the Heart
• Four chambers– Two upper chambers known as atria– Two lower chambers known as ventricles
• Deoxygenated blood• Oxygenated blood
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Anatomy of the Heart
• Coronary arteries
• Click here to see an animation
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Electrical Conduction System of the Heart
• Sinoatrial (SA) node• Atrioventricular (AV) node• Bundle of His and Purkinje fibers
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Electrical Conduction System of the Heart
• Systole and diastole• Impulses can be recorded on ECG paper or
displayed on oscilloscope
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The Cardiac Cycle and the ECG Cycle
• Baseline or isoelectric line• Positive deflection• Negative deflection• Each cardiac cycle takes about 0.8 second
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The Cardiac Cycle and the ECG Cycle
• P, QRS, and T waves
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Calculation of Heart Rate
• On ECG graph paper:– Every fifth line is darker than other lines– Time is measured on horizontal line– Voltage is measured on the vertical line
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Types of Electrocardiographs
• Single-channel ECG >>• Multichannel ECG• Automatic ECG machines
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Types of Electrocardiographs
• ECG telephone transmissions• Facsimile electrocardiograph• Interpretive electrocardiograph
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ECG Equipment
• Electrocardiograph paper– Black or dark blue– Wax or plastic coated– Heat and pressure sensitive– Heat of stylus can be adjusted to obtain a sharp tracing
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ECG Equipment
• Electrolyte– Help pick up electrical current produced by contraction
and relaxation of heart– In form of gel, lotion, paste, or pre-saturated pads
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ECG Equipment
• Sensors or electrodes– Disposable sensors – Detect electrical impulses on body surface from the
myocardium and relay them through cables
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ECG Equipment
• Lead wires– Once self-adhesive sensors
are placed, lead wires from the ECG machine are attached
• Caring for equipment
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Lead Coding
• 12 leads recorded using 10 lead wires• Necessary for identification and mounting
purposes• Newer ECGs automatically mark (code)
each lead
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The Electrocardiograph and Lead Placement
• 12 leads record heart’s electrical activity• Allows for 3D interpretation of activity• Amplification of electrical activity
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The Electrocardiographand Lead Placement
• Galvanometer changes voltage into mechanical motion
• Stylus records motion
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The Electrocardiographand Lead Placement
• Types of leads– Standard limb or bipolar
leads– Augmented leads– Chest leads, precordial
leads, or V leads
• Placement of electrodes
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Standardization of the Electrocardiograph
• Value of recording depends on accuracy• Universal measurements• One millivolt of cardiac electrical activity
will deflect stylus exactly 10 mm high
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Standard Resting Electrocardiography
• Performing 12-lead electrocardiogram
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Standard Resting Electrocardiography
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Mounting the ECG Tracing
• Commercially prepared mounting forms• Mount completed tracing after provider has
reviewed entire recording• Identify patient, date, age, blood pressure,
height and weight, and cardiac medications
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Interference or Artifacts
• Somatic tremor artifacts• Alternating current (AC) interference• Wandering baseline artifacts• Interrupted baseline artifacts
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Cardiac Conditions and Diseases
• Myocardial infarctions (heart attack)– Primary cause of death in U.S.– Offer patient health tips as part of patient education
• Behaviors to adopt for a healthy heart
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Cardiac Arrhythmias
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Cardiac Arrhythmias
• Atrial arrhythmias– Premature atrial contractions (PAC)– Paroxysmal atrial tachycardia (PAT)– Atrial fibrillation
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Cardiac Arrhythmias
• Ventricular arrhythmias– Premature ventricular contractions (PVCs)– Ventricular tachycardia– Ventricular fibrillation
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Defibrillation
• Electrical device that applies countershocks to heart through electrodes or pads placed on chest wall (AED)
• Can convert cardiac arrhythmia into normal sinus rhythm
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Holter Monitor
• Portable ambulatory electrocardiograph– Portable continuous recording of cardiac activity for a
24-hour period– Noninvasive test– Helps diagnose cardiac arrhythmias by correlating them
with patient’s symptoms
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Holter Monitor
• Medical assistant’s role– Preparing patient– Instructing patient– Applying and removing
monitor
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Holter Monitor
• Patient activity diary– Record all activities, emotional states, and time of their
occurrence– Record chest pain and other symptoms and time of their
occurrence
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Holter Monitor
• Removing the Holter Monitor– Patient returns to office– Tape is analyzed by scanner or computer– Written report sent to physician
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Other Diagnostic Tests
• Treadmill stress test – Diagnose heart disorders and probable cause of
patient’s chest pain– Assess patient’s cardiac ability following cardiac
surgery– Noninvasive test– Patient exercises on treadmill at varying rates of speed
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Other Diagnostic Tests
• Loop ECG• Thallium stress test• Echocardiography/ultrasonography
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Cardiac Procedures
• Coronary angioplasty with and without stent– Balloon inflated inside coronary artery with or without
stent– Keeps artery open
• Coronary artery atherectomy– Cutting away of plaque in blocked coronary artery
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Other Cardiac Diagnostic Tests
• Coronary artery bypass– Vein transplanted into blocked coronary artery(ies)– Blood supply reestablished to myocardium
• Cardiac computerized tomography and cardiac magnetic resonance