Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 37 Electrocardiography

Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.

Chapter 37

Electrocardiography


Anatomy of the Heart

• Four chambers– Two upper chambers known as atria– Two lower chambers known as ventricles

• Deoxygenated blood• Oxygenated blood


Anatomy of the Heart

• Coronary arteries

• Click here to see an animation


Electrical Conduction System of the Heart

• Sinoatrial (SA) node• Atrioventricular (AV) node• Bundle of His and Purkinje fibers


Electrical Conduction System of the Heart

• Systole and diastole• Impulses can be recorded on ECG paper or

displayed on oscilloscope


The Cardiac Cycle and the ECG Cycle

• Baseline or isoelectric line• Positive deflection• Negative deflection• Each cardiac cycle takes about 0.8 second


The Cardiac Cycle and the ECG Cycle

• P, QRS, and T waves


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


Types of Electrocardiographs

• Single-channel ECG >>• Multichannel ECG• Automatic ECG machines


Types of Electrocardiographs

• ECG telephone transmissions• Facsimile electrocardiograph• Interpretive electrocardiograph


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


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


ECG Equipment

• Sensors or electrodes– Disposable sensors – Detect electrical impulses on body surface from the

myocardium and relay them through cables


ECG Equipment

• Lead wires– Once self-adhesive sensors

are placed, lead wires from the ECG machine are attached

• Caring for equipment


Lead Coding

• 12 leads recorded using 10 lead wires• Necessary for identification and mounting

purposes• Newer ECGs automatically mark (code)

each lead


The Electrocardiograph and Lead Placement

• 12 leads record heart’s electrical activity• Allows for 3D interpretation of activity• Amplification of electrical activity


The Electrocardiographand Lead Placement

• Galvanometer changes voltage into mechanical motion

• Stylus records motion


The Electrocardiographand Lead Placement

• Types of leads– Standard limb or bipolar

leads– Augmented leads– Chest leads, precordial

leads, or V leads

• Placement of electrodes


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


Standard Resting Electrocardiography

• Performing 12-lead electrocardiogram


Standard Resting Electrocardiography

Click Here to play the video


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


Interference or Artifacts

• Somatic tremor artifacts• Alternating current (AC) interference• Wandering baseline artifacts• Interrupted baseline artifacts


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


Cardiac Arrhythmias

Click Here to play the video


Cardiac Arrhythmias

• Atrial arrhythmias– Premature atrial contractions (PAC)– Paroxysmal atrial tachycardia (PAT)– Atrial fibrillation


Cardiac Arrhythmias

• Ventricular arrhythmias– Premature ventricular contractions (PVCs)– Ventricular tachycardia– Ventricular fibrillation


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


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


Holter Monitor

• Medical assistant’s role– Preparing patient– Instructing patient– Applying and removing

monitor


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


Holter Monitor

• Removing the Holter Monitor– Patient returns to office– Tape is analyzed by scanner or computer– Written report sent to physician


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


Other Diagnostic Tests

• Loop ECG• Thallium stress test• Echocardiography/ultrasonography


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


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

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Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 37 Electrocardiography