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Electrocardiography
Anatomy of the Heart
Circulation
Electrical Conduction
System of the Heart
 Sinoatrial (SA) node
 Atrioventricular (AV) node
 Bundle of His and Purkinje fibers
 Systole and diastole
 Impulses can be recorded on ECG paper or
displayed on oscilloscope
The Cardiac Cycle
and the ECG Cycle
 Baseline or iso-electric line
 Positive deflection
 Negative deflection
 Each cardiac cycle takes about 0.8 second
 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
 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
 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
The Electrocardiograph and Lead
Placement
 12 leads recorded using 10 lead wires
 Necessary for identification and mounting
purposes
 Newer ECGs automatically mark (code) each lead
 12 leads record heart’s electrical activity
 Allows for 3D interpretation of activity
 Amplification of electrical activity
The Electrocardiograph
and 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
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
 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
 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