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1. Medical assistant
2. Electronic records
3. Medical terminology and anatomy
4. The fundamentals of infection control
5. Introduction to vital signs
6. The patient interview and history
7. The physical examination
8. Appointment scheduling
9. Insurance billing
10. Diagnostic coding and the ICD-10-CM System
11. Procedural coding
12. Medical billing and reimbursement essentials
13. Assisting with medical specialties
14. Assisting with the musculoskeletal system
15. Assisting with the cardiovascular system
16. Assisting with the respiratory system
17. Assisting with the nervous system
18. Anatomy and physiology of the urinary system
19. Assisting in obstetrics and gynecology
20. Assisting in endocrinology
21. Assisting in ophthalmology & otolaryngology
22. Assisting in gastroenterology
23. Assisting in the immune & lymphatic systems
24. Assisting in pediatrics: the developmental stages and care
25. The medical assistant’s role in caring for the older patient
26. The role of the medical assistant in physical therapy examination and assessment
27. Preparing for minor surgery: room, solutions, and supplies
28. Introduction to the clinical laboratory
29. Urinalysis
30. Blood collection
31. Analysis of blood
32. Electrocardiography and heart structure
32.1 The principles of electrocardiography
32.2 ECG terminology, waves, and intervals
32.3 Rhythm analysis and arrhythmias
32.4 The electrocardiograph and ECG preparation
32.5 Troubleshooting and evaluation
32.6 Stress testing
33. The principles of pharmacology
34. Essential calculations and measurement systems
35. Solid, liquid, & solutions medication doses
36. Administering medications
37. Metabolism and core nutrient roles
38. Medical emergencies in the healthcare setting
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32.5 Troubleshooting and evaluation
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32. Electrocardiography and heart structure
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Troubleshooting and evaluation

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Troubleshooting artifact

Artifact is signal distortion or unwanted, erratic movement of the stylus caused by outside interference. The medical assistant needs to identify the type of artifact and then take actions to prevent the artifact. The leads can be viewed on the screen or after printing the ECG tracing. Carefully look for artifact. The following sections discuss the appearance and causes of the common types of artifact and ways to prevent them.

Wandering baseline

Wandering baseline artifact is an upward and downward movement of the waveform. The isoelectric lines shift locations. This artifact can be the result of the following:

  • Poor skin preparation: The patient has oily skin or used lotion. The electrodes are falling off.
  • Old electrodes: The electrodes are dirty or expired, or the gel on the electrodes is dried.
  • Placement of electrodes: The electrodes are placed on bony areas.
  • Movement: The movement of breathing can also be the cause of this artifact.
  • The medical assistant should take these steps:
    • Clean the skin with alcohol and allow it to dry. Slightly abrade the skin with a gauze pad or fine sandpaper tape to help the electrodes stick to the skin.
    • Replace the electrode with a new one. Ensure the electrodes are not expired and the gel is not dried.
    • Make sure all electrodes and lead wires are firmly attached.
    • Make sure the baseline filter is turned on (if it is a feature of the machine).

Somatic tremor

Somatic tremor artifact, also called muscle artifact, appears as jagged peaks with irregular heights and spacing. There are several causes:

  • Involuntary movement: Tremors from disease conditions (e.g., Parkinson disease), shivering due to coldness
  • Voluntary movement: Talking, chewing gum, supporting arms or legs because the table is too small for the person

The medical assistant should take the following steps:

  • Help the patient relax. Cover the patient with a blanket if cold.
  • Remind the patient not to move or talk during the tracing.
  • Watch for a pattern with involuntary movements. Take the tracing when the movements lessen.
  • Use a larger exam table for the procedure.
  • If the machine has a muscle tremor filter, make sure it is turned on.
EEG showing somatic tremor artifact across multiple channels.
Somatic tremor artifact on EEG

AC interference

Alternating current (AC) interference artifact, also called 60-cycle interference artifact, appears as a series of small spikes that creates a thick-looking tracing. Electrical interference causes AC interference artifacts. Electrical interference arises due to a number of factors:

  • There are too many electrical devices in the area.
  • The patient cable and lead wires are wrapped closely together.
  • An electrical cord is under the exam table, and an electrical outlet is improperly grounded.
  • A cell phone in a patient’s pocket or a smartwatch may also cause interference.

The medical assistant should do the following:

  • Unplug the ECG machine.
  • Unplug or remove nearby electrical devices (e.g., laptops, pagers, cell phones).
  • Separate the lead wires so they do not overlap.
  • Move the table away from the wall or move to another room for the procedure.
  • Ensure that no cell phones are near the procedure area.
EKG tracing showing AC interference artifact
AC interference artifact

Interrupted baseline

Interrupted baseline artifact (also called intermittent signal artifact) occurs when the tracing looks normal at the beginning but then disappears or goes all over when the electrical connection is interrupted. When the electrical connection is interrupted, interrupted baseline artifact occurs. The electrical connection is interrupted when a cable or lead wire becomes loose or a cable, clip, or lead wire is broken. If the lead wire or electrode falls off, an isoelectric line will appear on the tracing.

The medical assistant should do the following:

  • Check that all electrodes and lead wires are attached.
  • If a broken wire is suspected, be prepared to supply a new cable.
EKG tracing showing interrupted baseline artifact
Interrupted ECG baseline artifact display

Evaluating an ECG tracing

The provider reads the ECG, but the medical assistant must be able to determine abnormal rates and rhythms that might be life threatening. This section discusses how to determine the heart rate, evaluate the ECG tracing, and identify abnormal rhythms.

Rate

Many machines indicate the heart rate. The medical assistant can also calculate the rate from the ECG tracing. Numerous methods can be used to calculate a regular heart rate when the paper speed (chart speed) is 25 mm/second:

  • Six-second method: Count the number of P waves in a 6-second strip (30 large boxes) and multiply by 10 (least accurate method).
  • 1500 method: Count the number of small boxes between two R waves or the two P waves. Divide the number into 1500.
  • Sequence method: Count the number of large boxes between the R waves.

Troubleshooting artifact

  • Artifact: unwanted signal distortion or stylus movement on ECG
  • Identify artifact type, then take corrective action
  • View leads on screen or printout to check for artifact

Wandering baseline

  • Upward/downward waveform shifts; isoelectric line moves
  • Causes:
    • Poor skin prep (oily skin, lotions, loose electrodes)
    • Old/dirty/expired electrodes, dried gel
    • Electrodes on bony areas, patient movement (breathing)
  • Prevention:
    • Clean/abrade skin, use fresh electrodes, attach wires firmly
    • Turn on baseline filter if available

Somatic tremor

  • Jagged, irregular peaks from muscle activity
  • Causes:
    • Involuntary movement (tremors, shivering)
    • Voluntary movement (talking, chewing, limb support)
  • Prevention:
    • Relax/cover patient, instruct not to move/talk
    • Use larger table, enable muscle tremor filter

AC interference

  • Small, regular spikes; thick tracing (60-cycle interference)
  • Causes:
    • Too many electrical devices nearby
    • Tightly wrapped cables/wires, ungrounded outlets
    • Cell phones or smartwatches near patient
  • Prevention:
    • Unplug ECG and nearby devices, separate wires
    • Move table away from wall, remove phones from area

Interrupted baseline

  • Tracing normal, then disappears or erratic due to lost connection
  • Causes:
    • Loose/broken cables, clips, lead wires, or electrodes
  • Prevention:
    • Check all attachments, replace broken wires if needed

Evaluating an ECG tracing

Rate

  • Heart rate can be machine-calculated or determined manually
  • Methods:
    • Six-second: count P waves in 6 seconds × 10 (least accurate)
    • 1500 method: 1500 ÷ number of small boxes between R waves
    • Sequence method: count large boxes between R waves

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Troubleshooting and evaluation

Troubleshooting artifact

Artifact is signal distortion or unwanted, erratic movement of the stylus caused by outside interference. The medical assistant needs to identify the type of artifact and then take actions to prevent the artifact. The leads can be viewed on the screen or after printing the ECG tracing. Carefully look for artifact. The following sections discuss the appearance and causes of the common types of artifact and ways to prevent them.

Wandering baseline

Wandering baseline artifact is an upward and downward movement of the waveform. The isoelectric lines shift locations. This artifact can be the result of the following:

  • Poor skin preparation: The patient has oily skin or used lotion. The electrodes are falling off.
  • Old electrodes: The electrodes are dirty or expired, or the gel on the electrodes is dried.
  • Placement of electrodes: The electrodes are placed on bony areas.
  • Movement: The movement of breathing can also be the cause of this artifact.
  • The medical assistant should take these steps:
    • Clean the skin with alcohol and allow it to dry. Slightly abrade the skin with a gauze pad or fine sandpaper tape to help the electrodes stick to the skin.
    • Replace the electrode with a new one. Ensure the electrodes are not expired and the gel is not dried.
    • Make sure all electrodes and lead wires are firmly attached.
    • Make sure the baseline filter is turned on (if it is a feature of the machine).

Somatic tremor

Somatic tremor artifact, also called muscle artifact, appears as jagged peaks with irregular heights and spacing. There are several causes:

  • Involuntary movement: Tremors from disease conditions (e.g., Parkinson disease), shivering due to coldness
  • Voluntary movement: Talking, chewing gum, supporting arms or legs because the table is too small for the person

The medical assistant should take the following steps:

  • Help the patient relax. Cover the patient with a blanket if cold.
  • Remind the patient not to move or talk during the tracing.
  • Watch for a pattern with involuntary movements. Take the tracing when the movements lessen.
  • Use a larger exam table for the procedure.
  • If the machine has a muscle tremor filter, make sure it is turned on.

AC interference

Alternating current (AC) interference artifact, also called 60-cycle interference artifact, appears as a series of small spikes that creates a thick-looking tracing. Electrical interference causes AC interference artifacts. Electrical interference arises due to a number of factors:

  • There are too many electrical devices in the area.
  • The patient cable and lead wires are wrapped closely together.
  • An electrical cord is under the exam table, and an electrical outlet is improperly grounded.
  • A cell phone in a patient’s pocket or a smartwatch may also cause interference.

The medical assistant should do the following:

  • Unplug the ECG machine.
  • Unplug or remove nearby electrical devices (e.g., laptops, pagers, cell phones).
  • Separate the lead wires so they do not overlap.
  • Move the table away from the wall or move to another room for the procedure.
  • Ensure that no cell phones are near the procedure area.

Interrupted baseline

Interrupted baseline artifact (also called intermittent signal artifact) occurs when the tracing looks normal at the beginning but then disappears or goes all over when the electrical connection is interrupted. When the electrical connection is interrupted, interrupted baseline artifact occurs. The electrical connection is interrupted when a cable or lead wire becomes loose or a cable, clip, or lead wire is broken. If the lead wire or electrode falls off, an isoelectric line will appear on the tracing.

The medical assistant should do the following:

  • Check that all electrodes and lead wires are attached.
  • If a broken wire is suspected, be prepared to supply a new cable.

Evaluating an ECG tracing

The provider reads the ECG, but the medical assistant must be able to determine abnormal rates and rhythms that might be life threatening. This section discusses how to determine the heart rate, evaluate the ECG tracing, and identify abnormal rhythms.

Rate

Many machines indicate the heart rate. The medical assistant can also calculate the rate from the ECG tracing. Numerous methods can be used to calculate a regular heart rate when the paper speed (chart speed) is 25 mm/second:

  • Six-second method: Count the number of P waves in a 6-second strip (30 large boxes) and multiply by 10 (least accurate method).
  • 1500 method: Count the number of small boxes between two R waves or the two P waves. Divide the number into 1500.
  • Sequence method: Count the number of large boxes between the R waves.
Key points

Troubleshooting artifact

  • Artifact: unwanted signal distortion or stylus movement on ECG
  • Identify artifact type, then take corrective action
  • View leads on screen or printout to check for artifact

Wandering baseline

  • Upward/downward waveform shifts; isoelectric line moves
  • Causes:
    • Poor skin prep (oily skin, lotions, loose electrodes)
    • Old/dirty/expired electrodes, dried gel
    • Electrodes on bony areas, patient movement (breathing)
  • Prevention:
    • Clean/abrade skin, use fresh electrodes, attach wires firmly
    • Turn on baseline filter if available

Somatic tremor

  • Jagged, irregular peaks from muscle activity
  • Causes:
    • Involuntary movement (tremors, shivering)
    • Voluntary movement (talking, chewing, limb support)
  • Prevention:
    • Relax/cover patient, instruct not to move/talk
    • Use larger table, enable muscle tremor filter

AC interference

  • Small, regular spikes; thick tracing (60-cycle interference)
  • Causes:
    • Too many electrical devices nearby
    • Tightly wrapped cables/wires, ungrounded outlets
    • Cell phones or smartwatches near patient
  • Prevention:
    • Unplug ECG and nearby devices, separate wires
    • Move table away from wall, remove phones from area

Interrupted baseline

  • Tracing normal, then disappears or erratic due to lost connection
  • Causes:
    • Loose/broken cables, clips, lead wires, or electrodes
  • Prevention:
    • Check all attachments, replace broken wires if needed

Evaluating an ECG tracing

Rate

  • Heart rate can be machine-calculated or determined manually
  • Methods:
    • Six-second: count P waves in 6 seconds × 10 (least accurate)
    • 1500 method: 1500 ÷ number of small boxes between R waves
    • Sequence method: count large boxes between R waves

More from Electrocardiography and heart structure

  • The principles of electrocardiography
  • ECG terminology, waves, and intervals
  • Rhythm analysis and arrhythmias
  • The electrocardiograph and ECG preparation
  • Stress testing