1. ©2012 Lippincott Williams & Wilkins. All rights reserved.
ECG Workout:
Chapter Review
Chapter 4
Cardiac monitors
©2012 Lippincott Williams & Wilkins. All rights reserved.

2. ECG monitoring
The electrocardiogram (ECG) is a recording of the electrical activity of the heart. The ECG records two basic electrical processes:
Depolarization – the spread of the electrical stimulus through the heart muscle, producing the P wave from the atria, and the QRS from the ventricles.
Repolarization – the recovery of the depolarized muscle to its resting state, producing the ST segment, the T wave, and the U wave. 2

3. Types of ECG monitoring
There are two types of ECG monitoring:
Hardwire (bedside monitoring) – electrode pads are placed on patient's chest and connected to a monitor at the bedside.
Telemetry (portable monitoring) – electrode pads are placed on patient's chest and connected to a portable monitor transmitter. 3

4. Hardwire monitoring — 5-lead system
With the hardwire 5-lead system, you can monitor two leads at the same time using a lead selector on the monitor. Leads placed in the arm and leg positions (shown in example A) allow you to view the limb leads (I, II, III, aVR, aVL, and aVF). To view the chest leads (V1 - V6) (shown in example B), the chest lead must be placed in the specific chest lead position desired. In example A, the chest lead is in V1 position. Generally a limb lead (usually I, II, or III) and a chest lead (usually V1 or V6) are chosen to be monitored.
A. Hardwire Monitoring — 5-Lead System
B. Chest Lead Positions
This illustration shows you where to place the electrodes and attach leadwires using a five-leadwire system. The leadwires are color-coded as follows:
white – right arm (RA)
green – right leg (RL)
brown – chest (C).
black – left arm (LA)
red – left leg (LL) 4

5. Hardwire monitoring — 3-lead system
This illustration shows you where to place the electrodes and attach leadwires using a three-leadwire system. The leadwires are color-coded as follows:
white–right arm (RA)
black–left arm (LA)
red–left leg (LL).
Leads placed in this position will allow you to monitor leads I, II, or III using the lead selector on the monitor. 5

6. Telemetry monitoring — 5-lead system
The 5-lead system for telemetry monitoring is connected in the same manner as the 5-lead system for hardwire monitoring. With this system, you can view any one of the 12 leads using a lead selector on the monitor. Leads placed in the limb leads allow you to view leads I, II, III, aVR, aVL, and aVF. To view chest leads V1 - V6, the chest lead must be placed in the specific chest lead position desired. Only one lead can be monitored at a time.
Telemetry Monitoring — 5-Lead System
This illustration shows you where to place the electrodes and attach leadwires using a five- leadwire system. The leadwires are color-coded as follows:
White–right arm (RA)
black–left arm (LA)
green–right leg (RL)
red–left leg (LL)
brown–chest (C). 6

7. Telemetry monitoring — 3-lead system
With the 3-lead system for telemetry monitoring, the leads are connected to positive, negative, and ground connectors on the telemetry transmitter and attached to specific lead positions ( leads I, II, or III). A lead selector is not available. Only one lead can be monitored at a time. 7

8. Attachment of electrode pads
Proper attachment of the electrode pads to the skin is the most important step in obtaining a quality ECG tracing. Good contact between the skin and electrode pads helps to prevent distortions of the ECG tracing.
Follow these steps:
Choose monitor lead that provides the best QRS amplitude and P wave identification.
Prep the skin.
Clip the hair from the skin using a clipper (hair interferes with the transmission of the electrical currents on the surface of the skin to the conducting gel in the electrode pad).
Attach electrode pads.
Remove electrodes from packaging and check for presence of moist conductive gel (dried gel will not conduct electrical activity).
Place electrodes on skin, pressing firmly around periphery of pad. Avoid bony areas. 8

9. Distortions of the ECG tracing
Distortions of the ECG tracing (artifacts) can be caused by activity that is non-cardiac in origin, such as:
patient movement
seizure activity
ineffective contact between skin, electrode, and lead (dried conductive gel, loose electrode pad, disconnected lead)
muscle tremors
weak ECG signals received over monitoring system
electrical interference
exaggerated respiratory movements (seen in severe lung disease).
  Artifacts on the ECG tracing can make identification of the cardiac rhythm difficult or trigger false monitor alarms. 9

10. Patient movement
Patient movement can activate the high-rate alarm (high-voltage artifact potentials are seen by the monitor system as QRS complexes).
Cause: Patient turning in bed; extremity movement
Solution: Avoid placing electrode pads in areas where extremity movement is greatest (bony areas such as the clavicles); problem is usually intermittent and will correct itself. 10

11. Seizure activity
Seizure activity may activate the high-rate alarm due to high-voltage artifact potentials.
Cause: Patient movement from seizure
Solution: Treat cause of seizure. 11

12. Continuous straight line
A continuous straight line will activate the low-rate alarm (the monitor system does not see QRS complexes).
Cause: Disconnected lead, disconnected electrode pad, or dried conductive gel
Solution: Check electrodes and leads; reattach disconnected electrodes and leads.
Note: A straight line could indicate an absence of electrical activity in the heart. Check patient immediately for pulse. 12

13. Intermittent straight line
An intermittent straight line may activate the low-rate alarm since the monitor system does not see the normal number of QRS complexes.
Cause: Ineffective contact between the electrode pads and skin surface
Solution: Make sure hair is clipped and electrode is placed on clean, dry skin. If diaphoresis is a problem, apply some type of skin prep adherent so electrode will adhere to skin surface. 13

14. Low-voltage QRS
Low-voltage QRS complexes may activate the low-rate alarm if the height of the QRS is too low for the monitor system to see it.
Cause: Low-amplitude QRS complexes in monitored lead
Solution: Turn up amplitude knob on monitor or switch to another lead. 14

15. Muscle tremors
Muscle tremors affect the baseline, making it difficult to identify the cardiac rhythm as well as changes in the ST segment and T wave.
Cause: Tense or nervous patient; patient shivering from being cold; patient shivering from elevated temperature; postanesthesia shivers
Solution: Treat cause. 15

16. Telemetry-related interference
Artifacts may occur on the ECG tracing related to problems associated with the telemetry monitoring system. Weak signals or a loss of signal may result in spikes on the tracing as well as straight lines.
Cause: Weak batteries; telemetry monitor too far away from antenna; problems with antenna system
Solution: Change batteries; keep patient within antenna range; check antenna system. 16

17. Electrical interference
Electrical interference results in a wide baseline with fine, even, rapid spikes between QRS complexes.
Cause: Patient using electrical device (electric razor, hair dryer); multiple electrical equipment plugged into same electrical area; improperly grounded equipment; equipment with exposed wiring
Solution: If patient is using electrical device, problem will correct itself. If multiple equipment is plugged into same electrical area, plug electrical equipment into different electrical areas in room. Remove any improperly grounded equipment from service; have electrical engineer check any equipment causing electrical interference or equipment with exposed wiring. 17

18. Wandering baseline
Wandering baseline is a monitor pattern that wanders up and down on the monitor screen, making it difficult to identify the cardiac rhythm as well as changes in the ST segment and T wave.
Cause: Exaggerated respiratory movements, usually seen in patient with severe lung disease (COPD)
Solution: Avoid placing electrode pads in areas where movements of chest muscles are most likely to occur (anterior chest wall). Arm leads may be placed on shoulders or upper back; leg leads may be moved to more lateral positions on chest wall. 18