Ch.18 Egans Flashcards
The _____ is the most important diagnostic tool that in some settings is obtained by the respiratory therapist
ECG
Why is the ECG so popular?
- inexpensive
- noninvasive
- easy to obtain
Why is the ECG used?
To help evaluate a pt with signs and symptoms of cardiac disease
What can an ECG also be used for?
To detect abnormalities that already occur in pts w/ an MI or preoperative screening
The muscle cells of the heart normally are stimulated and pace by the electrical activity of the cardiac______?
Impulse conducting system
The cardiac muscle cells generate electrical imbalance across the cell membrane with a ________charge on the outside, and a _______charge on the inside
Positive ; negative
What is the resting or polarize state?
When there is no electrical activity
Stimulation of _______ cells causes an influx of ______into the interior portion of the cell?
Polarized ; Na+
An influx of Na+ into the interior portion of the cell is called what?
Depolarization
Depolarization causes the cardiac muscle cells to ________momentarily?
Contract
Depolarization is immediately followed by what?
Repolarization
What is a repolarization?
A rapid return of the cell to the “polarized” position in which an electrical imbalance across the membrane is reestablished
The impulse conduction system has three types of cardiac cells capable of electrical excitation. What are they?
• Pacemaker cells
• specialized rapidly conducting tissue
• AV muscle cells
The ability of the cells to depolarize without stimulation is known as_______?
Automaticity
The impulse conduction system is responsible for_____ and _______? It also does what?
Initiating the heartbeat ; controlling the heart rate ; coordinates the contraction of the heart chambers
A deceptive the impulse conduction system may lead to what?
Inadequate cardiac output and decreased tissue perfusion
Where is the SA node located?
Upper portion of the right atrium
T or F the SA node has the greatest degree of automaticity and paces the heart
True
The AV node is the _______ pacemaker
Backup
T or F the AV node has the second greatest degree of automaticity in a healthy heart
True
The AV node paces ventricular activity at a lower heart rate of _______?
40 to 60 bpm
Once the impulse exits the AV node where does it go?
It enters the bundle of His and rapidly moves to the bundle branches
The bundle branches_______ the purkinje fibers
Terminates
What is the equipment that is gathered for a 12 lead ECG?
• portable ECG unit
• lead wires
• electrodes
The 12 leads are subdivided into two groups:
6 extremity (limb) leads
6 chest (percordial) leads
The 12 leads are bipolar which means what?
They permit the measurement of electrical activity in two different directions
What are the limb leads called?
1,2,3,aVr, aVL, aVf
What are the six chest leads called?
V1, V2, V3, V4, V5, V6
Where is the V1 lead located?
The fourth intercostal space to the right of the sternum
Where is the V2 lead located?
In the fourth intercostal space just to the left of the sternum and ending with a V6
How large is one box on an ECG?
0.20 seconds
How large is one small box within one box on the ECG?
0.04 seconds
If the QRS complex is longer than three small boxes, what does that mean?
There are ventricular problems
The QRS complex on the ECG equals how many small boxes?
3 small boxes