Ch. 9: Cardiac Monitoring Flashcards
What is known as the pacemaker of the heart?
SA node
The sinoatrial node usually intiates about ____ impulses/min
75
Once an impulse has been initiated by the SA node, the impulse travels down to the ______________.
atrioventricular (AV) node
Where is the Bundle of His located?
Interventricular septum
After contraction, repolarization occurs, and the heart is in a resting state, what is this called?
Diastole
What is the term used for the heart in contraction?
Systole
The device to which the electrodes are attached is the _________________.
Electrocardiograph
The electrical activity of the heart recorded on graph paper is called the ____________ and may be displayed continuously on an ECG monitor, called an oscilloscope.
Electrocardiogram
State the order of the electrical conduction of the heart.
- SA node
- AV node
- Bundle of His
- Right/Left bundle branches
- Purkinje fibers
Standard 12-Lead ECG has how many lead systems?
3
The leads are placed on the right arm, left arm, and left leg.
Standard limb leads (1, positive pole; 2, negative pole; and ground)
Which limb lead measures the electrical potential between the right arm and left arm?
Limb lead I
Standard limb leads (1, positive pole; 2, negative pole; and ground)
Which limb lead measures the electrical potential between the right arm and left leg?
Limb lead II
Standard limb leads (1, positive pole; 2, negative pole; and ground)
Which limb lead measures the electrical potential between the left arm and left leg?
Limb lead III
Standard limb leads (1, positive pole; 2, negative pole; and ground)
Where is the ground limb lead placed?
Right leg
Precordial (chest) leads (six leads)
Lead 1 (V1) is positioned at the ________ intercostal space at the ________ border of the sternum.
Lead 1 (V1) is positioned at the fourth intercostal space at the right border of the sternum.
Lead 2 (V2) is positioned at the ________ intercostal space at the ________ border of the sternum.
Lead 2 (V2) is positioned at the fourth intercostal space at the left border of the sternum.
Where is Lead 3 (V3) positioned?
In a straight line between leads 2 and 4.
Where is Lead 4 (V4) positioned?
At the midclavicular line and at the fifth intercostal space.
Where is Lead 5 (V5) positioned?
At the anterior axillary line, level with lead 4 horizontally.
Where is Lead 6 (V6) positioned?
At the midaxillary line, level with leads 4 and 5 horizontally.
Long-term ECG Monitoring - 3 LEAD PLACEMENTS
Where is the first electrode placed?
Upper right side of the chest (-).
Long-term ECG Monitoring - 3 LEAD PLACEMENTS
Where is the second electrode placed?
Lower left side of the chest (+)
Long-term ECG Monitoring - 3 LEAD PLACEMENTS
Where is the third electrode placed?
It is used as a ground and may be attached to any location that is convenient.
The ECG paper is made up of very small squares, which represent ____ seconds horizontally.
0.04
The ECG paper is made up of very small squares, which represent ________ vertically (voltage axis).
0.5 mV
Is the P wave a postive or negative wave?
Positive
What does the P wave represent?
Atrial depolarization (contraction)
What is the duration of the P wave?
0.06 to 0.10 seconds
Is the Q wave a positive or negative wave?
Negative
An absence of this wave may be seen even in healthy people. What is this wave called?
Q wave
Is the R wave a positive or negative wave?
Positive
Is the S wave a positive or negative wave?
Negative
What does QRS complex measure?
Ventricular depolarization
What is the duration of the QRS complex?
0.06 to 0.10 seconds
In what instances is a wide QRS complex seen?
- Right bundle branch block
- Premature ventricular contractions (PVCs)
What does the T wave represent?
Ventricular repolarization
What does an inverted T wave indicate?
Coronary artery disease
How is the PR interval measured?
Measured from the beginning of the P wave to the beginning of the Q wave.
What is the duration of the PR interval?
0.12 to 0.20 seconds.
What represents the time it takes for the impulse to travel from the SA node through the AV node?
PR Interval
How is the ST segment measured?
Measured from the end of the S wave to the beginning of the T wave.
____________ measures the time that is required for ventricular repolarization to begin.
ST segment
The ST segment may be elevated above the baseline or depressed below the baseline. What is this an indication of?
Cardiac ischemia
Cardiac ischemia results from a decreased amount of oxygenated blood delivered to the left ventricle because of narrowed coronary arteries. If the blood supply is not restored, ventricular muscle may die; this is called infarction. ST segment elevation or depression is a sign of coronary artery disease.
Cardiac impulse travels to the AV node, bundle of His, and the Purkinje fibers, which are represented on the ECG as the what?
PR interval
Ventricular repolarization is represented on the ECG as the __________.
ST segment and T wave
How do you calculate the HR on an ECG?
Count the number of R waves in a 6-second period and multiply by 10
Normal HR
60-100 beats/min
Define bradycardia
<60 beats/min
Define tachycardia
> 100 beats/min
How to determine the regularity of a heart rhythm on an ECG?
Using calipers, measure the distance between a pair of R waves. Leave the calipers at that distance, and measure the next pair of R waves to determine whether the distance is the same.
What does it mean if the PR interval is longer than 0.20 seconds with a regular rhythm?
First- or second-degree heart block is present.
List some causes of bradycardia
- stimulation of vagus nerve (e.g., during tracheal suctioning)
- hypothermia
- increased intracranial pressure (ICP)
- may be normal in well-conditioned athletes
What is treatment of bradycardia?
If accompanied by shortness of breath, hypotension, or abnormal beats, atropine is used; a pacemaker may also be indicated.
List some causes of tachycardia
- Hypoxemia
- Increased sympathetic nervous system stimulation (e.g fear, anxiety)
- Medication
What is the treatment for tachycardia?
- Stop underlying cause
- Administration of digitalis or beta blockers
How would you identify a sinus arrhythmia on an ECG?
The distance between the R wave of the QRS complex varies and is inconsistent.