Chapter 38
1. Which of the following accurately describes the Q wave?
1. First negative deflection after the P wave
2. Rounded and upright and precedes the QRS complex
3. Negative deflection following the R wave
4. Rounded and upright and follows the QRS complex
Answer: First negative deflection after the P wave
Rationale:
The Q wave is the first negative deflection following the P wave. The negative deflection
following the R wave is the S wave. P waves are rounded and generally upright and precede
the QRS, while T waves are generally rounded and upright and follow the QRS complex.
2. The normal PR interval represents the amount of time it takes for the impulse to travel
from the:
1. SA node to the ventricles.
2. AV node to the ventricles.
3. Bundle of His to the ventricles.
4. Purkinje fibers to the ventricles.
Answer: SA node to the ventricles.
Rationale:
The PR interval, sometimes referred to as the PRI or PR segment, represents the time it takes
for the impulse to travel from the SA node down the intra-atrial pathways to the ventricles.
The normal PR interval is 0.12 to 0.20 seconds. In other words, it represents the beginning of
the atrial contraction to the beginning of the ventricular contraction.
3. Which interval represents atrial contraction?
1. PR interval
2. QRS complex
3. QT interval
4. R to R interval
Answer: PR interval
Rationale:
The PR interval represents atrial contraction. The QRS complex represents ventricular
contraction. The QT interval measures depolarization and repolarization of the ventricles. The
R to R interval measures pulse regularity.
4. The nurse is told in report that the client’s PR interval is within normal limits. Which of the
following would the nurse anticipate as a result of receiving this information? The client’s PR
interval would:
1. Be between 0.12 and 0.20 seconds.
2. Be between 0.06 and 0.12 seconds.
3. Be between 0.34 and 0.43 seconds.
4. Extend between 8.5 to 11 small boxes on the ECG paper.
Answer: Be between 0.12 and 0.20 seconds.
Rationale:
If a PR interval is within normal limits, it will be between 0.12 and 0.20 seconds, which is
equal to 3 to 5 small boxes. The normal QRS width is between 0.06 and 0.12 seconds, which
is equal to 1.5 to 3 small boxes. The normal QT interval is between 0.34 to 0.43 seconds,
which is equal to 8.5 to 11 small boxes.
5. The nurse obtains an ECG monitor strip and makes the following analysis: no apparent P
waves, ventricular rate 152 beats per minute and regular, and narrow QRS complex (0.08).
The nurse interrupts this rhythm as:
1. Supraventricular tachycardia.
2. Sinus tachycardia.
3. Atrial fibrillation.
4. Ventricular fibrillation.
Answer: Supraventricular tachycardia.
Rationale:
Supraventricular tachycardia (SVT) is a tachycardia that is generated somewhere above the
ventricles. This general term encompasses all fast (tachy) rhythms with normal QRS
complexes and heart rates greater than 100 beats per minute. There are no apparent P waves;
thus it cannot be called “sinus” tachycardia. Atrial fibrillation does not have P waves present,
but it is always irregular. Ventricular fibrillation would have no P waves, but the QRS
complexes would be > 0.12 second.
6. The nurse admits a client into the emergency department who complains of lightheadedness and nausea. During the assessment, the nurse determines that the radial pulse is
42 and regular, QRS complex is within normal limits, and there is no measurable PR interval
because there is not a consistent relationship between the P waves and the QRS complexes.
The nurse would interpret this dysrhythmia as:
1. Third-degree AV heart block.
2. Sinus bradycardia.
3. Sinus arrest.
4. Supraventricular tachycardia.
Answer: Third-degree AV heart block.
Rationale:
Third-degree AV block, or complete block, is the independent excitation and contraction of
the atria and ventricles due to the inability of any atrial impulses to reach the ventricles. In
other words, the top and bottom of the heart are not communicating; they are beating
independently. This is why there are no consistent PR intervals. Sinus bradycardia occurs
when the SA node is firing at a rate of less than 60 beats per minute. There is a consistent PR
interval with sinus bradycardia. Sinus arrest is a momentary cessation of sinus impulse
formation (SA node failure), causing the absence of the PQRST complex. The remainder of
the beats have normal PR intervals. Supraventricular tachycardia has a rate of greater than
100 beats per minute.
7. Which of the following are characteristics of atrial fibrillation?
Select all that apply.
1. The ventricular rhythm is irregular.
2. The QT interval cannot be measured because the T waves are buried in the “f” waves.
3. P waves are replaced by “f waves,” which are due to atrial quivering.
4. The PR intervals are measurable.
5. The atrial rate can be calculated by counting the P waves in 6 seconds and multiplying by
10.
Answer: 1. The ventricular rhythm is irregular.
2. The QT interval cannot be measured because the T waves are buried in the “f” waves.
3. P waves are replaced by “f waves,” which are due to atrial quivering.
Rationale:
The ventricular rhythm is irregular. The ventricular rhythm is irregular in atrial fibrillation.
The QT interval cannot be measured because the T waves are buried in the “f” waves.
Because T waves are buried within the “f’ waves, the QT interval cannot be measured. P
waves are replaced by “f waves,” which are due to atrial quivering. Waves that are seen
between R-to-R intervals are called “f” waves and are due to atrial quivering. The PR
intervals are measurable. Because there are no P waves, the PR interval cannot be measured.
The atrial rate can be calculated by counting the P waves in 6 seconds and multiplying by 10.
In atrial fibrillation there are no P waves, therefore the atrial rate cannot be counted.
8. While admitting a client to the emergency room, the nurse observes the cardiac monitor
and identifies the following rhythm: one inverted P wave for every QRS complex and a
regular heart rate of 46 beats per minute. The nurse interprets this rhythm as:
1. Junctional escape rhythm.
2. Normal sinus rhythm.
3. Mobitz II heart block.
4. Complete heart block.
Answer: Junctional escape rhythm.
Rationale:
Junctional escape rhythm results from either an irritable focus in the junctional tissue that
discharges before the SA node has had a chance to or because the SA node has failed to fire,
thereby making junctional node the secondary pacemaker. The impulse is initiated in the AV
junctional tissue and must travel in a backward (retrograde) direction to activate the atria.
Therefore, the P wave is inverted or negatively deflected, due to this retrograde conduction,
and may occur before, after, or buried in the QRS complex. The intrinsic rate of the AV
junction is 40 to 60 beats per minute. This is not normal sinus rhythm because it is not
initiated by the SA node. Both Mobitz II and complete heart block are rhythms that occur
below the AV junction and have normal P waves.
9. Which of the following ECG findings is present in a client who has both a first-degree
heart block and a bundle branch block?
1. A PR interval of 0.24 second and a QRS complex width of 0.16 second
2. An ST segment elevation and an inverted T wave
3. A QT interval of > 0.44 second and a PR interval of 0.16 second
4. An ST segment elevation and a QT interval of 0.20 second indicates first-degree block, and a QRS complex with of >
0.12 seconds is bundle branch block. ST segment elevation and inverted T waves are both
indicative of myocardial ischemia/injury. A QT interval of > 0.44 is abnormal but is not
related to first-degree block or bundle branch block.
10. The nurse observes sinus bradycardia on a client’s monitor. Which of the following data
sets would indicate the client is in need of treatment for this rhythm?
1. Client is lightheaded and complaining of chest discomfort.
2. Client is alert, oriented X3, and blood pressure is 120/60, with no other complaints.
3. Client’s heart rate is 50 and blood pressure is 110/62, with no other complaints.
4. Client’s respiratory rate is 16, blood pressure is 114/70, and client is pain-free.
Answer: Client is lightheaded and complaining of chest discomfort.
Rationale:
Sinus bradycardia requires treatment when the client is exhibiting a decrease in cardiac
output manifesting itself in complaints of angina, syncope, dizziness, shortness of breath,
weakness, and possible changes in mental status. As a result of decreased cardiac output, the
client may manifest hypotension. The other answer choices do not present a need for
treatment.
11. The nurse admits a client into the emergency department who complains of lightheadedness and nausea. During the assessment, the nurse determines that the radial pulse is
42 and regular, the cardiac monitor shows there are P waves present, the QRS complex is
within normal limits, but there is no measurable PR interval because there is not a consistent
relationship between the P waves and the QRS complexes. The nurse would interpret this
dysrhythmia as:
1. Complete heart block.
2. Sinus bradycardia.
3. Atrial fibrillation.
4. Supraventricular tachycardia.
Answer: Complete heart block.
Rationale:
Third-degree AV block, or complete block, is the independent excitation and contraction of
the atria and ventricles due to the inability of any atrial impulses to reach the ventricles. In
other words, the top and bottom of the heart are not communicating; they are beating
independently. This results in no consistent meaningful PR interval. Sinus bradycardia and
supraventricular tachycardia have consistent normal PR intervals. Atrial fibrillation does not
have P waves, and therefore there is no PR interval.
12. The clinical significance for a client who is having premature ventricular contractions
(PVC) is that they:
Select all that apply.
1. Indicate myocardial ischemia and injury.
2. Could become the dominant pacemaker.
3. Are a life-threatening cardiac rhythm.
4. Are not significant; PVCs are not dangerous.
5. Show that the rhythm is regular.
Answer: 1. Indicate myocardial ischemia and injury.
2. Could become the dominant pacemaker.
3. Are a life-threatening cardiac rhythm.
Rationale:
Indicate myocardial ischemia and injury. When the cardiac muscle does not receive adequate
blood supply, the muscle becomes ischemic and irritable, resulting in PVCs. Could become
the dominant pacemaker. With a PVC that becomes the dominant pacemaker, the rhythm is
ventricular tachycardia, which is life threatening and must be terminated. Are a life-
threatening cardiac rhythm. Ventricular dysrhythmias are considered to be very serious lifethreatening dysrhythmias, mainly because they drop cardiac output. Are not significant;
PVCs are not dangerous. Ventricular dysrhythmias are considered to be very serious, lifethreatening dysrhythmias, mainly because they drop cardiac output. Show that the rhythm is
regular. When PVCs occur, the rhythm is irregular, not regular.
Test Bank for Timby's Introductory Medical-Surgical Nursing
Loretta A Donnelly-Moreno, Brigitte Moseley
9781975172237, 9781975172268
