Chapter 5

Question 1

Why is there a delay in the electrical impulse?

Answer 1

Allows the atria to contract and complete filling of ventricles before the next ventricular contraction

Question 2

Job of the Bundle of His?

Answer 2

Connects AV node with bundle branches

Has pacemaker cells capable of discharging at a rhythmic rate of 40-60bpm

Question 3

When would the AV junction assume responsibility for pacing the heart? Why?

Answer 3

The AV junction will assume responsibility when the SA node fails to discharge (sinus arrest)

SA node impulse is generated but blocked as it exists the SA node (SA block)

The rate of discharge of the SA node is slower than that of the AV junction (sinus bradycardia or the slower phase of the sinus arrhythmia)

An impulse from the SA node is generated and is conducted through the atria but is not conducted to the ventricles (AV block)

Question 4

In what direction does the electrical impulse travel to activate the atria?

Answer 4

If the AV junction paces the heart, the electrical impulse must travel in a backward (retrograde) direction to activate the atria

Question 5

Sinus arrest

Answer 5

Missing beat - SA node not firing properly - after missing beat, next one is late

Question 6

AV junction (P waves)

Answer 6

1. With a sinus rhythm, the P wave is positive (upright) because the wave of depolarization is moving toward the positive electrode
2. P wave associated with a junctional beat may be inverted (retrograde) and appear before the QRS
3. P wave may be hidden by the QRS
4. P wave can appear after the QRS

Question 7

Premature Junctional Complexes (PJC)

Answer 7

Occurs when an irritable site within the AV node junction fires before the next expected sinus beat

QRS will usually measure 0.11sec or less (narrow QRS - supraventricular)

Often followed by a noncompensatory (incomplete) pause

May occur in patterns

Question 8

How to recognize PJCs?

Answer 8

Rhythm: irregular because of the premature beats

Rate: usually within normal range but depends on underlying rhythm

P waves: may occur before, during or after the QRS; if visible, the P wave is inverted in leads II, III, and aVF

PR interval: if a P wave occurs before the QRS, the PR interval will usually be 0.12 sec or less; if no P wave occurs before the QRS, there will be no PR interval

QRS duration: 0.11sec or less unless abnormally conducted

Question 9

What causes PJCs?

Answer 9

1. Acute coronary syndromes
2. Digitalis toxicity
3. Electrolyte imbalance
4. Heart failure
5. Mental and physical fatigue
6. Rheumatic heart disease
7. Stimulants (caffeine, tobacco, cocaine)
8. Sympathomimetics
   9.valvular heart disease

Question 10

What to do about PJCs?

Answer 10

Most individuals with PJCs are asymptomatic

PJCs may lead to symptoms of palpitations or the feeling of skipped beats

Lightheadedness, dizziness, and other signs of decreased cardiac output can occur if PJCs are frequent

If PJCs occur because of the ingestion of stimulants or digitalis toxicity, these substances should be withheld.

Question 11

Junctional Escape Beats

Answer 11

Junctional escape beat originates in the AV junction and appears LATE (after the next expected beat of the underlying rhythm

A JEB is protective - preventing cardiac standstill

Question 12

Characteristics of a Junctional escape beat

Answer 12

Rhythm: irregular because of the late beat

Rate: depends on rhythm

P waves: inverted before or after QRS or absent

PR interval: 0.12-0.20sec and constant

QRS duration: 0.11sec or less (narrow)

Question 13

Junctional Escape Rhythm

Answer 13

When you have 3 JEB in a row, it is called a junctional escape rhythm

Several sequential junctional escape beats

Intristic rate of the AV junction is 40-60bpm

If the AV junction paces the heart at a rate slower than 40bpm, the resulting rhythm is called junctional bradycardia

Question 14

How to recognize junctional rhythm?

Answer 14

Rhythm: regular

Rate: 40-60bpm

P waves: may occur before, during or after the QRS; if visible, the P wave is inverted in leads II, III, and aVF

PR interval: if P wave occurs before QRS, the PR interval will usually be 0.12sec or less; if no P wave occurs, there will be no PR interval

QRS duration: 0.11sec or less unless abnormally conducted (narrow)

Question 15

Causes of junctional rhythm

Answer 15

1. Acute coronary syndrome (notably inferior wall MI)
2. Effects of medications including amiodarone, beta blockers, calcium channel blockers, digitalis
3. Hypokalemia
4. Immediately after cardiac surgery
5. Increased parasympathetic tone
6. Obstructive sleep apnea
7. Rheumatic heart disease
8. SA node disease
9. valvular disease

Question 16

What to do about junctional rhythm? (asymptomatic)

Answer 16

Patient may be asymptomatic or may experience signs and symptoms associated with the slow heart rate and decreased cardiac output

If the patient is experiencing symptoms, try to determine their frequency, timing, duration, severity, longevity, circumstances, triggers, and alleviating factors

Question 17

What to do about junctional rhythm? (Signs and symptoms related to slow heart rate)

Answer 17

1. Apply a pulse oximeter
2. Administer supplemental oxygen, if indicated
3. Establish intravenous (IV) access
4. Obtain a 12 lead ECG
5. Administer IV atropine
6. Reassess the patient; continue monitoring

Question 18

Accelerated Junctional Rhythm

Answer 18

An ectopic rhythm caused by abnormal automaticity of the bundle of his

Results in regular ventricular response at rate of 60-100bpm

Question 19

How to recognize atrial junctional rhythm?

Answer 19

Rhythm: regular

Rate: 60-100bpm

P waves: may occurs before, during or after the QRS; if visible, the P wave is inverted in leads II, III, and aVF (retrograde P waves)

PR intervals: if a P wave occurs before the QRS, the PR interval will usually be 0.12sec or less; if no P wave occurs before the QRS, no PRI

QRS duration: 0.11sec or less unless abnormally conducted (narrow)

Question 20

What causes AJR?

Answer 20

1. Acute myocardial infraction
2. Cardiac surgery
3. Chronic obstructive pulmonary disease
4. Digitalis toxicity
5. Hypokalemia
6. Rheumatic fever

Question 21

What to do about AJR?

Answer 21

Patient may be asymptomatic but monitor closely

If the rhythm is caused by digitalis toxicity, this medication should be withheld

Question 22

Junctional tachycardia

Answer 22

Ectopic rhythm that begins in the bundle of his

Exists when three or more sequential PJCs occur at a rate more than 100bpm

Question 23

How to recognize junctional tachycardia?

Answer 23

Rhythm: ventricular rhythm usually regular, but may be irregular

Rate: 101-220bpm

P waves: may occur before, during or after the QRS; if visible the P wave is inverted in leads II, III, aVF (retrograde P waves - before QRS)

PR interval: none

QRS duration: 0.11sec or less - narrow QRS

Question 24

Nonparoxysmal (gradual onset) junctional tachycardia

Answer 24

Benign dysrhythmia that is usually associated with a gradual increase in rate

Rarely exceeds 120bpm

Question 25

Paroxysmal junctional tachycardia

Answer 25

Starts and ends suddenly Often precipitated by a PJC Ventricular rate is generally faster, at a rate of 140bpm or more

Question 26

What causes junctional tachycardia?

Answer 26

Disorder of impulse formation (automaticity) Uncommon in adults but may occur because of -acute coronary syndromes -digitalis toxicity -heart failure -theophylline administration

Question 27

What to do about junctional tachycardia?

Answer 27

Patient may be asymptomatic With sustained ventricular rates of 150bpm or more, the patient may complain of fatigue, palpitations or chest discomfort or may experience syncope Decreased cardiac output may result because of the fast ventricular rate Depending on severity of the symptoms Observe patient and if symptomatic: -apply pulse oximeter, administer oxygen -establish IV access -obtain 12 lead ECG -Vagal maneuvers, adenosine -Possible beta blocker, calcium channel blocker, if no contraindications exist -synchronized cardioversion is not indicated

Question 28

Select the correct statements about PJCs A. A noncompensatory (incomplete) pause often follows a PJC B. Unlike premature atrial complexes, PJCs do not occur in patters C. If seen, the P wave of a PJC is negative and may appear before or after the QRS complex D. A PJC begins within the AV junction and appears earlier than the next expected beat of the underlying rhythm

Answer 28

A, C, D A PJC occurs when an irritable site within the AV junction fires before the next essay no impulse is ready to fire, interrupting the underlying rhythm. PJCs may occur as single beats or patterns (couplets, bigeminy, trigeminy, quadrigeminy). Noncompensable (incomplete) often follows a PJC. This pause represents the delay during which the essay note resets its rhythm for the next beat. When the P wave of a PJC is seen, it is a negative and may appear before or after the QRS complex

Question 29

An accelerated junctional rhythm is identified by a regular ventricular response occurring at the rate of: A. 20 to 40bpm B. 40 to 60bpm C. 61 to 100bpm D. 101 to 180bpm

Answer 29

C An accelerated junctional rhythm is dysrhythmia originating in the AV bundle with a ventricular rate between 61 and 100 Bpm

Question 30

The term junctional bradycardia is used to describe a rhythm that is junctional in origin with: A. An atrial rate of 40 to 60bpm B. An atrial rate slower than 60bpm C. A ventricular rate of 40 to 60bpm D. A ventricular rate slower than 40bpm

Answer 30

D If the AV junction paces the heart at a rate slower than 40bpm, the resulting rhythm is called junctional bradycardia. This wording may seem confusing because the AV junctions normal pacing rate (40 to 60bpm) is Bradycardic. However, the term junctional bradycardia refers to a rate slower than normal for the AV junction.

Question 31

When viewing a junctional rhythm in lead II, where is the P wave location on the ECG if ventricular depolarization precedes atrial depolarization? A. Before the QRS complex B. During the QRS complex C. After the QRS complex

Answer 31

C If the AV junction paces the heart, the electrical impulse must travel in a backward (retrograde) direction to activate the atria. If a P wave is seen, it will be converted in leads II, III, and aVF because the impulse is traveling away from the positive electrode. If the atria depolarize before the ventricles, an inverted P will be seen before the QRS complex, and the PR interval will usually measure 0.12 seconds or less. The interval is shorter than usual because an impulse that begins in the AV junction does not have to travel as far to stimulate the ventricles. The atria ventricles depolarize at the same time, a P wave will not be visible because it will be hidden in the QRS complex. When the atria are depolarized the ventricles, the P typically distorts the end of the QRS complex and an inverted P wave will appear after the QRS

Question 32

In rhythms originating from the AV junction, the QRS duration is typically _________ or less unless an intraventricular conduction delay exists A. 0.04sec B. 0.11sec C. 0.14sec D. 0.20sec

Answer 32

B The QRS duration associated with a rhythm that begins in the AV junction measures 0.11 second or less if conduction through the bundle branches, Purkinje fiber, and ventricles is normal

Question 33

Select the correct statements regarding junctional dysrhythmias A. The intrinsic rate of the AV junction is 40 to 60bpm B. Junctional dysrhythmias may be seen in acute coronary syndromes C. An accelerated junctional rhythm is a potentially life threatening dysrhythmia D. The ventricular rhythm associated with junctional dysrhythmias is usually very regular

Answer 33

A, B, D The patient with an accelerated junctional rhythm is usually a symptomatic because the ventricular rate is 61 to 100 bpm which is the same rate as sinus rhythm

Question 34

The primary waveform used to differentiate PJCs from PACs is the A. P wave B. Q wave C. R wave D. T wave

Answer 34

A You can usually tell the difference between a PAC and a PJC by the P wave. A PAC typically has an upright P way before the QRS complex in Leads II, III, aVF. A P we may or may not be present with a PJC. If a P is present, it is inverted (retrograde) and may precede or follow the QRS. PJCs can be misdiagnosed when the P wave of a PAC is buried in the proceeding T wave

Question 35

A 63 year old man is complaining of dizziness that began about 45min ago while cleaning his garage. Because the patients oxygen level on room air was 88%, supplemental oxygen is being administered. The cardiac monitor has been applied, revealing the rhythm in Fig. 5.10. A coworker is attempting to establish intravenous access. Which of the following statements are true about this patients cardiac rhythm? A. The atrial rhythm is regular B. The QRS complex is narrow C. ST segment elevation is present D. The ventricular rhythm is regular E. There are more P waves than QRS complexes

Answer 35

B, D In this rhythm strip the atrial rate and rhythm cannot be determined because P waves are not visible. The ventricular rhythm is regular and the QRS is narrow, measuring 0.08 seconds

Question 36

A 63 year old man is complaining of dizziness that began about 45min ago while cleaning his garage. Because the patients oxygen level on room air was 88%, supplemental oxygen is being administered. The cardiac monitor has been applied, revealing the rhythm in Fig. 5.10. A coworker is attempting to establish intravenous access. The rhythm shown on the cardiac monitor is A. Sinus bradycardia B. Junctional bradycardia C. Junctional escape rhythm D. Accelerated junctional rhythm

Answer 36

B The cardiac monitor shows junctional bradycardia at 32 bpm with ST segment depression and inverted T waves

Question 37

A 63 year old man is complaining of dizziness that began about 45min ago while cleaning his garage. Because the patients oxygen level on room air was 88%, supplemental oxygen is being administered. The cardiac monitor has been applied, revealing the rhythm in Fig. 5.10. A coworker is attempting to establish intravenous access. The patients blood pressure is 82/50mm hg. Ventilation is 16. He states his normal blood pressure is about 130/80mm hg. The patient denies chest discomfort and states that he takes no prescription medication. His skin is cool, pink and moist, and his breath sounds are clear. Intravenous access has been successfully established. Based on the information provided, which of the following states is true regarding this patient situation? A. Because the patient is symptomatic with this rhythm, a vagal maneuver should be attempted B. The patient is symptomatic with this rhythm. Obtain a 12 lead ECG then administer atropine IV C. Therapeutic interventions are not indicated because there is no evidence of ST segment elevation on the cardiac monitor D. Although the patient is complaining of dizziness, this symptom does not warrant any further intervention other than cardiac monitoring at this time

Answer 37

B Although there is no evidence of ST segment elevation on the cardiac monitor , this patient is symptomatic with his heart rate, evidenced by his dizziness and hypertension. Treatment of symptomatic bradycardia should include applying a pulse oximeter, administering supplemental oxygen (if indicated), and establishing IV access, which has already been done. Obtain a 12 lead ECG and then administer atropine IV. Reassess the patient response to your interventions and continue monitoring. Because vagal maneuvers are used to attempt to slow the heart rate of some tachycardia, and this patient is bradycardic, vagal maneuvers are contraindicated in the situation