Quiz 2 -- PR Segment, PR Interval, and AV Blocks

Question 1

What is the PR Segment and where should it be?

Answer 1

• Part of the PR interval

- Should be at baseline

Question 2

What could cause PR Segment Depression?

Answer 2

1. Normal variant (less than or equal to 0.8 mm from baseline)
2. Pericarditis MOST COMMON (greater than 0.8 mm from baseline)
3. Atrial Infarction (very rare)

Question 3

A patient with pericarditis will present with?

Answer 3

1. Tachycardia (generally)
2. PR Segment Depression
3. Diffuse ST elevation
4. Notching of last part of QRS in lateral leads

Question 4

Where do you measure the PR Interval, and what should it normally be?

Answer 4

• Measure it in several leads and take the LONGEST value.

- Normally 0.12 to 0.20 seconds (3 to 5 small boxes)

Question 5

What would cause a short PR Interval?

Answer 5

1. Junctional Rhythm (inverted P waves)
2. Lown-Ganong-Levine Syndrome (LGL)
3. Wolff-Parkinson-White (WPW) Syndrome

Question 6

What would constitute a short PR Interval?

Answer 6

Less than 0.12 sec (2 small boxes)

Question 7

This is a benign syndrome that can be associated with tachycardias and has a short PR interval, normal P wave, and normal QRS.

Answer 7

Lown-Ganong-Levine Syndrome

Question 8

What causes the Short PR Interval in LGL?

Answer 8

Impulse travels through the James Fiber and bypasses most of the AV node.

Question 9

This is a syndrome that can be associated with tachycardias and has a short PR interval, normal P wave, wide QRS, delta wave, ST-T wave changes.

Answer 9

Wolff-Parkinson-White Syndrome

Question 10

What causes the Short PR Interval in WPW?

Answer 10

Impulse bypasses AV node through the Bundle of Kent

Question 11

What is a prolonged PR Interval indicative of? What is the criteria of a prolonged PR interval?

Answer 11

• Assc with AV blocks (Heart blocks)
• AV block = problem with conduction in the AV node or bundle of His
• *Different than BBP**

Criteria = > 0.2 seconds (1 big box)

Question 12

What is an AV Block?

Answer 12

Atria are not communicating as expected with the ventricles. Conduction is delayed, intermittent or absent. May be transient or permanent.

Question 13

What are the types of AV Blocks?

Answer 13

1. First degree
2. Second degree - Type 1 (Mobitz I or Wenkebach)
3. Second degree - Type II (Mobitz II)
4. 2:1 AV Block
5. Third degree
6. AV Dissociation

Question 14

Questions to ask regarding heart block

Answer 14

1. Are all of the PR intervals the same or do they differ?
2. Are there grouped beats (pattern)?
3. Are the P’s married to the QRS complexes?

Question 15

What is a first degree AV block?

Answer 15

Conduction delay occurring at or near the AV node.

Question 16

What are the EKG findings of a First degree AV block?

Answer 16

1. Consistently prolonged PR interval ( > 0.20 sec)
2. P wave is present and is married to every QRS
3. QRS is narrow
4. Variable rate; Regular
5. No dropped beats!!!

Question 17

What are the EKG findings of a Second degree AV block, Mobitz I, Wenckebach?

Answer 17

• P waves are present, QRS is usually narrow
• P waves are married to the QRS
• Progressive prolongation of PR interval
• Dropped beats
• Regularly Irregular pattern

Question 18

What are the EKG findings of a Second degree AV block, Mobitz II?

Answer 18

• Rate variable
• Irregular
• P wave present
• Narrow QRS
• Married to QRS
• PR Interval constant – usually normal
• INTERMITTENT DROPPED BEAT

Question 19

What is different about a 2:1 AV Block?

Answer 19

• When every other beat is dropped (2:1 ratio of P:QRS)

- Can’t tell if it’s Mobitz I or II, so you assume Mobitz II! (Assume the worst!!)

Question 20

<p>

| What are the EKG findings of a Second degree AV block, Mobitz III?</p>

Answer 20

<p>
- Complete dissociation of the P waves and QRS complexes. - Nothing is being conducted through the AV node and/or Bundle of His - Always more P waves than QRS complexes - Regular but slow rate - P waves present but not related to the QRS - WRS width depends on the type of escape rhythm (junctional vs. ventricular) - NO MARRIAGE OF P to QRS - no consistent PR interval - Atrial rate higher than ventricular rate (P > QRS)</p>

Question 21

This is a broader term for heart block. Complete Heart block is a “subset” of this, but it is not the same.

Answer 21

AV Dissociation