What is the PR Segment and where should it be?
- Part of the PR interval
- Should be at baseline
What could cause PR Segment Depression?
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)
A patient with pericarditis will present with?
1. Tachycardia (generally)
2. PR Segment Depression
3. Diffuse ST elevation
4. Notching of last part of QRS in lateral leads
Where do you measure the PR Interval, and what should it normally be?
- Measure it in several leads and take the LONGEST value.
- Normally 0.12 to 0.20 seconds (3 to 5 small boxes)
What would cause a short PR Interval?
1. Junctional Rhythm (inverted P waves)
2. Lown-Ganong-Levine Syndrome (LGL)
3. Wolff-Parkinson-White (WPW) Syndrome
What would constitute a short PR Interval?
Less than 0.12 sec (2 small boxes)
This is a benign syndrome that can be associated with tachycardias and has a short PR interval, normal P wave, and normal QRS.
What causes the Short PR Interval in LGL?
Impulse travels through the James Fiber and bypasses most of the AV node.
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.
What causes the Short PR Interval in WPW?
Impulse bypasses AV node through the Bundle of Kent
What is a prolonged PR Interval indicative of? What is the criteria of a prolonged PR interval?
- 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)
What is an AV Block?
Atria are not communicating as expected with the ventricles. Conduction is delayed, intermittent or absent. May be transient or permanent.
What are the types of AV Blocks?
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
Questions to ask regarding heart block
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?
What is a first degree AV block?
Conduction delay occurring at or near the AV node.
What are the EKG findings of a First degree AV block?
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!!!
What are the EKG findings of a Second degree AV block, Mobitz I, Wenckebach?
- 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
What are the EKG findings of a Second degree AV block, Mobitz II?
- Rate variable
- P wave present
- Narrow QRS
- Married to QRS
- PR Interval constant -- usually normal
- INTERMITTENT DROPPED BEAT
What is different about a 2:1 AV Block?
- 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!!)
What are the EKG findings of a Second degree AV block, Mobitz III?
- 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)