This document discusses P-wave morphology and its relationship to various cardiac rhythms. It begins by defining the P-wave and establishing criteria for normal P-wave characteristics. It then explores how deviations from these criteria can indicate conditions like atrial enlargement or ectopic rhythms. Specific arrhythmias like atrial fibrillation, flutter, sinus arrest and junctional rhythms are examined in terms of their P-wave patterns. The document emphasizes analyzing P-waves to help identify the origin of the cardiac rhythm and any underlying conduction abnormalities.

1. By: Devon Fuller EMT-P
P-WAVE AXIS AND ATRIAL
ESCAPE RHYTHMS

2. INTRODUCTION
• Proper interpretation of P-Wave axis
• P-Wave focus and morphology
• Ectopic beats involving P-Wave
• Escape rhythms and what to expect with treatment

3. P-WAVE
• Technically defined as “a summation wave generated by the depolarization front as it
transits the atria”
• This translates to the first positive deflection on an ecg that represents atrial
depolarization
• The P-Wave has criteria for being normal like the rest of the ECG
• Can be inverted, different shapes, tall, small, or even absent.
• The typical intrinsic rate represented by the depolarization of the P-Wave is 60-100 BPM
• If the P-Wave is present and the rate is below 60 BPM= Sinus Bradycardia
• If the P-Wave is present and the rate is above 100 BPM= Sinus Tachycardia
• If P-Wave is present, usually represents a normal sinus rhythm

4. P-WAVE RULES
• Normal P-Wave morphology is as follows
 Present
 Upright
 < 2.5 mm in limb leads and <1.5mm in precordial leads
 Not wider than 120 ms
 Remains same shape throughout 6 second strip
 1 P-Wave preceding a QRS complex
 Regular or Irregular

5. P-WAVE RULES CONT.
• If all of the preceding rules are in effect, the P-Wave is indicated as “regular”
• P-Waves may be notched or biphasic and still represent a normal sinus rhythm
• Use the spacing between R-R intervals to indicate if the rhythm is regular or irregular
• Equal spacing between the R-R intervals indicates “regular”
• Any deviation from these rules indicate a possible ectopic beat

6. P-WAVE CONT.
• Present
• Upright
• < 2.5 mm tall
• < 120 ms
• Same shape (assume)
• Preceding a QRS
• Regularly-Regular (assume)

7. P-WAVE AXIS
• Generally between 0 and +75
• Upright in leads I, II, and III
• Inverted in AVR
• Normal variant to be biphasic in V1 however not obvious
• If obviously biphasic in V1, a conduction issue is present
• First 1/3 of the P-Wave represents Right atrial contraction
• Last 1/3 of the P-Wave represent Left atrial contraction
• Middle 1/3 represents the signal across the Bachman Bundle (Intra-atrial bundle)
• If all are upright and symmetrical, the axis of the P-Wave is normal
• If byphasic or notched, the axis has shifted to the left or to the right

8. P-WAVE AXIS
• P-Wave axis is 62 degrees, normal variant

9. P-WAVE AXIS CONT
• Skewed axis is derived from primarily 3 determined conditions
• LAE- Left atrial enlargement
• RAE- Right atrial enlargement
• BAE- (No, not THAT bae)- Bi-atrial enlargement

10. RAE
• In right atrial enlargement, right atrial depolarization lasts longer than normal and its
waveform extends to the end of left atrial depolarization.
• Although the amplitude of the right atrial depolarization current remains unchanged, its
peak now falls on top of that of the left atrial depolarization wave.
• The combination of these two waveforms produces a P waves that is taller than normal (>
2.5 mm), although the width remains unchanged (< 120 ms).

11. LAE
• In left atrial enlargement, left atrial depolarization lasts longer than normal but its
amplitude remains unchanged.
• The height of the resultant P wave remains within normal limits but its duration is longer
than 120 ms.
• A notch (broken line) near its peak may or may not be present (“P mitrale”).

12. BI-ATRIAL ENLARGEMENT
• Combination of both LAE and RAE
• First 1/3 of the P-Wave will be peaked
• Middle 1/3 may be notched or sloped but the conduction will be delayed
• Last 1/3 will be delayed >120 ms as it reaches the isoelectric line
• P-Wave will be biphasic in lead V1

13. OTHER P-WAVE ABNORMALITIES
• Notched
• Biphasic
• Longer
• Shorter
• Taller
• Absent
• Inverted
• “Saw Tooth” – Flutter waves, AKA “F” waves
• Independent

14. P-WAVE IN ASSOCIATION TO RHYTHMS
• Normal Sinus Rhythm
 P-Wave normal, upright, preceding a QRS, same shape in 6 second strip, rhythm is
“regularly-regular”

15. ECTOPIC ATRIAL RHYTHMS
• Atrial Fibrillation
• Atrial Flutter
• Wandering Atrial Pacemaker
• Sinus Arrest
• Sinus Arrhythmia
• Sinus Exit Block
• Sick Sinus Syndrome
• Junctional Rhythm

16. ATRIAL FIBRILLATION
• Atria are not in sync
• Too much either electrical interference, electrolyte imbalance, too many pacemaker sites,
atrial hypoxia, trauma, congenital, etc..
• Can be extremely tachycardic as the signal from the atria is continuously sent to the
ventricles
• Rule for A-Fib
 P-Wave must be absent with notable electrical disturbances between the T wave and the
following QRS complex

17. ATRIAL FIBRILLATION
• Follow P-Wave Rules
• Present= No
• Upright= No
• Under 2.5 mm tall= No
• Not wider than 120 ms = No
• Same shape= No
• Preceding a QRS= No
• Irregularly-Irregular

18. ATRIAL FLUTTER
• Atria are firing too fast but IN SYNC with electrical flow
• Caused conduction delay to the ventricles either by the Internodal Pathways, Bundle of
His, AV-Node.
• Generally presents in a “Saw Tooth” pattern between QRS complexes but is technically
called F-Waves
• Will generally follow the proper rules for P-Wave morphology although will have many P-
Waves between QRS complexes.

19. ATRIAL FLUTTER
• Present= Technically yes
• Upright= Yes
• Under 2.5 mm tall= Yes
• Not wider than 120 ms= Yes
• Same shape= Yes
• 1 wave preceding a QRS= NO
• Irregularly-Regular
• Conduction deficit may be documented in coordination with P-wave to QRS ratio, I.e. 3:1

20. WANDERING ATRIAL PACEMAKER
• One of the rarest ectopic beats seen in the prehospital setting
• Patients generally know they have this condition and take medication for the same
• Often a precedes A-Fib in evolution of rhythm disturbances
• Different shapes of the P-Waves represent atrial depolarization, however from different
pacemaker sites
• Rules
 P-Waves present
 Must have 3 P-Waves that are different shapes in a 6 second strip to be considered WAP
 Still must precede a QRS complex

21. WANDERING ATRIAL PACEMAKER
• Present= Yes
• Upright=Yes
• Under 2.5 mm tall= Possibly
• Not wider than 120 ms= Possibly
• Same Shape= NO
• Preceding a QRS= Yes

22. SINUS ARREST
• Also known as Sinus Pause
• The electrical conduction from the Sinoatrial Node ceases temporarily
• If this ceases permanently, the patient goes into a Junctional rhythm
• Only 1 rule is technically defined for Sinus arrest/ Sinus pause
 Must have at least 2 seconds between electrically conducted beats with no electrical
conduction resulting on the ECG
• Often the rhythm will resume with normal P-QRS-T waves, but another pacemaker site
may generate the electrical charge if the SA node does not resume conduction
• Most commonly found on patients who take beta-blockers and calcium channel blockers

23. SINUS ARREST
• Present= Yes
• Upright= Yes
• Under 2.5mm Tall= Yes
• Not wider than 120 ms= Yes
• Same shape= Yes (depending)
• Preceding a QRS= Yes
• Regularly-Irregular

24. SINUS EXIT BLOCK
• Result of the sinoatrial signal being blocked from continuing on its conduction vector
• Often confused with a sinus pause/ sinus arrest
• Difference will be between the P-P intervals
• Sinus arrest has NO P-Wave
• Sinus exit block will have a p-wave but will appear as a “bleb” between the ECG traced
beats
• This “bleb” will only be represented by the first 1/3 of the P-Wave (right atrial conduction)
• The conduction delay may last longer than 2 seconds but other than a dropped QRS, the
rhythm will remain regular

25. SINUS EXIT BLOCK
• Present= Yes
• Upright= Yes
• Under 2.5 mm Tall= Yes
• Not wider than 120 ms= Yes
• Same Shape= Yes
• Preceding a QRS=Yes
• Regularly- Irregular

26. SINUS EXIT BLOCK VS. SINUS PAUSE

27. SINUS ARRHYTHMIA
• EVERYONE HAS IT!!
• Considered benign by most means
• Defined as a normal increase in heart rate upon inspiration
• Not considered normal if at rest, the heart increases and decreases upon no general
increase in inspiration or expiration
• General rules to follow are not set in stone, however one rule definitely remains
 AT REST, a general increase AND decrease in heart rate in otherwise healthy adults may
be defined as a malignant condition is other arrhythmias occur on an ECG tracing

28. SINUS ARRHYTMIA
• Present= Yes
• Upright= Yes
• Under 2.5 mm Tall= Yes
• Not wider than 120 ms= Yes
• Same Shape= Yes
• Preceding a QRS= Yes
• Regularly- Irregular

29. SICK SINUS SYNDROME
• Pretty easy to detect
• Technically defined as a group sinoatrial disorders
• May have two or ALL of the prior beats involved on an extended ECG tracing
• Tachy-brady disorder is often associated as the most common variant of SSS
• There are no real rules to follow in the pre-hospital setting for SSS
• You can be aware of a possibility if the patient notes to drop P-waves, become
tachycardic, bradycardic, form a junctional rhythm, atrial flutter, back to normal sinus, and
continue with a variation of ectopic rhythms

30. SICK SINUS SYNDROME
• P-wave rules?
• Nope, not this time
• Only cardia condition to have a 3 name process: Regularly-irregularly-irregular

31. JUNCTIONAL RHYTHM
• Absent or retrograde (inverted) P-Waves
• Intrinsic rate between 40-60 BPM
• Narrow QRS
• If above 60 BPM : Accelerated Junctional
• If below 40 BPM: Junctional Bradycardia
• If above 100 BPM: Junctional Tachycardia

32. JUNCTIONAL RHYTHM CONT
• SA node fails to fire, will no longer fire, is hypoxic, or dead
• The Bundle of His or the AV node takes over
• You can tell where the conduction signal is originating from depending on the ECG tracing
 If NO P-Wave is present, the origin is below the atria, typically from the Bundle of His
 If a RETROGRADE P-Wave is present, the origin of conduction is coming from either the
AV node or an additional pacemaker site at the Atria-ventricular junction, AKAABOVE the
ventricles
• In order for the rhythm to be considered Junctional, you must have absent or retrograde
P-Waves present
• In some cases, the conduction vector will be just below the Bundle of His causing a delay
in conduction backwards towards the Atria. This results in P-Waves in the ST segment

33. JUNCTIONAL RHYTHM
• Present= N0
• Upright= Absent
• Under 2.5 MM tall= Absent
• Not wider than 120 ms= Absent
• Same shape= Absent
• Preceding a QRS= Absent
• Irregularly-regular
• Possible conduction origin?

34. JUNCTIONAL RHYTHM
• Present= Yes
• Upright= No
• Under 2.5 mm tall= retrograde
• Not wider than 120 ms= yes
• Same shape= Yes
• Preceding a QRS=Yes
• Irregularly- regular
• Possible origin of conduction?

35. ST-SEGMENT P-WAVES
• Conduction origin just below the Bundle of His
• Still results in a narrow QRS
• Delay from the BOH results in ST-Segment P-Waves
• ST-Segment P-Waves may be upright, inverted, biphasic, or notched

36. SUMMARY
• Remember the rules for P-Wave determination and axis
• If the P-Wave is inverted, notched, or biphasic the axis is deviating away from the
traditional conduction vector
• Make sure the P-Waves are as follows
• Present
• Upright
• Under 2.5 mm tall
• Not wider than 120 ms
• Same shape
• 1 preceding a QRS complex

37. REFERENCES
• Skillstat.com
• Wikipedia
• Practicalclinicalskills.com
• AAOS Paramedic Tenth edition
• McGraw Hill “Paramedic”
• Clinical Cardiology: Current Practice Guidelines
• Cardiology Essentials
• http://lifeinthefastlane.com/ecg-library/basics/p-wave/