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
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
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”
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
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/
