The P wave is the first positive deflection on the ECG. It represents atrial depolarisation. Normal duration: < 0.12 s (< 120ms or 3 small squares)

1. - Dr. Akif A.B

4. P Wave
 The P wave is the first positive deflection on the
ECG
 It represents atrial depolarisation
 Normal duration: < 0.12 s (< 120ms or 3 small
squares)

5. Characteristics of the Normal
Sinus P Wave
 Morphology
 Smooth contour
 Monophasic in lead II
 Biphasic in V1
 Duration
 < 0.12 s (<120ms or 3 small squares)
 Amplitude
 < 2.5 mm (0.25mV) in the limb leads
 < 1.5 mm (0.15mV) in the precordial leads
 Atrial abnormalities are most easily seen in the inferior leads
(II, III and aVF) and lead V1, as the P waves are most prominent
in these leads

6. Normal P-wave Morphology –
Lead II
 The right atrial depolarisation wave (brown)
precedes that of the left atrium (blue)
 The combined depolarisation wave, the P wave,
is less than 120 ms wide and less than 2.5 mm
high

7. Normal P-wave Morphology –
Lead V1
 The P wave is typically biphasic in V1, with
similar sizes of the positive and negative
deflections

8. Inverted P Waves
 P-wave inversion in the inferior leads indicates
a non-sinus origin of the P waves
 When the PR interval is < 120 ms, the origin is
in the AV junction (e.g. accelerated junctional
rhythm)

10.  When the PR interval is ≥ 120 ms, the origin is
within the atria (e.g. ectopic atrial rhythm)

11. MULTIFOCAL ATRIAL RHYTHM
 The presence of multiple P wave morphologies
indicates multiple ectopic pacemakers within the
atria and/or AV junction
 If ≥ 3 different P wave morphologies are seen,
then multifocal atrial rhythm is diagnosed

12. MULTIFOCAL ATRIAL
TACHYCARDIA
 If ≥ 3 different P wave morphologies are seen and
the rate is ≥ 100, then multifocal atrial
tachycardia (MAT) is diagnosed

14. Right Atrial Enlargement –
Lead II
 In right atrial enlargement, right atrial depolarisation lasts
longer than normal and its waveform extends to the end of left
atrial depolarisation
 Although the amplitude of the right atrial depolarisation current
remains unchanged, its peak now falls on top of that of the
left atrial depolarisation 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)

15. ECG Criteria of Right Atrial
Enlargement
 Right atrial enlargement produces a peaked P
wave (P pulmonale) with amplitude:
 > 2.5 mm in the inferior leads (II, III and AVF)
 > 1.5 mm in V1 and V2

17. Causes of Right Atrial
Enlargement
 The principal cause is pulmonary
hypertension due to:
 Chronic lung disease (cor pulmonale)
 Tricuspid stenosis
 Congenital heart disease (pulmonary stenosis,
Tetralogy of Fallot)
 Primary pulmonary hypertension

18. • Right atrial enlargement: P pulmonale
• P wave amplitude > 2.5mm in leads II, III and aVF

19. Right atrial
enlargement:
P wave amplitude > 1.5 mm
in V1 and V2

20. Left Atrial Enlargement

21.  Left atrial enlargement (LAE) is due to pressure
or volume overload of the left atrium
 LAE is often a precursor to atrial fibrillation

22. Left Atrial Enlargement – Lead
II
 Left atrial depolarisation lasts longer than
normal but its amplitude remains unchanged
 Therefore, 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”)

23. P wave changes with Left Atrial
Enlargement

24. ECG Criteria for Left Atrial
Enlargement
 LAE produces a broad, bifid P wave in lead II
(P mitrale) and enlarges the terminal negative
portion of the P wave in V1.
 In lead II
 Bifid P wave with > 40 ms between the two peaks
 Total P wave duration > 110 ms

25.  In V1
 Biphasic P wave with terminal negative portion >
40 ms duration
 Biphasic P wave with terminal negative portion >
1mm deep

26. Causes of left atrial
hypertrophy
 In isolation:
 Classically seen with mitral stenosis
 In association with left ventricular
hypertrophy
 Systemic hypertension
 Aortic stenosis
 Mitral incompetence
 Hypertrophic cardiomyopathy

28. Biatrial Enlargement Definition
 Biatrial enlargement is diagnosed when criteria
for both right and left atrial enlargement are
present on the same ECG
 The diagnosis of biatrial enlargement requires
criteria for LAE and RAE to be met in either lead
II, lead V1 or a combination of leads

29. ECG Criteria for Biatrial
Enlargement
In lead II
Bifid P wave with
Amplitude ≥ 2.5mm AND
Duration ≥ 120 ms
In V1
Biphasic P waves with
Initial positive deflection ≥ 1.5mm tall AND
Terminal negative deflection ≥ 1mm
deep AND
Terminal negative deflection ≥ 40 ms
duration

30. Biphasic P waves in V1 with a very tall positive deflection (almost 3
mm in height) and a negative deflection that is both deep (> 1 mm)
and wide (> 40 ms)

31. Biatrial enlargement:
• P waves in lead II are tall (> 2.5mm) and wide (> 120
ms)
• P waves in V2 are tall (> 1.5 mm), while the terminal
negative portion of V1 is deep (> 1mm) and wide (> 40
ms)

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