P WAVE IN ECG,ABNORMALITIES OF P WAVE IN ECG

P WAVE AND ITS ABNORMALITIES IN ECG

1. P WAVE Dr.G.VENKATA RAMANA MBBS DNB FAMILY MEDICINE

2. P Wave Overview F irst positive deflection on the ECG R epresents atrial depolarisation Characteristics of the Normal Sinus P Wave Morphology Smooth contour Monophasic in lead II Biphasic in V1 Axis Normal P wave axis is between 0° and +75° P waves should be upright in leads I and II, inverted in aVR 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

3. The Atrial Waveform – Relationship to the P wave Atrial depolarisation proceeds sequentially from right to left, with the right atrium activated before the left atrium The right and left atrial waveforms summate to form the P wave F irst 1/3 of the P wave  R ight atrial activation F inal 1/3 of the P wave  L eft atrial activation M iddle 1/3 of the P wave  C ombination of the two In most leads (e.g. lead II), the right and left atrial waveforms move in the same direction, forming a monophasic P wave However, in lead V1 the right and left atrial waveforms move in opposite directions This produces a biphasic P wave with the initial positive deflection corresponding to right atrial activation and the subsequent negative deflection denoting left atrial activation

4. 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

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

6. P WAVE Present or Absent If P waves absent Completely absent Intermittently absent Present but not obvious If P waves present look for Morphology Uniformity Amplitude Duration No of P waves per QRS complex

7. P waves are completely absent A trial fibrillation S inus arrest or SA block (prolonged) Hyperkalemia P waves are present but not obvious AVNRT Third degree AV block P waves are intermittently absent S inus arrest or SA block (intermittent ) Are any P waves inverted? If ‘yes’, consider: E lectrode misplacement D extrocardia R etrograde atrial depolarization

8. Atrial fibrillation Irregular ventricular response Coarse fibrillatory waves are visible in V1 “ Sagging” ST segment depression is visible in V6, II, III and aVF , suggestive of  digoxin effect

9. SINUS ARREST OR SA BLOCK Anatomical Basis The SA node consists of two main groups of cells: A central core of  pacemaking cells ( P cells ) that produce the sinus impulses An outer layer of transitional cells ( T cells ) that transmit the sinus impulses out into the right atrium. Sinus node dysfunction can result from either: Failure of the P cells to produce an impulse This leads to sinus pauses and sinus arrest Failure of the T cells to transmit the impulse This leads to sino -atrial exit block

10. Common P Wave Abnormalities P pulmonale (peaked P waves), seen with right atrial enlargement P mitrale (bifid P waves), seen with left atrial enlargement P wave inversion, seen with ectopic atrial and junctional rhythms Variable P wave morphology, seen in multifocal atrial rhythms

11. Right Atrial Enlargement 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 ) 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

12. Causes of right atrial enlargement Primary pulmonary hypertension Secondary pulmonary hypertension chronic bronchitis emphysema massive pulmonary embolism Pulmonary stenosis Tricuspid stenosis

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

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

15. P Pulmonale The presence of tall, peaked P waves in lead II is a sign of  right atrial enlargement, usually due to  pulmonary hypertension  (e.g.  cor pulmonale  from chronic respiratory disease)

16. Left Atrial Enlargement In left atrial enlargement, 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 ”) 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 In V1 Biphasic P wave with terminal negative portion > 40 ms duration Biphasic P wave with terminal negative portion > 1mm deep

17. P Mitrale The presence of broad, notched (bifid) P waves in lead II is a sign of  left atrial enlargement, classically due to  mitral stenosis

18. P waves with terminal portion > 1mm deep in V1

19. Biatrial Enlargement Biatrial enlargement is diagnosed when criteria for both right and left atrial enlargement are present on the same ECG The spectrum of P-wave changes in leads II and V1 with right, left and bi-atrial enlargement:

20. Inverted P Waves P-wave inversion indicates a non-sinus origin of the P waves Causes Dextrocardia Abnormal atrial depolarization A trial ectopics AV junctional rhythms V entricular tachycardia ( retrogradely conducted) V entricular ectopics ( retrogradely conducted )

21. Variable P-Wave Morphology 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:

22. If ≥ 3 different P wave morphologies are seen and the rate is ≥ 100, then  multifocal atrial tachycardia (MAT)   is diagnosed: