ECG Level 3 Tutorial: Chamber Sizes
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Tutorial: Chamber Sizes
Learn to assess atrial enlargement and ventricular hypertrophy on ECG.
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Tutorial: Chamber Sizes Right atrial enlargement
Lessons
42
Times Practiced
1284
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
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1 Left Atrial Enlargement Left Atrial Enlargement
Current lesson 2 Right atrial enlargement Right atrial enlargement
3 Left Ventricular Hypertrophy Left Ventricular Hypertrophy
4 Right Ventricular Hypertrophy Right Ventricular Hypertrophy
Right atrial enlargement
Right atrial enlargement is abbreviated RAE. Leads II and V1 show the P waves the best. We will focus on these leads.

When the right atrium enlarges the electrical signal becomes stronger in the direction of the axis of lead II:
   


As a result, the P wave in lead II is taller. A P wave that is > 2.5 mm in lead II is diagnostic of RAE.  These P waves are taller than 2.5 mm. Red arrow = P wave, blue arrow = QRS, green arrow = T wave.
  

The P wave shape is often pointy. This is another finding of RAE.

The enlarged RA will also create a stronger electrical signal toward V1 as seen in the diagram. This will result in a taller P wave in V1, but only for the first half of the P wave.


A P wave that is 1.5 mm tall in V1 is suggestive of RAE. This finding however, is not required to make the diagnosis.
Red arrow = P wave     Blue arrow = QRS


If the RA gets really big, it can grow toward the left. (see diagram below). If it does this, then the final part RA depolarization will be away from V1 and cause an inverted waveform. This is similar to LEFT atrial enlargement, but it does not mean the LA is enlarged.


In contrast to LEFT atrial enlargment, the P wave duration is normal (< 120 ms or 3 little squares) with RAE. Check the ECG above to see that even though there is a biphasic P wave in V1 (suggesting LAE), the P wave width is < 120 ms.

Of course, you can have RAE and LAE at the same time, so a wide P wave does not rule out RAE.

Summary of diagnostic criteria for RAE:  (in brackets = minor criteria)
  • P wave taller than 2.5 mm in lead II
  • P wave is usually pointy
  • (P wave taller than 1.5 mm in lead V1)
  • (P wave duration < 120 ms)