Diagnostic criteria

  Only one of three, four or more P waves is conducted to the ventricles.

 
Most of the P waves are not followed by a QRS complex.





ECG 1a. The patient's cardiac rhythm on admission is atrial tachycardia, complete AV block and nodal rhythm (narrow QRS
rhythm).
P waves are regular but the rate is > 100/minute . P waves are NOT related to QRS complexes .
Narrow QRS complexes
denote nodal rhythm
.


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ECG 1b. Next day, his ECG shows 2:1 AV block. Her
Only 1 of every 2 P waves can be conducted to the ventricles.


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ECG 1c. 3:1 AV block (high degree AV block). Only one of every 3
P waves can be conducted to the ventricles.
The PR intervals of the conducted P waves are fixed (200 ms).


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ECG 1d. The same patient's ECG 4 days later: complete AV block and nodal rhtyhm (narrow QRS rhythm) is seen but now
there is no atrial tachycardia.
P waves are regular but not tachycardic . P waves are not related to the QRS complexes .


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ECG 2. 5:1 AV block (high degree AV block). Only
1 of every 5 P waves can be conducted to the ventricles, while 4 of them
cannot be conducted.


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ECG 3a. The ECG tracing above is from the Holter recording of a 77 years-old woman complaining of dizziness. She was
referred to a Cardiologist by the Neurologist. This Holter tracing has 3 channels and the tracing below is the continuation of
the above rhythm. The tracing shows high degree AV block. On the left side of the upper tracing, there is
a normally
conducted P wave
. Then an ectopic atrial focus fires but fails to depolarize the ventricles . After this premature atrial beat
with a negative P wave configuration,
sinus P waves follow but they also fail to depolarize the ventricles resulting in
a pause of 6.5 seconds. At the end of this pause
P waves again start to be conducted to the ventricles.


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ECG 3b. Another tracing from the same patient's Holter recording: At the left side of the upper tracing
a normally conducted
P wave
is seen. Then an ectopic atrial focus fires but cannot succeed to depolarize the ventricles . Then sinus P waves follow
but they fail to depolarize the ventricles
resulting in a pause of 6.2 seconds. At the end, a nodal escape beat comes .
The
P wave coming at the same time coincides with the ST segment of the nodal escape beat.
Afterwards, normal conduction of
the P waves to the ventricles resume.


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ECG 3c. Another tracing from the same patient's Holter recording: At the left side of the upper tracing
a normally conducted
P wave
is seen. Later on a pause of 8.3 seconds follows throughout which no P wave can be conducted to the ventricles . Then
a junctional escape beat comes . But the following 5 P waves still cannot be conducted to the ventricles . There is another
nodal escape beat
at the right lower corner of the tracing. The P wave preceeding the second nodal beat is not related to it,
since
the interval between them is longer than a normal PR interval (compare it to the PR interval following the P wave at the
left upper corner
).