ECG Recognition:
A junctional impulse depolarizing both the atria and ventricles is characterized by:
- Negative or inverted P wave in II, III and aVF, upright in aVR and isoelectric in I.
- The negative P wave can be seen before or after the QRS.
- P wave is not seen if both the atria and ventricles are activated simultaneously because the P wave is buried in the QRS.
- In the absence of AV conduction abnormality, the PRI and RP interval is approximately 0.12 and 0.19 sec, respectively.
- An isolated inverted P wave may be seen if it failed to conduct to the ventricles
- QRS may be normal in the absence of a bundle branch block or aberration.
- Junctional rhythm rate varies from 40-60 bpm (may be as low as 30).
- Accelerated junctional rhythm is between 60-100 bpm.
- Junctional tachycardia rate is above 100 bpm.
Junctional Rhythm - This is a regular narrow
QRS complex rhythm with no distinct P waves at a rate of
about 43 bpm (1500/35 small squares).
Junctional Rhythm with a
bundle branch block. This is regular wide QRS complex rhythm with no distinct P waves at a rate of
about 38 bpm (1500/39 small squares). If this was a ventricular rhythm, the T
wave should be opposite the direction of the R wave
in lead II. Thus, it is possible to have a junctional rhythm with a bundle
branch block.
Accelerated Junctional
Rhythm -
This is a regular narrow QRS complex rhythm with an inverted P wave before the QRS with PRI of about 0.12 sec. The
rate is about 75 bpm.
Junctional
rhythm. This is a
regular narrow QRS complex rhythm with no P waves seen. The rate is about
25 bpm. The rate is computed using the 6-second method (1500/58 = 26 bpm).
Junctional Tachycardia. This is a regular narrow
QRS complex tachycardia with an inverted P wave before the QRS with a PRI of about 0.08 sec.
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