Why Junctional rhythm has huge variation in P wave morphology ?
P waves in junctional rhythm can be
- Upright
- Iso-electric
- Inverted
- or even absent
It depends upon the origin of junctional focus
- Site of entry into RA
- Ability to capture inter -nodal pathways and inter -atrial pathways ,
- VA conduction velocity
Further ,the appearance and timing of P waves will be determined by the underlying structural heart disease also.
Final message
Medical students have grown up with the belief that AV junction is a single focused point .It is true in terms of electrical circuitry of normal AV conduction .However during pathological electrical disorders ( Which arise often because of structural disorder) it should be realised the AV junction is a huge plane . Arrhythmia can occur anywhere from this plane .The entire plane can become electrically active which may also acquire the ability to conduct bi-directionally .
Dr.S.Venkatesan MD 
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