P WAVES

qrs complexes ⇢ ⇠ invervals
ecg steps

Are they uniform ?

yes

all P waves look the same

electrical waves originate from the same automaticity focus

(e.g. normal sinus rhythm, atrial tachycardia, junctional escape rhythm)

no

P waves look different from each other

electrical waves originate from multiple different automaticity foci

(e.g. mutifocal atrial tachycardia, wandering atrial pacemaker)

Are they upright or inverted ?

upright

P waves are positively deflected

atrial depolarization waves run towards ECG leads

(e.g. normal sinus rhythm, sinus or atrial arrhythmias)

inverted

P waves are negatively deflected

atrial depolarization waves run away from ECG leads

(e.g. atrial or junctional arrhythmias)
 

Is there atrial enlargement ?




Normal atria: RA depolarization moves towards lead V1 (solid arrow). LA depolarization moves away from lead V1 (dashed arrow). Both atrial depolarization move towards lead II.

Enlarged RA: Large RA produces stronger depolarization thereby pulling the net electrical vector towards V1 (positive deflection in first 1/3 of P wave) and towards II (higher positive deflection of P).

Enlarged LA: Large LA produces stronger depolarization thereby pulling the net electrical vector away from V1 (negative deflection in last 1/3 of P wave) and towards towards II (bifid P).

Enlarged RA+LA: Combined effect of enlarged RA and LA

qrs complexes ⇢ ⇠ intervals
related topics



sinus arrhythmia
atrial arrhythmia
junctional arrhythmia
ecg home page
conduction system
hypertrophy
arrhythmia