The Normal P Wave

Lead ll therefore normally shows a uniphasic upright P wave which consists of overlapping right and lett atrial components.

In Lead ll the normal P wave does not exceed 2.5 mm in height or 0.12 sec in duration.

V1 normally shows a biphasic P wave with an initial positive and a subsequent negative component.

ln the normal P wave in V1 the area of the negative component does not exceed the area of the positive component which precedes it.

 

Right Atrial Hypertrophy, P pulmonale

The P wave in lead ll; The right atrial component is increased. So the P wave in II in right atrial hypertrophy is abnormally tall.

The P wave in V1; The right alrial component is increased. So the P wave in V1 in right atrial hypenrophy has a tall initial positive component.

ECG; Right Atrial Hypertrophy (+RVH)

The primary electrocardiographic change in right atrial hypertrophy is therefore an increase in the voltage of the P wave in Lead ll. There is a good deal of variation in the dominant direction ot right atrial depolarisation in the horizontal plane and as a result of this changes in the P wave height in V1 do not reliably occur in right atrial hypertrophy. The diagnosis of right atrial hypertrophy can therefore only safely be made from the P waves in the frontal plane leads. Lead ll usually shows the changes best.

The mean frontal plane QRS axis is + 165. There is right ventricular hypertrophy, right atrial hypertrophy and clockwise cardiac rotation.

 

 

Left Atrial Hypertrophy, P Mitrale

 

The P wave in lead II; The left atrial component is increased. The P wave in lead ll in left atrial hypertrophy is notched and broad. The second component may be tall.

The P wave in V1; The left atrial component is increased. The P wave in Lead V1 in lett atrial hyperlrophy has a dominant negative (terminal) component. It is called "P-Wave Terminal Force".

 

ECG; Left Atrial Hypertrophy

The P waves are broad and bifid in Lead ll and there is a dominant negative component to the P wave in V1. The changes are indicative of left atrial hypertrophy. ln other respects the record is within normal timits.