#p wave

[Photo 1: The P Wave

P wave represents:

atrial depolarization

electrical impulse from SA (sinoatrial) node to AV (atrioventricular) node through internodal pathways)

P wave should be:

0.08-0.11 seconds (2-3 small boxes)

(+) [positive] in I, II, V4, V5, V6

(-) [negative] in aVR

either in III, aVL, aVF, V1, V2, V3

P wave morphology

SA node [upright and symmetrical]

other high atrial pacemaker [upright and skewed left]

lower atrial pacemaker [inverted and asymmetrical]

morphology can help you find APCs (atrial premature complexes] (with different P waves than other complexes)

Inverted P waves indicate either:

junctional rhythm (short PRI [P-R interval]) OR

low atrial pacemaker, near AV node (normal PRI)

P-mitrale

m-shaped p wave

> [greater than] 0.12 s [seconds] in limb leads (II, III)

space between bumps > [greater than] 0.04 s [seconds] (one small box)

indicate LAE (left atrial enlargement) due to mitral stenosis (severe mitral valve dz [disease]), notched due to prolonged conduction time to L [left] atria

*memory tool* mITRALE=LAE [shape of p wave resembles m]]

[Photo 2: The P Wave (cont.)

P-pulmonale

peaked p wave AND

> [greater than] 2.5 mm high (usually in II, III)

indicate RAE (right atrial enlargement), cannot tell on ECG if hypertrophy or dilation

*memory tool* teePEE = p-Pulmonale

Intraatrial conduction delay (IACD) biphasi p waves in V1

indicate usually atrial enlargement, but not enough to form p-mitrale or p-pulmonale

RAE (right atrial enlargement) likely:

first 1/2 of biphasic p wave in V1 is taller than first 1/2 of p wave in V6

causes of RAE: COPD, pulmonary emboli, pulmonary htn [hypertension], mitral, tricuspid, or pulmonary valve dz [disease]

LAE (left atrial enlargement) likely:

second 1/2 of p wave wider and deeper than 0.04 seconds (one small box)

causes of LAE: severe systemic htn [hypertension], aortic or mitral valve dz [disease], restructive cardiomyopathy, LV [left ventricle] failure

*memory tool* Left = Longer and deeper

Bilateral enlargement

evidence of both LAE and RAE

ie: [peaked p wave in II, evidence of p-pulmonale (RAE) + wide and deep second 1/2 of biphasic p wave in V1, evidence of LAE]

OR [first 1/2 of biphasic p wave in V1 taller than first 1/2 of p wave in V6, evidence of RAE + wide and deep second 1/2 of biphasic p wave in V1, evidence of LAE]