P wave Flashcards
What does P-wave represent?
P wave represents depolarization of the atria. It begins with impulse originating at the SA node, spreading through the atria and then reaching the AV node
Normal conduction pathways in p-wave?
Impulse originates from the SA node and then travels through fast conduction pathways (similar to Purkinjie fibers) via the anterior, middle and posterior internodal pathways. The Bachmann bundle is an internodal pathway connecting the two atria. This causes synchronized innervation of the atrial mycocytes and then impulse then finally reaches the AV node.
Normal P-wave orientation?
P waves are usually upright in II, III and aVF. There also usually positive in I, V4 to V6.
P-waves are negative in aVR and can be negative in the other leads
Inverted P-waves ?
These occur when the impulse initiation is at or below the level of the AV node. Such as in junctional rhythms. P-waves will move away from the positive electrodes of II, III and aVF giving inverted p-waves in these leads.
Using -waves to determine normal sinus rhythm?
Check the rate at which p-waves are marching to determine if they do so at similar intervals which makes the rhythm regular
Check if there are p-waves before each QRS
All p waves are of similar morphology
P-waves are upright in II, III and aVF and negative in aVR
Premature atrial complexes features?
These occur from a focus other than the SA node and therefore, will have two important features:
(1) . Different PR interval
(2) Different P-wave morphology
We can measure the normal P-P interval by placing calipers on tips of the p-wave and then for a PAC we will notice that the P-wave occurs before the regular P-P interval. If the sinus node was not reset then the next normal p-wave will occur at 2X (P-P) and this would be a compensatory pause keeping the next beats in sync. However, if the sinus node was reset then the next normal sinus beat with be before 2X.
Wandering pacemaker features?
Here we have multiple pacemakers in the atria that are sending impules. We will note the following featrues:
(1) Greater than 3 different p-wave morphologies with different PR intervals
(2) Superimposed P-waves on T-waves
Inverted P-waves in lead II ?
If we see inverted p-waves in lead II, III or aVF we should think about retrograde conduction. P-waves can be coming from the AV node which would be junctional rhythm or a low atrial ectopic pacemaker. In case of junctional rhythm, the retrograde p-wave occurs much earlier than ventricular depolarization giving a short PR interval usually less than 0.11 seconds. If a low ectopic atrial pacemaker then we will have retrograde p-waves but with a normal PR interval.
Note: LVH strain pattern on the EKG. We see aVL >11mm and deep R waves in I and S waves in V1-V3. Features of LVH strain pattern include downsloping ST-depressions and T-wave inversions in lateral leads. ST-elevations usually concave in V1-V3. Prolonged Rwave peak time >45 msec and usually LAD can be seen.
P-mitrale features and significance?
P-wave is called P-mitrale when it has following in limb leads I, II, III
Note: Does not need to be present in all leads!
(1) P-wave is longer than 0.12 seconds
(2) Has a notched M shape
(3) Duration between to top of the humps is greater than 0.04 seconds
P-mitrale indicates left atrial enlargement. It is due to severe MS, MR, AI etc. We cannot tell if this is due to hypertrophy or dilation so we use the term LAE.
Features in this EKG?
In this EKG we see P-mitrale in leads II and III indicative of LAE. We also see deep S waves in V1-V2 with ST-elevations which could be due to LVH. However, we don’t see increased voltages in lateral leads and this could be due to a prior infarct, left sided pleural effusion or obesity.
Features and significance of P-pulmonale?
P-pulmonale occurs when there is a teepee shaped p-wave in the limb leads usually II and/or III which is > 2.5 mm in height.
It signifies severe right atrial enlargement.
Features in this EKG?
Here we see a P-pulmonale
We also see that the third beat is a PAC (different morphology and PR interval)
Beat 9 has an upright p-wave in aVR and therefore, is a premature junctional complex
Note: We should compare PR intervals and P-P intervals to spot premature beats!
Other features to pay attention to when p-pulmonale is present?
We should check for right strain pattern:
(1) RBBB or RBBB type morphology (Positive R waves in V1-V3 with slurred S-waves in I, V5-V6 even if QRS <120)
(2) Right axis deviation
(3) P-pulmonale
This indicate RV and RA enlargement due to cor-pulmonale and pulmonary disease
Features of MAT?
In MAT we have the following:
(1) HR >100
(2) Three or more p-wave morphologies with varying PR intervals
(3) Superimposed P and T-waves. The atrial pacemakers are firing and ventricles are depolarizing. However, some atrial pacemakers are still firing when the ventricles are in repolarization giving P on T wave
Significance of bi-phasic p-waves in V1?
Biphasic p-waves are frequently seen in V1
These could indicate inraatrial conduction delay (IACD) which could be due to a non specefic conduction problem in the atria. Usually it is caused by atrial enlargement but the enlargement isnt severe to cause a p-mitrale or p-pulmonale. However, criteria are present to determine if bi-phasic p wave is indicative of LAE or RAE
Biphasic p-wave in V1 and LAE?
When the second half of the p-wave is wider and deeper that 0.04 s , LAE is very likely.
If the product of the height times width of the last half of the p wave is greater than or equal to 0.3 ( mm x sec) the probability of LAE is > 95%
Causes of LAE include:
hyptertension, aortic or MV disease, LV failure, RCM
Biphasic p-wave in V1 and RAE?
RAE is probably present when the first half of the biphasic p-wave is taller in V1 than the first half of the p-wave in V6.
Causes of RAE include:
COPD, PE, pulmonary HTN, MV, TV disease or left to right shunt
Evaluate for atrial enlargement in this EKG?
There is a biphasic p-wave in V1. The first part is taller than the p-wave in V6. This makes RAE likely.
Note: There is also LAD and PRWP
Evaluate of atrial enlargement in this EKG?
P-waves in precordial leads are wide but there is no notching so it is not p-mitrale pattern. The product of the width (0.7 sec) and depth (2.3 mm) of the second half of the p- wave in V1 is greater than 0.3 (1.61.) so this is LAE
Evalaute this EKG for atrial enlargement?
The biphasic p-waves in V1 are width (0.7 sec) x depth (1 mm) which is 0.7 well above 0.3 therefore giving LAE.
Note: There are symmetrical T-wave inversions which are more common in ischemic syndromes, intracranial pathology or electrolyte abnormalities. Assymetrical T-wave inversions are more common in strain patterns and benign etiologies.
Q- waves are pathological if wider than 0.03 seconds OR deepers than one third the height of the R-wave. Of these width > 0.03 s is more specefic. The Q-wave in II is slightly greater than 0.03.
Evalaute this EKG for atrial enlargement?
Here if we analyze p-waves in limb leads such as lead II we don’t have criteria for p-mitrale or p-pulmonale. We should then analyze if there is a biphasic p-wave in V1.
Here the product of width and height in V1 is > 0.3 consistent with LAE
Note: There is a flipped QRS and T-wave in V1. The R:S ratio is greater than 1 which is consistent with RVH. Another possible criteria is ST-depression in V1 to V2 which is not present here. ST-T wave abnormalities appear in right precordial leads in most cases of RVH. We should look for a prior EKG to see if these changes are new or not.
Evaluate atrial enlargement in the EKG?
In this EKG we have a prolonged QT interval and the T-wave is very close to the P-wave. We should look for a lead where p-wave and PR interval are easy to find such as V1 or V4 and then transfer it to other leads. Here we have evidence of LAE.
Making measurements when baseline seems depressed or the PR interval is depressed?`
When we measure P wave height we should measure from TP segment which is the baseline. This segment is from T of one wave to the P of another wave.
Evaluate this EKG for atrial enlargement?
P waves in lead II are 2.4 to 2.5 mm high and therefore borderline p-pulmonale. However, at the end of the P-waves they are 0.5 to 1 mm deeper. This is because the PR interval is slightly depressed. We should measure the baseline from the TP segment.
How do we diagnose biatrial enlargement on EKG?
When there is evidence of both RAE and LAE.
Evaluate EKG for atrial enlargement?
Limb leads show a p-wave which is consistent with p-pulmonale and biphasic p -wave in v1 is consistent with LAE so patient had biatrial enlargement
Also note patient had LVH with slight St elevation in V1-V3 and ST depressions in V4 to V6
Evaluate this EKG for atrial enlargement?
Here we see a P-pulmonale in Lead II
There is also a biphasic p-wave in V1 with second half of the p-wave greater than one small box (greater than 1 mm and wider than 0.04 s) which indicates LAE.
Note: There is global ST-segment depression in the setting of tachycardia. This could be due to ischemia or a Tp wave (atrial repolarization which is usually burried in the QRS complex but can appear in tachyarrythmias as a depressed ST)
