You have been logged out, please login to use this function.
Login
Remember me on this computer
Forgot your password?
Resend verification email?
Practice any time
anywhere
Join Teaching Medicine to get personalized help with what you're practicing or to learn something completely new. We'll save all of your progress.
Help students
succeed with
personalized
practice
Assign our practice cases
Our Software does all the marking
Our algorithms generate feedback
You download the scores
Join Teaching Medicine For Free as
a learner
an instructor
or assistant
Continue
Learner
Instructor or Assistant
Account Details
Learner
Instructor or Assistant
Verify Account
We sent your 6 digit code to your email.
Please enter it below
Send another verification email
Practice anyone
anywhere
Join Teaching Medicine to get personalized help with what you're practicing or to learn something completely new. We'll save all of your progress.
Help students
succeed with
personalized
practice
>Find standards-aligned conten
Assign practice exercises
Track student progress
Join millions of teachers and students
Join Teaching Medicine For Free as
a learner
an instructor
or assistant
Continue
Learner
Instructor or Assistant
Account Details
Email
Please fill in the email address you used for registration. An email with a password reminder will be sent to you.
Back to login
An email has been sent to you with a temporary code. Use this code to login now, and you can change your password after you are logged in.
Resend verification email?
Reset Password
Verify Account
Resend verification email?
Skills
Dx Wisely
ECG
Chest X-ray
Blood Gases
Echocardiography
Ultrasound
CT Head
Dermatology
Neuro
Communication
For Instructors
For Researchers
About
Contact Us
Login
Sign Up
Skills
Login
Sign Up
Dx Wisely
ECG
Chest X-ray
Blood Gases
Echocardiography
Ultrasound
CT Head
Dermatology
Neuro
Communication
Inactivity Log Out
You will be logged out in
.
For your security, your session will automatically end after 20 minutes of inactivity unless you choose to stay logged in.
ECG
Level 3
Tutorial: Chamber Sizes
Please wait...
Tutorial: Chamber Sizes
Learn to assess atrial enlargement and ventricular hypertrophy on ECG.
How to level up?
Develop your skills by completing our
Practice Cases!
Choose Level
Tutorial: Chamber Sizes
Left Atrial Enlargement
Lessons
42
Times Practiced
1284
Cases Completed
1h 24m
Total Time spent
1m 24s
Average Time
Progress
Accuracy
Efficiency
Accuracy
Efficiency
1
Left Atrial Enlargement
Left Atrial Enlargement
2
Right atrial enlargement
Right atrial enlargement
3
Left Ventricular Hypertrophy
Left Ventricular Hypertrophy
4
Right Ventricular Hypertrophy
Right Ventricular Hypertrophy
Next
Next Lesson
Left Atrial Enlargement
Left atrial enlargement is abbreviated LAE. Leads II and V
1
show the P waves the best. Therefore, we will focus on those 2 leads.
The SA node is located in the right atrium (RA). Therefore, atrial depolarization starts in the RA and terminates in the left atrium (LA). Normally, the RA and LA depolarize virtually at the same time due to fast conduction through the atrial conducting fibers called Bachmann's bundle. However, in diseased states of the left atrium, conduction becomes abnormal and depolarization through the LA is delayed and/or prolonged.
Therefore, in LA disease, the first "half" of the P wave mostly represents the RA and the second "half" represents the LA. The second half of the P wave is called the
terminal portion
of the P wave. Although this is not entirely true, it is helpful to think of the P wave this way.
When the left atrium enlarges, it enlarges posteriorly and downward. The image below shows yellow lines that roughly indicate the posterior enlargement of the LA:
The RA deporalizes first with electrical activity moving
toward
V
1
seen below by the blue arrows:
Next, the LA depolarizes
away
from V
1
:
Therefore, with LAE, the P wave in V
1
will be
initially upgoing
for the first portion (red arrow below) and then
downgoing in the terminal portion
(blue arrow). This is called
biphasic
. The green arrow points to the QRS. The T wave is not seen in this image.
LAE produces a biphasic P wave in V
1
.
Here are two more examples of biphasic P waves in
V
1
:
One final detail: the width of the inverted (second) part of the P wave should be at least 40 ms (1 little square) wide. In other words, a very small downward deflection is not significant. Can you see in the above examples that the width of the downgoing part is easily > 1 little square?
In
lead II
, the findings are different. Remember that lead II measures electrical activity in the coronal plane (first image). The direction of travel of atrial depolarization is virtually parallel to the lead II (last 2 images). Therefore, P waves show up very well in lead II, but since we are measuring in a different "plane" compared to lead V
1
, the P wave changes with LAE are different.
When the LA enlarges, wave of depolarization measured in lead II behaves like 2 separate waves. The first one is the right atrium and the second one is the left atrium. The 2 waves partly overlap each other, so it creates an
M shaped P wave in lead II
. This is also called a
notched P wave
. In the diagram below, there is an extra blue and red fuzzy line to show the 2 different atrial waves:
Here are 2 examples of M shaped P waves in lead II:
One more thing: when one atrium is enlarged, it will take more time for the wave of depolarization to travel across both atria. Therefore, another diagnostic feature of LAE is a "wide" P wave, defined as > 120 ms (3 little squares). This is easy to remember because it is the same criteria for a wide QRS.
Summary of Diagnostic Criteria for LAE:
wide P wave > 120 ms
M shaped P wave in lead II
biphasic P wave in lead V
1
(initally upward, terminal portion downward)
terminal portion of V
1
is at least 1 little square wide
Next
Next Lesson