Lecture 7: EKG Flashcards
Standard 12-lead ECG. Where do you put leads I, II, and III?
6 precordial (V1 - 6), 6 limb leads (I, II, III, aVR, aVL, aVF); I = right arm, II = left arm, III = left leg
V1
Right 4th intercostal space
V2
Left 4th intercostal space
V3
Halfway between V2 and V4
V4
Left 5th intercostal space, mid clavicular line
V5
Horizontal to V4, anterior axillary line
V6
Horizontal to V5, mid-axillary line
Lead I lies at __ degrees and represents…
0; right arm –> left arm
Lead II lies at __ degrees and represents…
+60; right arm –> left leg
Lead III lies at __ degrees and represents…
+120, left arm –> left leg
Heart lies between…
0 and 90 degrees
aVR is at ___ degrees
-150
aVF is at ___ degrees
+90
aVL is at ___ degrees
-30
In a normal heart, what leads should be upright?
Lead I, II, III, aVF, aVL
What should be upside down?
aVR
II, III, aVF…
Inferior wall of L ventricle
I, aVL…
Lateral wall of L ventricle
What else tells us about the lateral wall?
V5, V6
Each small box is…(horizontally)
40 ms
Each small box is…(vertically)
0.1 mV
P wave is depolarization of the…
SA node (time it takes for wave to spread through atria)
Time it takes depolarization to get from SA node to the AV node
PR interval
Time it takes ventricles to depolarize after AV node. How long?
QRS interval; 100 ms
What is the “Q”
First negative deflection
What is the “S”
Second negative deflection
T wave is…
Repolarization
Normal EKG requires looking for…
Normal waves (P, QRS, T) and intervals (PR, QRS, QT); normal rate, rhythm, axis
Abnormal P wave (left/right)
Height > 2.5 mm in lead II = R atrial enlargement; two humps in lead II = L atrial enlargement
Where is the best place to view P wave?
Lead II because SA node is ~60 degrees axis
Normal PR interval; what lead?
120 - 200 ms (3-5 small squares); no particular lead (all should have same interval)
Normal QRS complex; what lead? What if it’s broad?
bundle branch block; V1
Normal QT interval requires you to know what two terms…How long?
QT and QTc (corrected for HR);
How to “cheat” calculate QTc
HR > 60, add 20 ms for each 10 increase in HR; if HR
EKG indication Normal Sinus Rhythm (3)
P wave upright in I, upright in II, inverted in aVR; each P wave followed by QRS, P wave rate = 60-100 bpm (
Premature atrial contraction. How do you know it’s atrial?
“Extra/Premature beat” coming from another (non-SA node) atrial foci…it’s atrial because you have a P wave.
Premature ventricular contraction. How do you know it’s ventricular?
“Extra/Premature beat” coming from a ventricular foci…it’s ventricular because the morphology of the QRS is BROAD (non-Purkinje fiber depolarization is slow)
How can we see dextrocardia?
P wave present but not in sinus node morphology (inverted in I, upright in II, inverted in aVR) w/ reverse R-wave progression along chest leads
How can we tell if we’ve switched the leads?
P wave present but not in sinus node morphology (inverted in I, upright in II, inverted in aVR) w/ normal R-wave progression along chest leads
How do you calculate rate?
1500/n (n = number of smalls squares between R-R)
How many boxes = 60 bpm. What are the other “Cheat” times?
5 big squares; 1 big square = 300, 150, 100, 75, 60…
-90 to 0
Left deviation
0 - 90
Normal
90 - 0
Right deviation
0 - -90
Indeterminant
If both I and aVF are upright…Normal/Abnormal?
Normal (normal people are always upright)
For axis, we look at which two leads?
Lead I and aVF
If Lead I is negative but aVF is positive, what happened?
Lead I is pointing 180 degrees (to the right), so right deviation (right people meet)
If Lead I is positie, but aVF is negative, what happened?
aVF is now negative, so you have left deviation (left don’t see eye to eye)
