The heard depolarizes from _____ to _____
bottom to top
EKG
Depolarization of the SA Node –>
2. internodal tracts–> AV node –> bundle of His –> R & L bundle branches –>purkinje fibers –>R & L Ventricles
Leads
-the sensing electrodes used to monitor electrical activity
Standard Limb Lead
Lead I: - electrode R arm; + electr L arm
Lead II: - electr R arm; + electr L leg
Lead III: - electr L arm; + electr L leg
Ground: R leg
(Frontal Plane)
Augmented (unipolar) limb leads
-Fills in gaps of standard (frontal)
Normal EKG Speed
25mm/sec
6 Major EKG Deflections
P Q R S T U
PR Interval
Length of PR Interval
- 3-5 small boxes
R
First + deflection
Small box dimensions
- width: 0.04 sec
Precordial (chest) leads
Transverse Plane
V1: R of sternum; 4th intercostal space V2: L of sternum; 4th IC space V3. between 2 & 4 V4: midclavicular; 5th IC space V5: ant axillary line; 5th IC space V6: mid axillary line; 5th IC space
Big square dimensions
P Wave
- can be positive/neg/biphasic; but must be the same each time
QRS Complex
Should be <2.5 small boxes
Length of QRS Complex
<2.5 small boxes
S
neg deflection after R
S^1
S prime
neg deflection following R prime
Q
Initial negative deflection before R
R^1
R prime
2nd + Deflection
QS
Total deflection
QT Segment
QT Segment Length
<1/2 distance from R to R