N434: EKG
Interpretation test
questions and answers
2025
Cardiac conduction
SA node --> atria contraction/depol -->
AV node --> bundle of His --> R./L. bundle branches -->
Purkinje fibers --> ventricles contraction
Parasympathetic nervous system (Vagus Nerve)
Decreases rate
Slows impulse conduction
Decreases force of contraction
Sympathetic nervous system
fight or flight; increase rate, conduction, contraction
How is EKG produced?
movement of charged ions across heart cells (Na, K)
Depolarization of heart
contraction
Repolarization of heart
relaxation
How much time is in one small square in EKG? One big square?
Small: 0.04 seconds
Big: 0.2 seconds
How do you calculate regular heart rate off of EKG?
300/# of big boxes between 2 R/R
How do you calculate irregular heart rhythm based on EKG?
, count R-R intervals in 6 seconds
multiply x10
What does each wave represent in EKG?
P: atria depol
Q: first negative deflection; vent depol
R: first postive deflection; vent depol
S: first negative deflection after positive; vent repol
T: vent. repol
Normal PR interval? What does this represent?
PR interval: artial depol --> purkinje fibers
normal: 0.12-0.2 seconds
Normal QRS complex? What does this represent?
QRS: vent depol
normal: <0.12 seconds
What does the ST segment represent?
ST segment: time b/w vent depol and repol
Normal QT interval? What does this represent?
QT interval: amount of time for vent depol and repol
normal: 0.34-0.43 seconds
Steps to identify a cardiac rhythm
count HR
Regular or irregular
P waves
measure PR interval
QRS duration
Assess ST segment
QT interval
Normal sinus rhythm
Interpretation test
questions and answers
2025
Cardiac conduction
SA node --> atria contraction/depol -->
AV node --> bundle of His --> R./L. bundle branches -->
Purkinje fibers --> ventricles contraction
Parasympathetic nervous system (Vagus Nerve)
Decreases rate
Slows impulse conduction
Decreases force of contraction
Sympathetic nervous system
fight or flight; increase rate, conduction, contraction
How is EKG produced?
movement of charged ions across heart cells (Na, K)
Depolarization of heart
contraction
Repolarization of heart
relaxation
How much time is in one small square in EKG? One big square?
Small: 0.04 seconds
Big: 0.2 seconds
How do you calculate regular heart rate off of EKG?
300/# of big boxes between 2 R/R
How do you calculate irregular heart rhythm based on EKG?
, count R-R intervals in 6 seconds
multiply x10
What does each wave represent in EKG?
P: atria depol
Q: first negative deflection; vent depol
R: first postive deflection; vent depol
S: first negative deflection after positive; vent repol
T: vent. repol
Normal PR interval? What does this represent?
PR interval: artial depol --> purkinje fibers
normal: 0.12-0.2 seconds
Normal QRS complex? What does this represent?
QRS: vent depol
normal: <0.12 seconds
What does the ST segment represent?
ST segment: time b/w vent depol and repol
Normal QT interval? What does this represent?
QT interval: amount of time for vent depol and repol
normal: 0.34-0.43 seconds
Steps to identify a cardiac rhythm
count HR
Regular or irregular
P waves
measure PR interval
QRS duration
Assess ST segment
QT interval
Normal sinus rhythm
