12-lead ch.6 Flashcards
What is a wave? segment? interval?
A wave is a deflection from the baseline that represents a cardiac event.
A segment is a specific portion of the complex as it is represented on the ECG.
An interval is the distance, measured as time, occurring between two cardiac events.
Describe the difference between R and R’
R is the first upward deflection from the baseline while R’ is an extra upward deflection within the qrs.
Which parts (waves) of the EKG reflect depolarization or repolarization? Of which chambers?
The P wave represents atrial depolarization
The qrs represents ventricular depolarization and atrial repolarization.
The T wave represents ventricular repolarization.
The U wave represents late ventricular repolarization
What are normal sizes for P waves? QRS?
P waves should be between .08 and .11sec. and no taller than 2.4mm high.
The qrs should be between .06 and .11sec.
What is a Tp wave? How will it appear in Sinus Tachy?
The Tp wave is an unseen wave which occurs within the qrs complex which is exactly a reflection of the p wave in a downward deflection. In sinus tachy it can make the st segment appear depressed because the atrial repolarization is slower than the ventricular depolarization in the qrs.
What is normal PR depression? What causes abnormal PR depression?
Normal PR depression can be less than .8mm. Otherwise consider pericarditis or rarely atrial infarct
What is the normal duration of the PRI? Which cardiac events are occurring?
.12-.20sec. The electrical impulse of the SA node until the ventricular depolarization are all seen in the PR interval.
What is the normal duration of the QRS? Which cardiac events are occurring?
Normal QRS is .06-.11sec. ventricular depolarization as well as atrial repolarization occurs.
What makes a Q wave significant?
.03sec wide or height is 1/3 or more of the R wave.
What is an intrinsicoid deflection? When would it be prolonged?
An intrinsicoid deflection is from the beginning of the qrs to the beginning of the downward slope of the R wave.
Prolongation would result from thicker myocardium (VH) or when it takes longer for the electrical system to conduct to that area because of an IVCD like LBBB.
What is occurring during the ST segment?
ST segment represents an electrically neutral time for the heart. The ventricles are between depolarization and repolarization. What could this represent on the action potential?
What does the T wave represent?
The T wave represents ventricular repolarization.
Why is a normal T wave the same polarity as the QRS while the atrial repolarization would be the opposite direction?
Because of increased pressure on the endocardium during contraction, the repolarization wave travels in the opposite direction from the epicardium back to the endocardium.
Symmetric T’s are usually a sign of__________.
pathology
Prolonged QT is usually a harbinger for _________
TDP
