Intro Stuff Flashcards
What is ECG paper?
Graph paper made up of small boxes and larger boxes
What does a small box on ECG paper represent?
0.04 sec
What does a large box on ECG paper represent?
0.2 sec
What do the black tick marks at the top of ECG paper represent?
3 sec intervals
What does any deflection from the baseline in an ECG represent?
Electrical activity in the heart
What does the P wave represent?
Atrial depolarization
What stimulates the P wave?
SA node in the right atrium
What are the characteristics of a normal P wave?
Positive, Present, and Preceding a QRS complex (PPP)
What does the PR interval represent?
Time for the impulse to travel through the atria and to the ventricles
How is the PR interval measured?
From the beginning of the P wave to the beginning of the QRS complex
What is the normal range for the PR interval?
0.12-0.20 sec
What does the QRS complex represent?
Depolarization of the ventricles
How is the QRS complex measured?
From where the QRS complex leaves the baseline until it returns to baseline
What is the normal duration for a QRS complex?
Less than or equal to 0.11 sec
What does the T wave represent?
Repolarization of the ventricles
What is a normal characteristic of the T wave?
Positive deflection
What does the QT interval represent?
Time for the ventricles to depolarize and repolarize
How is the QT interval measured?
From the beginning of the QRS complex to the end of the T wave
What is considered a prolonged QT interval in men? in women?
0.47 sec or longer in men and 0.48 sec or longer in women
What is considered a prolonged QT interval in this course?
0.50 sec or longer
What medications can prolong the QT interval? (Name one category)
Antidysrhythmics
Antidepressants
antipsychotics
Antibiotics
+Others (ondansetron)
What does the ST segment represent?
Early part of ventricular repolarization
What does an abnormal ST segment indicate?
Cardiac ischemia
What is the J-point in ECG interpretation?
Point where the QRS changes direction into the baseline or T wave
What does the U wave represent?
Late repolarization of the purkinje fibres
What does the P-P interval represent?
A full cardiac cycle using atrial depolarization as a reference
How is the P-P interval measured?
From the beginning of one P wave to the beginning of the next P wave
What does the R-R interval represent?
A full cardiac cycle using ventricular depolarization as a reference
How is the R-R interval measured?
From the tip of one QRS complex to the tip of the next QRS complex
What does artifact in an ECG represent?
Movement or respiratory interference with the ECG monitoring system
What should be noted about the T wave in the interpretation?
If the T wave is positive, inverted (below the baseline), biphasic (both above and below the baseline - shown), or peaked (more than half the height of the QRS complex)
If there is only one visible wave between QRS complexes, which wave form is it most likely and why?
Because the ventricular muscle mass is larger than that of the atria, in some arrhythmias, the P wave will be buried within the T wave rather than the other way around. In other words, if there is only one visible wave between the QRS complexes, it is more likely to be a T wave than a P wave.
Why is a prolonged QT interval concerning?
The increased risk of R-on-T phenomenon in which the next QRS falls on the T wave, too close to the absolute refractory period and initiates a ventricular arrhythmia
What is the QRS complex?
It represents ventricular depolarization and is a combination of Q wave, R wave, and S wave
If it is entirely positive wave form, labelled R wave
if the complex is entirely negative wave form is called a QS wave
What is a peaked T wave?
A t wave that has a height on ecg that is half (or more) of the height of the QRS
