35 Questions
What is the PR interval measured from?
The beginning of the P wave to the beginning of the QRS complex
What does the PR interval include physiologically?
Atrial depolarization and the propagation of the impulse through the AV node
What is the normal PR interval in adults?
0.12 s to 0.20 s
What is the PR segment?
The part of the ECG that represents the propagation of the impulse through the AV node
What is the duration of one small square in the ECG?
0.04 s
In which direction does the cardiac impulse cause depolarization of the atria?
From right to left
What is the result of the impulse being conducted slowly in the AV node?
No electric change
Which part of the ventricular muscle is the first to be activated?
The interventricular septum
What is the direction of depolarization of the interventricular septum?
From left to right
What is generated by the depolarization of the left and right ventricular free walls?
The R-wave
Which of the following structures conducts the impulse quickly?
The bundle of His
What is the reason for no electric changes being recorded after the ventricles are completely depolarized?
The ventricles are in a plateau phase of action potential
What is the direction of ventricular muscle repolarization?
From epicardium to endocardium
Why are the recordings from all the bipolar limb leads similar to one another?
Because they all record positive P waves and positive T waves
What is the relationship between the algebraic sum of LII and the algebraic sum of L1 and LIII?
LII = L1 + LIII
What is the difference between the recordings from the augmented limb leads and the standard limb leads?
The recordings from the augmented limb leads are inverted
What is the significance of the similarity between the recordings from the three standard bipolar limb leads?
It makes it easier to diagnose cardiac arrhythmias
What is the direction of septum depolarization?
Left to right
What is the characteristic of QRS recordings in leads V1 and V2?
Mainly negative
Which leads overlie the anterolateral wall of the left ventricle?
V5 or V6
What is the significance of a negative aVR wave in an ECG?
Correctly placed leads
What is the normal duration of the P wave in a normal heart?
0.08 to 0.10 seconds
Which of the following ECG components is occasionally present in normal persons?
U wave
What occurs during the PR segment?
Impulse traveling within the AV node
What is the significance of a P-R interval greater than 0.20 seconds?
AV conduction block
What is the normal duration of the QRS complex?
No more than 100 ms
What is the significance of a prolonged QRS complex?
Impaired conduction within the ventricles
What is the QRS complex representative of?
Ventricular depolarization
What is the effect of altering the site of the recording electrode on the QRS complex?
The shape changes
What is the characteristic of the T wave in relation to the QRS complex?
It has a longer duration
In which leads can T wave inversion be diagnosed?
Leads with large R waves
What is the significance of a prominent U wave?
It indicates underlying pathology or conditions affecting repolarization
Which of the following is not an indication for ECG recording?
Pneumonia
What is the normal direction of the T wave in leads with large R waves?
Upright
In which leads is the U wave best seen?
V2-V3
Learn about the PR interval in ECG, including its measurement, normal values, and what it represents. Understand the importance of the PR interval in cardiac rhythm analysis.
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