12/8/2014 Medical Physiology Cardiac Electrophysiology II Eric Olson Flashcards
A positive and negative electrode pair constitutes:
A single lead. A single lead measures the voltage difference between two electrodes.
In physiology, the flow of what ions is considered a positive current?
Positive ions
Te first part of the EKG is called:
the P wave
The P wave is produced by:
the depolarization of the atria.
When the atrial depolarization reached the AV node, the AV node depolarizes slowly. Is this event represented on the EKG?
Yes, by a pause before the QRS complex.
What actions in the heartbeat make up the QRS complex?
Depolarization of the bundle of His to the left and right bundle branches and Purkinje fibers (ventricular contraction)
The repolarization of the ventricles produces what on the EKG?
T wave
What extra wave is produced in about 50% of people?
The U wave
In EKG, 5 mm along the time axis = how long?
0.2s
In EKG 5 mm along the voltage axis = ?
0.5 mV
What is the QT interval?
The period from the beginning of the QRS complex to the end of the T wave.
T/F: The T wave is a positive deflection on the EKG.
True, despite that it’s the repolarization event.
What pathology can invert the T wave?
Ischemia
What pathology can disrupt the T wave?
Potassium channel blockade
T/F: Depending on the placement of the leads, the QRS complex will be the different for the same heartbeat.
True
What placement of the electrodes would produce an isoelectric QRS wave?
Electrode is orthagonal to wave travel (depolarization passes from left to right)
What does orthagonal mean w/r/t EKG and lead placement?
“At a right angle to” meaning that isolelectric EKG traces
A depolarization wave traveling in the direction of the lead towards the positive end produces a _____ signal on the EKG.
positive
What does aVR stand for?
Augmented voltage right
aVL is what lead?
Augmented voltage left
aVF is what lead?
Augmented voltage foot
The aV leads are sometimes called:
unipolar leads
The largest QRS complex is normally detected between what degrees?
-30 and 0
Between 0 and 90 degrees is called:
the primary axis
If both aVF and lead I show a positive QRS complex, then the axis is:
Normal
A QRS axis that shows lead I is positive, but aVF is negative, what pathology is suggested?
LV hypertrophy
Left anterior fascicular block
A QRS axis that shows a negative aVF and negative lead I are seen when?
Never, this is “no man’s land.”
A QRS axis that shows a negative lead I and positive aVF suggest what pathology?
RV hypertrophy
Left posterior fascicular block
What are the six chest leads on the EKG?
V1-V6
