Physiological Basis of EKG Flashcards
What are the nine EKG electrodes?
RA, LA, LL
V1, V2, V3, V4, V5, V6
What are the heart rates of the big boxes on an EKG tracing?
300, 150, 100, 75, 60 , 60 , 43
What is the directional axis of the aVL tracing?
- 30 degrees
- left axis deviation
What is the directional axis of the I tracing?
0 degrees
What is the directional axis of the aVR tracing?
- 150 degrees
- extreme right axis deviation
What is the directional axis of the II tracing?
60 degrees
-normal axis
What is the directional axis of the aVF tracing?
90 degrees
What is the directional axis of the III tracing?
120 degrees
-right axis deviation
What does the I tracing represent?
bipolar representation from RA to LA
What does the II tracing represent?
bipolar representation from RA to LL
What does the III tracing represent?
bipolar representation from LA to LL
What does the aVR tracing represent?
the average of the LA and LL electrodes, heading in the direction of the RA electrode
What does the aVL tracing represent?
the average of the RA and LL electrodes, heading in the direction of the LA electrode
What does the aVF tracing represent?
the average of the RA and LA electrodes, heading in the direction of the LL electrode
What do the precordial (chest) leads detect?
what’s going on electrically immediately beneath the electrode’s placement
What is represented by the P wave on the EKG?
atrial depolarization
What is represented by the QRS complex on the EKG?
ventricular depolarization
What is the relationship bw the duration of the QRS complex in relation to the P wave, and why?
they are similar, bc even though the ventricular ctx is larger, the conduction velocity of the electric impulse is faster in the ventricles than in the atria
What is represented by the T wave on an EKG?
ventricular repolarization
What is the PR interval on an EKG?
time bw initial atrial depolarization and initial ventricular depolarization
What does the length of the PR interval represent?
the time for AV node conduction
What is the QT interval on an EKG?
initial ventricular depolarization to final ventricular repolarization
What does the ST segment represent on an EKG?
the plateau of ventricular action potential
phase 2
What is the normal time duration of the P wave?
- 06-0.11 seconds
1. 5-2.75 small boxes
What is the normal time duration of the PR segment?
0.12-0.20 seconds
3-5 small boxes
What is the normal time duration of the QRS wave?
0.08-0.10 seconds
2-2.5 small boxes
What is the normal time duration of the QT segment?
0.36-0.44 seconds
9-11 small boxes
What is the normal time duration of the ST segment?
0.08 seconds
2 small boxes
What is the normal time duration of the T wave?
- 1-0.25 seconds
2. 5-6.25 small boxes
What will happen to the EKG tracing if the conduction velocity through the atria decreases?
P wave will get longer in duration
What will happen to an EKG tracing if the right atrium is enlarged?
P wave will get taller
What does a wide QRS complex indicate?
bundle branch block
What will happen to an EKG tracing in the case of left ventricular hypertrophy?
tall QRS complex
What will happen to an EKG tracing in the case of lost ventricular myocardium?
short QRS complex
What does a tall T wave indicate?
hyperkalemia
What will happen to an EKG if the patient has an AV block?
PR segment will lengthen horizontally
What would happen to an EKG tracing in a case of hypokalemia?
QT segment will lengthen horizontally
What might a depressed ST segment indicate?
hypokalemia
What might an elevated ST segment indicate?
MI or pericarditis
What does an EKG electrode detect?
the extracellular voltage
What is the mechanism for how an EKG electrode detects a positive voltage during depolarization?
as the atria or ventricles depolarize from upper R to lower L, the extracellular space on the L now has a positive charge when compared to the extracellular space on the R
What two leads are considered when determining the deviation of axis?
I and aVF
What is the deviation of the axis if the QRS complexes in both I and aVF are upright?
normal
What is the deviation of the axis if the QRS complex in I is upright, but aVF is inverted?
left axis deviation
What is the deviation of the axis if the QRS complex in I is inverted, but aVF is upright?
right axis deviation
What is the deviation of the axis if the QRS complex in I is inverted and also inverted in aVF?
extreme right axis deviation
What kind of axis deviation would left ventricular hypertrophy cause?
left axis deviation
What kind of axis deviation would right ventricular hypertrophy cause?q
right axis deviation
