Physiological Basis Of The EKG Flashcards
What does the ECG measure
Extracellular potential
Wen is a deflection caused with an ECG
Part of the cardiac excitable tissue is at a different membrane potential than the rest of the heart
Why does the ECG not measure difference between the atria and the ventricles
Electrical insulation from the fibrous skeleton
When there is a depolarization, what is happening in the extracellular portion that the ECG records
What about for Repol.
- outside (+ inside)
+ outside (- inside)
Ventricles depol in what direction
What about repol
R to L
Apex to Base
Interior to Exterior
Just the reverse for repol
All atrial cells are depolarized when
At the end of the P wave
All ventricular cells are depolarized when
By the ST segment
Define the PR interval
Beg of atrial depol to delay in AV node
Define QT interval
Vent. Depol
Define PR segment
End of atrial depol, this is solely the AV delay
What does aVF read
(RA + LA) to LL
What does aVR read
(LL + LA) to RA
What does aVL read
(LL + RA) to LA
V1 and V2 are generally what
Negative
V4, V5, V6 are generally what
Positive
Each of the precordial leads acts as what
A positive electrode
Elevation in the inferior leads means a blockage where
RCA
Elevation in the septal leads means a blockage where
The LAD
Elevation in the anterior leadfs means a blockage where
LAD
Elevation in the Lateral leads means a blockage where
The circumflex A.
Define mean electrical axis deviation
Average direction of spreading AP in ventricles
What can cause a shift in the axis
Hypertrophy, MI, BBB
Lead I Positive and Negative directions
Positive - R - L
Negative - L - R
Define aVF Positive and negative directions
Pos - top to bottom
Neg. - bottom to top
If lead I is negative, what does this mean
R axis deviation
RVH
Is lead I is positive, but AvF is negative, what does this mean
left axis deviation
LVH
The p-wave begins before what
Atrial contraction
The QRS complex begins before what
Ventricular contraction
The T wave begins before what
Ventricular relaxation
