Question | Answer |
Cellular electrophysiologists measure potentials by | measuring the inside of the cell with respect to the outside of the cell |
Electrocardiographers depend on | Surface electrodes |
Measurements are recorded as the ________ between two electodes | Potential difference |
When the depolarizing wave approaches the positive electrode, the deflection is _______ | upward |
Fully Depolarized | All positive inside
all negative outside |
Repolarization occurs in the _________ direction | opposite |
The last to depolarize is the __________ to repolarize. | first |
Sequence of electrical activation and teh ECG | Endo -> Epi -> Apex -> Base |
Q wave | depolariztion of the sepum |
P wave | depolarization of the atria |
S | Late lateral depolarization of the left base |
ST segment | Full depolarization |
T | repolarization |
U | Late repolariztion of mid cells in myocardium |
QRS | Ventrical depolarization |
PR segment | time between atrial activation and ventricular activation |
If conduction is slowed through the AV node, what happens to the PR interval? | Lengthens |
Bundle Branch Block | Wide QRS |
cardiac ion channelopathies that can lead to long _____________ | QT intervals |
Lead I | + left arm
- right arm |
Lead II | + Left Leg
- Right arm |
Lead III | + left leg
- left arm |
aVF | + left foot
- Head |
aVR | + right arm |
aVL | + left arm |
Downward deflection of QRS normal in lead | aVR |
Horizontal plane | V1-V6 |
Interpretation of ECG | rate
rhythm
vector in frontal plane
hypertorphy
infarction |
Rate = | (60s/min) / R-R interval |
Large box = | .2 seconds |
1 Large box | 300 bpm |
2 large box | 150 bpm |
3 large box | 100 bpm |
4 large box | 75 bpm |
5 large box | 60 bpm |
6 large box | 50 bpm |
LAD | I = upward
aVF = Downward |
Normal axis | I = upward
aVF = upward |
RAD | I = downward
aVF = upward |
Extreme RAD/LAD | I = downward
aVF = downward |
I | 0 degrees |
II | 60 degrees |
III | -60 degrees |
avF | 90 degrees |
avL | -30 degrees |
avR | -150 degrees |
Quick and easy devation method | 1. find isoelectric line
2. find vector that is perpendicular....is it up or down?
3. up is positive vector down is negative vector |
Hypertrophy vector movement | vector moves toward hypertrophy |
infaction vector movement | vector moves away infarction |