12 lead EKG Flashcards
what is the axis?
- the primary direction of electricity flow during depolarization
- mean QRS vector
- most of the flow of energy goes toward the left ventricle
- indicative of long term heart conditions
what leads can determine normal axis or axis deviation?
leads I and aVF
- with a normal axis, both leads have positive deflections (0-+90 degrees)
- circle divide into four: right side(looking towards LV) + LI, left side (-) LI; bottom + aVF, top - aVF (both cross at bottom right (left side of heart), where both positive)
clockwise movement of QRS vector indicates what?
- right axis deviation (+90-+180 degrees)
* will still see a + aVF but a - lead I
counterclockwise movement of the QRS vector indicates what?
left axis deviation (0- -90 degrees)
*will still see a + lead I but a -aVF
what does both a (-)aVF and (-) lead I indicate?
extreme right axis deviation (-90 –180 degrees)
what are causes of axis deviation?
- infarct (electricity doesn’t flow well through infarcted tissue, so deviates away)
- hypertrophy (fatter the muscle the more electricity needed to depolarize so deviates towards)
- anatomical shifts
- obesity and pregnancy shift left
- extremely thin shift right
what indicates a bundle branch block?
- wide QRS complex >.12 sec
- either two R waves OR deep Q wave present
what lead is good to find BBB?
V1
what is seen with a right BBB?
two upright R waves (rsR wave)
what is seen with a left BBB?
deep downward Q wave (Qs wave)
what should be considered with a new Left BBB?
-treat as a MI until proven otherwise, especially with CV symptoms
what needs to be considered with a BBB when placing a pulmonary artery catheter?
- if there is a LBBB already in place, the PAC may stimulate a RBBB
- *LBBB and RBBB combined= complete heart block (3rd)
- *must remove catheter, transcutaneous pace, and Epi
what leads look at septal wall of LV?
V1 and V2
what leads look at anterior wall of LV?
V3 and V4
what leads look at lateral wall of LV?
I, aVL, V5,V6
what leads look at inferior wall of LV?
II,III, aVF
what coronary artery supplies the septal wall?
LCA and RCA (V1 and V2)
what coronary artery supplies the anterior wall?
LCA-left anterior descending (LAD) (V3 and V4)
what coronary artery supplies the lateral wall?
LCA-circumflex (I, aVL, V5 and V6)
what coronary artery supplies the inferior wall?
RCA (II, III, aVF)
what must be identified to determine that ischemia/injury/infarction is present?
similar changes in 2 or more leads that represent the same area of the heart
what EKG changes indicate ischemia?
- tall T waves or peak T waves
- inverted symmetrical T waves
- ST depression
- O2 demand is greater than supply
- stress of surgery increases CO, which increases O2 demand
what EKG changes indicate injury?
ST elevation (above isoelectric line)
what EKG changes indicate infarction?
- Q wave formation (not always present in less severe infarction)
- normal is < 1/3 ht. of R wave
- if outside parameters, indicative of infarction
