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
what are the steps to determine a 12 lead?
- determine baseline rhythm
- determine any areas of cardiac compromise
- determine the level of compromise
what action is important with any type of ischemia?
increase O2 supply and decrease demand
the right coronary feeds what parts of the heart?
- SA node
- inferior wall
- RV
what can be seen with a right coronary artery event?
- prominent EJ
- increased CVP
- slowed HR
- clear bilateral breath sounds (no pulmonary edema)
how is a right sided EKG done?
V leads are placed anatomically in the same place but on the right sied, V1 and V2 are simply switched
what is the purpose of a right sided EKG?
- to evaluate the right ventricle, not normally seen on a 12 lead
- if RCA is occluded and shown through an inferior event, may be occluded higher in the vessel causing right sided ischemia
- any ST/T change in the inferior leads is an indication for Right side 12 lead
what is different about treatment for a right ventricular infarction?
- same goal: reperfusion
- because of the reduction in the entire capacity of the heart to pump (LEFT AND RIGHT) significant potential for hypotension
- NTG used cautiously
- large bore IV and volume administered
- may need pacing for SA node MI
which lead is best for detecting atrial dysrhythmias?
lead II
which lead is best for detecting ischemia?
lead V5 (detects 75% of events)
lead II and V5 added detect how much of ischemia?
80%
leads V5 and V4 added detect how much of ischemia?
90%
leads II, V5, and V4 combined detect how much of ischemia?
96%
what leads detect hypertrophy?
V leads
what is observed for atrial hypertrophy?
p waves
what is observed for ventricular hypertrophy?
R and S waves
what are signs of left atrial hypertrophy?
- notched P wave in V1
- an up and down shaped (biphasic) or widened (> 2.5 mm wide) P wave
- best seen in lead I or V1 (can look in Lead II if V1 not good)
- takes longer to reach and depolarize left atrium
what indicates right atrial enlargement?
tall peaked P wave (> 2.5 mm high)
what is seen with bi atrial enlargement?
tall and wide P waves
how is left ventricular hypertrophy determined?
- measure the depth of the S wave in V1
- measure the height of the R wave in V5 or V6
- if the two measurements added are greater than 35mm, LVH is present
- look at tallest S wave between V1 and V2 and tallest R wave b/w V5 and V6
what may cause LVH?
- long standing extensive HTN
- aortic valve stenosis
- idiopathic hypertrophic subaortic stenosis (IHSS)
what should be avoided with LVH?
- spinals
- vasopressors that increase HR (if caused by aortic stenosis)
