EKG- How to Read Flashcards
leads I, II and III … what orientation in space do they “see”?
Lead I: RA (-) to LA (+) (Right Left, or lateral)
Lead II: RA (-) to LL (+) (Superior Inferior)
Lead III: LA (-) to LL (+) (Superior Inferior)
3 augmented unipolar limb leads: what do they “see” ?
Lead aVR: RA (+) to [LA & LL] (-) (Rightward)
Lead aVL: LA (+) to [RA & LL] (-) (Leftward)
Lead aVF: LL (+) to [RA & LA] (-) (Inferior)
unipolar chest leads: what do they “see” ?
Leads V1, V2, V3: (Posterior Anterior)
Leads V4, V5, V6:(Right Left, or lateral)
what is the sequence of activation of the ventricles?
- septum
- left ventricle
- right ventricle
6 things that EKG assess for?
Rate of heart Rhythm of heart Axis of ventricle and atria Intervals between waves normal Hypertrophy Infarction
rate of SA node, Atria, AV junction, Ventricles … why do we care about the rate of the areas other than SA node?
SA node: 60-100 bpm
atria: 60-80
AV node: 40-60
Ventricles: 20-40 Automaticity Foci take over if SA node fails- these are places in the conducting system that can take over the pacing responsibility
in what situation would AV node pick up the pacemaking responsibility over the SA node?
- The SA node and atrial foci fail
- There is a complete conduction block in the proximal AV node . The atrial stimuli can’t get to the rest of the system
* only has foci at DISTAL end of node, not at proximal
how can the rate of the heart be estimate on the EKG?
Can be estimated by number of cycles (P wave to T wave) seen in one minute
Or counting # heavy lines from R to R
how to estimate HR from R to R
If next R wave one HEAVY line away rate is 300bpm Two lines away 150 bpm Three: 100 bpm Four: 75bpm Five 60 bpm Six: 50 bpm
estimate Rate for someone with bradycardia or an irregular rhythm?
methods for the “normal” person would be inaccurate for these.. so different method:
Each EKG has 3 second marks, count how many cycles for two intervals and multiple by 10
what is the bottom line on the EKG?
rhythm strip
S3 is usually from what? S4 is usually from what?
S3: fluid overload, S4: hardened (non-compliant) ventricle
Sinus arrhythmia (normal variant): how will the EKG look?
- Irregular rhythm
- The distance between P waves varies (hence the irregularity) but still have a P wave before each QRS complex and each P wave is same shape (meaning staring from the same spot, the SA node)
- happens w/ respiration
if the variants for sinus arrhythmia are not met (aka P wave not present, or varying P wave shapes)… what does that mean?
its an ABNORMAL variant and a different type of arrhythmia
what is the QRS axis ?
The direction in which most of the electricity is traveling through the ventricles is called the QRS axis
- measure as circle superimposed on chest and measured in degrees
I at 90 degrees and AVF at 90 degrees (II as a tie-breaker- pos. = normal, neg =left deviation)
hypertrophy will cause the QRS axis to deviate ____ the area of hypertrophy?
towards
infarction will cause the QRS axis to deviate ____ from the area of infarction
away
QRS axis: what degrees constitute the different deviations?
Normal: 0 to +90
Right axis deviation (RAD): +90 to 180 (neg I, pos AVF)
Left axis deviation (LAD): 0 to -90 (pos I, neg AVF)
Extreme axis deviation: -90 to 180 (neg I, neg AVF)
how are time intervals represented on the EKG?
Remember: horizontal axis is time each block is 0.04 seconds
0.20 sec= 5 blocks
0.12 sec=3 blocks
Intervals we look at: PR, QRS, QT
how can you have a STEMI without ST elevation
full thickness injury that has not progressed to cause ST elevation yet. (ST elevation on an EKG shows ischemia)
PR interval
Normal is 0.12-.20 seconds
If PR>.20 going through AV node slowly, called 1st degree AV Block
2nd and 3rd degree block result in not normal sinus rhythm-later
QRS
Measure first deflection of Q or R until returns to baseline at end
Time it takes for ventricles to depolarize
If QRS duration < 0.12 seconds then normal
QT interval
From beginning of Q to end of T
> 0.44 sec or 11 blocks is prolonged and increases risk of arrhythmia
what can cause a long QT interval?
Hereditary: Increased risk of ventricular arrhythmias
Can also be caused by drugs
Atrial hypertrophy on EKG
See in P wave, best in V1
Two ways:
P wave above and below baseline, biphasic
P wave > 2.5 boxes= right atria enlarged
left atrial enlargement on EKG
biphasic in V1 with larger downward deflection half
right atrial enlargement on EKG
P waves are larger than normal (it swallows up the left) - look at lead II in picture
tall P wave = big muscle mass on right side
where ok the EKG and from what leads is ventricular hypertrophy seen?
QRS complex, chest leads
right ventricular hypertrophy on EKG
R wave big in V1 and gets progressively smaller across chest leads as head to V4
left ventricular hypertrophy on EKG
Large amplitude (voltage) QRS
Large S in V1 and tall R in V5
S V1 + R in V5 > 35mm (35 small boxes)
infarction vs ischemia?
Infarction- heart muscle is dead
Ischemia-heart muscle not getting enough blood
what are “contiguous leads”
Contiguous leads are next to one another anatomically speaking. They view the same general area of the heart (specifically the left ventricle)
3 areas on EKG where you will see infarction or ischemia?
T waves
ST segments
Q waves
elevation of ST are ____ depressions are ____
elevations: infarctions
depressions: ischemia
T wave
T wave is repolarization of ventricles- relaxation
Most labile and easily changed wave
which leads are the T waves normally upright and which are the T waves normally inverted? concern it?
Normally upright in I, II, V3,V4,V5,V6. Inverted in AVR. Can be either way in AVL, AVF, III, V1 and V2 If inverted (not going their "normal" direction- concerned sign of MI
what constitutes the ST segment?
From end of S wave (at point returns of baseline) to beginning of T wave
if they have a Q where they didnt used to have a Q wave? ….
an old infarct
ST depression on stress test (horizontal or down sloping) think______
ischemia or drugs
where are Q waves?
First downward stroke of QRS complex
Anything positive before it then no Q wave
3 non-significant Q waves…
Don’t mean a lot if:
Qs in AVR
If isolated
If < 1 square wide or 1/3 of QRS high
significant Q waves
> One small square wide or 1/3 of QRS amplitude
If significant Q waves present think MI > 7 days old
when are EKG patterns more significant
Each of theses changes (T waves, ST segment and Q waves) are more significant if in a pattern that suggests anatomical area of heart
If isolated changes (just in one lead) or in leads that are not in adjacent area of heart then the changes might not be due to if MI or ischemia could be wrong lead placement
lateral leads?
I, aVL, V5 and V6
septal leads ?
V1 V2
inferior leads?
II and III
anterior leads?
V3 and V4
lead with no pattern significance
aVR
wolf-parkinson- white syndrome
Extra bundle of tissue (accessory) in AV conduction pathway
Depolarization can go through here faster
Called pre-excitation
Gives a Delta wave on QRS
Looks like a short PR
what are you at risk for with WPW?
At risk for SVT with rapid conduction- can get very high ventricular rates
