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100 Cards in this Set

  • Front
  • Back
Why is SA node a pacemaker cell, but Purkinje cells, ect are not?
SA node cells - phase 4 depolarization is not flat b/c of leaky calcium channels, which allows spontaneous depolarizations
Purkinje cells - flat phase 4 so no pacemaker function, no spontaneous depolarizations
How is phase 1 of depolarization different in a pacemaker cell verses a non-pacemaker cell.
Pacemaker cell: phase 1 due to calcium influx

Non-pacemaker cell: phase 1 due to sodium influx
What are the degrees of limb leads I, II, III, avR, aVL, aVF?
I: 0 degrees
II: +60 degrees
III: +120 degrees
aVR: -150 degrees
aVL: -30 degrees
aVF: +90 degrees
What are leads V1 - V6 called?
precordial chest leads
What are 4 anterior leads?
V1, V2, V3, V4
What are 4 left lateral leads?
I, aVL, V5, V6
What are 3 inferior leads?
What are the 2 components of vectors?
Magnitude & Direction
What are resolving vectors?
vectors perpendicular to actual vector (0 degrees)
What do resolving vectors look like on an EKG?
Isoelectric leads - balanced voltage (+ & -)
What do isoelectric leads tell you on an EKG? What does it help you find?
Isoelectric leads tell you that the actual impulse is +90 or -90 (perpendicular to) away.
This helps you find the direction of QRS depolarization, called the QRS axis. (Look @ lead I to know if axis is +90 or -90 to isoelectric lead)
What is the sequence of cardiac depolarization? (5 places)
1) Sinoatrial (SA) node - pacemaker
2) Atrioventricular node
3) Bundle of His
4) Bundle braches
5) Purkinje fibers
What does P wave, QRS complex, & T wave represent?
P wave - atrial depolarization
QRS - ventricular depolarization
T wave - ventricular repolarization
What prolongs QRS complex?
anything that slows conduction in the venticles prolongs QRS
What does QT interval represent? What prolongs it?
QT = from start of ventricular depolarization to end of repolarization
Prolonged QT is due to stuff that prolongs ventricular repolarization
What is Q?
What is R?
What is S?
Q = 1st negative portion
R = 1st postitive portion
S = 2nd negative portion or a negative portion after an R
On ECG graph paper (x axis), how many seconds is 1 small box? how many sec is 1 large box?
Sm box = 0.04 sec
Lg box = 5 sm boxes = 0.2 sec
On ECG graph paper (y axis) how many small boxes makes up 1 mV?
1mV is 10 small boxes or 2 large boxes
What is normal axis?
Normal axis is between -30 and +90 degrees.
What are the 3 steps to finding the QRS axis?
1) look for most isoelectric lead (ex. aVF equal + & - so isoelectric lead is +90)
2) axis is +90 or -90 from isoelectric lead (ex. 0 or 180)
3) look to see if lead I is + or - (ex. Lead I + so axis is 0 degrees)
What is Left Axis deviation (LAD)?
LAD occurs when the QRS axis is more negative than -30. (ex. an axis of -60)
If an EKG shows that aVR is the isoelectric lead, what are the 2 choices that the axis will be? How do you know which is correct?
Isoelectric lead: aVR (-150)
Axis: -60 or +120
Lead I: + (bt +90 & -90)
Lead II,III: - (not in an inferior direction)
These additional leads tell you axis is -60.
If the axis is -60, how is the QRS deviating?
to the left
What is Right Axis Deviation (RAD)?
RAD occurs when axis is greater than 90 degrees (more positive).
If isoelectric lead is in aVR, what are the 2 choices for axis? How do you determine which is correct?
Isoelectric lead: aVR (-150)
Axis: -60 or +120
Lead I: - (axis cannot be between -90 to +90)
Axis is +120 degrees!
What is an example of a condition that might lead to RAD?
pulmonary hypertension
If the isoelectric lead is Lead III, and Lead I is positive, what is the QRS axis?
Lead III = +120
Axis is either -150 or +30
Since Lead I is +, QRS axis is +30
How do you find the QRS axis if there is no isoelectric lead?
If no isoelectric lead, look for most positive lead. The axis has to be close to the axis of that lead. Check adjacent leads to "fine tune" your estimate of axis.
What is the sequence of boxes to find the heart rate (ex. 1 lg box over is ?, 2 lg boxes over is ?, etc)
1 box = 300
2 boxes = 150
3 boxes = 100
4 boxes = 75
5 boxes = 60
6 boxes = 50
7 boxes = 43
8 boxes = 37
Where is PR interval? What is normal time of this interval? What does it measure?
PR interval is start of P wave to start of QRS;
120 - 200 ms (.12 - .2 s)
(< 1 big box or < 5 sm boxes)
measures atrial depolarization & delay in AV node (prolonged if problem w/ AV node) eventually atrial rate will differ from ventricular rate
What prolongs PR interval (>200ms)?
What makes PR interval short (<120ms)?
PR interval prolonged if problem w/ AV node - eventually atrial rate will differ from ventricular rate;
PR interval short if impulse not being delayed - bad - extra pathway that bipasses AV node
What does QRS complex measure?
QRS complex measures how fast/slow ventricular depolarization is
What is QT interval a measure of? How many ms (sec) long should QT interval be?
QT interval is a measure of ventricular depolarization & repolarization
QT should be <450ms (.45sec)(just over 2 big boxes) QT should be < 1/2 of R-R interval
What might prolong QT interval?
QT interval prolonged due to electrolyte imbalance & drug effects (ex. decreased serum calcium) (ex. gene mutation - pass out for no apparent reason)
What is the direction of normal atrial depolarization?
down & to the left (according to patient perspective or about +45 degrees)
Which 3 leads always have a + or upright P wave in Normal sinus rhythm?
NSR - P wave upright in 3 leads:
Lead I, Lead II, aVF
What if P waves are not upright in these leads? What are exceptions?
If p waves are not upright in Lead I, II, & aVF, patient is not in sinus rhythm.
Exceptions: sinus invertus where SA node is high & in left atria or if leads are hooked up wrong
If isoelectric lead is -30 & Lead I is upright, what is the axis?
Isoelectric lead is aVL = -30
Axis = +60 or -120
Lead I is upright, so has to be between -90 & +90 so axis is +60
What are the 2 conditions necessary for Normal Sinus Rhythm (NSR)?
1) Normal P wave morphology
2) Normal P wave axis - usually around 60 degrees (upright in Leads I, II, aVF)
Do you need to look at the QRS to determine if a patient is in sinus rhythm?
No! What the ventricles may (or may not) be doing is IRRELEVANT as to the determination of NSR.
What are 3 causes of P wave varients (abnormal P waves)?
1) ectopic origin &/or sequence of atrial depolarization
2) Right atrial abnormality ("right atrial enlargement")
3) Left atrial abnormality ("left atrial enlargement)
What will the P wave look like if there is an ectopic origin &/or sequence of atrial depolarization?
NOT sinus morphology
What will the P wave look like if there is a right atrial abnormality ("right atrial enlargement")?
> 2.5mm in II, III, & aVF
What will the P wave look like if there is left atrial abnormality ("left atrial enlargement")?
Notched in II, III, aVF,
Biphasic in V1 & V2
In what direction is initial depolarization & why?
Initial depolarization (septal depolarization) is from left to right because electrical current from the bundle of His goes through left bundle branch faster (summary: 1st impule from left to right)
What will the first impulse (septal depolarization) look like in Lead I?
Inital depolarization will be negative in Lead I (Q wave) because it goes lt to right, and Lead I goes the opposite, right to left.
After initial depolarization, what direction is depolarization? What deflection is seen in Lead I & what is it called?
After initial septal depolarization, direction of ventricular depolarization is from right to left (somewhat downward too). This shows a positive deflection in Lead I, called an R wave.
What magnititude is the initial impulse verses the subsequent impulse.
septal depolarization is small while ventricular depolarization is larger
What do these 2 impulses look like on V1? on V6?
V1 is an anterior precordial lead: 1st impulse towards, 2nd away so small R wave, large S wave
V6 is a left lateral lead so 1st impulse is away & 2nd is towards so small Q wave & large R wave
Which precordial leads will look similar to Lead I?
V5 & V6 will look similar to Lead I
Which precordial leads will be mirror images of each other?
V1 & V6 will be mirror images
In which leads should you normally see small Q waves?
small Q waves in I, V5, V6, & occationally inferior leads (II, III, aVF)
The 1st impulse should show a small R wave in which precordial lead?
Small r wave in V1
What is the R wave trend in precordial leads?
Gradual increase in R wave amplitude from V1 - V5
What precordial lead has the tallest R waves?
Which deflection combination (QRS) is always abnormal?
QS is always abnormal
What are 3 examples of conduction delays?
1) Right Bundle Branch Block RBBB
2) Left Bundle Branch Block (LBBB)
3) Intraventricular conduction delay
What is the problem in intraventricular conduction delay & how does it show up on the EKG?
Intraventricular conduction delay is due to problems with purkinje fibers going throughout the ventricle.
QRS is wide b/c taking longer for ventricles to depolarize
What happens if both bundles are out?
get no ventricular depolarization, leads to death
In RBBB are 1st & 2nd depolarizations normal in V1?
Yes, V1 shows normal R & S deflections.
What additional deflection is seen after R & S deflections in V1 & what kind of pattern does this create?
R prime deflection is seen after initial R & S deflections, creating a saw-tooth appearance in V1.
Why does RBBB show an R prime deflection in V1?
R prime is b/c myocardium has to bring impulse to Rt ventricle since Rt bundle branch is blocked, which takes longer
What are the 2 major changes that occur in LBBB & why?
1) No septal Q wave deflection in leads I, V5, & V6 where they should normally be b/c there is no septal depolarization (no initial impulse from L to R)
2) Wide QRS b/c all depolarization comes from R bundle to get to left ventricle so depolarization is slower, widening QRS in all leads
What are 2 conditions that can lead to abnormal ventricular depolarization?
1) Hypertrophy [Rt ventricular hypertrophy (RVH) or LVH]
2) Myocardial infarction
What leads might show what changes in left ventricular hypertrophy?
Large (-) S wave in V1 & V2
Large R wave in V5 & V6
[can measure heights to determine if patient has LVH]
What is the hallmark abnormality seen in myocaridal infarctions?
Development of abnormal Q waves (ex. abnormally large Q waves)
ECG changes in Leads II, III, & aVF might indicate what type of MI?
What location of acute MI will you see changes in V1-V2?
What location of acute MI will you see changes in V5-v6?
What location of acute MI will you see changes in V1-V6?
Anterolateral or "extensive" anterior
What location of acute MI would cause changes in aVL?
high lateral
What location of acute MI would cause mirror image V1-V2?
True posterior
What areas does the left anterior descending artery (LAD) perfuse?
lateral (diagonal branches),
septal (septal brances)
What areas does the circumflex artery perfuse?
lateral (obtuse marginal brances)
occaionally inferior
What areas does the right coronary artery (RCA) perfuse?
What artery is probably occluded in an anterior MI?
What artery is probably occluded in a posterior MI?
circumflex or RCA
What artery is probably occluded in an inferior MI?
RCA or circumflex
What supplies the apex?
The apex receives blood from all 3 arteries.
What are the 2 types of ischemia (that lead to 2 types of MI) & how do they cause the ST segment to change?
1) transmural ischemia - leads to ST elevation [1st sign you see of transmural MI before big Q waves]
2) subendocardial ischemia - leads to ST depression (subversion)
What are 3 ECG changes you might see with subendocardial ischemia?
1) ST depression - horizontal
2) ST depression - downsloping
3) T wave inversion
What does ST elevation indicate (what type of ischemia)?
transmural ischemia (see in V5 on this graph)
Bruce stress test in which exercise produces ST depression, what is the pathology?
subendocarial ischemia: during exercise, can't get adequate blood flow for demand & subendocardium 1st to get ischemia (endocardium is still perfused by blood traveling via heart)
What are 2 repolarization abnormalties that are not due to ischemia?
1) electrolyte imbalance
2) drugs
What are 2 ways to get extrasystoles?
1) Atrial Premature Beats (APB) - initiated by a premature p wave
2) Ventricular Premature Beats (VPB)
What might a premature P wave leading to an extra systole (QRS complex) look like on an EKG?
can distort (be inside of) the
T wave
What is the difference in the morphology of QRS complex if there is a APB verses a VPB & why?
APB: normal looking QRS that follows a premature P wave
VPB: QRS is WIDE b/c it originates in the ventricular myocardium so is slower
What are the 4 narrow complex tachycardias?
1) sinus tachycardia (normal)
2) Paroxysmal supraventricular tachycardia
3) Atrial flutter (p wave pattern)
4) Atrial fibrillation (no p wave pattern)
Why does the body go into sinus tachycardia & what are the relationship bt P & QRS?
sinus tachy to get more cardiac output &
P wave before each QRS
What is the difference bt atrial flutter & atrial fibrillation?
A flutter: extra P waves but in a predictable pattern
A fib: exta P waves that have no pattern
What are 2 ways to get wide complex tachycardia?
1) Ventricular tachycardia: criteria is 3 or more concecutive PVCs & rate >100/min
2) Supraventricular tachycardia, or atrial fib or flutter w/ aberrant ventricular conduction (atrial tach problem with a BBB) (ex. Rt bundle fatiques b/c of sinus tachy)
Why do you need to fix V tach right away?
V tach can cause cardiac output to fail, need to restore to normal rhythm or patient might die
What are the 2 general types of bradyarrhythmias?
1) Sinus bradycardia & its variants
2) Atrioventricular (AV) block
How many different heat blocks are there?
1st degree heart block
2nd degree heart block
Type I
Type II
Complete (3rd degree) heart block
What does 1st degree heart block?
1st degree heart block: P waves are equal to QRS but
Long PR interval
(does NOT cause Bradycardia)
What is 2nd Degree heart block?
2nd degree heart block: 1 or more P waves are not conducted (more P waves than QRS)
What is 2nd degree heart block type I?
2nd degree Mobitz type I (Wenkebach):
progressive PR prolongation until a P wave is non-conducted ("dropped")
What is 2nd degree heart block type II?
2nd degree Mobitz type II:
CONSTANT PR interval until 1 or more P waves are dropped (PR is NOT prolonged)
What is 3rd degree heart block?
3rd degree heart block: complete A-V disscocitation (complete heart block) atrial (p waves & QRS have own rhythems, not nsync) PR interval all over the map, no relationship bt P & QRS
What is the tx for 3rd degree heart blocK?