Lecture 10/30: EKG continued Flashcards
Test 4
Vetocardigrams were onces analyzed by ___________
Oscilloscopes
Why would we have an inverted T-wave?
Repolarizing the ventricular endocardium, and then the epicardium
What is a biphasic T-wave?
T-wave has both negative and positive deflections (a dip & a hill)
This indicates the tissue repolarizing in an abnormal way
L axis deviation could be:
BBB
R axis deviation could be:
Problem with atria
Long/Tall QRS in Lead I indicates:
Very long time to depolarize
usually d/t stretched out L ventricle
What do bunny ears represent?
BBB
What does Bunny ears in lead III mean?
L BBB
What happens in the ventricles when you have a bundle branch block?
If you have a R or L BBB it causes resistance in that side of the ventricle and the opposite side depolarizes faster.
This causes the vector to shift towards the tissues that is still resting (towards the block)
What causes large QRS complexes in lead III?
R ventricular hypertropy
If an area is chronically depolarized, where is the vector going to point at rest?
Towards the resting tissue
What is a COI?
Current of injury
shows current from injured area when there should be no current
Where is there no current in a healthy heart?
End of T-wave & beginning of P-wave
An area of injury is a piece of tissue that is stuck in a ___________ state
depolarized
What does a vector tell you?
Direction: where injury is
Magnitude: How big the injury is
When there is suppose to be no current & there is current, what does this mean?
There is an area of injury that is generating a current of injury
Where is the J-point?
End of S-wave
What does a positive (+) COI in V2 represent?
posterior injury
What does a negative (-) COI in V2 represent?
anterior injury
What lead tells us whether it is a posterior or anterior injury?
V2
If the beginning of the P wave is below the J-Point, what type of injury do you have?
(-) COI
If the beginning of the P wave is above the J-Point, what type of injury do you have?
(+) COI
What does the J-point represent?
End of S-wave
All of Ventricles depolarized
When plotting COI, the mean vector points _______ the injury
away from
A small area of injury in the ventricles is _________ . An area of injury that involves the entire wall ventricles is an_______. Both are more likely to originate in the ________ layer in the ______ ventricle due to high pressures.
Ischemia
Infarct
Subendocardium
Left
Where are Infarcts and Ischemia more likely to happen?
Subendocardium of L ventricle
Describe how ischemia would look in Lead II on an EKG? Why?
Ischemia is normally in the subendocardium in the L ventricle, which will still cause the vector to point to the L foot.
You will be able to see a (+) COI in lead II after the T wave and before the P-wave.
Since the T-P segment has RAISED UP, including the P-wave reference point. The J-point is low.
It will appear that the ST segment is lower
ST DEPRESSION
Describe how an infarct would look in Lead II on an EKG? Why?
Infarcts are large and are normally in the subendocardium in the L ventricle, which will cause the vector to point to the R arm.
You will be able to see a (-) COI in lead II after the T wave and before the P-wave.
Since the T-P segment has DROPPED DOWN, including the P-wave reference point. The J-point is high.
It will appear that the ST segment is higher
ST ELEVATION
What is the difference between ischemia and infarct?
Ischemia = blood obstruction to small part of heart
Infarct = blood obstruction to large part of ventricle wall
both normally orginiating in subendocardium L ventricle
You will have a ______ vector in infarcts than ischemia
bigger
A bigger vector means a ________ area is effected
bigger/larger
In a L ventricle infarct, which way will the vector point?
R arm
In L ventricular ischemia, which way will the vector point?
L foot
ST elevation is associated with _______ and ST depression is associated with ________.
Infarcts
Ischemia
What is your reference point when determining your point of injury?
J-point
isoelectric point
Which 2 areas should always be on the same line in an EKG in a healthy heart?
J-point & T-P segment
What is the bottom of the heart?
Apex
If the mean COI vector is pointed up, what part of the heart is affected?
apex
T/F: EKG machines can zero each lead to identify J-point?
F
In L-type V-G Ca++ , where is the activation & inactivation gate?
Activation = outer
Inactivation = inner
What is the top of the heart called?
The base
What is the activation gate called in V-G Ca++ channels?
D-gate
What is the inactivation gate called in L-type V-G Ca++ channels?
F-gate
V-G L-type Ca++ channels work similar to which channels? And how are they different?
V-G Na++ channels
The gates have different nicknames
Na+: inactivation-h
activation-m
Ca++: activation-d
inactivation-f
L-type Ca++ is slow to open & slower to close (therefore stays open longer)
T/F: L-type V-G Ca++ channels can inactivate themselves
T
In order to use a cell again, what do we need to happen?
The gates need to be reset, cells need to be repolarized
What is a slow AP? Why?
SA node AP
The slope in phase 0 is not steep compared to fast AP in ventricular conduction system caused mostly by fast Na+ channels
Phase 4 in________ AP is steeper and fastest. It is also called __________.
SA node
Diastolic Depolarization
Describe Na+ involvement in SA node AP?
Phase 4: a small amount of Na+
Phase 0: No Na+
What is the theory about V-G Na+ channels in SA nodal tissue?
- There are none
- Vrm doesnt get low enough to activate them
At what voltage can L-type Ca++ channels reset?
-55 mV
What happens when we increase Vrm in ventricular conduction system AP?
Lose Fast Na++ channels
Slope of phase 0 tapers
Peak of phase 1 wont be as high
if very high
No fast Na+ channels will be involved & will look like SA node AP
What happens if your Vrm is so positive that you lose VG Ca++ channels?
“AP becomes a squiggly line”
Asystole/Afib
What are the top reasons that your Vrm becomes so positive that you lose fast Na++ channels and VG L-type Ca++ channels?
- High levels of K+
- Acidosis (Increase H+; pH less than 7.4)
- MI (ischemia/infarct)
How does acidosis increase Vrm?
Prevents enzymes from catalyzing chemical reactions at optimal speeds for resetting cells needed for provind energy to cells
In SA node: What does increasing Ach does?
Bind to mAch-R –> increase K+ permeability –> decrease Vrm –> decrease HR
In SA node: What does decreasing Ach does?
decreases K+ permeability –> increases Vrm –> increases HR
In SA node: what effect does the mAch inhibitory-R have?
Inhibits Adenylyl cyclase –> decreases HCN channels –> decreases Vrm –> increases phase 4 –> decreases HR
In SA node: what effect does a Beta-R have?
With agonist: increases adenylyl cyclase
With antagonist: decreases adenylyl cyclase
In SA node: What channel can be attached to a Beta-R?
HCN channel
Increasing cAMP increases _________
PKA (Protein kinase A)
In SA node: What does PKA phosphorylates? How does this work?
- L-type Ca++ channels: makes them more sensitive & easier to open; increasing HR
- Phospholamban: inhibits SERCA pump in cardiac myocyte; increases speed of SERCA pump; increases HR
- Troponin I: Increases contractile sensitivity to Ca++; increases crossbridge generating filaments; increases HR
In SA node: How does HCN channels effect HR?
Increase permeability to Na+/Ca+ during phase 4 –> makes slope steeper –> increases HR
cAMP =
Cyclic Adenosine Monophosphate
In SA node: Which Beta stimulation in reference to increasing PKA and phosphorylation is more dangerous? Why?
Phosphorylating L-type Ca++ channels
This causes heart attacks.
If too sensitive, will open & generate an AP when there should be one.
What is DAD and EAD? What contributes to this? Why is this relevant?
Delayed after depolarization
Early after depolarization
This is present in some arrhythmias
L-type Ca++ channels contribute to this
T/F: cAMP falls apart on its own
T
What breaks down cAMP?
PDE (Phosphodiasterase)
What happens when we give PDE?
Decrease cAMP –> decreases PKA –> decreases HR
What happens if we inhibit PDE?
Increase cAMP –> increase PKA –> increase HR
What is a normal QT interval?
0.25 - 0.35 seconds
