A&P Test 4 Flashcards
what does a small arrow mean when talking about mean electrical currents?
what does a big arrow mean when talking about mean electrical currents?
small= a small amount of current
large= a large amount of current
what is a hypotenuse?
The longest side of a right angle triangle
When the interventricular septum is first depolarizing, it goes in what direction?
How does this show on an EKG?
from right to left.
as a small (because there is only a small amount of depolarized tissue able to send electrons out) negative (because it is moving from right to left) depolarization known as the Q wave
where in the interventricular septum do the bundle branches feed into?
on the left side
which lead is least likely to have an S wave?
Lead 1
what do the letters stand for in aVF, aVR, and aVL
augmented
voltage
the positive end of the specific lead you’re looking at (right, left, foot)
what is used as the negative end of the augmented leads?
the average of the two leads on either side of it
i.e. (average of lead 1 and 3 is the negative end of lead aVR)
where are the positive and negative ends on electrode aVR?
positive: right arm
Negative: average of lead 1(left arm) and 3(left foot)
where are the positive and negative ends on electrode aVL?
positive: left arm
Negative: average of lead 1(right arm) and 3(left foot)
majority of the deflections that are picked up in lead aVR are going to be
negative
which augmented lead is used the least?
aVR
where are the positive and negative ends on electrode aVF?
positive: left foot
Negative: average of lead 2(left arm) and 1(right arm)
Do you have to put more stickers on the patient to get the aVF, aVR, or aVL views?
No. A normal 3 lead ekg set up would work if it is wired to read the augmented leads too.
angle of lead 1
0 degrees
What is the angle between the standard leads and augmented leads?
30 degrees
angle of aVF
90 degrees
angle of lead 2
60 degrees
angle of lead 3
120 degrees
angle of aVL
-30 degrees
angle of aVR
210 degrees
what is shown as a downward deflection in aVR?
p
qrs
t
What deflections would you expect in a normal aVL and aVF?
Positive P, QRS, and T
what is the normal magnitude of aVL and aVR?
1.5mV
What is another name for “chest leads”?
precordial leads
what do the precordial leads use as the the negative electrode?
an average of the 3 standard leads
where are the first 2 precordial leads placed?
either side of the sternum at the 4th intercostal space
where are the first 2 precordial leads called?
why?
septal leads
on either side of the septum at the 4th intercostal space
which leads are the anterior leads?
v3 and V4
which leads are the lateral leads?
V5 and V6
which intercostal space should leads V4, V5, and V6 be placed?
5th intercostal space on the left side
where is lead V3 placed?
sandwiched between lead V2 andV 4
what deflection would you expect to see in lead V1?
large negative QRS deflection
p wave is inverted
what deflection would you expect to see in lead V2?
negative QRS
which lead is used to find anterior or posterior ischemia in the heart?
why?
v2
it’s location right in the middle of the heart gives us a great view
What kind of depolarization would you expect to see if the posterior side of the heart is depolarized from injury but the anterior part of the heart has repolarized?
electrons from sick part of posterior heart should go towards the positively charged areas in the anterior parts of the heart
This current is going straight for the “eyeball” of lead V2 and should show up as a positive deflection
What is happening in the heart if you have a negative current of injury in lead V2?
The anterior portion of the heart is injured and constantly depolarized while the posterior portion is reset. The electrons from the anterior portion of the heart would move towards the back of the heart, away from lead V2 showing as a negative deflection.
Which leads should have the larger deflections on 12 lead EKG?
The precordial leads, because they are closer to the heart
If you have to pick, which lead is the most helpful/useful on a 12 lead?
Lead V2
As you move farther out on the chest wall you would expect the deflection to be _____
smaller
which lead has the most positive deflection if the heart is normal?
v4
A long time ago, how were heart voltages and waves read?
using oscilloscopes
how did oscilloscope works?
You would see a line moving around in time in a certain pattern.
The read out on the screen was a depiction of the electrical activity in the heart.
It was a product of different vectors called a vectorcardiogram.
Which part of the heart is the first to reset
epicardial tissue at the front of the heart
What does an inverted T wave mean?
That the ventricles are resetting in an unusual fashion, probably from inside to outside. (generally isn’t a good thing)
If we have an abnormal repolarization of the ventricle what results on the EKG?
an abnormal T wave.
what is a biphasic t wave?
when the t wave is both half down half up. The tissue is repolarizing in an abnormal way, Smidt doesn’t know how else to explain this.
How to decide the magnitude of a vector from looking at an EKG?
Determine the height of the QRS by subtracting the negative portion form the positive portion.
When looking at an EKG, what are the steps to diagnosing what is wrong with the patient’s heart?
Pick two leads to find the mean electrical axis, usually leads I and III.
Look at the QRS to determine which direction the vector should point and the magnitude/height of the vector.
Plot these vectors.
Draw perpendicular lines on the points of both arrows. Where these lines intersect is the average electrical axis.
compare this to normal to decide what is wrong with the heart.
Draw the vectors and mean electrical axis for this EKG.
What kind of axis deviation is this?
What would cause this?
right axis deviation
right ventricular hypertrophy
Draw the vectors and mean electrical axis for this EKG.
What kind of axis deviation is this?
What would cause this?
Left axis deviation
d/t left bundle branch block
What does “rabbit ears” mean on a QRS?
bundle branch block
Draw the vectors and mean electrical axis for this EKG.
What kind of axis deviation is this?
What would cause this?
right axis deviation d/t right ventricular hypertrophy
Why is repolarization harder than depolarization?
There are a lot of factors that have to be working correctly(i.e. Na+/K+ pump) and all of those things require energy. If there isn’t enough energy for each of these(could be from a clot) then you get a current of injury.
Where on an EKG might you see a current of injury? what might this look like?
Between the T wave and next P wave when the entire heart is supposed to be resting.
ST segment Depression
ST segment elevation
what does the angle and length of the arrow denote when talking about mean electrical axis?
angle= direction of mean electrical axis
length= magnitude of electrical activity/current
What is a vector?
a little arrow with a dot at one end
