Exam 4 - Lecture 4 Flashcards
Just inside fibrous pericardium is
Serious Pericardium, Parietal layer.
Directly connected to fibrous pericardium
Very very very thin stretchy layer that sits between parietal pericardium and the heart and what does it do?
Visceral layer
It is very clear and can hardly see it, allows heart to slide around easily
The more straight up and down phase 0 is, the more
fast sodium channels
Action potentials between 2 adjacent heart cells is done via
Gap junctions, mostly sodium, extremely low resistance and very fast.
Initiated by cells upstream
Downside of using gap junctions in heart
Bi-directional, can cause rogue electrical activity
APs can go backwards if hit at wrong time and cause alot of problems
What protects us from rogue action potentials in gap junctions in the heart?
Absolute refractory periods of cells in nodal tissue
Cell will not fire an AP in refractory period
3-lead EKG setup terms
Frontal/Coronal plane
Coronal or frontal plane can use
augmented leads or 3-lead ekg
the A in aVR, aVL means
augmented
Eyeball/sensor that is looking at current going towards or away from it is the
positive electrode
If current is going away from positive eyeball it will be
negative deflection
If current is going towards positive eyeball will be
positive deflection
Best lead that will see positive deflection in healthy patient
lead II on left foot/hip
Lead II eyeball on left foot/hip is positive or negative?
positive electrode
Lead I will have a positive or negative on left side of body? right?
positive left shoulder, negative right hand
There will always be _____ on left foot, _____ right arm, and _____ on left arm
2 positive electrodes (lead II and III); 2 negatives (Negative lead II, lead I); Positive lead I/negative lead III
Lead III will have a positive or negative electrode on left foot? left arm?
Positive left foot
Negative left arm
Which leads are on left foot? Number and charge
2 positives; Lead II and III
Which leads are on right arm? Number and charge
2 negatives; Lead II and I
Which leads are on left arm? Number and charge
Positive lead I, Negative lead III
In einthovens triangle, where are the leads on each side? charges?
Top side: lead I (left negative, right positive)
Left side: Lead II (Top negative, bottom positive)
Right side: Lead III (top negative, bottom positive)
Keep in mind, the bottom part of triangle is positive for both left and right, therefore the top is negative both sides. Lead I on top has left to right negative to positive.
what is the degree axis of the bottom side of Lead III of einthovens triangle?
top?
120 degrees
-60 degrees or +300 degrees
Who is einthoven
someone from europe, maybe a Duetsche scientist
What is the degree axis that the bottom side of Lead II of einthovens triangle? top?
60 degrees; -120 degrees, or +240 degrees
What is the degree axis of lead I?
Left side: 180
Right side: 0
Equipment needed for ekg
Lead selector/amplifier to amplify the signals
Chart recorder
Mean electrical axis of heart
59 degrees
Lead II angle is
60 degrees
Left axis deviation of MEA per this class? what about textbook def?
anything less than 59 degrees
<0 degrees
Right axis deviation of MEA per this class? what about textbook def?
anything more than 59 degrees
> 90 degrees
Normal deviation of MEA in this class? What about textbook definition?
59 degrees
0 to 90 degrees
Left axis deviation means
the heart is tilted towards left arm (counter-clockwise)
Right axis deviation means
The heart is tilted towards right arm (clockwise)
What can swing axis one direction or other?
Bundle branch block, depending which side
If you have COPD/huge lungs, what happens to axis?
Heart is pointing straight up and down, 90-degree axis
If we took all the air out of our lungs, what happens to axis?
Left axis deviation
If we took a huge deep breathe, what happens to axis?
Right axis deviation
If textbook tells you the MEA is -90 degrees, it means its also
270 degrees
-90 would just mean counterclockwise from 0 degree
270 is the clockwise orientation from 0 degree
Counter-clockwise means the degree is going to be
negative
Clockwise means the degree is going to be
positive
right wall of right ventricle will be ________, why?
thinner because it only pumps against the pulmonary circulation
Left ventricle will be ____, why?
Thicker, thats why it takes longer time for action potential, also bc its furthest away from AV node, pumps against more pressure.
Direction of depolarization, and starting at where?
Interventricular septum, goes up and around the ventricles to the inside of ventricle and outside of ventricle, and through the ventricle walls
Why is P-wave positive?
Electrons are moving towards lead II during depolarization
If repolarization started at SA node, what would the deflection be?
Negative
The walls of atria are very _____ compared to ventricles
thin
Why does atrial repolarization get hidden?
QRS of ventricles is much stronger, hiding the repolarization of smaller atrial muscles
If we had action potentials being generated at AV node, what can happen to P-wave?
Negative deflection if AP is going backwards
If the atrial t-wave was visible, would it be positive or negative?
Negative, because repolarization happens in same direction
Einthovens law
magnitude of Lead I + lead III = magnitude of Lead II
order of the 3 leads, what is the order of magnitude of EKG reading be in a healthy heart from largest to smallest?
Largest: Lead II
Middle: Lead III
Smallest: Lead I
If the MEA is -150 degrees, what would be the magnitude detected in Lead III? Why?
0 degrees; its perfectly perpendicular to the 120 degree angle of lead III
If the MEA is -90 degrees, what would be the magnitude detected in lead I?
0 degrees; its perfectly perpendicular to the 0 degree angle of lead I
What are the angle degrees of Lead II? Positive and negative?
+60 degrees, + 240 degrees
-300 degrees, -120 degrees
What are the angle degrees of Lead III? Positive and negative?
+120, + 300
-60, -240
What are the angle degrees of lead I? Positive and negative?
0 and +180
0 and -180
If the MEA is right axis deviated, whats the direction of deflection in lead I?
negative
If the MEA is left axis deviated to 20 degrees, whats the direction of deflection for lead III?
negative deflection
If the MEA is left axis deviated to 35 degrees, whats the direction of deflection for lead III?
Positive
what degree range will all 3 leads be positive?
Lead III needs to be between >30 degrees and <210 degrees
Lead II needs to be between >-30 and <150 degrees
Lead I needs to be between >-90 and <90
Therefore, for all 3 to be positive, the angle of MEA needs to be between 31 and 89 degrees.
What angle does Lead III need to be positive?
Lead III needs to be between >30 degrees and <210 degrees
What angle does Lead II need to be positive?
Lead II needs to be between >-30 and <150 degrees
What angle does Lead I need to be positive?
Lead I needs to be between >-90 and <90
The net deflection in lead II will have to equal
the net deflection of lead I and III
einthovens law
When using einthovens law, you MUST include the ___ deflection of each lead.
NET
subtract the negative deflection from the positive deflection for EACH lead!
Once you get past 50% depolarization, how do the QRS waves and the arrow on destructured einthovens triangle react?
Still positive, but just less positive than before
arrow is shorter
Is the endocardium depolarized or resting here?
Resting. Only the interventricular septum is depolarized at this exact moment.
Where will the direction be towards? What will the leads read? What wave is this most likely?
Up towards left arm; lead III is very negative, lead II is very slightly negative, and lead I is still positive; likely S wave
What are the leads reading right here?
Absolutely nothing. The heart is completely depolarized, there is no electron movement.
Will lead I read an S-wave?
likely not, as lead I should be seeing positive current during S-wave.
Bundle branches will depolarize the ______
little slice of tissue of LEFT ventricular side depolarizes first, then sending current toward right arm, creating that negative deflection shown in Q-wave
Is the Q-wave positive or negative in lead III?
Positive, cause its moving to the right side of the body
