EKG/Cardiac pt 3 Flashcards
Exam 4
The main ion responsible for transmission of AP through gap junctions is _____
Na+
- Ca++ bigger, and therefore slower
AP are bidirectional because they are _____ synapses
electrical, not chemical
______ periods prevent retrograde AP
refractory
EKG set ups that look at the frontal/coronal plane
3 lead and augmented leads
Where are the +/- electrodes for lead I?
(-) R arm
(+) L arm
Where are the +/- electrodes for lead II?
(+) L foot
(-) R arm
Where are the +/- electrodes for lead III?
(+) L foot
(-) L arm
What is the name of the triangle that connects the 3 leads?
Einthoven’s triangle
Lead II is oriented at a ____ degree angle
60 - lines up with mean electrical axis
A normal mean electrical axis of the heart is _______
0 to +90°
A right deviation of the mean electrical axis of the heart is _______
> 90°; aka more than 59°
A left deviation of the mean electrical axis of the heart is _______
<0°; aka less than 59°
What are the different causes of axis deviation?
- Bundle branch block
- Larger lungs - COPD (straight up and down)
- Ventilation - decreases = left, increases = right
- Hypertrophy
If you see a mean electrical axis described as a positive number we should move in a ______ direction until we meet the described angle.
clockwise
If you see a mean electrical axis described as a negative number we should move in a ______ direction until we meet the described angle
counter-clockwise
The mean electrical axis of a P wave is expected to be headed towards the
left foot - same as QRS, but smaller d/t thinner atrial muscle
Einthoven’s Law
Lead I + Lead III = Lead II
Deflection magnitude
Where is the last part of the heart depolarized? Why?
Top left (left lateral) ventricle, farthest away from AV node
Repolarization of the atria is usually obscured by the QRS complex. If it was not, would it be positive or negative?
Negative - same sequence and direction as depolarization
What are the angles of the 3 leads?
I: 0°
II: 60°
III: 120°
Which lead would show the largest deflection?
Lead II
When Schmidt references an “eyeball” looking at an electrical impulse he is using this term to represent
The direction “looking” from the positive lead toward the corresponding negative lead.
What are the 3 augmented leads?
aVR, aVL, aVF
Which of the augmented leads is used the least? Why?
aVR - because deflections are almost always negative
There are ___ angles between Standard Leads and Augmented Leads
30°
The angle of aVF is ___
90°
The angle of aVL is ___
-30°
The angle of aVR is ___
210°
If the mean electrical axis was pointed down at 90°, which lead would have 0 deflection?
Lead I
The first portion of ventricular depolarization will happen where? How is this represented on an ECG?
On the left lateral side of the interventricular septum - Q wave, negative deflection
Which of the 3 leads has a Q wave?
I and II (negative), but not III - positive deflection - no Q wave
Which of the 3 leads doesn’t have an S wave?
lead I - positive deflection
Describe the location of the precordial (chest) leads
V1 and V2 - septal leads, on either side of the septum/sternum, in the 4th intercostal space
V3 and V4 - anterior leads
- V3 - between the V2 and V4
V5 and V6 - lateral leads
- V4-V6 - 5th intercostal space
In the R wave, what would you expect to see in each of the 3 leads?
All positive deflections
The chest leads/precordial leads cathode is represented by the position of ______ while the negative electrode is a combination of _______
The corresponding V lead (V1-V6); All of the 3 standard leads (LA, RA, LL)
If something is positive in lead II it will likely also be positive in which augmented leads?
aVL and aVF
In lead V1 we would expect to see an inverted ______ and a(n) _______ QRS complex
P-wave; inverted
What lead is utilized to determine if we have an anterior vs posterior tissue injury to the heart?
V2
If the current of injury is positive in lead V2 then we could confidently say the injury is _______
on the posterior portion of the heart.
If the current of injury is negative in lead V2 then we could confidently say that the injury is _______
On the anterior portion of the heart.
Which lead is right in the “middle” of the heart?
V2
We would expect the precordial leads to have a _______ magnitude when compared to the limb leads because ______
Larger; they are nearer the heart tissue that is being measured.
Of the chest leads we would expect to see the most positive deflection of the the QRS complex in lead
V4 - in line with normal electrical axis of heart
An inverted T wave would likely mean the ______ is repolarizing first.
endocardium
Right ventricular hypertrophy would show up as a __________ deviation. And a ______ deflection in lead I
Right axis; negative
A “rabbit ears” in a QRS complex is indicative of a ________
bundle branch block
You have identified a bundle branch block in the QRS complex. How do we differentiate a right from left bundle branch block?
A left bundle branch block would have a left axis deviation. A right bundle branch block would have a right axis deviation.
We expect there to be no electrical current in the heart after the ventricles have repolarized. This is the ______ segment
TP
Electrical current during the TP segment would indicate _______
A current of injury
