12 Lead Interpretation Flashcards
What are the 4 primary characteristics of cardiac cells?
1) Automaticity
2) Excitability
3) Conductivity
4) Contractility
Describe the Action Potential in Depolarization?
A five cycle phase in which the electrical charge changes in the intra/extracellular space through the cell membrane
Na and Ca move in (-)
K and Cl move out (+)
Describe Syncytium?
Cardiac muscle cells are grouped together and function as a unit and therefore will normally depolarize as a unit.
What is the Polarized state (resting potential) of the heart?
the resting state of the cardiac cell where the inside of the cell is electrically negative relative to the positive exterior of the cell.
Right before depolarization
What is the Depolarization (action potential) of the heart?
An electrical occurrence normally expected to result in myocardial contraction
Movement of ions back to a homeostasis point
What is the Repolarization (recovery state) of the heart?
The depolarized cell is polarized and positive changes are again on the outside and negative charges on the inside of the cell.
At homeostasis
When is the Absolute Refractory Period?
When the cardiac cell is unable to respond to any new electrical stimulus.
- When depolarization just happened (EARLY)
- Non - Conductive PAC’s
When is the Relative Refractory Period?
There period in which depolarization is almost complete and the cardiac cell can be stimulated to contract prematurely if the stimulus is stronger than normal
- Almost all of the ventricle has recovered from depolarization (LATE)
- BBB’s
Which leads are Bi-Polar leads?
I, II, III
- Also known as limb leads
Which leads are Uni-Polar leads?
AVR, AVF, AVL, V1- V6
- V1 - V6 also known as chest leads
How do you place a 15 - Lead EKG, and what does it show us?
V4 = V4R - 5th ICS to the right midclavicular line V5 = V8 - 5th ICS midscapular V6 = V9 - 5th ICS between V8 and the spine
Shows the Posterior Part of the Heart (V8 - V9)
Shows the Right side of the heart (V4R)
Which Ions are found inside the cell? and which are found outside?
Na and Ca are extracellular
K and Cl are intracellular
What is the “P” Wave? and what is a normal PR interval?
Atrial depolarization
0.12 - 0.2 seconds
What is the “QRS” Wave? and what is the normal QRS interval?
Depolarization of the Ventricles
less than 0.12
Describe “R” wave Progression?
As you go through V1 to V6 the R wave starts low then Peaks up and then back down
What is the “T” wave?
Repolarization of the Ventricles
Where is the “J” Point?
The junction between the ARS and the ST- segment
Where is the “QT” segment? and what does it represent?
- The beginning of the QRS to the end of the “T” wave
- Represents the duration of activation and recovery of the ventricular muscle
- Normal QT is 0.41 seconds
What is occurring during the “ST” segment and what does any change mean?
- It is the time between completion of depolarization and the onset of repolarization
- Elevation greater than 1 mm indicated infarction
- Depression greater than 0.5 mm indicate ischemia
Where is the “U” wave found?
After the “T” wave
What does it mean when there is a larger than normal Q wave?
Old MI
- Usually occurs 20 hours after a MI
Which leads look at the INFERIOR surface of the left ventricle?
II, III, AVF
- Predominantly supplied by the Right Coronary Artery (RCA)
Which leads look at the ANTERIOR surface of the left ventricle and septum?
V2, V3, V4
- Mostly perfused by the Left Anterior Descending branch of the left artery (LAD)
Which leads look at the LATERAL surface of the left side wall of the left ventricle?
I, AVL & V5, V6
- Mostly perfused by the Circumflex branch of the left artery (LCX)
