5 - EKG #1 Flashcards
What are the learning objectives?
1) Describe the principle of how an EKG works
2) Describe the electrical physiology within the heart including:
a) Myocardial action potential generation
b) Overall direction of electrical activity
c) Intrinsic rates of specialized cells
3) Recall the names of the 12-leads on an EKG and list the anatomic area of the heart they represent
4) Label the 5 waves (PQRST) on a normal EKG
5) Calculate heart rate on an EKG using an equation and a visual method
6) State a normal adult heart rate
What is an electrocardiogram?
A medical device that provides a recording of electrical activity of the heart
What does an EKG provide?
Information regarding abnormal electrical activity
Who developed the first electrocardiogram?
Willem Einhoven
Myocardial Action Potential:
Describe Phase 0
K+ moves out
Na+ moves in
+30mV
Myocardial Action Potential:
Describe Phase 1
K+ moves out
Na+ channels close
Cl- comes in
+10mV
Myocardial Action Potential:
Describe Phase 2
K+ moves out
Ca2+ moves in
+5mV
**plateau phase
Myocardial Action Potential:
Describe Phase 3
K+ moves out (3x amount)
Ca2+ channels close
-90mV
Myocardial Action Potential:
Describe Phase 4
K+ moves out
Na+/Ca2+ moves in
- 70mV
- gap junction
What is resting membrane potential?
-70mV
_____:
Pacemaker, pathways transmit signal to AV node
SA Node (internodal pathways)
_____:
Communicates signal from atria to ventricles
AV node
________:
From AV node to the left and right bundle branches
Bundle of His
__________:
Facilitates ventricular contraction
Pukinje Fibres
How fast does it fire?
SA node (pacemaker)
60-100 bpm
How fast does it fire?
Atrial cells
55-60 bpm
How fast does it fire?
AV node
45 - 50 bpm
How fast does it fire?
Bundle of His
40 - 45 bpm
How fast does it fire?
Bundle branch
40 - 45 bpm
How fast does it fire?
Purkinje cells
35 - 40 bpm
How fast does it fire?
Myocardial cells
30 - 35 bpm
Where does V1 and V2 go?
septum
Where does V3 and V4 go?
anterior left ventricle
Where does V5 and V6 go?
lateral left ventricle
V1-V6 are called _____ leads
precordial
Where does aVR go?
Right atria
Where does 2, 3, and aVR go?
inferior wall (RCA)
Where does 1, aVL, V5 and V6 go?
lateral wall (circ/LAD)
What does P represent?
atrial contraction (depolarization)
What does QRS represent?
ventricular contraction (depolarization) & atrial repolarization
What does T represent?
ventricular depolarization
The rhythm strip:
Each small box = ____
0.04 seconds
The rhythm strip:
Each large box (containing 5 small boxes) = _____
0.2 seconds
Formula for rate (bpm) ?
Rate (bpm) = 1500/# of small boxes between R waves
What is a normal PR interval?
120-200ms
What is a normal QT interval?
360-440ms
Where does PR start and end?
Atrial depolarization to the beginning of the QRS complex
Where does QT start and end?
The duration of ventricular depolarization & repolarization
Drugs can prolong PR and QT intervals and lead to ______
arrhythmias
