EKG Tutorial Lecture Notes Flashcards
Convention: conceive of electrical waves of the heart as
positive wave moving across muscle
positive wave moving to positive electrode yield what in electrocardiogram
positive peak
in most cases atria are electrically isolated from ventricles by what
fibrous tissue in the AV ring
Separate electrical activity
terminal purkinje fibers
fibers that innervate myocardial cells
R and left ventricle depolarize in what amount of time
less than 120 milliseconds
any initial negative deflection is called
Q wave
all positive deflections are called
R waves
All neg deflection that following a positive deflection
an S wave
exception: an initial negative deflection is called
a Q or QS wave
if no S wave then it is called
called a QR wave
If no Q wave then it is called
RS wave
Duration of normal QRS lasts
120 milliseconds
ST segment
plateau that signifies no waves toward or away from electrode
T wave represents
ventricular repolarization (also plateau???)
most of the time,
the wave of depolarization and repolarization is in the same direction
- opposite signed waves moving in opposite directions so wave is in same direction
- depol occurs endocardium to epicardium while repol occurs from epicardium to endocardium
repolarization can be considered
negative wave moving through heart muscle
PR interval
time it takes the impulse to go through Av node
P wave represents
atrial depolarization
atrial repolarization
such small volume of electrical activity (overwhelmed by QRS complex
EKG
plot of voltage vs Time
small squares: 1 mm by 1 mm
big squares: 5 mm x 5 mm
speed of standard EKG: 25 mmm per second
- time between 1 mm lines is 0.04 sec
- time between 5 mm line is 0.2 sec
PR interval lasts
0.16 secs (normally no more than 4 blocks)
QRS complex
0.08 secs (normally less than 0.120 sec)
where are electrodes placed
right arm
left arm
left leg
lead one
neg on right arm and positive electrode in left arm
