Normal EKGs Flashcards
What does a P wave represent?
atrial depolarization and contraction
What does a P-R interval represent?
How long should it be?
time from SA node to ventricular muscle fiber
0.12 - 0.20 sec
How long should a QRS complex be?
0.05 - 0.10 sec
How long should a Q wave be?
not more than 0.03 sec
1-2 mm in height is normal
What should ST segment look like?
should be isoelectric
not elevated more than 1 mm in std leads and 2 mm in chest leads
never normally depressed more than 1/2 mm
How do you calculate the HR from an ekg?
300/# of big boxes btw QRS complexes
What does it mean if there is an ST depression?
subendocardial ischemia
What does it mean if there is an ST elevation?
subepicardial or transmural injury or ischemia
What does a T wave represent?
ventricular repolarization
On what leads should a T wave be upright?
Inverted?
1, 2, V3 - V6
inverted: AVR
variable 3, AVL, AVF, V1-V2
What should the height of a T wave be?
not greater than 5 mm in std leads, not greater than 10 mm in precordial leads
What is the height of each box on an EKG?
1 mm
How long is one box on an EKG?
0.04 sec –> big box = 0.2 sec
What does the QT duration represent?
length of ventricular systole
What pathology is associated with an inverted T wave?
ischemic pattern
What is your left thumb when looking at an EKG?
lead I
What is your right thumb when looking at an EKG?
AVF
Is it ok for T waves to sometimes be exaggerated upright?
yes, this can be a normal variant in african americans
only if asymptomatic
What type of diseases cause a shortened P-R interval?
A-V junctional and low atrial rhythms wolff-parkinson-white syndrome lown-ganong-levine syndrome glycogen storage disease some hypertensive pts
What do you see in wolff-parkinson-white syndrome?
shortened PR interval
What do you see in lown-gangong-levine syndrome?
shortened PR interval
What would you see in anterior infarction?
deeply inverted symmetrical T wave
What would you see in inferior infarction?
tall upright symmetrical T wave
What is considered tachycardia?
> 100 bpm
What is considered bradycardia?
< 60 bpm
What are automaticity foci?
Where are they located?
potential pacemakers that, under normal conditions, are electrically silent
in atria, ventricles, and AV junction
What is the pace of the automaticity foci of the AV junction?
40-60 bpm
What is overdrive suppression?
The idea that the fastest automaticity foci will overpower and silence the slower centers
(this is why the SA node controls everything, bc it fires at the fastest rate)
Where are foci located on the AV node?
proximal end has no foci
AV junction has foci of automaticity called “junctional foci”
