Cardiac Rhythms Flashcards
SA node intrinsic rate
60-100
AV node intrinsic rate
40-60
purkinje fibers intrinsic rate
<40
energy moving towards a positive electrode =
upright waveform
energy moving towards a negative electrode
inverted waveform
big box =
0.2s
p wave represents
time it takes for impulse from SA to spread throughout atria (atrial depolarization)
small box =
0.04s
PR interval represents
time it takes for atria to depolarize and impulse to move through AV
normal PR interval
0.12-0.20s
QRS complex represents
time it takes for impulse to travel through ventricles
normal QRS duration
<0.12
ST segment represents
end of ventricular depolarization + beginning of ventricular repolarization
T wave represents
ventricular repolarization
QT represents
time from beginning of ventricular depolarization through end of ventricular repolarization
QT duration
</= 1/2 R-R (0.36-0.44)
what is the relative refractory area where it could result in lethal rhythm
downslope of T wave
calculating rate
number of squares between 2 R waves divided by 1500 (regular rhythms only)
1 big box = how many small box
5
what is a sinus rhythm
originates from the SA node
how long after an MI can ST elevation persist?
48hr, look for downtrends
what two components make up the AV junction
bundle of HIS + AV node
AV node function
slow conduction of electrical impulses from the atria
characteristics of P wave in junctional rhythm when atria depolarize first
inverted P hugs QRS + PR < .12s
characteristics of P wave in junctional rhythm when ventricles depolarize first
QRS followed by inverted P wave
characteristics of P wave in junctional rhythm when atria + ventricles depolarize at same time
no p wave, hidden in QRS
rate for junctional rhythm
40-60
rate for accelerated junctional rhythm
61-100
junctional tachycardia rate
101-150
5 instances of risky PVC
new onset/6 or more per min/coupled or sequential/multifocal/occurring on vulnerable T wave
what are AV heart blocks
block between SA and terminal purkinje fibers
first degree AV block characteristics
PR >0.20 everything else regular
2nd degree AV wencheback characteristics
PR longer longer longer drop + irregular rhythm
2nd degree AV mobitz characteristics
constant PR interval for those QRS that have P’s
3rd degree AV block characteristics
PR interval is random and no relationship of P to QRS wave
in paced rhythms what does firing mean
electrical impulse that generates a spike
in paced rhythms what does capture mean
response to pacemaker impulse generating a waveform
in paced rhythms what does sensing mean
is the HR at least 60 + are there any spikes in places that dont make sense?
who is at risk for sudden death
EF 35% or less and wide QRS
what is failure to capture
pacemaker fires appropriately but pacer spike is not followed by a waveform
what is failure to pace
pacemaker fails to fire leading to asystole or bradycardia
what is failure to sense
pacemaker fails to see intrinsic electrical activity
what are bundle branch blocks
impulse is stopped by bundle branch and will redirect through the unaffected side causing a widening QRS
difference between SVT and ST
SVT HR = 150-250 + p waves are hidden or abnormal in appearance
characteristics of idioventricular rhythm
HR = 20-40 + wide QRS and QT
standard ECG settings
10mm amplitude + 25mm/s
when is posterior MI suspected
ST depression/upright T waves/tall broad R waves in V1-V3
when is 15 lead indicated
posterior MI suspected
when is 18 lead indicated
inferior wall MI present and R ventricular wall suspected
