B4.017 Prework 1 Labeling an Abnormal Rhythm Flashcards
what is a conduction block
delay in normal propagation of depolarizing myocardium
normal atrial conduction velocity
PR interval
time between start of SA node and AV node firing, this occurs due to a “pause” effect of the AV node
time = 0.2 s, 200 mS, 5 small boxes
normal ventricular depolarization velocity
QRS interval
time to depolarize all of the ventricular myocardium
time = 0.12s, 120 mS, 3 small boxes
normal ventricular repolarization velocity
QT interval
time to repolarize all of the ventricular myocardium
time = 0.44 s, should shorten with tachycardia
features of a 1st degree AV block
regular rate and rhythm, doesn’t change over the course of the strip
long PR segment (more than 5 small boxes)
can be caused by antiarrhythmics or ischemic heart disease
features of 2nd degree AV block: Mobitz type 1
PR interval progressively longer, followed by a nonconducting P wave (not followed by a QRS)
low grade
treated medically
usually no worsening
features of 2nd degree AV block: Mobitz type 2
consistent PR intervals, followed by a nonconducting P wave
can advance to unstable rhythm
can lead to heart failure
pacemaker candidate
features of a “complete” or 3rd degree AV block
dissociation between electrical activity of atria and ventricles
both regular, but not in relation with one another
unstable conduction block
need pacemaker
can cause bradycardia
asystole
no electrical activity
check leads
check gain
some causes of sinus tachycardia
anemia anxiety infection exercise hypoxemia etc
what are supraventricular tachycardias?
originate above the AV node
-narrow QRS, so you know they don’t originate in ventricles
features of atrial flutter
cyclical depolarization wave in atria
sawtooth baseline pattern
features of atrial fibrillation
more common than atrial flutter
irregularly irregular R-R interval (pulse)
increases incidence of thromboembolic stroke
require blood thinner therapy
if you can’t determine the cause of a supraventricular tachycardia, how can you possibly get more clues?
give adenosine
slows conduction through AV node
helps you get a better look at the rhythm on ECG
features of monomorphic ventricular tachycardia
QRS wider than 120 mS
- depolarization wave through ventricle moves outside of the normal His/Purkinje system of conductance
- originated in ventricle, likely from the same place since all regular and look the same