ECG V: Atrioventricular blocks Flashcards
a first degree AV block has a PR interval of what duration?
over 0.20 s
are first degree AV blocks related to ischemic heart disease?
no
definition: second degree AV block
one or more (not all) atrial impulses fail to reach the ventricles, with no prematurity
what is the ECG manifestation of type I second degree AV blocks?
grouped QRS complexes
what are three common etiologies of second degree AV block?
vagotonia
acute MI
drugs (beta blockers, antiarrhythmics)
where does a type I second degree AV block occur? type II?
type I - AV node
type II - Purkinje system
what is the cause of type I second degree AV block?
AV junction refractory period is longer than it should be
do the PR intervals change in type II second degree AV block?
no
type II second degree AV blocks are almost always preceded by what pattern?
BBB
what is the difference in PR intervals between type I and type II second degree AV blocks?
type I - PR intervals lengthen
type II - PR intervals do NOT lengthen
a third degree AV block is equivalent to what type of BBB?
bilateral (trifascicular)
AV dissociation indicates the presence of what phenomenon?
independent atrial and ventricular rhythms
what are three causes of AV dissociation?
- acceleration of subsidiary pacing site (increased AVN automaticity)
- decreased sinus node automaticity
- reentrant ventricular tachycardias (AVN refractoriness)
how can AV dissociation be explained?
no blockage of impulse
two areas (top and bottom) are competing
what is the comparison of rates between the atria and ventricles in AV dissociation?
similar rates
