junctional arhythmias Flashcards
what is the AV junction?
AV node and bundle of HIS
what are junctional arrhythmias usually caused by?
automaticity or re-entry
how does the P wave and QRS appear in junctional arrhythmias ? P interval?
p wave usually appear inverted or oppositely formed from the sinus’ and QRS width is normal
p interval will be < .12 seconds indicating it came from the AV junction and not in the sinus node
why is the p wave inverted in junctional arrhythmias?
because the stimulus occurred at the AV junction and gone back up into the atria to depolarize the atria first and has also gone down into the ventricles producing a normal QRS
why does the p wave occur before the QRS>? what happens if its after?
because the atria has depolarized first
if its after ventricles depolarize first and then back into the atria in a “retrograde” fashion
what are premature junctional contractions/
extra ventricular contractions that originate from an ectopic focus in the AV junction that oct before the next expected beat.
what are some ECG clues of premature junctional contractions?
p waves are absent, buried in QRS, opposite deflection of sinus p and interval will be < .12
qrs is usually normal but ay be wide
rhythm is irregular (incomplete pause)
what are the possible causes of premature junctional contractions?
can be normal
dig too
inc vagal tone (parasympathetic -n+V, valsalva maneuver, carotid pressure, MI inferior),
inc sympathetic tone (hypoxia, electrolyte imbalance)
excessive dosage of antiarrythmic
what are some hemodynamic effects of premature junctional contractions?
asymptomatic
if pt on dig and it is toxic - may lead to serious arrythmias
treatment of premature junctional contractions?
treat underlying cause
what is a junctional escape?
occurs when there is a delay in an impulse arriving from the SA node and the AV junctional takes over as a back up pacemaker at ar ate of 40-60 bpm
clues of junctional escape?
p waves are absent, buried in QRS, opposite deflection of sinus p and interval will be < .12
qrs normal
rhythm regular
possible causes of junctional escape?
normal Sinus response when sinus node fails
dig tox
inc vagal tone (N+V, valsalva maneuver, MI, myocardial ischemia)
hypoxia
electrolyte imbalance
dec sympathetic tone (hypothermia, hypothyroidism, beta blocking drugs)
other drugs (anesthesia, morphine, antiarrhythmic drugs)
what are the hemodynamic effects of junctional escape?
asymptomatic
symptomatic
-usually if rate is dec or loss of atrial kick
dec SV
dec CO
dec BP (light headedness, dizziness, syncope)
treatments for junctional escape?
correct underlying cause
inc heart rate with atropine
pacemaker
what is accelerated junctional/junctional tach/paroxysmal junctional tachy?
if rate of the AV junction exceeds 60/min, it is referred to as accelerated. if the rate exceeds 100/min (junctional tacky). when the rate exceeds 160 and the onset is abrupt (paroxysmal junctional tach)
what are the clues for accelerated junctional/junctional tach/paroxysmal junctional tachy?
p waves are absent, buried in QRS, opposite deflection of sinus p and interval will be < .12
qrs normal
rhythm regular
what are the causes of accelerated junctional/junctional tach/paroxysmal junctional tachy?
inc sympathetic tone - pain/stress/anxiety, hypoxia, myocardial schema/MI
stimulants (coffee/tea, alcohol, nicotine, street drugs), electrolyte abnormalities, dig tox
what are some hemodynamic effects of accelerated junctional/junctional tach/paroxysmal junctional tachy?
may be asymptomatic
symptomatic inc rate loss of atrial kick dec SV dec CO dec BP (light headedness, dizziness, syncope)
treatment of accelerated junctional/junctional tach/paroxysmal junctional tachy?
underlying cause
what is a wandering atrial pacemaker?
the focus moves back and forth between the SA node and an ectopic pacemaker in the atria or AV junction resulting in p waves that vary in shape and size
what are some clues of wandering atrial pacemakers?
p waves vary in shape and size
QRS rate usually normal
rate slows and picks up so rhythm may be regular
cause of wandering atrial pacemaker?
normal phenomenon especially in young and athletic individuals
chronic atrial hypertrophy
vagal effects that vary with respiration
hemodynamic effects of wandering atrial pacemaker?
usually asymptomatic or symptomatic if rate slows excessively
treatment of wandering atrial pacemaker?
none or atropine if symptomatic
