unit 5 big test Flashcards
what is cardiac output- definition and formula
how effectively the heart is pumping. stroke volume multiplied by HR
what does automaticity refer to
the ability to initiate signals
what does irritability refer to
the ability to respond to signals
what does conductivity refer to
the ability to pass on a signal
what is the path of electricity in the heart
the SA node, intraarterial tracts and Backman’s Bundle, internodal tracts, the AV node, the bundle of His, bundle branches, purkenji fibers
what brings the electrical impulse to the LA
Bachman’s bundle
what happens to the impulse at the AV node
it pauses, allowing the atria to empty
what is the inherent rate of the SA node
60-100
what is the inherent rate of the AV junction
40-60
what is the inherent rate of the purkenji fiberes
20-40
what does the P wave represent
atrial depolarization
what does the PR segment represent
atrial systole and the pause at the AV node
what does the PR interval represent. where do you measure it?
the whole atrial cycle except repolarization. measure from beginning of P to Q
what does the QRS complex represent
ventricular depolarization
what does the ST segment represent. where do you measure it
from the end of S to the beginning of T. it represents ventricular systole.
what does the QT interval represent
the complete ventricular cycle
what does the t wave represent
ventricular repolarization
what does the U wave represent
late repolarization, which is not usually seen
what does the Ta wave represent
atrial repolarization, not usually seen as it’s hidden in the QRS
what is the appropriate measurement for the PR interval
0.12-0.20 seconds
what is the appropriate measurement for the QT interval
0.36-0.44 seconds
how do you use the 6 second method
count number of QRS in six seconds and multiply by 10
how do you use the 1500 method
count the small boxes between QRS complexes and divide 1500 by the number you counted.
how do you use the 300 method
count the number of big boxes between QRS and divide 300 by the number of boxes
what makes a rhythm regular
when the R-R interval varies by no more than 2 little boxes
what happens if the sinus node fails
a lower pacemaker will take over at its slower inherent rate
what controls conduction in sinus rhythms
the sympathetic and parasympathetic nervous systems
symptoms of decrease cardiac output
pallor (paleness), dizziness (vertigo), chest pain (angina), SOB, confusion, decreased urine output, hypotension, diaphoresis
what is atropine used for
accelerates HR in symptomatic bradycardia
what are beta blockers used for
to block heart beats. slows the heart in symptomatic tachycardia.
what is digitalis used for
to increase the strength of contraction (might also slow the heart)
acetaminophen brand name
tylenol
ibuprofen brand name
motrin
what is the tendency of atrial rhythms
rapid rhythms that usurp the sinus
where do impulses originate from in atrial rhythms
one or more irritable foci
what shapes can P waves be in atrial rhythms
flat, pointy, notched, biphasic, hidden in T
non conducted PACs lack what
PR intervals and QRS complexes
what does a T wave that is suddenly different from previous ones indicate
it is probably hiding a P wave
what are non conducted PACs
when the premature beat comes before ventricles have repolarized
when is there an emergency in sinus arrest
a true pause you miss at least one QRS, emergency comes when the pause lasts greater than 6 seconds
what is the affect of Afib on cardiac output
the atria will not contract, so you lose atrial kick (atrial systole), which is responsible for 15-30 of cardiac output
where does conduction originate in junctional rhythms
close the the AV node and the bundle of His, but not in the node itself. they can originate in high, low, or mid AV junction.
what does retrograde mean
the impulse in a junctional rhythm goes backwards to the atria
why is P inverted in junctional rhythms
because electricity is moving up and to the right towards the atria, instead of down and to the left
what does it mean if you have an early beat and you see no P wave
if there is no change in the previous T wave, it is a PJC. if the previous T wave looks different than the rest, it is a PAC
junctional tachycardia with no visible P wave is called
SVT
which rhythms are the most lethal
ventricular. almost all cause symptoms of decreased cardiac output, including cardiac arrest
when viewing ventricular rhythms from lead 2, which way will the QRS face
down
where do impulses originate in ventricular rhythms
in one or more irritable foci and travel slowly through the ventricular tissue
what is the name for two PVCs in a row, PVC occurring every other beat, and PVCs occurring every 3rd beath
couplets, bigeminy, and trigeminy
when are PVCs emergencies
when there are more than 6 in a minute, when they are multifocal (mirroring each other), and when R is on T
bundle branch blocks
they cause a delay as the impulse travels through the block, causing a wide QRS. P wave will be present.
what are pacemakers, what are they used for
devices that send electrical signals to cause depolarization. they are used to maintain a reasonable HR with bradycardia.
what is the difference between a fixed rate and demand pacemaker
fixed rates are rarely used. they send signals at a specific interval regardless of the actual rhythm the patient has. demand pacemakers send a signal only if the rate drops below the threshold that is set.
what is a captured versus not captured pacemaker spike
captured are spikes that are followed by a P or a QRS. not captured are not
what do ST segment changes (elevation, depression) indicate
MI
what do flat T waves indicate
hypokalemia
what do peaked T waves indicate
hyperkalemia
what do pathological Q waves indicate
MI
