NUR 414 Exam 2 Dysrhythmias (CH. 34)

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NUR 414 Exam 2
Dysrhythmias

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NUR 414 Exam 2 Dysrhythmias (CH. 34):
Look @ 1st 5 Chapters of EKG books before next week

Cardiac Conduction System:
• The heart has a couple different functions  electrical system and mechanical system
o Electrical system causes impulse to travel throughout cardiac tissue that will then initiate a
mechanical contraction of the heart
• Normally these impulses sent throughout tissue  stimulus to heart  causes contraction – if you do not
have contraction of heart then you do not have cardiac output
• Heart is simply a pump
• 4 chambers:
o atria top, ventricles bottom
• SA node:
o located in right atrium, pacemaker of the heart, this tissue is what causes an automatic
stimulus (leads to heart beat), normal HR is 60-100
o Supplied by sympathetic and parasympathetic nervous system
o anxiety can cause the sympathetic nervous system to stimulate HR to go up
• On EKG monitor we can see electrical activity- as stimulus going through atrial tissue it will show up
as a P wave on monitor = atrial depolarization – SA  AV node
• AV node:
o in the middle right above the septum (separates l and r side), slight delay here,  we want
impulse to travel through atrial tissue so it will contract and push blood from atria to
ventricles.
See delay between P and Q wave on EKG monitor
• After AV node impulse goes to bundle of his --> ? This is QRS on monitor – the ventricle (big muscle
of heart contract and cause big spike
• On EKG monitor at the end we see T wave – it is at rest and is about to start this cycle again
• SA  AV ()slight delay  bundle his  r and l bundle branches  perkinje fibers  start over
(ventricle gets ready to start process again)




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Conductivity or Electrical activity is different than the mechanical action of the heart beating


Properties of Cardiac Cells:
• Conductivity:
o each cell has the ability to transmit an impulse from one cell membrane to the next, how
we can have this conduction system from SA node  AV node, etc.
• Automaticity:
o talking about pacemaker cells only – nothing tells them they have to beat and send stimulus
out; they do all on own without any outside source telling them to do – independent of
anything else. Spontaneously initiates this
• Excitability:
o occurs with NON-pacemaker cells  ability to pick up an impulse and stimulus causes a
contraction. They’re excitable- respond to this stimulation
o All non-pacemaker cells can have stimulus to make them have a contraction (electrolyte
imbalances, etc. – any cell can initiate a stimulus because they are all excitable  leads to
dysrhythmia)
• Contractility:
o the ability of cells/muscle fibers to shorten when stimulated and cause a contraction causing
blood flow
• Refractory period:
o period where a stimulus will or will not cause a contraction to occur, unless there is a very
strong stimulus
▪ Absolute refractory period:
• time when regardless of how strong an impulse is, if it hits in this part of
cardiac cycle it WILL NOT cause a dysrhythmia, it is a SAFE ZONE!
Beginning of QRS and upslope of T wave
▪ Relative refractory period: Very strong stimulus can cause heart to go out
of rhythm. May put heart into a lethal dysrhythmia
• area we worry about
and get concerned –
vulnerable
period/danger zone –
when T wave down
slopes – if impulse is
strong enough and hits
here  dysrhythmias,
can lead to ventricular
dysrhythmias and can
be fatal –
VULNERABLE AREA
ON THAT T WAVE
DOWNWARD
SLOPE!




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ECG/EKG Monitoring:
• EKG- Measure electrical activity
o EKG is a one time reading, stop in time! 12 leads- 12 different views of the heart – limb leads
(electrodes) = on arms and legs, chest leads – on chest – benefit= provides a lot of different
views of heart that telemetry does not
▪ We want to see a change here, if they are having chest pain, check for ischemia
or infarction, electrolyte imbalance
o If change in cardiac rhythm (see change on telemetry) doctor will order EKG to confirm it
o Pt comes in think having heart attack – order 12 lead EKG bc looking at that will show what
artery is occluded causing this
o May order 12 lead EKG for electrolyte imbalance
o Gives 12 different views, pt must hold still to get good tracing
• Telemetry- portable EKG monitoring, 3-5 leads, tracing/ekg recording is only as good as electrodes
are place on pts. Need good skin prep and good placement of electrodes! – skin cleaned, dried,
won’t stick if sweaty or oily, may need to shave hair (won’t get good conduction) ideally electrodes
need flat surface on skin – do not put over bones-bone will act like an insulator (sternum, clavicle,
ribs-- but them in between)
o Telemetry is continuous monitoring
o Electrodes need to be moist, can’t be dried out
o Reapply every 24 hours, clean skin, reposition often
o Interpret strips in lead 2

ECG/EKG Paper:
• Vertical side – amplitude or voltage  not too concerned about this
• We are concerned about horizontal – looking at time, how we can interpret different dysrhythmias
• Tiny box = 400ths of a second = 0.04
• Big box = 5 little boxes = 2/10ths of a second = 0.20
• 5 big boxes = 1 second
• When interpreting strips – 6 second strip  have to have 30 large boxes


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