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cardiac + arrhythmias Flashcards

1
Q

4 properties of cardiac cells

A

automaticity
excitability
conductivity
contractility

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2
Q

automaticity

A

ability of cardiac pacemaker cells to spontaneously generate an electrical impulse

SA node, AV junction, Purkinje fibers

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3
Q

excitability

A

ability of cardiac cells to respond to an electrical impulse

depolarization occurs when cells become electrically excited

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4
Q

conductivity

A

ability of cardiac cells to transmit an electrical impulse to neighboring cardiac cells

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5
Q

contractility

A

ability of cardiac cells to shorten in response to electrical stimulation (mechanical event)

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6
Q

cardiac action potential

A

change in electrical charge inside the cardiac cell when it is stimulated

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7
Q

polarization

A

electrical state of cardiac cell membrane when cell is at rest
no electrical activity occuring
ECG is flat, isoelectric line

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8
Q

depolarization

A

electrical event that results in a contraction of cardiac muscle

P wave = atrial depolarization
QRS complex = ventricular depolarization

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9
Q

repolarization

A

restoration of polarized state of cell membrane

ST segment and T wave = ventricular repolarization

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10
Q

absolute refractory period

A

brief period during depolarization when the cells will not respond to further stimulation, no matter how strong the stimulus

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11
Q

relative refractory period

A

vulnerable period during which some cardiac cells have repolarized but may respond to a stronger-than-normal stimulus

can cause v-fib
“R on T phenomenon”

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12
Q

cardiac conduction system

A

SA node
AV node
Bundle of His
Purkinje fibers

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13
Q

SA node

A

pacemaker of the heart located in right atrium
generates impulses at 60-100 bpm
P wave = atrial depolarization

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14
Q

AV node

A

electrical pathway between atria and ventricles located in lower right atrium behind tricuspid valve
generates impulses at 40-60 bpm
isoelectric line after P wave

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15
Q

Bundle of His

A

where ventricular conduction system originates
penetrates AV valves then bifurcates into L/R branches to Purkinje fibers
QRS complex on ECG
generates impulses at 20-40 bpm

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16
Q

Purkinje fibers

A

can act as pacemaker if there are no impulses from SA or AV nodes

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17
Q

ECG leads

A

6 limb leads provide view of frontal plane of heart

6 chest leads provide view of horizontal plane of heart

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18
Q

speed of ECG monitors

A

25 mm/sec

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19
Q

vertical line of ECG

A

represents voltage/amplitude of waveforms

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20
Q

waveform

A

either a deflection upward or downward from baseline of ECG recording

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21
Q

segment

A

line between waveforms that usually falls on ECG baseline

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22
Q

interval

A

a waveform and an adjoining segment

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23
Q

complex

A

made up of multiple deflections, such as QRS

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24
Q

P wave

A

start of cardiac cycle

SA node fires and results in atrial depolarization

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25
PR segment
after P wave, short segment that usually falls on isoelectric line
26
PR interval
P wave + PR segment following P wave reflects atrial depolarization and impulse delay through AV junction (PR segment) beginning of P to beginning of QRS complex 0.12-0.2 seconds
27
QRS complex
Q wave - first negative deflection after P wave R wave - first positive deflection of the complex S wave - downward deflection following R wave depolarization of both ventricles measured from where Q leaves baseline to where last wave levels out at baseline <0.12 seconds
28
ST segment
isoelectric line between QRS and T wave early repolarization of ventricles considered elevated or depressed if it deviates above or below the isoelectric line by more than 1 mm
29
T wave
follows ST segment represents ventricular repolarization usually rounded
30
QT interval
QRS complex + ST segment + T wave total time required for ventricular repolarization 0.38-0.42 seconds
31
7 steps to interpreting cardiac rhythm
1. determine heart rhythm 2. determine HR 3. examine P waves 4. examine P to QRS ratio 5. measure PR interval 6. examine QRS complex 7. interpret the rhythm
32
heart rate
normal 60-100 bpm atrial and ventricular rates should be the same 6-second method large-box method
33
normal sinus rhythm (NSR)
originates at SA node P to P and R to R intervals are regular P waves are uniform and upright with ONE P wave preceding each QRS complex
34
sinus arrhythmia
AKA respiratory sinus arrhythmia originates at SA node but is irregular with repetitive variation in cycle length PR interval and QRS duration are normal and consistent (not a true arrhythmia)
35
sinus bradycardia
``` originates in SA node but <60 bpm regular P to P and R to R intervals P waves are uniform and upright with one P wave per QRS complex PR interval is between 0.12-0.2 seconds QRS complex is <0.12 seconds ```
36
sinus tachycardia
``` originates in SA node at >100 bpm regular P to P and R to R intervals P waves are uniform and upright with one P wave per QRS complex PR interval is between 0.12-0.2 seconds QRS complex is <0.12 seconds ```
37
atrial dysrhythmias
originate in atria but outside of the SA node | P wave configuration will be upright, but shaped differently than P waves originating in SA node
38
premature atrial complexes (PACs)
early beats that most often originate from an irritable focus in the atria single early beats with an underlying rhythm rather than an abnormal rhythm itself P wave may be hidden in preceding T wave
39
causes of atrial dysrhythmias
``` emotional stress/anxiety fatigue nicotine, medications, alcohol, caffeine infection electrolyte imbalances CHF, myocardial ischemia ```
40
supraventricular tachycardia (SVT)
rapid dysrhythmia that originates above the ventricles in either the atria or the AV junction >120 bpm (usually 150-250 bpm)
41
atrial flutter
regular atrial rhythm; ventricular rhythm may or may not be regular depending on AV conduction initiated by irritable focus in atria causes rapid depolarization (250-350 bpm) usually no P wave, instead "flutter" waves with saw-toothed appearance
42
atrial fibrillation
occurs from rapid firing of multiple irritable foci in atria no effective atrial contraction bc no uniform wave of depolarization decreased cardiac output atrial rate 350-600 bpm no P wave, instead fib waves with wavy baseline
43
atrial kick
blood pushed out of the atria into the ventricles after they depolarize and contract together lost in A-fib
44
atrial dysrhythmia collaborative care
rate control with chronic anticoagulation (usually Coumadin) beta blockers and calcium channel blockers for rate control digoxin if no response to BBs or CCBs cardioversion TEE
45
ventricular dysrhythmias
originate in ventricles ventricles may take over as the pacemaker for the heart if: SA node fails to discharge an impulse impulse is blocked and does not reach the ventricles SA node and AV node are pacing slower than impulse generation of ventricles an irritable site in one of the ventricles produces a rapid rhythm
46
premature ventricular complexes (PVCs)
an early beat with an underlying rhythm initiated by an irritable focus in one of the ventricles no PR interval no P wave may be unifocal or multifocal
47
unifocal PVCs
look the same and originate from the same irritable focus in the ventricles
48
multifocal PVCs
look different and may originate from different irritable foci in the ventricles
49
ventricular escape rhythm | AKA idioventricular rhythm
occurs in ventricles with no association in atria may exist when both SA and AV nodes fail to pace the heart or when their impulses are blocked P waves usually absent
50
ventricular tachycardia | AKA VT, VTach
``` run of 3+ PVCs in succession ventricular rate 110-250 bpm regular rhythm P waves absent or hidden in QRS wide QRS ```
51
ventricular fibrillation
severe electrical chaos in ventricles multiple irritable foci firing in erratic, disorganized manner no ventricular contraction no cardiac output/systemic perfusion fatal within minutes without intervention
52
Torsades de pointes
type of ventricular tachycardia that can become ventricular fibrillation
53
ventricular asystole
AKA cardiac standstill no ventricular activity no cardiac output flatline ECG
54
pulseless electrical activity (PEA)
organized electrical activity is present pulseless due to absent mechanical activity or inability of heart to fill/contract poor prognosis unless reversible cause is rapidly ascertained and treated
55
defibrillation
unsynchronized shocks that use higher energy level than cardioversion used for shockable pulseless arrests including VF, VT must call "all clear" before delivering shock
56
cardioversion
synchronized with pt's QRS complex must use "synchronize" button on defibrillator shock occurs on R wave
57
cardioversion indications
unstable SVT atrial fibrillation atrial flutter ventricular tachycardia (with a pulse)
58
pacemaker
device designed to assist in stimulating the heart when the natural pacemaker is too slow or its impulses are blocked from reaching the ventricles
59
external temporary pacemaker
used in emergency situations for pts with unstable bradycardia most defibrillators can perform this function AKA transcutaneous pacing
60
internal temporary pacemaker
AKA transvenous or epicardial pacing insertion of pacing wire into either right atrium or right ventricle via central venous catheter epicardial pacing wires may be placed during an open chest cardiac procedure
61
permanent pacemaker
used to resolve dysrhythmias that are not temporary | involves placing one or more wires into the heart chambers
62
demand (synchronous) pacing
synchronized with pt's HR
63
fixed-rate (asynchronous)
fires continually at a preset rate regardless of pt's intrinsic HR
64
failure to pace
pacemaker fails to deliver an electrical stimulus absence of pacer spikes on ECG pt may become bradycardic and hypotensive
65
failure to sense
pacer fails to recognize pt's natural electrical activity | seen on ECG as pacer spikes too close behind QRS complex
66
oversensing
pacer senses extraneous electrical stimuli or artifact for actual atrial or ventricular depolarization fails to fire
67
implantable cardioverter-defibrillator
similar in size and placement to pacemaker constantly monitors HR and rhythm programmable to deliver pacing, cardioversion, and/or defibrillation
68
implantable cardioverter-defibrillator indications
pts at risk of sudden cardiac death 2/2 VF | pts who have experienced one or more episodes of VT or VF unrelated to an MI
69
radiofrequency catheter ablation
treats tachydysrhythmias (SVT, atrial flutter, A-fib) performed in EP lab under conscious sedation high frequency electrical current creates small necrotic lesions in the heart by means of thermal injury
70
MAZE procedure
series of incisions arranged in maze-like pattern in atria used for pts in chronic A-fib who are scheduled for an open heart procedure for other cardiac problems largely replaced by RFCA
71
cardiac/EP mapping
multiple flexible wires are threaded into the heart catheters have miniature electrodes that act as antennae and receive signals from all around the heart chamber computer process into 3D image of chamber

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