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APEX-Equipment > EQUIPMENT-cardiac rhythm monitors > Flashcards

EQUIPMENT-cardiac rhythm monitors Flashcards

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1
Q

What are the 3 internodal tracts that travel from the SA node to the AV node

A
  1. Anterior internodal tract (Bachmann bundle)
  2. Middle internodal tract (Wenckebach tract)
  3. Posterior internodal tract (Thorel tract)
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2
Q

Compare the conduction velocities of the cardiac conduction pathway from fastest to slowest

A 
SA node
AV node
His Bundle
Bundle branches
Purkinje fibers
Myocardial muscle cells
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3
Q

Conduction velocity is a function of what 3 factors

A
  1. Resting membrane potential
  2. Amplitude of the AP
  3. Rate of change in the membrane potential during phase 0
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4
Q

What 5 factors affect conduction velocity

A
  1. ANS tone
  2. Hyperkalemia induced closure of Na+ channels
  3. Ischemia
  4. Acidosis
  5. Antiarrhythmic drugs
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5
Q

Atrial depolarization occurs during which EKG events (2)

A 
P wave (begins)
Pr interval (ends)
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6
Q

Atrial repolarization occurs during which EKG event

A

QRS complex

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7
Q

Ventricular depolarization occurs during which EKG events

A 
QRS complex (begins)
ST segment (ends)
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8
Q

Ventricular repolarization occurs during which EKG events

A 
T wave (begins)
After T wave (ends)
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9
Q

P wave:
Duration=
Amplitude=

A 
Duration= 0.08 - 0.12 sec
Amplitude= <2.5 mm
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10
Q

PR interval

A

0.12 - 0.20 sec

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11
Q

Q wave:
Duration=
Amplitude=

A 
Duration= < 0.04 sec
Amplitude= <0.4 - 0.5 mm
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12
Q

QRS complex:
Duration=
Amplitude=

A 
Duration= <0.10 sec
Amplitude= progressive increase from V1 to V6
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13
Q

What does a biphasis P wave indicate

A
  1. Mitral stenosis

2. LA enlargement

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14
Q

What does a tall P wave suggest

A
  1. Cor pulmonale

2. RA enlargement

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15
Q

What does a prolonged PR interval indicate

A

1st degree HB

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16
Q

What does PR interval depression indicate

A
  1. Viral pericarditis

2. Atrial infarction

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17
Q

What 3 alterations in the Q wave can indicate MI

A
  1. Amplitude greater than 1/3 of R wave
  2. Duration > 0.04 sec
  3. Depth > 1 mm
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18
Q

What 4 abnormalities occurs with increased QRS complex duration

A
  1. LVH
  2. BBB
  3. Ectopy
  4. WPW
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19
Q

QTc interval:

Duration =

A

Men <0.45

Women < 0.47

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20
Q

What are 3 causes of elevated ST segment

A
  1. MI (> 1 mm)
  2. Hyperkalemia
  3. Endocarditis
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21
Q

Describe causes of negative T wave

A
  1. MI

2. BBB

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22
Q

What are 3 causes of peaked T wave

A
  1. MI
  2. LVH
  3. ICH
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23
Q

When is a U wave present

A

hypokalemia?

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24
Q

How is ST segment elevation or depression determined

A

By measuring the beginning (J point) relative to the PR segment
+/- 1 mm is significant

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25
What 6 EKG changes occur with elevated K+ | From early to late appearance
1. Narrow, peaked T 2. Short QT 3. Wide QRS 4. Low amplitude P 5. Wide PR 6. Nodal block
26
What 4 EKG changes occur with low K+
1. U wave 2. ST depression 3. Flat T wave 4. Long QT interval
27
What EKG changes occur when Ca++ is abnormal High= Low=
``` High= short QT Low= Long QT ```
28
What EKG changes occur when Mg++ is severely abnormal High= Low=
``` High= heart block, cardiac arrest Low= Long QT ```
29
What does a positive deflection indicate in EKG
Depolarization travels TOWARD positive electrode
30
What does a negative deflection indicate for EKGs
Depolarization travels AWAY from positive electrode
31
What does a biphasis deflection indicate for EKGs
Depolarization travels PERPENDICULAR to the positive electrode
32
What is the directionality of depolarization
Base to apex | Endocardium to epicardium
33
How does polarity of the myocyte change during depolarization
Myocyte goes from internally NEG to internally POS | This produces positive electrical current
34
What is the directionality of repolarization
Apex to base | Epicardium to endocardium
35
How does polarity of the myocyte change during repolarization
Myocyte foes from internally POS to internally NEG | Produces negative electrical current
36
Why is the T wave positively reflected during repolarization
Because repolarization travels in the opposite direction with a negative current (double negative)
37
What are the bipolar leads
Leads I, II, III
38
What are the limb leads
Leads aVR, aVL, aVF
39
What are the precordial leads
Leads V1 - V6
40
What do leads II, III, aVF monitor | Vessel and location
Inferior | RCA
41
What do leads I, aVL, V5, V6 monitor | Vessel and location
Lateral | CxA
42
What do leads V1 - V4 monitor | Vessel and location
Septum | LAD
43
What does the EKG axis represent
The direction of the mean electrical vector in the frontal plane
44
What is the easiest method to determine axis deviation
Examine lead I aVF
45
What does normal axis deflection look like
Lead I = + | Lead aVF= +
46
What does left axis deviation look like
Lead I = + | Lead aVF= -
47
What does right axis deviation look like
Lead I = - | Lead aVF=+
48
What does extreme right axis deviation look like
Lead I = - | Lead aVF= -
49
What are 5 common causes of right axis deviation
1. COPD 2. Cor pulmonale 3. Acute bronchospasm 4. PE 5. Pulm HTN
50
What are 5 common causes of left axis deviation
1. Chronic HTN 2. LBBB 3. AS 4. AI 5. Mitral regurg
51
What is normal axis deviation measurement Left axis= Right axis=
``` Normal= -30 to +90 degrees Left= more neg than -30 Right = more pos than +90 ```
52
Where does the mean electrical vector tend to point
1. TOWARDS areas of hypertrophy - more tissue to depol 2. AWAY from areas of infarction - vector moves around MI
53
What reflex mediates sinus arrhythmia
Bainbridge reflex | SA node pacing varies with respirations (d/t changes in intrathoracic pressure)
54
How is glucagon useful in some bradycardias
Useful for BB or CCB overdose | Glucagon receptors are stimulated on myocardium, increasing cAMP and HR
55
What is the dose for glucagon for BB/CCB OD
``` Initial = 50 - 70 mcg/kg Infusion = 2-10 mg/hr ```
56
1st line treatment for bradycardia | Treatment for symptomatic bradycard
1st line = atropine Symptomatic = transcutaneous pacing
57
1 physiologic causes of ST
1. increased intrinsic firing of SA node | 2. SNS stimulation
58
How does ST affect myocardial O2 supply and demand
``` Demand = increased Supply = decreased ```
59
Why is ST not tolerated in pts with poor cardiac reserve or CAD
Poor reserve = Precipitate MI or CHF | CAD = precipitate ischemia or infarction
60
How does AFib affect CO
1. Loss of atrial kick 2. Reduced diastolic filling time with RVR 3. Decreased CO
61
What medications are used to treat afib
1. BB 2. CCB 3. Digoxin 4. Anticoags to prevent thrombus
62
Initial cardioversion energy for acute onset a-fib
100 joules
63
How does a-flutter differ from a-fib
A-flutter has an organized supraventricular rhythm | Atrial rate >250
64
Describe a-flutter
Each atrial depolarization produces an atrial contraction | Not all atrial depolarization conduct past AV node
65
Initial cardioversion energy for a-flutter
50 joules
66
When does a junctional rhythm occur
When AV node functions as dominant pacemaker | Rate 40 - 60 bpm
67
Why is junctional rhythm slower
Rate of phase 4 depolarization of the AV node is slow
68
2 causes of Junctional rhythm
1. SA node depression (volatile anesthetics) 2. SA node block 3. Prolonged conduction at the AV node
69
What are premature ventricular contractions (PVCs)
Contractions that originate from foci below the AV node | -reason for wide QRS
70
What are 7 conditions that can develop PVCs
1. SNS stimulation 2. MI 3. Valvular dz 4. Cardiomyopathy 5. Prolonged QT interval 6. Hypokalemia 7. Hypomagnesemia 8. Digitalis tox 9. CVC
71
How can PVCs lead to further dysrhythmias
If PVC lands on second half of T wave, can precipitate R on T phenomenon
72
What medication can be given for symptomatic PVCs
Lidocaine 1.0 - 1.5 mg/kg
73
Treatment for V fib
Immediate CPR | Defibrillation
74
Treatment for asystole
CPR | NO shocks
75
What is Brugada syndrome
Na+ ion channelopathy in heart | Can lead to V-Tach or V-Fib
76
What are diagnostic EKG changes of Brugada syndrome
RBBB w/ ST-segment elevation in leads V1-V3
77
Treatment and considerations for patients with Brugada syndrome
ICD placement | Pad placement during surgery
78
Describe a 2nd-degree Mobitz type 1 block
PR interval progressively longer | P wave drops QRS
79
Describe a 2nd-degree Mobitz type 2 block
Some Ps conduct to ventricle, other Ps drop QRS | NO PROLONGATION
80
Treatment for 2nd-degree blocks Type 1 Type 2
Type 1 = atropine | Type 2 = pacing (atropine NOT useful)
81
Describe a 3rd-degree heart block
The atria and ventricle each have their own rates | AV dissociation
82
Treatment for 2rd-degree heart block
1. pacemaker | 2. Isoproterenol
83
What altered conduction regions produce the following block 2nd degree T1 2nd degree T2
2nd degree T1 = AV node | 2nd degree T2 = His bundle or bundle branches
84
``` What is the mechanism of class 1 antiarrhythmic drugs Ex: ```
Inhibition of fast Na+ channels | Ex: lidocaine, procainamide, phenytoin
85
``` What is the mechanism of class 2 antiarrhythmic drugs Ex: ```
Decrease the rate of phase 4 depol | Ex: BB
86
``` What is the mechanism of class 3 antiarrhythmic drugs Ex: ```
Inhibits K+ ion channels and prolongs phase 3 repol | Ex: amiodarone
87
``` What is the mechanism of class 4 antiarrhythmic drugs Ex: ```
Inhibits slow Ca++ channels, slows conduction velocity through AV node Ex: CCB, diltiazem, verapamil
88
What is the mechanism of action and dose for adenosine
MOA = Slows conduction through AV node by stimulating adenosine-1 receptor, causing K+ efflux and hyperpolarizing the cell membrane Dose = 3 mg - 12 mg IVP
89
In which dysrhythmic conditions is adenosine useful
SVT | WPW w/ narrow QRS
90
In which pts should adenosine be used with caution and why
Asthma pts | Can cause bronchospasms
91
What are 3 causes of re-entry pathways
1. Conduction occurs over a long distance 2. Conduction velocity is too low 3. Refractory period is shorter
92
What are 2 ways to disrupt a reentry circuit
1. Slow the conduction velocity through the circuit | 2. Increase the refractory period of the cells at the location of the unidirectional block
93
What is the most common cause of tachydysrhythmias
Re-entry pathway
94
How can mitral stenosis cause a re-entry pathway
Conduction must occur over a longer distance
95
how can ischemia cause a reentry pathway
Conduction velocity through the affected region is too slow
96
How can epinephrine cause a reentry pathway
It shortens the duration of the refractory period
97
What is the defining feature of WPW
An accessory conduction pathway (Kent's bundle) that bypasses the AV node (connect atrium and ventricle) There is a conduction delay
98
What is a key diagnostic feature of WPW on EKG
delta wave
99
What is the most common tachydysrhythmia associated with WPW
AV nodal reentry tachycardia
100
What is the morphology and treatment (6) for orthodromic AVNRT
Morphology = narrow QRS Treatment = increase refractory period at AV NODE -vagal maneuver, amio, adenosine, BB, CCB, cardiovert
101
What is the morphology and treatment (2) for antidromic AVNRT
Morphology = wide QRS complex Treatment = increase refractory period of the ACCESSORY pathway -procainamide, cardiovert
102
What agents (5) should be avoid when treating antidromic AVNRT
Medications that increase the refractory period (opposite of orthodromic AVNRT) -adenosine, digoxin, CCB, BB, lidocaine
103
``` What do each of the following positions categorize in pacemakers Position 1 Position 2 Position 3 Position 4 Position 5 ```
``` Position 1 = chamber paced Position 2 = chamber sensed Position 3 = response to sensed activity Position 4 = programmability options Position 5 = PM can pace multiple sites ```
104
How are the following pacing modes indicated in their settings Asynchronous = Single-chamber= Dual-chamber=
``` Asynchronous = AOO, VOO, DOO Single-chamber= AAI, VVI Dual-chamber= DDD ```
105
What does failure to capture indicate
The PM delivers an electrical stimulus but fails to trigger myocardial depolarization
106
What does magnet placement do to a PPM
Converts the PM to asynchronous mode
107
What does a magnet placement do to an ICD
Suspends the ICD and prevents shock delivery
108
What does a magnet placement do to a PM/ICD
Suspends ICD | No effect on PM function
109
Which setting of electrocautery causes more EMI with a PM
coag > cutting
110
What type of cautery causes more EMI in pts with PM
Monopolar > bipolar=US harmonic
111
When is EMI risk highest in the presence of electrocautery
When tip is used w/in 15 cm radius of pulse generator
112
Where should the cautery ground pad be placed in pts with PM/AICD
As far away from pulse generator and in location that prevents a direct line of current through PM

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