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Medical Conditions > Electrophysiology & ECG Interpretation > Flashcards

Electrophysiology & ECG Interpretation Flashcards

1
Q

Transmembrane potential in neurons and cardiomyoctes

A

-70 mV

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2
Q

Describe homeostasis and it’s importance in diffusion

A

Homeostasis is a dynamic equilibrium acheived through the diffusion of molecules to evenly distribute throughout a cell when they move down a concentration gradient

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3
Q

Factors affecting diffusion

A

Magnitude of gradient
Permeability of membrane
Surface area for diffusion
Temperature
Mass of diffusing substance
Diffusion distance
Charge/Polarity of the Molecule

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4
Q

T or F: With decreased blood flow, the sodium/potassium pump stays normal

A

FALSE
The Na+/K+ pump becomes abnormal with decreased b.f.

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5
Q

Describe hyperkalemia and it’s consequences

A

Excess Potassium circulating in the blood from muscle breakdown
Creates an abnormal membrane potential/reduced diffusion gradient
K+ stays inside & membrance becomes more positive which causes nervous transmission & muscle contraction defects

Common w/ kidney disease

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6
Q

How does hyperkalemia affect Threshold Potential for APs

A

Due to being more +, reaches threshold more readily and begins to fire APs uncontrollably (abnormal mm. firing)

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7
Q

Hyperkalemia Values

A

> 5.3 mEq/L

Critical Value: > 7 mEq/L

Signs/Symptoms: Fatigue, mm. weakness, flaccid paralysis, paresthesias

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7
Q

How does Hyperkalemia affect the ECG

A

widening of QRS progresses to ventricular tachycardia/firbrillaion
Risk of cardiac arrest

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8
Q

Hypokalemia Values and Signs/Symptoms

A

< 3.5 mEq/L

Critical Value: < 3 mEq/L
Fatigue, mm. weakness, fasciculations, paralysis, respiratory failure

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9
Q

How does Hypokalemia affect ECG

A

ST segment depression
PVC/PVAC
Ventricular & Atrial tachyarrhythmias
Ventricular fibrillation
AV block

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10
Q

Cardiomyocyte Properties

A

Excitability
Contractility
Automaticity (sets own APs via SA, AV, Purkinje)
Conductivity

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11
Q

What does an ECG measure

A

The electrical impulses (depolarization adn repolarization of myocardium) which hopefully lead to heart muscle contractions

But the mechanical activity of the heart is just as important to measure (BP, pulse, etc)

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12
Q

T or F: The SA node can’t be picked up with electrodes

A

True! It is too small baby

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13
Q

What does the P-T complex represent?

A

The SA node impulse spreading through the cardiac muscle

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14
Q

What does the P wave represent?

A

Activation of the atria / atrial depolarization

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15
Q

What does the QRS complex represent?

A

Activation of the ventricles / ventricular depolarization

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16
Q

What does the T wave represent?

A

Recovery wave / ventricular repolarization

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17
Q

Describe the Cardiomyocyte’s Action Potential phases using the image
INSERT IMAGE

A

Phase 0: depolarization, Na+ in
Phase 1: small efflux of K+ via opening of K+ channels
Phase 2: Addl. K+ channels open (K efflux) and opening of Ca2+ channels (Ca influx)
cancel eachother out for prolongued repolarization
Phase 3: massive K+ eflux turns cell membrane negative
Phase 4: Activation of Na+ (in) & K+ (out) pump again

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18
Q

How does blocking of Ca2+ channels to lower HR change the AP?

A

prolongues Phase 2

19
Q

How does the sympathetic stimulation of cardiomyocytes influence the threshold potential?

A

Sypmathetic stimulation alters SA node cells due to increase in NE which increases the permeability of the cell membrance and increases the firing rate of NA (?)

(shifts curve to the left)

20
Q

How does vagal stimulation of pacemaker cells change the threshold potential?

A

Release of ACh reduces firing rate

?

21
Q

T or F: Premature ventricular contraction (PVC) during the relative refractory period is lethal

A

True!
It all comes down to a crazy timing of events but it does happen and is not good

22
Q

Dysrhythmia

A

occur as a result of altered conduction and/or automaticity
Classified by origin site

23
Q

Elements assessed with a 3-lead ECG System

A

HR and Heart Rhythm

24
Why is a 12-Lead nice
Can identify what area of heart had an myocardial infarction HR Rhythm Hypetrophy Infarction
25
P Wave ECG Timing
<0.12 s (3 small boxes)
26
PR Interval ECG Timing
0.12 - 0.20 s (3-5 small boxes)
27
QRS Complex ECG Timing
0.04 - 0.11 s (1.5-2.5 small boxes)
28
QT Interval ECG Timing
0.32 - 0.4 s
29
How can we calculate HR on an ECG
Use the R-R interval
30
What can ECG *not* determine
Mechanical functions of the heart: CO SV pulse quality BP
31
6 Steps to Naming Rhythms
Regularity Rate P Waves PR Interval QRS Complex Pt. Observation
32
Determining Regularity
R-R intervals P-P intervals
33
Sinus / Normal Rhythm
Regular Rhythm 60-100 bpm Normal P wave before ORS PR = 0.12-0.2 s QRS <0.12 s
34
Premature Atrial Contraction
Irregular Rhythm, Rate, P-Wave Normal PR-Interval and QRS Complex
35
Atrial Tachycardia
Regular Rhythm, P-R, ORS Rate: 150-250 bpm P-Wave not visible / burried by preceding T-Waves *try valsalva maneuver*
36
Atrial Flutter
Rhythm Can be Reg or Irreg Rate: 250-300 P-Waves: "Flutter or Sawtooth" PR: Non-discernable QRS Normal *only a certain number of atrial firing is actually reaching the ventricles*
37
Atrial Fibrillation
Irregular Rhythm Rate can be Controlled (<100) or Uncontrolled (>100) Absent P and P-R Normal QRS *loss of atrial "kick" causes "quivering" muscle that doesn't fully fire and contract*
38
Implications of Atrial Fibrillation
decreases preload Possible decreases SV and CO = decreased BP *not all blood gets pumped and can lead to coagulation that causes stroke, MI etc*
39
HEART BLOCKS
40
Premature Ventricular Contraction
Irregular, Underlying Rhythm and Rate P-Wave and PR Underlying/ Absent at PVC ORS wide, bizzare at PVC (>0.12 s) *PVCs can signify increased irritation to ventricles (esp. multifocal); greater the frequency the greater the risk of developing VT/VF*
41
Ventricular Tachycardia
Regular Rhythm Rate 100-250 bpm Absent P and P-R QRS Wide and Bizarre *life threatening* CO & BP will likely substantially decrease *non-sustained ventricular tachycardia*
42
Ventricular Fibrillation
EVERYTHING ABSENT GET HELP *limited to no CO; lethal rhythm*
43
Idioventricular Rhythm
Regular Rhythm Rate: 20-40 P and PR Absent QRS Complex Wide *ventricle is the rate setter*
44
R on T Phenomena
PVC occurs on the T-Wave during the relative refractory period May lead VT/VF

Medical Conditions (3 decks)

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