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Block 3 Found Sci > 3-ECG > Flashcards

3-ECG Flashcards

1
Q

what electrodes measure

A

flow of current in/out of cell
-will not record anything when no charge is moving so when fully de/polarized

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2
Q

ohms law

A

I = (Va-Vb)/Rab

current = diff b/t mem voltage divided by resistance of gap junctions to flow

current flows towards the pos pole

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3
Q

positive deflections

A

neg pole @ A pos pole @ B so current flow A>B TOWARS pos pole

so Va-Vb is positive bc A depolarizes first then becomes neg bc A will repolarize first

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4
Q

negative deflections

A

current flow/impulse AWAY from positive pole (switch so pos pole @ A and neg @ B)

Vb-Va negative since A still depolarizes first then becomes pos bc A repolarizes

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5
Q

flat recording

A

will show flat/no deflections if pole is not oriented right, if its perpendicular to axis

polarization still happens its just not picked up/captured

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6
Q

standard ECG calibrations

A

chart speed = 25 mm/sec (every line/box is 1 mm^2)

10 mm = 1.0 mV
5 mm = 0.2 sec, 1 mm = 0.04 sec

Y axis = voltage mV
X axis = time msec

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7
Q

leads/cameras

A
  1. 6 @ frontal plane- standard bipolar limb leads + augmented unipolar limb leads
  2. 6 @ transverse/horizontal plane- chest leads/precordial
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8
Q

augmented unipolar limb leads

A

aVR + aVL + aVF

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9
Q

chest leads

A

V1-6
V7-9 used to examine posterior heart

show ant-post view and R (v1) to L (V6)
-assume leads are left centered unless R sided electrical activity is suspected

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10
Q

lead 1

frontal plane

A

R arm > L arm (+)

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11
Q

lead 2

frontal plane

A

R arm > L foot (+)

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12
Q

lead 3

frontal plane

A

L arm > L foot (+)

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13
Q

lead aVR

frontal plane

A

from lead 3 (L arm > L foot) > R arm

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14
Q

lead aVL

frontal plane

A

lead 2 (R arm-L foot) > L arm

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15
Q

lead aVF

frontal plane

A

lead 1 (R-L arm) > foot

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16
Q

V1

chest lead

A

@4th intercostal space, R sternal border

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17
Q

V2

chest lead

A

@4th intercostal space, L sternal border

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18
Q

V4

chest lead

A

@5th intercostal space, midclavicular line

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19
Q

V3

chest lead

A

b/t V2 and V4

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20
Q

V5

chest lead

A

in line with V4 anterior axillary line

21
Q

V6

chest lead

A

in line with V4 and 5, mid axillary line

22
Q

recording electric activity

A

ECG records instantaneous changes in membrane potential in heart cells
-single depolarizing impulse recorded from different angles/electrodes
-only surface tho so will get mem potential changes of large number of cells detected

23
Q

QT interval

A

ventricular myocyte action potential

24
Q

deflections in ECGs

A
  1. P wave
  2. QRS complex
  3. T wave
25
Q

intervals of ECGs

A
  1. PR interval
  2. ST segment
  3. QT interval
26
Q

P wave

A

summation of atrial myocytes depolarizing, phase 0 of atrial myocytes

pos charge towards electrode = upward deflection

27
Q

QRS complex

A

ventricular depolarization event, phase 0 of vent myocytes

Q = slight neg deflect from depolar in septum, any neg before R
R = pos deflect from depolar spread toward electrode, down apex, any pos before S
S = neg deflect from depolar spread away from electrode, vent free walls, any neg after R

can be uppercase (big deflect) or lowercase (small deflect)

L vent takes longer to depolar bc bigger

28
Q

QRS complex

A

ventricular depolarization event, phase 0 of vent myocytes

Q = slight neg deflect from depolar in septum, any neg before R
R = pos deflect from depolar spread toward electrode, down apex, any pos before S
S = neg deflect from depolar spread away from electrode, vent free walls, any neg after R

can be uppercase (big deflect) or lowercase (small deflect)

L vent takes longer to depolar bc bigger

29
Q

T wave

A

summation of ventricular cells repolarizing, phase 3
- direction same ‘concordant’ as QRS bc reversal of charge movement, upward

30
Q

T wave concordance

A

ventricle repolarizes opposite direction than depolarized (reversal of charge)

depolar start @endocardium > epicardium
repolar start @epicardium > endocardium

31
Q

PR segment

A

P wave + flat line before QRS
= depolar of atria, AV node, bundle His, bundle branches, purkinje aka everything upstream of ventricles

32
Q

QT interval

A

start at beginning of QRS - ends wherever T wave returns to baseline
-AP of vent myocytes

33
Q

ST segment

A

flat line b/t QRS complex and T wave aka phase 2/plateau vent myocytes
-isoelectric so no current detected

34
Q

J point

A

junction of termination of QRS and ST segment

35
Q

ECG NOT detect

A
  1. SA node
  2. Atria
  3. AV node
  4. bundle His
  5. bundle branches
  6. purkinje fibers
36
Q

finding heart rate

A

use R-R interval (but techncially any deflection can be used)
-gives time b/t ventricular depolars/contracts

P-P is atrial depolar

37
Q

methods for calculating HR

A
  1. small boxes, (1500 mm/min) / boxes b/t R peaks
  2. big boxes, 300/big boxes
  3. 3 sec marker, count # QRS in 3 sec x 20
  4. 10 sec strip, QRS in 10 sec x 6

3 and 4 good for irregular

38
Q

bradycardia

A

HR < 60 beats/min

sinus bradycardia = slow heart beat og @ sinus node
-slow diastolic depolar in sinoatrial nodal cells

junctional bradycardia = slow heart beat og @ AV junction

39
Q

tachycardia

A

HR > 100 beats/min

sinus tachycardia og @ sinus node
-fast diastolic depolar in sinoatrial nodal cells

40
Q

sinus rhythm rules

A
  1. every P wave followed by QRS
  2. every QRS preceeded by P wave (bc could have QRS without)
  3. P waves move upward increasingly leads I/II/III
  4. P wave interval in more than 0.12 sec (>3 small boxes) and not more than 0.2 sec
  5. normal rhythm HR b/t 60-100 and meets 1-4
  6. sinus bradycardia <60 and meets criteria, sinus tachycardia >100 and meets criteria
41
Q

P wave abnormalities

A

if R atrial enlargement then P waves tall in I/II/III/AVF

if L atrial enlarge then P in II are broad/notched, in V1 are deep/wide
-slightly exaggerated in both

42
Q

wide QRS complex

A

wide = greater than 3 boxes/0.12 sec

means depolar does not occur thru specialized conduction system, not regular
-vents taking a long time

43
Q

if voltage lower than expected

A

bc small size heart, fluid interference

limb leads under 5 mm
precordial/chest leads under 10 mm

44
Q

voltage higher than expected

A

more muscle mass/cells contributing to deflection, less interference

precordial leads good for hypertrophy

45
Q

R wave progression

A

inc size from V1-6 bc depolar starts to the R then moves L

damage to muscle cells or ischemia change movement

46
Q

tissue hypoxia-ST segment

A

hypoxia dec ATP + act K channels = mem potential inc/less neg

dec ATP = dec act of Na/K ATPase

47
Q

infarct - ST segment

A

mem potential of larger affected area depolars so shift baseline lower
-big infarct/areas of tissue damage = ST elevation
-small ischemia = ST depression

48
Q

hexaxial coordinate system

A

I = 0 degrees
II = 60
III = 120

aVF = 90
aVR = 210
aVL = -30

frontal plane

49
Q

how to determine axis

A
  1. look at net direction to find quadrant
    -lead I = R/L + lead aVF = up/down
  2. find most isoelectric (perpendicular)
  3. check by looking at 90 (parallel lead)

Block 3 Found Sci (60 decks)

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