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PHYSIO EXAM 2 > L17/18 EKG > Flashcards

L17/18 EKG Flashcards

1
Q

Electrical dipoles

A

At rest no change in voltage detected (even though has membrane potential)

Depolarizing - differential in voltage detected

Fully depolarized returned to resting conditions

Repolarizing - differential in voltage detected

At rest no differential

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2
Q

Dipole

A

Pos and neg charge separated by smaller distance which generates local current flow and electrical field

Dipoles close together in space and time can summate

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3
Q

Vectors

A

Physical quantities with magnitude and direction represented by arrows

Tell what is primary way heart is depolarizing

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4
Q

Cardiac vectors

A

The resultant sun of all dipoles during cardiac cycle

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5
Q

Electrocardiogram

A

Record of overall speed of activity throughout the heart during depolarization and repolarization

Record of part of electrical activity induced in body fluids by cardiac impulses that reach body surface (not direct actual electrical activity of heart)

Comparisons in voltage detected by electrodes at two different points on body surface
Not actual potential generated
Does not record potential when muscle is completely depolarized or repolarized

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6
Q

As a positive wave of depolarization within the myocytes flows

A

Towards a positive electrode, there is a positive deflection recorded on the ekg

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7
Q

Lead arrangements

A 
Limb leads (frontal) 
  Bipolar leads 
      I, II, III
  Augments unipolar leads 
    aVR, aVL, aVF

Chest leads (transverse)
Precordial leads
V1-V6

Makes combination that allows to create vector

Gives all different perspective of the heart

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8
Q

Standard limb leads give

A

Einthovens triangle

Bipolar limb
Frontal plane

Bipolar leads - each lead made up of two active electrodes (+ and -)

+ and - are attached to the arms and legs

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9
Q

Augmented limb leads

A

Unipolar limb lead
Oriented on frontal plane

Active (exploring) electrode plus an indifferent electrode

Form
Intermediate angles btw standard limb leads

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10
Q

Precordial leads

A

Unipolar chest leads

6 additional leads consisting of 6 active electrodes positioned on the chest (indifferent electrode is the central terminal)

Positioned perpendicular to the plane of the limbs leads

Oriented to obtain info on the transverse and sagittal planes

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11
Q

Twelve lead system

A

Gives you 360 of frontal plane and horizontal plane

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12
Q

What info can be obtained from ekg?

A

Pattern and frequency of events
Rhythm (reg or irreg)
Rate (atrial and ventricular)

Conduction time
Intervals/segments btw waves indicate conduction
Width of waveforms indicates conduction time through an area

Axis determination
Direction of depolarization and repolarization of cardiac structures

Size of chamber
Amplitude is proportional to mass of currently active cells

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13
Q

What an ekg can’t tell you?

A

Doesn’t tell much about mechanical activity ( contraction, relaxation) except during ventricular fibrillation

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14
Q

Deflections in ekg

A
  1. Depolarization of atria
    P wave
    (SA node not seen because too small)
  2. Flat is AV delay (isoelectric pt)
  3. QRS complex (ventricles depolarizing) downward deflection, very large upward, another downward deflection (atria is repolarizing simultaneously but masked but QRS
  4. Upward wave T wave (repolarizing of ventricles) pos because direction of current, traveling alway from electrodes (neg and away = pos)
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15
Q

TP interval

A

Ventricles completely relaxed and refilling

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16
Q

Waves

A

Simple upward or downward deflection of ekg

Electrical impulses originating in the SA node produce various waves on the ekg as they spread throughout the heart

Movement away from the baseline in either pos or neg direction

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17
Q

Segments

A

Period of time btw waveforms

Normally isoelectric

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18
Q

Interval

A

A period of time that includes waves

19
Q

P wave

A

1st wave in cardiac cycle

Depolarization of both atria

Normal duration (0.08-0.10 s)

Enlarged aorta = larger deflection of P wave

20
Q

QRS complex

A

Depolarization of both ventricles

Q wave: first neg deflection following the P wave

R wave: first pos deflection following P wave

S wave: a negative wave following R wave

Q,R,S waves may not be present in al QRS

Ventricular hypertrophy - QRS complex will change

21
Q

T wave

A

Repolarization of ventricles

T wave inversion (neg T wave) May indicate coronary ischemia or left ventricular hypertrophy

Tall and narrow (peaked/tented) symmetrical T waves may indicate hyperkalemia

Flat T waves may indicate coronary ischemia or hypokalemia

22
Q

Where is the wave corresponding to atrial repolarization?

A

Rarely observed

23
Q

Where are waves of depolarization of SA node and AV node cells?

A

Events not reflected by any wave in ekg

Mass of tissue is too small

24
Q

PR and ST segments

A

PR- Not PQ
Btw end of P and very begging of Q

ST - is isoelectric (can be deflection, pathological)

25
Q

PR segment

A

Period btw atria and ventricular depolarization

Isoelectric period btw end of P wave and beginning of QRS complex

Not same as PR interval

Used as baseline to evaluate the ST segment displacement

26
Q

ST segment

A

Btw completion of ventricular depolarization and begging of ventricular repolarization

Period btw end of QRS complex and beginning of T wave

Corresponds to plateau of ventricular AP

Normally isoelectric

Does not mean ventricles are at rest

27
Q

PR interval

A

Beginning of P wave to beginning of QRS

Represents time for atrial depolarization and the delay through the AV node

Easier to identify

Last about 1 large box (~.2 sec) anything longer start thinking AV nodal delay or conduction block

Denotes conduction of the impulse from the upper part of atrium to the ventricles

28
Q

QT interval

A

Measured from onset of QRS complex to end of T wave

Time for ventricular depolarization and repolarization

Approximates the time for a ventricular AP

Denotes the electrical systole of the heart

Very dependent on heart rate

29
Q

QT interval and heart rate of

A

QTc: heart rate correlation for QT Interval

QTc=QT/ sq rt R-R

Pathology: long QT syndrome ( timing of depolarization to repolarization of ventriculars prolonged)

Always changing with heart rate!

30
Q

Ekg and ventricular AP

A

Phase 0 matches QRS complex

Phase 3 matches T wave

Anytime change in QT interval or ST segment you’d see a change in the plateau phase

31
Q

P-P interval and R-R interval

A

Can be used to determine heart rate

P-P atria to atria
R-R ventricle to ventricle
Different but coupled so should be close to each other (if different, they’re not coupled and pathology)

Ventricular is easier to find

32
Q

Standard calibration of ekg recordings

A

Horizontally (time)
Tiny box = 1mm~0.04s
Large box =5mm~0.20s

Vertically (voltage)
Small = 1mm ~0.1mV
2 large boxes= 1cm ~1mV

33
Q

Heart rate equation

A

Rate (bpm) = beats per 6 sec x 10

6 sec = 30 large boxes
60 sec = 300 large boxes

Quick estimation
HR = 300/# large squares per cycle

34
Q

From an ekg we typically determine

A

Vectors/ vector analysis

Net vector: sum of the pos and neg deflections of the waveform

QRS net vector (has pos and neg components, sub neg from pos and obtain net vector)

Determine mean axis of depolarization of ventricles

Used to obtain info about the conduction, pathway, anatomical abnormalities

Expect vector to be pointing downward (because ventricles) and deflect not too far to right or left (implies anatomical abnormality or conduction abnormality)

35
Q

Mean axis of depolarization

A

Normal QRS axis - 0-90 degrees

Outside that - mean axis deviation

36
Q

Left axis deviation

A

mean QRS axis more neg than 0 degrees

Point too far up and left

Causes:
LV hypertrophy
Obesity (pushes heart up)
Pregnancy (pushes heart up)

37
Q

Right axis deviation

A

mean QRS axis more pos than 90 degrees

Points too far down and right

Causes:
RV hypertrophy
LV infarct
Tall, thin body type

38
Q

Abnormalities in rate

A

Tachycardia- faster than 100bpm
QRS happen at fast frequency

Bradycardia- slower than 60rpm
QRS occurs less frequently
R to R interval prolonged

Normal: 60-100bpm

39
Q

Abnormalities in rhythm

A

Arrhythmia - variation from normal rhythm and sequence of excitation of heart

Ex:
Atrial flutter
Atrial fibrillation (absence of P waves)
Ventricular fibrillation (bizarre waveforms/ unidentifiable QRS)
Heart block

40
Q

A-V nodal conduction blocks

A

Partial or complete failure of AV node to spread the AP from atria to ventricles

Fairly common

Duration of PR interval is key

Prolonged PR interval (>200ms)

Actually PR segment but it’s so small so interval is assessed

41
Q

First degree AV block

A

Prolonged PR interval (>200ms) due to slowed conduction through AV node or bundle of his

One P wave for every QRS complex

Patients usually asymptomatic

42
Q

Second degree AV block

A

Partial dissociation of atria and ventricles

Not every P wave is followed by QRS complex
Roughly 2:1

May require artificial pacemaker

43
Q

Third degree AV block (complete heart block)

A

No conduction through AV node

Complete dissociation of atria and ventricles

P and QRS act totally independent of each other

May require artificial pacemaker

PHYSIO EXAM 2 (5 decks)

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