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Physiology > Electrocardiogram > Flashcards

Electrocardiogram Flashcards

1
Q

Standard Calibration of ECG Recording

A

2 Speeds:

1) 50 mm/sec - 1mm = 0.02 sec
2) 25 mm/sec - 1mm = 0.04 sec

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2
Q

Lead Placement

A

1) Place patient in R LATERAL RECUMBANCY
2) Attach electrodes on skin just proxiaml (above) to elbows and stifles
3) Wet electrodes with alcohol

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3
Q

Ground Lead

A

R Leg

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4
Q

3 Bipolar Limb Leads

A

Lead I = RA to LA
Lead II = RA to LL
Lead III = LA to LL

NEGATIVE TO POSITIVE

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5
Q

Augmented Unipolar Limb Leads

A

Lead aVR = LA & LL to RA
Lead aVL = RA & LL to LA
Lead aVF = RA & LA to LL

NEGATIVE (2) TO POSITIVE

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6
Q

Chest Leads

A

Unipolar Precordial Chest Limbs

Record electrical activity from dorsal and ventral surface of heart

RA, LA, and LL are connected to for a zero reference at center of heart

ECG measures voltage from heart to the selected electrode on chest

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7
Q

Axis of Leads

A

Einthoven’s Triangle

Lead I = 0 Degrees
Lead II = 60 Degrees
Lead III = 120 Degrees
Lead aVR = 210/ -150 Degrees
Lead aVL = -30 Degrees
Lead aVF = 90 Degrees
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8
Q

Determination of POS or NEG Waves

A

1) Direction of Wave
2) Depolarization or Repolarization
3) Amount of Tissue
4) Axis of Lead

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9
Q

Depolarization Waves

A

1) Impulses from the heart that travels towards the positive electrode produce and upward deflection on the ECG
2) Towards negative = downward deflection

3) Electrical forces are equal = Isoelectrc trace
Impulse = PERP to a lead
Cancel each other out

4) No electrical activity = baseline trace
Tissue is FULLY REPOLARIZED OR DEPOLARIZED

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10
Q

P Wave

A

Atrial Depolarization

Impulse originates at SA Node and spreads over atria

Electric vector = downward and to the left

Upward Deflection in ECG Tracing = Leads 1 and aVF

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11
Q

QRS Wave

A

Direction of wave and amount of tissue depolarizing changes as the impulse travels through the heart = positive and negative deflections

Dep in 3 diff directions: Septal, Apical, Late Ventricular

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12
Q

Septal Depolarization

A

1st part of QRS Wave

After a brief delay at AV Node, impulse travels through common bundle of His and right and left bundle branches, then it enters the interventricular septum

R AND DOWNWARD = small negative deflection in lead I (Q Wave) and small upward deflection in Lead aVF (R wave)

NOT A LOT OF CURRENT = not a lot of tissue

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13
Q

Apical Depolarization

A

2nd Part of QRS Wave

Impulse continues causing apical (apex) vent dep

L AND DOWNWARD = large positive deflection in lead I (R Wave) AND extends R wave in lead aVF

MORE CURRENT

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14
Q

Late Ventricular Depolarization

A

3rd Part of QRS Wave

Depolarization over ventricles = points back up

Base of Heart

L and UPWARD = Upward deflection in Lead I (extending R Wave) AND downward deflection in Lead aVF (S Wave)

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15
Q

T Wave

A

Ventricular Repolarization - Rep of one cell does not cause rep of next cell

Cells rep based on length of action pot

Epicardium (near apex) rep first first = same direction as dep
Then Endocardium

SO T wave in same direction as major wave (R) as QRS

WIDE WAVE

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16
Q

Tracing

A

P Wave
Baseline = Atria fully dep and Ventricles fully Rep
QRS Wave
Baseline = Ventricles dully Dep and Atria fully Rep (ST Segment)
T Wave
Baseline = Atria and Ventricle fully Rep

17
Q

P-Q / P-R Interval

A

From Beginning of atrial electrical excitation to the beginning of ventricular electrical excitation

P-R if no Q is present

0.16 sec

18
Q

Q-T Interval

A

Length of time of contraction of ventricles

0.35 sec

19
Q

Determining Heartrate from an ECG

A

Heart Rate = reciprocal of the time interval between 2 heartbeats (2 R to Rs)

50 mm/sec = beats per 3 marks (3 sec) x 20

25 mm/sec = beats between 2 marks (3 sec) x 20

20
Q

Mean QRS Vector

A

+59 Degrees

21
Q

What part of the Atrial system is repolarized first?

Ventricular Sytem?

A

SA Node (rep vector direction is opp of dep vector)

Epicardium near the apex
The rest of the Epicardium
The Endocardium
vector is same direction as dep vector

22
Q

During most of vent dep, direction of electrical potential is from ——– to ———

A

Base to Apex of the heart

23
Q

Mean Electrical Axis

A

Average Direction of Ventricular Dep (Base to Apex)

Normal Range = +40 - +100 Degrees
Average Normal = +59 Degrees

24
Q

Mean Electrical Axis - Shifts to the Left

A

1) After Deep Expiration
2) Lying Down
3) Obesity (Diaphragm pushes against heart

25
Q

MEA - Shifts to the Right

A

1) End of deep inspiration
2) Standing up
3) Tall, Lanky People (heart hangs downward)

26
Q

MEA - Hypertrophy of One Ventricle

A

Shift of MEA to the same side at the hypertrophied ventricle

27
Q

MEA - Bundle Branch Block

A

Block of one side of purkinje branches = the other side ventricle depolarizes faster

Left Block = Left shift of axis
Right Block = Right shift of axis

28
Q

Determiningg MEA

A

1) Look for largest net deflection of QRS

2) If QRS has UPWARD DEFLECTION = MEA is toward positive electrode of lead
If QRS has DOWNWARD DEFLECTION = MEA is toward negative electrode of lead

3) Look at lead perpendicular to this
4) Adjust MEA based of isoelectric lead:

If more pos = adjust towards pos electrode of PERP LEAD
If more neg = adjust toward neg electrode of PERP LEAD
If isoelectric = NO ADJUSTMENT

29
Q

If any lead is isoelectric =

A

MEA is in the perpendicular direction (DO NOT NEED ISOELECTRIC DEFLECTION FOR MEA TO EXIST)

30
Q

Methodical Approach to the ECG

A

1) Identify waves (P, QRS, T, PR Interval) and evaluate DURATION and AMPLITUDE
2) MEA
3) Det Heartrate - Det normal or abnormal (Bradycardia/Tachycardia)

Reciprocal of time between 2 R-R Intervals

4) Is rhythm reg or irreg? Look at R-R INTERVALS
5) Are there P wavs? QRS complexes?
6) Is there a P wave for every QRS complex?
7) Is there a QRS complex for each P wave?
8) Are the Ps and QRSs consistently related?
9) Do all the Ps and QRSs look alike?

31
Q

Normal ECG Values

A

1) Heart Rate = 70-160 bpm (60-140 bpm for giant breeds; up to 180 for toy breeds; up to 220 for puppies)
2) Normal rhythms = Normal sinus rhythm, Sinus arythmias, and Wandering pacemaker

3) P Wave = Width (max) = 0.04 sec
Height (max) = 0.4 mV

4) P-R Interval = 0.06 - 0.13 sec

5) QRS Complex = Width (max) = 0.05 sec
Height (max) = 3.0 mV (large)
2.5 mV (small)

6) T Wave = positive, negative, or biphasic
7) Electrical Axis = +40 - +100 Degrees

32
Q

Right Atrial Enlargement

A

INCREASED P WAVE AMPLITUDE

Associated Conditions: Chronic respiratory disease, congenital heart defects, interatrial septal defect

33
Q

Left Atrial Enlargement

A

INCREASED P WAVE DURATION (P mitrale)

NOTCHING of P waves = due to superimposition of asynchronous right and left atrial conduction (not lined up)

Associated Conditions: Mitral valve insufficiency, aoritc stenosis, ventricular septal defect, patent ductus arteriosis

34
Q

Conditions that cause shifts in axis, abnormal voltages and duration of QRS Complexs

A

Excessive generation of electrical potential in a particular direction

More time required for depolarization wave to travel through muscle

R and L Ventricle Enlargements

35
Q

Right Ventricular Enargement

A

ECG = Large S waves in I, II, and aVF
MEA of 100 Degrees and Clockwise

Possible Causes = pulmonary stenosis, intraventricular septal defect, heart worm disease, and inc pulmonary vascular resistance

36
Q

Left Ventricular Enlargement

A

Dilation or Hypertrophy

ECG = abnormalities not always observed bc L side of heart is already bigger than R

Associated Conditions - aortic stenosis, mitral insufficiency, and hypertension

37
Q

Left Bundle Branch Block

A

DELAY or BLOCK of conduction in left branch bundle

At MAIN BRANCH or at level of the ANT or POST FASCICLES

ECG:

1) QRS Complex > 0.08 sec
2) Wide pos deflection in I, II, III and aVF AND inverted inverted in aVR and aVL
3) L Bundle Branch must be differentiated form L ventricular enlargement (thoracic radiography)

Can OCCUR simultaneously w/ L ventricle hypertrophy

38
Q

R Bundle Branch Block

A

DELAY or BLOCK of conduction in left branch bundle

At MAIN BRANCH or at level of the ANT or POST FASCICLES

ECG:

1) QRS > 0.08 sec
2) R axis deviation
3) Large S waves in I, II, III and avF
4) Must be differentiated from R vent enlargement with thoracic radiography

Physiology (16 decks)

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