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CAEM Pt. 2 > Cardio: ECG > Flashcards

Cardio: ECG Flashcards

1
Q

What can an ECG tell you (9)?

A

1) Heart rate (atrial and ventricular)
2) Rhythm
3) Conduction pattern
4) Chamber enlargement (less than rads, echo)
5) Myocardial condition (inflammation, necrosis, epicardial dz)
6) Electrolyte abnormalities
7) Effusions (pericardial, pleural)
8) Drug toxicities or effects
9) Sympathetic or parasympathetic tone alterations

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2
Q

Reasons to perform an ECG (9)

A

1) Congenital heart disease in younger dogs
2) Valvular disease (Ex: Cavalier spaniel)
3) Myocardial disease (Ex: Dobermans)
4) Monitor drug therapy or suspected drug toxicity (Ex: digoxin, anti-arrhythmics)
5) Evalulate arrhythmias
6) Evaluate syncope or weakness
7) Pre-anesthetic or anesthetic monitoring
8) Electrolyte screening (Ex: post parathyroidectomy)

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3
Q

Four prep steps in performing an ECG

A

1) RIGHT lateral recumbency
2) Electrodes above the elbows and stifles
3) Alcohol to couple signals to electrodes
4) Light restraint

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4
Q

Sequence of electrical activation in the heart

A

1) Starts in the sinus node (SA) = pacemakers that initiate electrical impulses
2) ATRIAL DEPOLARIZATION
3) Impulse slowed by the AV node = specialized conduction tissue that separates the atria from ventricles
4) Conduct via the Bundle of His
5) Conduct via Purkinji fibers for VENTRICULAR DEPOLARIZATION

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5
Q

What does an ECG tell you (and not tell you) about the heart?

A

Only explains the ELECTRICAL ACTIVITY of the heart, says nothing about the mechanical functionality

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6
Q

What is the P wave?

A

Atrial depolarization

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7
Q

What is the QRS complex?

A

Ventricular depolarization

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8
Q

What is the T wave?

A

> Ventricular repolarization

- Can be negative or positive

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9
Q

What is the PR/PQ interval?

A

> AV nodal conduction

- Time needed for conduction from the the SA node through the AV node to the ventricular myocardium

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10
Q

What is the Q wave?

A

First negative deflection before a positive deflection

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11
Q

What is the R wave?

A

The first positive deflection in the QRS complex

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12
Q

What is the S wave?

A

Negative deflection after the positive deflection

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13
Q

What is the ST segment?

A
  • Duration of phase 2 of the AP during repolarization

- No change in electrical charge = equal to baseline (PR) = isoelectric

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14
Q

What is the QT segment?

A

> Ventricular systole

- Time of ventricular depolarization and repolarization

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15
Q

Difference between paper speed on the ECG and writings?

A
  • Quicker = things are farther apart

- Slower = things are written closer together

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16
Q

Which lead sees the largest QRS deflection?

A

Lead II = where we do our ECG measurements from

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17
Q

What is the calibration of the ECG?

A

> “Sensitivity” = 10 mm = 1 mV

  • Usually increased with cats = 2x –> 1 mV = 1 cm
  • Usually decreased with dogs = 1/2x –> 1 mV = 1/2 cm
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18
Q

How do you determine the HR from the ECG?

A

[Each box = 1 mm]

1) Count 25 or 50 mm (depending on speed) = equals one second
2) Count the number of QRS complexes for 3 seconds
3) Multiply those QRS complexes x 20s

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19
Q

Does size of the dog (animal) affect the HR on the ECG?

A

NO - all dogs should have similar heart rates

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20
Q

Normal heart rate for a dog

A

70-140 bpm

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21
Q

Normal heart rate for a cat

A

160-220 bpm

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22
Q

WHAT IS A SINUS RHYTHM?

A

Upright P waves, in lead II, at a rate the sinus node can fire

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23
Q

What is the mean electrical axis and what is normal for the MEA?

A

> Defines the orientation of the average wave of ventricular depolarization
- Normal = left (of the animal) and towards the feet

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24
Q

How do we calculate the mean electrical axis (MEA)?

A

1) Measure the positive boxes from baseline (PR) to the top of the QRS
2) Measure the negative boxes below baseline of the QRS
3) Add them together for your lead total (on each perpendicular lead)
4) Connect the point where the two leads intersect
5) Draw a line from the belly button to that point = MEA

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25
Q

Two reasons for right axis ECG deviation

A

1) Right ventricular enlargement

2) Conduction disturbance, particularly in the right bundle branch

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26
Q

Two reasons for left axis ECG deviation

A

1) Left ventricular enlargement

2) Conduction disturbance, particular in the left bundle branch

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27
Q

What does tall P waves indicate?

A
  • “P pulmonale” = right sided pulmonic valve

|&raquo_space; Right atrial enlargement

28
Q

What does wide P waves indicate?

A
  • “P mitrale” = left sided mitral valve
    » Left atrial enlargement
  • Takes a longer time to depolarize = wider waves
29
Q

What does tall and wide P waves indicate?

A

Biatrial enlargement

30
Q

What does tall or wide QRS complexes indicate?

A

> > Left ventricular enlargement

- Either due to dilation or hypertrophy

31
Q

What do we see with right ventricular enlargement?

A

> Usually only seen with severe disease (needs to overcome the large left ventricular mass)

  • See S waves in leads I, II, III, and aVF
  • Right axis shifts
32
Q

Four differentials for a wide QRS complex

A

1) Bundle branch block
2) Ventricular espace (late) complexes
3) Ventricular premature (early) complexes
4) Ventricular enlargement

33
Q

What can cause bundle branch blocks?

A

> > Result from damage to the bundle branches from STRETCHING

  • Hypertrophy
  • Infiltrative diseases
  • Infarction
  • Idiopathic degeneration
  • Surgical manipulation
  • Congenital heart disease
  • Acquired heart disease

*Need to distinguish from ventricular ectopic beats (VPC’s and escape beats)

34
Q

Axis deviation (which direction) with right bundle blocks

A

Right axis deviation = slower depolarization on the right side because it doesn’t go through the normal right sided His-Purkinje fibers

35
Q

Consequences on the ECG with right bundle blocks

A
  • Right axis deviation
  • WIDE and NEGATIVE QRS complex in leads I, II, and aVF
  • NORMAL P wave and PR interval –> differentiate between right bundle block and VPC’s
    +/- Abnormal T wave (abnormal depolarization may affect the repolarization)
36
Q

How do you differentiate between VPC and ectopic beats AND right bundle blocks?

A

Right bundle blocks conduct through the His-Purkinje system = normal P wave and PR interval

37
Q

Consequences on the ECG with left bundle blocks

A
  • WIDE and POSITIVE QRS in leads I, II, III, and aVF

- NORMAL P wave and PR interval

38
Q

Two types of ventricular ectropy

A
  • Premature (VPC’s) ventricular complexes

- Escape (late) ventricular complexes

39
Q

What is a sign of ventricular ectopy on an ECG?

A
  • WIDE and BIZARRE QRS complexes

- NOT associated with P waves (didn’t originate from the SA node)

40
Q

Three reasons for wide and bizarre QRS complexes

A

1) Premature (VPC’s)
2) Escape (late) ventricular complexes
3) Bundle blocks

41
Q

Four causes of depression of the ST segment

A

1) Myocardial ischemia (endocardial)
2) Acute infarction
3) Hyper/hypokalemia
4) Trauma

> > Never returns to PQ baseline
*Worry about ischemic heart disease

42
Q

Four causes of elevation of the ST segment

A

1) Myocardial hypoxia, esp EPIDCARDIAL
2) Pericarditis
3) Myocardial infarction (transmural)
4) Trauma

43
Q

Two reasons for abnormal T waves

A

1) Abnormal ventricular depolarization or conduction –> abnormal repolarization
2) Hyperkalemia, looks tented or spiked

44
Q

Reasons for prolonged QT intervals

A
  • Varies with HR
  • Hypocalcemia
  • Hypokalemia
  • Hypomagnesemia
45
Q

Reasons for shortened QT interval

A
  • Varies with HR
  • Hypercalcemia
  • Hyperkalemia
46
Q

Cause of short/attenuated or low-voltage QRS complexes (4)

A

> “Insulator” that decreases the QRS voltage (in the way)

1) Pericardial effusion
2) Pleural effusion
3) Hypothyroidism
4) Obesity

47
Q

Causes of arrhythmias

A

1) Primary cardiac disease
2) Sepsis
3) Drugs and toxins
4) Medical = metabolic, electrolyte, neoplastic
5) Hypoxia
6) Autonomic tone, Ex: vagal or sympathetic tone

48
Q

Sinus bradycardic rates for dogs and cats

A
  • Dogs < 60-70 bpm
  • Cats < 140 bpm

*Can be normal in a dog = parasympathetically driven

49
Q

ECG signs of a wandering pacemaker

A

> High vagal tone

  • See different P wave morphologies, depending on where the SA node fires
  • Still upright P waves
50
Q

Sinus tachycardic rates for dogs

A
  • Dogs > 140 bpm
  • Still upright P waves
  • Normal sinus rhythym
51
Q

Sinus arrest - ECG

A

> Two RR intervals without anything happening = NO P waves

- No sinus node activity

52
Q

**Junctional escape complexes - ECG

A

> Junction = AV node = SUPRAVENTRICULAR

  • Escape complex = comes in late
  • Doesn’t originate from the SA node = no P waves
  • COMPENSATORY from the ventricular His-Purkinje system = upright and narrow
53
Q

**Ventricular escape complexes - ECG

A
  • Normal sinus rhythm = sinus tachycardia, upright P waves
  • Ventricles are not seeing the AV node signals = not conducting SA nodes through the AV node
  • Jumping in late
54
Q

Atrial premature complexes - ECG

A
  • Premature and abnormal atrial depolarization
  • Jumps in early before the next scheduled P wave
  • SA node is firing + something else extra fires in the left atria
  • Normal conduction through His-Purkinje (normal/upright QRS complex)
55
Q

Ventricular premature complexes - ECG

A

> Wide and bizarre QRS = slowly conducted
- Something abnormal fires in the ventricular system that’s not a part of the His-Purkinje
+/- Abnormal T waves

56
Q

Ventricular bigeminy - ECG

A

Specific type of ventricular premature complex where the wide and bizarre QRS occurs every other normal QRS (jumps in before the next scheduled P wave)

57
Q

Atrial tachycardia - ECG

A
  • Atrial cells (not SA node) are generating impulses
  • Normal, upright P waves
  • Jump in early = type of APC?
    » Three or more in a row = atrial tach
    *Will feel pulse deficits = heart doesn’t have time to fill
58
Q

Atrial fibrillation - ECG

A

> Occurs supraventricular, above the AV node

  • NO P WAVES
  • Irregular rhythm = hundreds of atrial impulses hit the AV node and only a few get through to the ventricles
  • Normal upright and narrow QRS (goes through His-Purkinje)
  • Tachycardic = as many of the atrial impulses as possible get through (240 of 500)
59
Q

Ventricular tachycardia - ECG

A

> Three or more VPC’s occurring in a row

  • Wide and bizarre - not going through the normal His-Purkinje system
  • Originating from somewhere else in the ventricles
60
Q

Paroxysm - ECG

A

Sustained run of tachycardia (sp v-tach)

61
Q

Ventricular fibrillation - ECG

A

No organized depolarization in the ventricles = FATAL if left untreated

62
Q

1st degree AV block - ECG

A

> Involving AV nodal conduction time

  • Too long of PQ interval
  • “Lazy gatekeeper” - signals getting through to the ventricles, but the AV node is lazy
63
Q

2nd degree AV block - ECG

A

> Involving the AV nodal conduction time

  • AV node is functioning some of the time = some of the impulse conduct to the ventricles and some don’t
  • “Sleepy” gatekeeper
64
Q

3rd degree AV block - ECG

A
  • “Dead gatekeeper”
  • No conduction between the atria and ventricles
  • Sinus node keeps firing, but ventricles need to create a compensatory escape complex
  • Slow (compared to faster premature VPC’s)
65
Q

Right bundle branch block - ECG

A
  • Wide, bizarre, and NEGATIVE QRS
  • Preceded by a normal P wave
  • Doesn’t require treatment (unlike VPC’s or v-tach)
66
Q

Left bundle branch block - ECG

A
  • Wide, bizarre, and POSITIVE QRS

- Preceded by a normal P wave

67
Q

Atrial standstill - ECG

A

Atria are paralyzed = no atrial depolarization = missing a P wave

CAEM Pt. 2 (27 decks)

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