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Year 3 MOD > Small Animal Cardiology and Respiratory Medicine: ECG/Interactive > Flashcards

Small Animal Cardiology and Respiratory Medicine: ECG/Interactive Flashcards

1
Q

What is the definition of an ECG?

A

A recording of the changed in electrical potential difference (voltage) in the heart occuring during depolarisation and repolarisation of the myocardium plotted against time

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2
Q

What part of the heart is the pacemaker?

A

Sinoatrial node

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3
Q

Describe how the PQSRT complex is formed?

A
  • SAN spontaneously depolarises and spreads across right and left atrium forming the P wave
  • As this reaches the AVN conduction is slowed giving the P-R interval
  • The wave reaches the bundle of His which branches to purkinje fibres and the ventricle depolarises forming the QRS complex
  • The ventricle then repolarises slowly giving the T wave
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4
Q

How should the patient be connected to the ECG machine?

A

Gently restrained in right lateral recumbancy

Crocodile clip electrodes attached to loose skin just above elbows and stifles

Red- right fore
Yellow- Left fore
Green- Left hind
Black- right hind- earth lead

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5
Q

Which ECG lead is themost important lead to examine and why?

A

Lead II

This shows the largest complexes in dogs and cats

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6
Q

Where do each of the leads record changes in electrical potential difference between?

A

Lead I- right fore and left fore

Lead II- right fore and left hind- parrallels the position of the heart

Lead III- the left fore and left hind

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7
Q

How can HR be worked out on an ECG?

A

Obtained over a 6 second strip- no of QRS complexes x 10

For dysrythmias it is better to determine mean HR over longer period of time

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8
Q

After HR is worked out what should be checked?

A

P: QRS ratio should be 1:1

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9
Q

When first looking at an ECG checking the predominant rhythm what should be checked?

A

Inspect regularity and morphology for any dysrythmia

P waves should be identified if possible- regularity and uniformity

QRS- normal and narrow

QRS always followed by T waves- can be negatie, positive or biphasic in dogs, cats usually positive

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10
Q

How do you measure and multiply an ECG?

A

Standard lead II measurments are taken at 50mm/s and a sensitivity of 1mv=1cm

1mm box is 0.1mV x 0.02s

Measure P wave amplitude (height) (mV)
Measure P wave duration (length)(seconds)
Measure P-R interval

Measure height of R wave
Measure duration of QRS complex
Measure QT interval

T wave is noted to be positive, negative or biphasic
ST segment should be at a similar level of the baseline P-QRS

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11
Q

What are some common ECG abnormalities from measurment?

A

Prolonged P wave- left atrial enlargment

Tall P wave- right atrial enlargment

Tall R wave- left ventricular enlargment

Prolonged QRS complex- ventricular enlargment

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12
Q

What is the name for normal heart rythm?

A

Sinus rhythm

P wave preceding every QRS complex and a QRS following a P wave

It can vary with respiration- sinus arrythmia- normal in dogs indicating normal, high resting vagal tone

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13
Q

How is a sinus arrest presented on an ECG?

What casues it?

A

The ECG shows a gap with no electrical activity for a period exceeding normal R intervals

Often a manifestation of high vagal tone- may be normal in brachiocephalics

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14
Q
A
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15
Q

What is an AV block and how many different types are there?

A

When the AV node either slows or blocks conduction of the atrial depolarisation into the ventricles

3 types- first degree, second degree, third degree

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16
Q

How is a first degree AV block presented on an ECG?

A

P:QRS ratio remains 1:1 but the P-R interval is longer than normal.

May be due to high vagal tone or effect of certain drugs/disease

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17
Q

How is a second degree AV shosn on an ECG?

A

Some P waves not followed by a QRS complexes

May be normal and physiological (horses) but may reflect disease of the AVN

QRS should look normal

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18
Q

What are the two types of second degree AV block and how are they different?

A

Wenckeback phenomenon- Mobitz type 1 AV block
Single non-conducted P wave- every now and then

Mobitz type 2 AV block
Every other P wave is non conducted or higher every 2/3

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19
Q

What is a 3rd degree AV block on an ECG?

A

P waves bear no relationship with the QRS complex

P waves occur at their own normal rate and QRS cmoplexes arise due to much slower automaticity of the purkinje system

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20
Q

What is atrial fibrillation?

A

When the atria are sufficiently large or stretched normal cell conduction representing P wave lost

Leads to many irregular depolarisations in the atria which randomly hit the AV node

QRS complexes and T waves look normal but rate is fast and the interval between them is highly variable- no P waves

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21
Q

What causes a supraventricular premature complex/supraventricular tachycardia?

A

If an ectopic focus in the atria or at the atrioventricular junction depolarises the atria prematurely a premature complex with the appearance of a normal QRS complex is produced

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22
Q

What is the name for a run of supraventricular premature complexes?

A

Paroxysmal supraventricular tachycardia

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23
Q

What causes a ventricular premature complex/ventricular tachycardia and how does this affect the complex?

A

An ectopic focus may also arise in the ventricular myocardium- it doesn’t follow the normal His-purkinje so is spread cell to cell- slow process so the complex is wide and bizarre

The T wave is in the opposite direction of the QRS complex

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24
Q

What causes paroxysmal ventricular tachycardia and sustained ventricular tachycardia?

A

A run or ventricular premautre complexes

If sustained it causes sustained ventricular tachycardia

25
Q

What are the hallmarks of ventricular premature complexes?

A

Ventricular ectopic complexes- Wide and bizzare

And slur into oppositely directed T waves

26
Q

How would you know a ventricular ectopic origniated in the right/left ventricle?

A

Ventricular ectopics which are positive in leads I and II with negative T waves are probably originating in the right ventricle

Negatvie leads in I and II with positive T waves probably originate in the left ventricle

27
Q

Describe a ventricular fibrillation ECG

A

Complete loss of coordinates ventricular depolarisation/repolarisation- chaotic

28
Q

What ‘other’ factors influence the ECG?

A

Autonomic nervous system- vagal tone, sympathetic drive

Electrolyte distrubances- electrical activity depends on conc of electrolyes

Cardiac disease- chamber enlargment

Other diseases- gastric stetch, spleen tumours

29
Q

What may hyperkalaemia show on an ECG?

A

Sinoventricular rythm but no discernable P waves

Normal QRS- tall spikey T waves

30
Q

What type of ultrasound transducers are required to get between ribs and lung lobes?

A

Sector transducers- inverted fan shaped image

31
Q

What is the difference between long axis and short axis views in echocardiography?

A

Long axis- base to apex

Short axis- cross sectional views

32
Q

What does the right pasternal long axis view show?

What is the right pasternal long axis view used for?

A

Shows all 4 chambers of the heart and thickness of the walls

Used for:

  • Assess LV shape- normal, elliptical, rounded
  • Subjectively assess contractility
  • Right should be no more then one third of left heart dimensions
  • LV walls should be one-quarter to one-thirds chamber diameter
  • Mitral valve assessed- regurgitation?
  • Can calculate EDV (start of QRS) and ESV (end of T wave/ smallest LV dimension)
  • Atrial septum is assessed
33
Q

What is seen with the RPS long axis 5 chamber view?

What can be assessed with this view?

A

All chambers and the aorta viewed

Used to assess abnormalities of the aortic valves

Colour flow can be used to look for turbulence in this region- stenosis

Colour flow can also be used to check septum for a ventricular septal defect

34
Q

What is seen with the right parasternal short axis view- papillary muscle level?

What is this view used for?

A

The RV and LV

Used to position the M-mode cursor- at chordae tendinae

35
Q

What is the M-mode cursor?

A

The M-mode cursor plots one dimension and is therefore a motion-time graph

Movement of the structures is displayed relative to the ECG

That wavy shit

36
Q

Name each of the views A-E

A

A- RPS short axis below papillary muscle

B- Between pappillary muscle level- mushroom view

C- Left ventricular M-mode- chordae tendinae level

D- RPS short axis- mitral valve level (fishmouth view of mitral valve)

E- RPS short axis view at level of aortic valves

37
Q

What is seen with M-mode cardiography?

A

Body wall
Right ventricle- only a bit
Intraventricular septum- IVS
Left ventricular lumen- LV
Left ventricular wall- LVpw

38
Q

What is measured with M-mode echocardiography?

A

End diastolic measurements- start of QRS- broadest levt ventricular lumen

Systolic measurments- smallest left ventricle lumen

Can also measure:

Intraventricular septum diastole/systole
LV posterior wall diastole/systole

Measurements compared to breed specific reference values

39
Q

How is fractional shortening calculated and what is normal?

When is fractional shortening not reliable?

A

LV internal diameter diastole - systole / diastole x100%

Normal is above 25%

Not reliable if- significanct mitral regurgitation, wall motion abnormalities, right sided heart disease with pressure overload

40
Q

What is fishmouth view/mitral valve used to measure?

A

AMV- anterior mitral valve leaflet and PMV- posterior mitral valve leaflet

Irregular thickening of leaflets with DVD

Can occasionally see mitral stenosis

Mitral E point to septal seperation (top of E to septum distance)- increases with LV dilations, rounding of LV or poor stoke volume

41
Q

What is the M-shape created from fishmouth M-mode?

A

The AMV inscribes the M-shape with two peaks

The E peak- Early passive diastolic filling- after T wave

The A Peak- Atrial contraction- after P wave

Posterior leaflet should do opposite- W shape

42
Q

How is the LV volumes and ejection fractions calculated?

A

In RPS long axis view

Work out EDV and ESV and %

Use simpsons method of discs

Normal is >50%

43
Q

What is the index of sphericity of the LV?

A

Attempting to quantify subjective assessment of rounding of LV

LV length- diastole / LV ‘width’ (M-mode)

anything above 1:7 normal

44
Q

What is the difference between concentric and eccentric hypertyrophy?

A

Concentric- thickening and reduced lumen

Eccentric- over all enlargment

Eccentric- big ego

45
Q

What disease is seen in cats and causes them to have thickened walls of the heart?

What needs to be ruled out?

A

Hypertrophic cardiomyopathy in cats

Things that cause pressure overload- Aortic stenosis and systemic hypertension

46
Q

What does the short axis view at the level of aortic valves show?

What can be measures and compared at this view?

A

Short axis of the left atrium and aortic leaflets seen (mercedes)

Measure aortic root and LA in diastole for 2D measurment

Normal LA:Ao is <1.5

47
Q

What is doppler echocardiography?

What are the three different types?

A

Doppler effect is noted when sound waves are transmitted and reflected off a moving target- RBCs
The difference between ultrasound frequencies transmitted and received is related to the velocity of the moving RBCs

Spectral
Colour flow
Tissue- myocardial motion

48
Q

What is required to make spectral doppler echocardiography accurate?

A

Must be parrallel to flow of blood

Otherwise velocities significantly underestimated

49
Q

How does blood moving towards the transducer and away show differently?

A

Blood moving towards the transducer is displayed above the baseline

Blood moving away from the transducer is displayed below the baseline

50
Q

How is laminar/turbulent flow indicated on pulsed wave doppler?

A

A clean envelope as blood accelerates and decellerates

Turbulent flow is indicated by spectral dispersion and loss of clean envelopes

51
Q

What is the difference between Continuous wave doppler and Pulse wave doppler?

A

PW- spatially specific, just sample RBC velocity within the sample volume.
But limit to depth you can sample and peak velocity you can record

CW- samples all along the cursor line- peak velocities displayed but not spatially specific
Can record depth and high peak velocities

52
Q

What is colour flow doppler?

A

Colour applied to how above or below baseline the velocity is

BART map- blue away, red towards transducer

53
Q

What is the Nyquist limit?

A

There is only a certain red level and velocity than can be reached which is the nyquist limit

It is a circle so becomes blue again and shows aliasing

54
Q

How does turbulence show in colour flow doppler?

A

Colour variance- green/yellow

55
Q

What view is used for aortic stenosis?

A

Sub-costal view

Optimal alignment with aortic outflow

56
Q

What is the modified bernouilli equation used for?

A

Calculates the pressure gradient difference- beterrn LV and Aorta

PG = 4V^2

0-40 mmHg- mild

40-80 mmHg- moderate

>80mmHg- severe

Normal aortic velocity -1.7m/s

57
Q

What are the normal cardiac pressures in aorta, LA, pulmonary artery, LV, RV, RA?

A

Aorta- 120/80 normal sytemic pressure

Left atrium- 6mmHg

LV- 120/0 mmHg

RV- 25/0 mmHg

RA- 4 mmHg

58
Q

What causes caval syndrome and does it cause and how is it treated?

A

Dirofilariasis worms in the RA

Causes pulmonary hypotension and thromboembolism and pressure overload on RV- right sided CHF

Need to extract worms via jugular vein

Year 3 MOD (42 decks)

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