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Equine > Equine cardiology > Flashcards

Equine cardiology Flashcards

1
Q

What cardiac issue is more likely to cause poor performance; rhythm disturbances or valvular disease

A

Rhythm disturbances
Horses have a high circulatory reserve capacity so it is rare for valvular disease to cause poor performance

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2
Q

What are the 3 mechanisms of oedema

A
  • Changes in oncotic pressure; from hypoproteinaemia
  • Changes in hydrostatic pressure e.g in congestive heart failure
  • Vasculitis which allows more leakage
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3
Q

How common is congestive heart failure in horses c/f dogs

A

Uncommon

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4
Q

What type of oedema does L vs R sided heart failure cause

A

Left sided causes pulmonary oedema
Right sided causes peripheral oedema; more common presentation and noticed more

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5
Q

Causes of L sided heart failure

A
  • Acute onset L sided disease e.g bacterial endocarditis, ruptures chorda tendinae
  • Pulmonary hypertension
  • Congenital disease
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6
Q

How to differential pulmonary oedema with L sided heart failure from asthma signs

A

Unlike asthma, horses with heart failure are tachcardic

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7
Q

What is a cause of right sided heart failre

A

Chronic endocardial disease

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8
Q

What severe consequence is pulmonary hypertension a risk factor for the development of

A

Vascular failure

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9
Q

What are primary and secondary causes of pulmonary hypertension

A

Primary = pulmonary disease from hypoxia
secondary = mitral valve regurgitation, aortic valve regurgitation, atrial fibrillation

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10
Q

Where to listen to mitral valve

A

LIC 5 (caudal on left side)

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11
Q

Where to listen to the aortic and pulmonic valves

A

LIC 4 i.e cranial on left side

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12
Q

How hard to press using stethoscope for high vs low freq sounds

A

Press lightly for low freq
Press hard for high freq

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13
Q

What are S4, S1, S2, S3 sounds assocaited with

A

S4 = onset of atrial systole
S1 = onset of ventricular systole with closure of AV valves (and opening of semilunar)
S2 = onset of diastole with closure of semilunar valve and opening of AV valves
S3 = assocaited with rapid ventricular filling in mid-diastole

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14
Q

Where is S1 loudest

A

Over LIC5 (i.e hear closing of mitral valve)

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15
Q

Where is S2 loudest

A

Over LIC 4; since listening to semilunar valves close

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16
Q

Where is S3 loudest

A

Over cardiac apex (towards sternum on LIC5) since listening to ventricular filling

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17
Q

When might we hear S4 and S3 heart sounds

A

S4 in 60% of TBs
S3 in 40% TBs

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18
Q

When might S1 be louder than normal

A

Hypertension, adrenaline, mitral valve disease

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19
Q

When might S2 be louder than normal

A

Fever, adrenaline, anaemia

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20
Q

What is a physiological murmur

A

One just caused by blood leaving the heart
= most common murmur

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21
Q

At which grade do we recommend that murmurs have further investigation

A

Grade 3

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22
Q

Grading system of heart murmurs

A

1 = quiet murmur that is hard to identify
2 = murmur quieter than heart sounds
3 = murmur at same volume of S1/S2
4 = murmur louder than S1/S2
5 = loud murmur with precordial thrill
6 = murmur audible with stethoscope off the thoracic wall

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23
Q

What direction does murmur radiate in AV regurgitation

A

Dorsally

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24
Q

What is a systolic vs diastolic murmur

A

Systolic = between S1 and S2
Diastolic = after S2

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25
Q

What does holo-systolic mean

A

Murmur filling time between S1 and S2

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26
Q

What does pan-sysolic mean

A

Murmur across heart sounds b/w S1 and S2

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27
Q

What does mid-systolic murmur mean

A

Murmur between S1/S2 but not filling whole time

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28
Q

What are two types of left sided systolic murmur

A

Physiological flow murmurs from aortic ejection

Mitral valve regurgitation

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29
Q

What are two types of right sided systolic murmurs

A

Tricuspic valve regurgitation

Ventricular septal defect

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30
Q

What are the types of diastolic murmurs

A

Aortic valve regurgitation

Physiological filling murmur

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31
Q

CHaracteristics of a left sided flow murmur

A

loudest cranially on left (because it is aortic ejection we hear)
Early/mid systolic
Low grade
Cranio-dorsal radiation

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32
Q

Characteristics of mitral valve insufficiency murmur

A

Loudest caudally on the left LIC5
Variable timing/intensity
Radiates caudo-dorsally
Band shaped

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33
Q

How can mitral valve insufficiency end up leading to poor performance

A

Via development of atrial fibrillation
- Because the jet of blood flowing backwards causes atrial expansion

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34
Q

What clinical signs can develop from mitral valve insufficiency

A

[usually incidental finding]
- Poor performance due to atrial fibrillation from atrial enlargement

  • Louder third heart sound since more passive filling occurs once atrium has enlarged

Pulmonary hypertension which can get worse until the point of vessel failure; collapse and death if pulmonary artery
+ pulmonary hypertension leads to right sided failure

Can get acute onset left sided failure if there is chorda tendinae rupture or bacterial endocarditis

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35
Q

What does a louder third heart sound indicate

A

Large heart; since it represents more passive filling from enlarged atria

36
Q

Negative prognostic signs on mitral valve insufficiency investigation; generally and on echo

A

> Grade 3 or above murmur
Loud third heart sound
Dysrhytmia (atrial fibrillation)
Congestive heart failure (may be left side or biventricular)
Bacterial endocarditis

+ on echo: pulmonary hypertension, left atrial enlargement

37
Q

What is the only regurgitant lesion on the right side of the heart

A

tricuspid

38
Q

Details of tricuspid regurgitation

A

Radiates dorsally
Common and largely well tolerated
= assocaited with fitness due to cardiac hypertrophy in training

39
Q

What dysrhythmia can tricuspid regurgitation predispose to

A

Atrial fibrillation due to right atrial enlargement
- This can then impact performance

40
Q

What murmur is associated with fitness

A

Tricuspid regurgitation due to cardiac hypertrophy

41
Q

what grade do we investigate tricuspid regurgitation in TBs

A

Grade 4 (vs grade 3 in other breeds)

42
Q

What should we consider as a rare but possible cause of a NEW tricuspid murmur

A

Bacterial endocarditis
e.g from septic jugular thrombosis due to catheter placement, from dental disease

43
Q

Negative prognostic signs with tricuspid regurgitation

A

Loud murmur >4 in TB
Loud third heart sound
Dysrhythmia (atrial fibrillation)
Congestive heart failure (right side)
Bacterial endocarditis

Look on echo for right atrial enlargement and pulmonary hypertension

44
Q

What breed is a ventricular septal defect common in

A

Welsh ponies

45
Q

Characteristics of a ventricular septal defect

A

Systolic murmur in Right IC4 which is high grade and radiates sternally
Largely well tolerated

+ get concurrent systolic murmur on LIC4 due to relative pulmonic stenosis

It is SIZE of defect not murmur grade that indicates significance

Can go on to get a diastolic murmur which is a negative prognostic indicator

46
Q

Why can horses with ventricular septal defect go on to get a concurrent diastolic murmur

A

Valves sucked through defect

47
Q

What can induce a diastolic physiological murmur

A

Stress

48
Q

Where can we hear physiological diastolic squeak best

A

LIC 5 often towards apex

49
Q

Where do we hear aortic regurgitation and what are the characteristics

A

Loudest over LIC4 and radiates widely
Variable grade
Either early or holo diastolic

Decrescendo
Progressive condition

50
Q

What other clinical sign might we find in horses with aortic regurgitation

A

Hyperkinetic pulses because the systolic pressure increases and diastolic decreases

51
Q

What are some potential consequences of aortic regurgitation

A

Can develop secondary mitral valve regurgitation

Ventricular dilation can lead to ventricular arrhythmias e.g vtac and collapse

52
Q

What do we advise for horses with aortic regurgitation that develop exercise induced ventricular arrhythmias

A

Stop riding them

53
Q

What are negative prognostic indicators with aortic regurgitation

A

Secondary mitral valve regurgitation
High pulse pressure >60mmHg
Congestive heart failure (left sided or biventricular)
Bacterial endocarditis

+ left ventricular enlargement on echo

NB: murmur grade not a useful indicator

54
Q

What extra test is a good idea with aortic regurgitation (safety)

A

Exercising electrocardiography to look for exercise induced ventricular arrhythmia

55
Q

Characteristics of pulmonic regurgitation murmur

A

Rare and rarely affects performance
Loudest on LIC 3 or 4

Diagnose by excluding aortic regurgitation on echo

Long and musical sound

56
Q

What consequences can develop from pulmonic insufficiency

A

Right ventricular hypertrophy leading to cor pulmonale

Pulmonary hypertension

+ eventually can get alveolar hypoxia and respiratory distress

57
Q

What can cause a continuous heart murmur and what other clinical sign do we tend to see with it

A

Aortic root rupture or aortocardiac fistula

Tend to see ventricular tachycardia >100bpm due to disruption to interventricular conduction tissue

58
Q

What signs can we see with bacterial endocarditis

A

Should suspect in any new murmurs assocaited with severe disease

  • Acute onset heart failure
  • Fever, tachypnoea, tachycardia, murmur
    Hyperfibrinogenaemia, anaemia, leucocytosis
59
Q

How to diagnose bacterial endocarditis

A

Blood culture 3X apart hourly via sterile procedure but still risk of false -ves

60
Q

What do we need to be aware with colic and heart murmurs

A

Colic can make horses present with new murmurs and even atrial fibrillation but this goes away when colic treated

61
Q

What makes us think that it is heart failure presenting as colic rather than colic presenting with a murmur

A

If the heart rate is much higher than would be expected for the clinical signs of pain

62
Q

What does endocardial disease vs myocardial disease manifest as

A

Endocardial: as cardiac murmurs
Myocardial: cardiac dysrhythmias (so can get collapse/sudden death)

63
Q

What conditions can lead to myocardial dysfunction

A

Electrolyte abnormalities e.g Ca2+, Mg2+, K+
Increased myocardial muscle mass
Increased heart chamber size
Myocarditis

64
Q

What might we see on bloods that indicates myocardial dysfunction

A

Cardiac troponin 1 is released when cell membrane severely damaged

Creatinine kinase is released with less severe damage (cell membrane dysfunction)

65
Q

What could cause myocarditis

A

Bacteria: S aureus, Strep equi equi, Clostridium, sepsis, pericarditis, endocarditis

Borrelia burdgdorferi

  • Viruses: EIA, EVA, African Horse Sickness
  • Parasites: Large strongyles, toxoplasma, sarcocystis
66
Q

What can cause dilated cardiomyopathy

A

Myocarditis
Congenital
Toxic most common e.g ionophores, sycamores

67
Q

How can we evaluate the myocardium

A

Echocardiography + mimic exercise via dobutamine-atropine stress echocardiography

Biopsies
ECG

68
Q

What are the two indications for ECG

A

Rhythm disturbances detected
Tachycardia that can’t be explained by other finding s e.g stress, grass sickness, pain, hypovolvaemia

69
Q

When must we be concerned about jockey safety in exercising ECG

A

Atrial fibrillation
Myocardial disease
Aortic valve regurg

70
Q

What type of AV block is a physiological response to high blood pressure

A

2nd degree AV block
= vagally mediated baroreceptor response

71
Q

How can we test if 2nd degree AVB is just physiological response

A

Cause a stress response to remove the vagal tone e.g bang stable door
This should eliminate the arrhthymia

72
Q

What is 1st degree AVB

A

Lengthening of the PR interval

73
Q

What is 3rd degree AVB

A

Where the atrium and ventricles are not coordinating their contractions
= always pathological

74
Q

When is 2nd degree AVB indicative of pathology

A

If beats are blocked during exercise

75
Q

What is atrial fibrillation

A

Where the atria are not contracting so don’t get the extra squeeze of blood into ventricles (~20% of heart function)
So can cause poor performance in athletes

76
Q

What are the 3 types of atrial fibrillation

A

Lone spontaneous disease
Secondary to cardiac disease via atrial enlargement
Paroxysmal atrial fibrillation

77
Q

ECG characteristics with atrial fibrillation

A

Absence of P waves
Normal QRS
See F waves of electrical activity instead

In horses it is a bradydysrhythmia (unlike in dogs)

78
Q

When might a atrial fibrillation bradydysrhythmia suddenly chnage to tachydysrhythmia

A

With colic since lose vagal tone

79
Q

What is paroxysmal atrial fibrillation

A

In fit horses at a gallop may convert to atrial fibrillation and heart rate increases massively to >220bpm meaning no time for diastolic filling from atria so get collapse

Only affects athletes since pleasure horses can cope without extra 20% of blood from atrial contraction and diastolic filling

Usually horses get back up quickly as heart rate reduces and they convert back to sinus rhythm within an hour

80
Q

Signs of atrial fibrillation on ausculatation

A

Irregularly irregular rhythm
Normal or slow rate
No 4th heart sound
Loud 3rd heart sound

+ something about jugular pulses

81
Q

Two treatment options for atrial fibrillation

A

Quinidine: riskier, only for acute <2-3 months

Transvenous cardioversion: safer; indicated with chronic AF, significant cardiac disease, ventricular tachycardia at exercise

82
Q

What are the side effects of quinidine

A

Severe colic and diarrhoea
Cardiac side effects e.g supraventricular tachycardia, ventricular tachycardia
Vasodilation

83
Q

Which dysrhythmias are not compatible with life

A

Asystole
VEntricular fibrillation

84
Q

How much do atria contribute to cardiac output

A

~15% so most horses can cope with atrial fibrillation

85
Q

When to treat ventricular tachycardia and how

A

WHen HR >100
Where there are multiple ventricular ectopic foci
When there is evidence of heart failure

Use lidocaine anti-dysrhythmic
Could start with magnesium sulphate since fewer side effects and ‘does no harm’

86
Q
A

Equine (19 decks)

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