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8- EQ- Cardiorespiratory Disease > Equine dysrhythmias > Flashcards

Equine dysrhythmias Flashcards

1
Q

Myocardial disease in horses causes

A

Dysrhythmias due to disruption of action potential propagation and abnormalities in contraction

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2
Q

Endocardial disease in horses causes

A

Murmurs, due to valvular regurgitation and jet lesions

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3
Q

List 4 ways that myocardial disease manifest

A

No clinical signs

poor performance- atrial fibrilation and ventricular premature depolarisation

Collapse- multiple ventricular premature depolarisations and Ventricular tachycardia

Death - Ventricular tachycardia progressing to Ventricular fibrillation

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4
Q

Describe how to diagnose cardiac dysrhythmias

A

ECG
evaluation of underlying cause using echocardiogram, blood tests ect

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5
Q

List the 4 conditions that may lead to myocardial dysfunction

A

Electrolyte abnormalities
Increased myocardial muscle mass
Increased chamber size
Myocarditis

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6
Q

Describe the Use of clinical pathology to evaluate the large animal myocardium

A

Sensitivity and specificity of these tests is questionable
-Proteins
- Enzymes
- Creatine kinase

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7
Q

List the bacteria that can cause myocarditis

A

Staph aureus
Strep equi
Clostridium chauvoei
Myocobacterium spp.
Secondary to sepsis, pericarditis, endocardititis

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8
Q

List the viral causes of mocarditis

A

FMD, EIA, EVA, EIV, AHS

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9
Q

Other than bacterial and viral what else can cause myocarditis in horses

A

Borrelia burgdorferi (Lyme disease)
Parasites- large strongyles, Toxoplasma, Sarcocystis
Thromboembolic disease

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10
Q

List the cardiomyopathies of large animals

A

Only DCM reported to be important (subacute to chronic, see a dilated ventricle)

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11
Q

Describe how we evaluate the myocardium using echocardiography

A
  • Assessment of myocardial appearance (long/short axis views),
  • Fractional shortening (at rest and following exercise to evaluate contractility),
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12
Q

Describe dobutamine atropine stress echocardiography

A

Causes a progressive increase in HR,
Allows function to be assessed as HR increases and how function is maintained,
Simulates exercise

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13
Q

Describe how myocardial biopsies can be performed

A

Can be done standing,
Ultrasound guided,
Biopsy instrument into heart via jugular vein

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14
Q

Describe a Standard equine ECG at rest

A

Complexes uniform, identical and at regular intervals

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15
Q

Describe how to assess an exercising equine ECG

A

Harder to assess, P and T waves are hard to see,
Assess the regularity of the R waves (downward projections)
Check intervals are regular and they look similar

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16
Q

What is the most common physiological dysrhythmia in horses

A

2nd degree AV block
considered normal in horses

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17
Q

what causes 2nd degree AV block

A

due to high vagal tone in autonomic control of the equine heart

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18
Q

describe what a 2nd degree AV block looks like on ECG

A

P wave not followed by a QRS complex (blocked by the AV node),

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19
Q

Are 2nd degree AV blocks of clinical concern

A

NO
will disappear when horse is stimulate

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20
Q

What is the most important cardiac dysrhythmia in the horse

A

Atrial fibrillation

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21
Q

why does Atrial fibrillation occur

A
  • Lack of coordinated atrial electrical activity
  • Can be triggered by electrolyte/acid-based imbalances, anaesthetic and drug administration (that causes bradycardia, exercise
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22
Q

List some horses which are more susceptible to atrial fibrilation

A

TBs, SBs, Draught horses- large horses
due to large atrial mass

23
Q

List the clinical signs of atrial fibrillation

A

None- most
Exercise intolerance/poor performance
Epistaxis

RARE presentations:
Weakness/syncope
Myopathy
Colic
CHF

24
Q

What are the 2 forms of atrial fibrillation

A

Paroxysmal
Sustained

25
Q

What is the difference between paroxysmal and sustained atrial fibrillation

A

Paroxysmal - Lasts less than 24-48hrs and spontaneously converts back to sinus rhythm,

Sustained (lasts longer than 24-48hrs)

26
Q

What can Paroxysmal atrial fibrillation be associated with

A

Potassium depletion (furosemide) and administration of bicarbonate

27
Q

List the things seen on clincal exam in horses with atrial fibrillation

A

Irregularly irregular rhythm (less irregular with chronicity),

HR and pulse quality varies on intensity (booming S1 and no S4),

Usually a normal or decreased HR, occasionally increased if associated with heart failure,

Abnormally high heart rates at exercise (can be associated with VPDs, should perform an exercising ECG)

28
Q

Describe how to diagnose atrial fibrillation

A

ausculatation and physical exam
resting ECG - confirms diagnosis
Further diagnostics PRIOR to attempting treatment

29
Q

what is seen on ECG with atrial fibrillation

A

No P wave
normal QRS complexes
F (fibrillation) waves

30
Q

How does the cause of atrial fibrillation being chamber enlargement affect diagnosis

A

Worse prognosis for return to sinus rhythm

31
Q

Describe the pharmacological treatment of atrial fibrillation

A

Quinidine sulphate
Is a Negative inotrope

32
Q

List the side effects of quinidine sulphate

A

Fatal dysrhythmias,
Colitis (drug irritant to mucosa),
Laminitis/nasal oedema/ataxia

Because of this need to be cautious when using

33
Q

Describe the Cautious use of quinidine sulphate

A

Need repeated physical exam
Auscultation
Continuous ECG at the time and 24hrs after
Check acid base and electrolytes prior to treatment

34
Q

Describe how to assess quinidine sulphate toxicity

A

by assessing prolongation of QRS complex (>25% of pretreatment value makes untoward effects more likely)

35
Q

What is DC cardioversion

A

Wires into the heart of an anaesthetised horse,
Positioned using ultrasound and radiography,
Increase current to try and stop heart and convert to sinus rhythm

36
Q

what does DC cardioversion treat

A

atrial fibrillation

37
Q

Where are the two wires places in electrocardioversion

A

One wire in left pulmonary artery,
Other wire in right atrium

38
Q

What is the Prognosis of paroxysmal atrial fibrillation

A

Excellent to good unless keeps recurring

39
Q

what is the Prognosis of sustained atrial fibrillation with no cardiac disease

A

<3 months - good either technique (quinidine or DC cardioversion)
>3 months better with DC cardioversion,
Risk of re-fibrillation

40
Q

what is the Prognosis of sustained atrial fibrillation with underlying cardiac disease

A

Average with DC conversion
More likely to re-fibrillate

41
Q

what is the Prognosis of sustained atrial fibrillation with heart failure

A

Poor to grave, no treatment

42
Q

What other dysrhythmias are seen in horses other than 2nd degree AV block and atrial fibrillation?

A

Atrial premature depolarisation
Ventricular premature depolarisation
Ventricular tachycardia
Third degree AV block
Asystole
Ventricular fibrillation

43
Q

List the Dysrhythmias which are not compatible with life

A

Asystole = lack of electrical activity,

Ventricular fibrillation = unusual in horses, leads to sudden death

44
Q

How can be treat ventricular dysrhythmias in horses

A

Lidocaine,
Magnesium,
Procainamide,
Amiodarone

45
Q

When is pharmacological management of acute tachyarrythmias in the horse warranted

A

Evidence of poor cardiac function (clinical signs)
Poor perfusion/ evidence of this
Malignant arrythmia = HR over 100bpm, multiform or polymorphic complexes, R-on-T

46
Q

What is the first line treatment for ventricular tachycardia

A

Lidocaine

47
Q

List the CNS adverse events associated with lidocaine to treat ventricular dysrhythmias

A

Nystagmus, muscle twitching, disorientation, excitement, convulsions

48
Q

when is magnesium used to treat ventricular dysrhythmias

A

if lidocaine treatment has failed

49
Q

When when can lidocaine treatment of ventricular dysrhythmias not be as effective

A

in hypokalaemia

50
Q

Describe what is seen on ECG with Torsades de pointes

A

Undulating baseline with no beginning or end to the complexes
basically looks wavy

51
Q

what is the prognosis for a horse with Torsades de pointes on ECG

A

BAD
this rhythm is not associated with life

52
Q

List 4 causes of bradyarrhythmias in the horse

A

Drugs,
Electrolyte derangements,
Intestinal disease,
Primary myocardial disease

53
Q

Describe how we can manage bradyarrhythmia’s in horses

A

Relevance of 2nd degree AV block is unknown, likely require further investigation if persistent at exercise,

Anticholinergics = Glycopyrrolate, atropine, hyoscine (buscopan),

Ventricular pacemaker

8- EQ- Cardiorespiratory Disease (18 decks)

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