Cardiovascular System Diseases

Question 1

In a normal horse where can you see the jugular pulse?

Answer 1

Caudal 1/3rd of neck

Question 2

List what S1, S2, S3 and S4 are.

Answer 2

Heart sounds (S1 and S2 main ones, S3 and S4 accessory)
S1 - lub. AV valve closing.
S2- dub. Semilunar & aortic & pulmonic closure.

Question 3

What are the general rules for systolic murmurs, diastolic murmurs and continuous murmurs in horses?

Answer 3

Systolic - AV valve regurgitation, VSD
Diastolic - aortic valve regurgitation
Continuous- PDA, pentalogy of fallot

Question 4

What is the most common murmur in aged horses? Explain.

Answer 4

Aortic regurgitation murmur.

Diastolic form and predisposes to atrial fibrillation (atria enlarges due to thin walls & blood pushing)

Question 5

What condition is considered a normal finding in foals in the first 3-4 days of life?

Answer 5

Patent ductus arteriosis.
Sounds like a continuous machinery murmur.
Can get prostaglandin E2 to maintain patency.

Question 6

Even though it’s an uncommon condition, in horses what is a predisposing cause to bacterial endocarditis?

Answer 6

Catheter site causing jugular vein thrombophlebitis

Question 7

What are the major signs that a horse has bacterial endocarditis and how would you confirm this?

Answer 7

Recent catheter.
Fever of unknown origin.
Do multiple blood cultures!

Question 8

Define congestive heart failure.

Answer 8

Failure of cardiac system to eject sufficient blood to meet tissue demands.

Question 9

Clinically what would you see in left sided heart faliure compared to right sided heart failure?

Answer 9

Left sided - pulmonary oedema, respiratory foamy discharge, laboured breathing, increase RR
Right sided - venous system congestion, oedema, pericardial effusion, jugular pulsations.

Question 10

What is your treatment approach to congestive heart failure?

Answer 10

Furosemide (pulmonary oedema) 
Angiotensin converting enzyme inhibitors (decrease vascular resistance) 
Digoxin (positive inotrope) 
Sodium restriction
Reduced exercise

Question 11

Describe arrhythmias.

Answer 11

Common benign important condition.

Primary (cardiac structure disorder) or Secondary (underlying systemic cause like electrolytes, toxins, drugs etc.).

Question 12

What do the following parts of the conduction pathway do?

Answer 12

SA node - generates impulse
Intermodal tracts - transmission
AV node - delays impulse to let atrium contract and fill ventricle
Bundle of His - continues impulse to ventricles
Purkinje - transmits impulse

Question 13

In an ECG what does the P, QRS and T waves represent?

Answer 13

P - atrial depolarisation
QRS- ventricular depolarisation
T- ventricular repolarisation
Remember the atrium repolarises while ventricle is doing it’s thang.

Question 14

Describe bradyarrhythmias like it’s an exam and you want to get good marks.

Answer 14

Non pathologic arrhythmias associated with a high sympathetic tone. The most common is a 2nd degree atrioventricular block.
CHECK OVER PICTURES FOR ECG

Question 15

**What is the difference between a 1st, 2nd and 3rd degree atrioventricular block?

Answer 15

1st deg- prolonged PQ interval
2nd deg - no transmission of P wave (prolonged PR interval and then block
3rd deg - complete loss communication with atria & ventricles. Always pathologic.

Question 16

On ECG what would you expect to see with a sinus bradycardia or a sinoatrial block?

Answer 16

SB - decreased rate but normal rhythm

Sino B- SA node impulse is blocked get a skipped QRS and everything.

Question 17

What is Bruit de Canon?

Answer 17

S4 on top of another heart sound (so you have the atria and ventricle contracting at the same time).

Question 18

Can you diagnose the three types of AV blocks on a ECG?

Answer 18

I hope so! Look at the photos!!

Question 19

How do you know if an AV block is pathologic?

Answer 19

More than 2 P waves are transmitted.

Question 20

How would you treat 2nd or 3rd deg AV blocks?

Answer 20

Anticholinergics like Atropine or Glycopyrrolate

Catecholamines like Dobutamine or Dopamine

Question 21

What’s the difference between Mobitz I and Mobitz II 2nd deg AV blocks?

Answer 21

Mobitz I - gradual PR interval prolongation and then block.

Mobitz II - constant PR interval and block

Question 22

Which AV block has P waves and QRS waves but they are not communicating?

Answer 22

3rd degree AV block

Question 23

What is a supraventricular premature depolarisation?

Answer 23

Get a T wave and P wave on top of eachother and short P P interval.
From post exercise (normal) or sepsis, toxins, hypoxaemia.
Lots of them = supraventricular tachycardia

Question 24

What is the most common cardiac dysrhythmia in the horse?**

Answer 24

Atrial fibrillation

Question 25

Describe atrial fibrillation.

Answer 25

Myocytes go crazy and depolarise crazily then AV node can't process this and get irregular rhythm with no S4. From high vagal tone, K depletion, atrial enlargement.

Question 26

What will you see on ECG that indicates atrial fibrillation?

Answer 26

``` F waves (Fibrillation waves) - tiny little P waves Saw tooth P waves (Atrial flutter). ```

Question 27

What are some clinical signs of atrial fibrillation?

Answer 27

Poor performance* Colic Incidental finding Weakness

Question 28

What are some things you should consider before treating atrial fibrillation?

Answer 28

Medications (could be causing condition) ECG Duration (better prognosis if hasn't been happening for over 16 weeks).

Question 29

Why is quinidine the number 1 treatment for atrial fibrillation?

Answer 29

Sodium channel blocker than prolongs the action potential so normalises the rhythm. Done IV or NGT only. BUT monitor QRS closely for widening which indicates quinidine toxicity.

Question 30

You are treating a horse with atrial fibrillation with Quinidine gluconate for 2 days with no improvement what next?

Answer 30

Consider combining quinidine with digoxin to increase quinidine activity (but increases toxic chance!)

Question 31

What is a ventricular premature depolarisation?

Answer 31

Missing P wave. More than 3 consecutive = ventricular premature deplarisations.

Question 32

What is your treatment of choice for ventricular issues?

Answer 32

Lignocaine hydrochloride

Question 33

What is Torsades de Pointes?

Answer 33

Enlargement and narrowing of full ECG (Looks like a streamer twisting around). Indicates quinidine toxicity.

Question 34

What will you see clinically with pericardial disease?

Answer 34

Muffled heart sounds | Get decrease QRS amplitude and electrical alternans (rhythmic QRS change)

Question 35

What are some cardiac toxins you should be aware of?

Answer 35

``` Ionophores (Monensin) that allows cation build up Cardiac glycosides (Oleander) stops impulse control Rhododendrons Avocados ```