Equine Cardiology 1

Question 1

Presentations that may prompt specific evaluation for cardiac disease.

Answer 1

Detection of murmur during routine exam.
Detection of arrhythmia during routine exam.
Altered demeanour.
Poor performance / exercise intolerance / fatigue.
Epistaxis.
Persistent unexplained tachycardia.
Weakness / collapse.
Dyspnoea / cough.
PUO.

Question 2

Cardiac-relevant CE.

Answer 2

HR, rhythm, murmurs.
Arterial pulses.
Jugular distension / pulsations.
MM colour.
RR.
Weight loss.
Ventral oedema.
Weakness, ataxia, syncope, exercise intolerance.

Question 3

Presentations of heart failure.

Answer 3

Reduced CO:
- Exercise intolerance.
- Tachycardia.
- Pale MMs.
- Weak pulses.
- Cold extremities.
- Collapse / syncope.
- Cachexia / weight loss.
Pulmonary venous hypertension (L CHF):
- Tachypnoea.
- Coughing.
- Crackles (pulmonary oedema).
Systemic venous hypertension (R CHF):
- Jugular vein distension.
- Pulsation of jugular vein extending beyond caudal third of neck.
- Pleural and peritoneal fluid (ascites) accumulation.

Question 4

Auscultation of left of horse.

Answer 4

Palpate apex beat - over mitral valve.
Place stethoscope over apex beat.
S1 is loudest here.
Listen carefully in systole and diastole, slowly move stethoscope in circles around mitral valve, keeping in contact w/ chest wall.
Move stethoscope cranial and slightly dorsal, where S2 becomes louder than S1.
- Over aortic valve here.
- Listen to diastole and systole and radiate stethoscope around.

Question 5

Auscultation of right of horse.

Answer 5

Try to palpate apex beat - more difficult.
Auscultate more cranially than on the L.
Forward placement of R FL helpful.
Hear tricuspid valve.
Radiate stethoscope around.
Usually quieter on R compared to L.

Question 6

Further diagnostic techniques if concerns on CE.

Answer 6

ECG.
Echocardiography.
Biomarkers.

Question 7

1. When can an ECG be taken in a horse?
2. Most commonly used manufacturer of ECG equipment used in UK equine practice.
3. Equipment in development - advantages and drawbacks.

Answer 7

1. At rest.
   During exercise.
   As a 24-hour reading.
2. Televet.
3. Smart phone ECG technology.
   - Cheap.
   - Quick traces stable side.
   - Basic screens of heart rhythm at rest.
   - Higher frequency of artefacts.
   - More difficult for complex arrhythmias.

Question 8

1. Leads for AliveCor (smart phone).
2. Leads for Televet.
3. Main lead used for equine interpretation.

Answer 8

1. Single lead.
2. 4 leads - red (negative, right arm), yellow (left arm), green (positive, left leg), black (earth).
3. Lead II (records between RA and LL electrodes).

Question 9

Standard ECG configuration in equine practice.

Answer 9

Base-apex configuration.
Red cranially to R scapula. Green just caudal to cardiac apex. Yellow just above green.

Question 10

Interpreting ECG.

Answer 10

HR
Assess overall rhythm.
Is there a P for every QRS?
Is there a QRS for every P.
Do all complexes look alike?
Any pauses or irregularities?

Question 11

Echocardiography - what can we assess for?

Answer 11

Severity of many forms of heart disease.
Identify CHF, valvular disease, contractility, measure heart size.

Question 12

Biochemical markers of CV disease in equids.

Answer 12

Cardiac troponin I.
- identifying myocardial disease (but uncommon in horses).

Question 13

1. What is rare and therefore disregarded as a differential Dx in equine cardiology?
2. In what heart valve is it rare for horses to experience significant disease?

Answer 13

1. Valvular stenosis.
2. Pulmonic valve.

Question 14

Equine physiological heart murmurs.

Answer 14

No cardiac pathology.
Particularly associated w/ LV ejection (blood flow into aorta).
Murmurs are quieter, soft and localised.
No precordial thrills.
Do not obscure heart sounds.

Question 15

Valvular regurgitation causes.

Answer 15

Degenerative processes.
Inflammatory processes.
Physiological - common in horses undergoing athletic training e.g. racehorses (remodelling). No pathology.

Question 16

Congenital defects.

Answer 16

Less common in horses.
Typically loud often w/ precordial thrills.
VSDs can be well tolerated so not detected until horse mature.
Complex defects will present in foals but are not common.

Question 17

Relationship between volume of murmur and its importance.

Answer 17

Louder = more important. (there are exceptions).

Question 18

Describing cardiac murmurs.

Answer 18

Systolic/diastolic.
Grade.
Characteristics.
Point of maximum intensity.
Radiate.

Question 19

Cardiac murmur grading.

Answer 19

1 = quiet, only heard w/ careful auscultation over localised area.
2 = quiet, less intense than transient heart sounds, heard immediately once stethoscope places over localise point of maximum intensity.
3 = Moderately loud, same intensity to transient heart sounds.
4 = Loud, louder than transient heart sounds, heard over widespread area, no thrill palpable.
5 = loud, w/ precordial thrill.
6 = loud enough to be heard w/ stethoscope raised just off chest surface.

Question 20

Causes of a left sided systolic murmur.

Answer 20

Mitral regurgitation.
Physiological ejection murmur.

Question 21

Causes of right sided systolic murmur.

Answer 21

Tricuspid regurgitation.
VSD.

Question 22

Causes of diastolic murmurs.

Answer 22

Aortic regurgitation.
Functional early diastolic murmur (physiological).

Question 23

1. Holosystolic.
2. Pansystolic.
3. Point of max. intensity of mitral regurgitation.
4. Best way to predict likely course of disease for mitral regurgitation?
5. What does severe mitral regurgitation lead to?
6. At what grade of murmur of mitral regurgitation should echocardiography be discussed with the owner?

Answer 23

1. Murmur between lub and dup.
2. Murmur louder than the lub and dup.
3. Over left heart apex or just dorsal to it.
4. Examine horse again in a few months and possibly perform serial echocardiographic examinations.
5. L atrium dilation which predisposes AF.
   CHF ultimately.
6. Grade 3/6 or higher.

Question 24

1. Terms for physiological ejection murmur.
2. Usual grade?
3. What point of systole?
4. Why do physiological ejection murmurs occur?
5. Point of max intensity?
6. When does murmur end?
7. Clinical consequences?

Answer 24

1. Physiological / ejection / functional / flow.
2. 1-3/6.
3. Early-mid.
4. Turbulence of blood due to high velocity and volume of blood flowing into the aorta.
5. Left side, at heart base (generally localised).
6. Before S2 (early-mid).
7. Typically none.

Question 25

1. PMI tricuspid regurgitation.
2. Grades of tricuspid regurgitation?
3. Cause?

Answer 25

1. On right side, over tricuspid valve.
2. 1-6/6. Most commonly 2-4/6.
3. Pathological changes rare in tricuspid valve. But regurgitation common. Proposed due to geometric changes in RV in response to hypertrophy. Unlikely to be clinically significant in racehorses.

Question 26

Most common congenital defect in horses.
Breed?
Location of defect?

Answer 26

VSD.
Welsh Mountain ponies.
Membranous (non-muscular) portion of septum.

Question 27

1. VSD shunt direction.
2. Murmur heard?
3. Px?
4. PMI?
5. Murmur grade of VSD?
6. VSD murmur radiation.

Answer 27

1. L to R.
2. Loud pansystolic coarse murmur over R side.
3. Dept. on size and location.
4. Ventral to R apex.
5. 4-6.
6. Cranial and ventral.

Question 28

Main diastolic murmur in horses.

Answer 28

Aortic regurgitation.

Question 29

1. Where can aortic regurgitation be heard?
2. Murmur heard?
3. Age affected.
4. Best indication for severity of aortic regurgitation.
5. Consequence of aortic regurgitation?

Answer 29

1. Initially over left hemithorax but over right hemithorax also as the murmur progresses.
2. Holodiastolic decrescendo, long, musical (vibration) murmur.
3. Middle-aged to older.
4. Quality of arterial pulses. Severe = firm but short lasting pulse (“waterhammer”).
5. Dilation of LV which may result in ventricular arrhythmias, putting horse at risk of sudden death.

Question 30

1. Duration of functional early diastolic murmurs.
2. When in the cardiac cycle do these occur?
3. Caused by?
4. Pitch?
5. PMI?

Answer 30

1. Short.
2. Just before S3.
3. High volume and velocity of blood flowing into ventricle during rapid filling and abrupt end of active relaxation.
4. High.
5. Just ventral to heart base on either side of the chest.

Question 31

Indications for echocardiography.

Answer 31

When a non-physiological murmur is heard and valvular or congenital heart disease is suspected.
- Aortic 3/6 or higher in a young horse, older horse still in work, with other concurrent murmurs.
- Mitral murmur 3/6 or higher.
- Tricuspid murmur more than 4/6 in racehorse, or 3/6 and higher in non-racehorse.
In association w/ pyrexia.
Other CS of CHF.
In association w/ AF.
In association w/ poor performance?
Concurrent exercising ECG also useful when evaluating safety to ride in horses w/ murmurs.