Equine cardiac exam refresher & murmurs

Where should you auscultate a horse?

Feel apex beat (mitral valve)

Pull leg forward to get triceps out the way

On right place stethoscope bell right under triceps just dorsal to point of elbow

Why do you need to cover all the cardiac window?

• To auscultate all three valves on left

  

• And tricuspid on right

  

• S4 loudest @ base & S3 loudest at apex (normal and abnormal vary in intensity)

Desribe the basic heart sounds

• Ventricles contract —> S1: shutting of AV valves (mitral & tricuspid)

  • LUB

• Ventricls relax —> S2: shutting of semilunar valves (aortic & pulmonic)

  • DUP

Which valve murmur may be heard on both left and right side?

Aortic regurgitation

Recall the basic heart sounds of a horse

S1 : Shutting of AV valves

S2 : Shutting of Semilunar valves

S3 End of rapid ventricular filling (Just after S2)

S4: Atrial contraction (Just before S1)

How can you tell when systole or diastole is?

• At normal heart rates systole much shorter than diastole

  • short gap between beat = systole

  • long gap between beat = diastole

• At a higher heart rate - S4,S1 (double heart sound) is at start of systole

  • duration of systole = duration of diastole

What factors cause turbulence? (Which in turn causes a murmur)

'Reynolds number'

• Diameter

• Velocity

• Density / viscosity

For example:

normal laminar flow = silent

What are the grades of heart murmur intensities?

• Grade 1: Barely audible

• Grade 2: Definite murmur quieter than S1&S2

• Grade 3: Obvious loud murmur as loud as S1&S2

• Grade 4: Very loud murmur louder than S1&S2

• Grade 5: Very loud and has a palpable thrill

• Grade 6: Audible with stethoscope just off chest wall

How can you describe a murmur?

• Intensity (grade 1-6)

• Timing: systolic/ diastolic/ continuous

  • Early, mid, late, 'pan' (covers whole time between heart sounds i.e. cannot hear S1 & 2), 'holo' (same as pan but can hear other heart sounds)

• PMI

• Radiation (away from PMI)

• Shape of murmur (Plateau, crescendo, descres, cres/decres)

• Quality of murmurs

  • Harsh/ Coarse/ Blowing/Honking? Buzzing

  • Pitch

How does aortic regurg murmur present on ausc?

• Holodiastolic

• Between aorta & LV

• Decrescendo

How does mitral valve regurg murmur present on ausc?

• Holosystolic

• Between LA & LV

• Plateau

What are the two types of physiological/ functional murmurs?

• Flow murmur

• FIlling murmur

Give an example of a flow murmur and explain its features

• Aortic flow murmur

  • Early-mid systole

  • Localised over heart base

  • Cres/Decres

  • Occurs immediately after S1, always finish before S2

  • May change intensity w/ HR / exercise

What are the features of a filling murmur?

• Early diastole, L or R

• Fit, young animals

• Squeak/whoop/click

• Short duration between S2 & S3

• Localised over base / apex

• May change intensity w/ HR

How common are pathological murmurs?

• Valvular regurg / congen 1° defects usually

• Hardly ever valvular stenosis

List the features of a mitral/ tricuspid regurg murmur

• holo/pansystolic

  • leaky valve throughout systole

• plateau / crescendo

• PMI @ heart apex

• may radiate dorsal & cranial

“LUB shh DUB”

When should you advise further investigation in MV/TV murmurs?

• Mitral Valve: Grade 3-6

• Tricuspid Valve Regurgitation: Grade 4-6

What are the features of a ventricular septal defect (VSD) murmur?

• Loudest on R (occ. left)

• Loud → thrill

• Radiate cranial/ventral

• Pansystolic (can’t hear heart sounds at all)

• Normally young horses

• Sometimes 2° L sided pulmonary a. flow murmur

What a ddx for VSD murmur?

Tricuspid insufficiency

What is this echo showing?

Ventricular septal defect → dextrapositioning of aorta (displaced over ventricular septum)

• Can measure size & velocity of jet through defect

What are the features of an aortic insufficiency murmur?

• Common older horses

• Descrescendo, buzzing / cooing

• Holodiastolic

• PMI left heart base

• May radiate ventrally

• 'Teenager murmur' because most common in older horses teens + and bc of sound

• Incr. resting HR to maintain CO

“UHHH”

What are the features of a patent ductus artierosus murmur?

• Cont.

• Between aorta & pulmonay a.

• Normal in neonates up to 5 days

• Should disappear within first few days of life

• PMI L heart base, also loud R heart base

• Waxes & wanes in intensity during cardiac cycle

Summary of the main murmurs and their locations

Physiologic

1. Aortic flow murmurs

2. Ventricular filling murmurs

Pathologic

1. Mitral/tricuspid valve regurgitation

2. Aortic regurgitation

3. Ventricular septal defect

4. (Patent Ductus arteriosus)