Equine Murmurs Flashcards
What are the 3 main causes of murmurs in horses?
> normal (physiological) - functional flow murmur due to valve regurgitation > valve pathology - endocardiosis (degeneration) - bacterial endocarditis - valve prolapse - ruptured chordae tendinae - valve regurgitation 2* to ventricular dilation > congenital - VSD - PDA, Valvular dysplasia
What are you looking for on auscultation of murmurs?
- timing, intensity, PMI (point of maxmimum intensity)
- pitch and quality
- radiation
- precordial thrill (“buzzing” with hand on chest)
Which heart sounds are normally audible in the horse?
SI, S2, S3, S4
What is the gold standard for murmur diagnosis? What else may be used diagnostically?
> Echo
- assess severity of lesion, confirm dx
- determine prognosis and suitability for ridden exercise
electrocardiography
- allow assessment of concurrent arrhythmias (not useful for murmur itself)
What can 2D and M mode echo be used for?
- assess valve structure and function (prolapse)
- assess chamber size (enlargement/colume overlaod)
- assess myocardium (hypertrophy)
- monitoring progression
What can Doppler (spectral and colour flow) echo be used for?
- semi-quantitive assessment of valvular regurgitation
- volume and velocity of regurgitant jets
What are physiological flow murmurs? Which horses commonly experience this?
- mainly TB horses in training
- mainly mitral and tricuspid valves (on auscultation)
- can also be aortic and pulmonic valves (on echo)
> these msut be differentiated from regurgitant murmurs due to pathology!
What is the most common congential abnormality in the horse?
Septal defects
What types of physiological flow murmurs are possible? When would these be heard and what would they sound like?
> aortic flow
- early-mid systolic [S1-S2] crescendo-decrescendo
- common
- quiet, local radiation only
- PMI heart base
- changes with exercise (usually disappears!)
- normal esp. in fit horses (1/3 TBs will have this)
ventricular (mitral and tricusp) flow
- early diastole (S2-S3)
- less common
- short duration, high pitched squeak
- PMI heart base or AV valves, L/R
- normal esp. young TB in training
remember they may also be associated with valve pathology and be sudden onset or cause collapse and death!
Which myocardial diseases common in small animals do not ococur in the horse?
Stenosis and pulmonary valve disease
Which valves are more / less likely to regurgitate in horses?
mitral>tricuspid>aortic
- due to different pressures placed on the valves eg. mitral closed during systole, aortic only has to hold back blood in aorta during diastole
Why may mitral regurgitation lead to collapse and sudden death?
Pulmonary artery rupture due to ^ pressures if severe
How do mitral regurgitation murmurs vary with severity?
intensity and radiation ^ (1-6 /6)
What shape are mitral and tricuspuid murmurs?
Plateau (band) shaped
What types of mitral and tricuspid regurgitation murmur are heard at different times?
- partial (early or mid systole)
- holo-systolic (S1-S2)
- pan-systolic (S1 buried)
PMI mitral regurge? radiates?
left 5th intercostal space
- radiates caudodorsally
PMI tricuspid regurge? radiates?
right 4th intercostal space
- radiates craniodorsally
What is aortic regurgitation often due to? Which horses are commonly affected?
- rarely functional
- often due to endocardiosis
- older horses
What type of disease is endocardiosis?
Progressive, intensity and radiation increase with severity -> eventually euthanized
Intensity, timing, shape and PMI and radiation of aortic regurgitation?
- grade 1-6
- timing holodiastolic (S2 - S3/4)
- shape decrescendo
- PMI: aortic valve (left basal area)
- radiation: caudoventrally to RHS (as aortic arch curves left - right)
When may mitral regurgitation be significant?
- poor performance
- resting tachycardia
- abnormal pulse quality, slow CRT
- signs of decompensated LCHF
- arrhythmias concurrently, esp. atrial fibrillation (due to volume and pressure overlaod -> atrial dilation)
- if louder than grade 4
- wide radiation
What is the normal HR of a horse?
30-40 (>50 = tachycardia)
When may tricuspid regurgitation be significant?
- poor performance
- resting tachycardia
- abnormal pulse
- signs of decompensated RCHF
- arrhythmias esp atrial fibrillation
- > grade 4
- wide radiation
When may aortic regurgitation be significant?
- poor performance
- resting tachycardia
- bounding (hyperkinetic) arterial pulse (due to large systolic/diastolic pressure difference from the regurgitation)
- slow CRT
- signs of LCHF
- arrhythmias, esp atrial fibrillation
What is the commonest form of valve pathology in horses? Which valves are usually affected?
- degenerative valvular heart disease 9endocardiosis)
- aortic valves mainly
> remember many valve regurgitations ARE NOT PATHOLOGICAL IN HORSES
Which animals are commonly affected by bacterial endocarditis?
> ruminants
- 2* to liver abscess, joint ill, metritis, mastitis, traumatic reticuliltis, naval abscess
horses less commonly
- site of sepsis often not IDed
- septic jugular thrombophlebitis from IV catheters possible
Why is prompt tx of bacterial endocarditis necessary?
large proliferative vegetative lesions develop, limiting return of valve function
How is Dx of bacterial endocarditis performed?
> clinical signs - CHF - fever - cardiac murmur - tachycardia and tachypnoea > lab - hyperfibrinogenaemia, anaemia, leucocytosis - blood culture (3x due to false negative) ideally when pyrexic, sterile collection (not via indwelling catheter)
Tx of bacterial endocarditis?
broad spec Abx based on sensitivity
prognosis of bacterial endocarditis?
guarded even after bacteriological cure
- permenant structural damage to valve
- in horses ,some right sided lesions may allow return to performance
- septic emboli may spread to distant sites (lungs from RH, kidneys/joints from LH)
Is valve prolapse pathological or physiological? which valves are affected? How is it diagnosed?
- physiological (relates to function of valve)
- NON-PROGRESSIVE regurgitation
- all valves can be affected
- may cause audible murmur
> diagnose on echo
Why may ruptured chordae tendinae occour?
- spontaneous
- 2* inflammatory or degenerative changes in chordae
which valves most commonly affected by ruptured chordae tendinae?
mitral
What is ruptured chordae tendinae characterised by? Prognosis?
- severe regurgitation with rapid change in haemodynamic status
- acute cardiac failure or sudden death
>Prognosis - can cpmpensate in long term if live beyond acute crisis, depending where chord is ruptured (close to papillary mm/leaflet edges)
When may AV regurgitation develop 2* to other disease?
- severe ventricular dilation (annulus ^ size)
- cardiomyopathy and myocardial disease
- aortic regurgitation and LV volume overload
> AV valve regurgitation appars later in disease (important to ID 1* cause of problem)
How can left ventricular volume overload be identified on echo?
ventricle become globoid shape with rounded apex
What situation may a transient mutmut be detected?
Hypovolaemia
- many horses presenting with acute colic/systemic disease develop cardiac murmurs
- these resolve once 1* disease has been treated
What type of physiological regurgitation may be seen in athletes? which valve commonly affected?
- RV/LV hypertrophy
- tricuspid
- usually mild and non-progressive
What are the 3 most common congenital abnormalities in horses? Which is MOST common?
- ventricular septal defect most common
- PDA
- valve dysplasia
Where is VSD found?
dorsal membranous septum
What type of murmur is VSD?
Diagonal (2 murmurs) > LHS murmur due to RV overload (sounds like pulmonic stenosis, kind of functional pulmonic stenosis due to ^ blood in RA) - holo-pansystolic - cres-decresc - grade 3-6 - wide radiation > RHS murmur due to LV-RV shunt - holo-pansystolic - coarse - plateaued - grade 3-6 - PMI tricuspid valve - wide radiation
How does intensity of VSD murmurs reflect severity?
INVERSELY proportional
- small hole = big noise
Does VSD affect performance?
May do but if small defect may not be noticed and horse may enter training
- keep this on differentials!!
how long is the ductus arteriosis normally patent for?
7-10d old foals
- closes earlier in farm animals
What type of murmur does PDA make?
washing machine continuous murmur
- grade 3-5
- wide radiation
- PMI left heart base
- radiates to RHS
