Cardiac murmurs in horses

Cardiac murmurs
in horses
Celia M Marr
celia.marr@rossdales.com
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Clinical
Priorities
in Equine
Cardiology
Cases
Clinical signs
consistent with
cardiovascular
disease
Specific Diagnosis
Prognosis
Athletic
Capability
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Rider
Safety
Presenting problems where heart
disease must be considered possible
•
Congestive Heart Failure
•
Exercise intolerance
•
Poor performance
•
"Routine" examinations
•
•
annual vaccination
•
prior to sedation
•
suitability for purchase
Unrelated examinations
•
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colic, coughing etc
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Congestive Heart Failure - differential
diagnosis:
•
Congenital anomaly
• usually complex defects
•
Severe valvular pathology
• infective endocarditis, valvular disruption, long-standing
severe degenerative valvular disease (endocardiosis)
•
Cardiomyopathy
• nutritional, toxic, idiopathic
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Congestive Heart Failure
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•
•
All causes: fairly uncommon
•
All causes: prognosis hopeless
All causes: palliative therapy over short to
medium term may have some effect
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What causes murmurs in horses
that otherwise seem fairly
healthy?
•
Forward flow
Systole+Ao= flow
• normal cardiac structure
• abnormal cardiac structure
•
Regurgitation
Diasystole+Ao= VR
• normal cardiac structure
• abnormal cardiac structure
•
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Flow through intracardiac shunts
© cmarr 2013
Systole+MV= VR
What is the prevalence of cardiac murmurs?
Stevens et al, 2009, Vet Rec, 164, 6-10
Findings in 1153 general riding/riding horses in SE England
18
16
< 7 yr
8 - 14 yr
15 - 23 yr
> 24 yr
14
12
%
10
8
6
4
2
0
AR
MR
Multiple
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TR
Flow
Cardiac murmurs: clinical categories
•
•
•
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Systolic, left side
Systolic, right side
Diastolic, either
side
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Common Differentials for a systolic
murmur on the left:
MITRAL
REGURGITATION
AORTIC FLOW
PULMONIC FLOW
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Systolic murmurs associated with forward
flow aka "physiological, ejection"
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•
Holo, mid, early or late
•
Loudest over semilunar
valves
•
Localised
•
Soft to moderate
•
Crescendo-decrescendo
•
Blowing
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Mitral Regurgitation
SIGNIFICANCE
• Form of valvular regurgitation most
likely to lead to poor performance or
CHF
MURMUR CHARACTERISTICS
• Grade 1 - 6/6
• Early, mid, holo or pan-systolic
• Band-shaped
• Left fifth intercostal space
• Radiating caudodorsally
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Equine Vavlular pathology
•
•
Degenerative lesions
Inflammatory lesions
•
•
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18
16
14
12
10
8
6
4
2
0
AR
Infective endocarditis
Non-septic valvulitis
•
•
Dysplasia
•
Ruptured valve cusp (semi-lunar
valves)
•
Cardiomyopathy
Ruptured chorda tendinea (AV
valves)
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MR
Multiple
TR
Flow
Mitral Insufficiency
Left atrial dilation
SYSTOLE
DIASTOLE
SYSTOLE
Increased ventricular filling: Increased ventricular work
increases regurgitant fraction
Loud third ©heart
sound
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PULMONARY ARTERY DILATION
AND RUPTURE
Where's the evidence?
•
Does physiological
regurgitation predispose to
valve pathology?
•
What proportion of horses
with mild-moderate MR
develop atrial fibrillation?
•
Does mild-moderate affect
future racing performance?
• What about other sports?
•
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Does MR shorten lifespan?
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Does left sided valvular regurgitation shorten lifespan?
LSVR = AR &/or MR
<7yr
No LSVR
LSVR
8-12yr
Text
14-23 yr
>24 yr
Age rather than LSVI increases the risk of dying
Stevens et al, 2009, Vet Rec, 164, 6-10
© cmarr 2013
Mitral Regurgitation: physiological
•
Young, LE, Rogers, K, Wood, JLN
(2008), JVIM, 22, 418-426
•
526 race fit horses in flat or jump
racing in UK
•
Prevalence on Auscultation
• Flat: TR 22%, MR 9%, AR 1%
• Jump: TR 43%, MR 19%, AR 4%
•
Prevalence of VR found with Doppler
echocardiography higher
•
No association with race performance
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Clinical decision making with MR
• Indications for further investigation
• Grade >3/6
• Audible over a wide area
• Resting tachycardia or dysrhythmia
• Lengthy career ahead
•
Desirable echocardiographic
characteristics
• Normal valve structure or prolapse
• Cardiac dimensions within normal limits
for breed and size
• Small or moderate regurgitant jet
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Common differentials for a systolic
murmur on the right
TRICUSPID REGURGITATION
VENTRICULAR SEPTAL DEFECT
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Tricuspid regurgitation
MURMUR
CHARACTERISTICS
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•
•
•
Grade 1 - 6/6
•
Right fourth intercostal
space
•
Radiating craniodorsally
Holo or pansystolic
Crescendo-decrescendo
or Band-shaped
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Clinical decision making with TR
•
TR murmurs are very common in racing Thoroughbreds and
Standardbreds
•
TR: flat 22%; jump 43%, Young et al, 2008
•
•
Increases in prevalence with age in both STBs and TBs
•
•
Less common in other breeds
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Indications for further investigation
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No difference in racing performance when TBs with and without TR
are compared
18
•
•
14
10
Grade > 4/6 in racehorses
8
Grade > 3/6 in other types
4
6
2
0
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© cmarr 2013
AR
MR
Multiple
TR
Flow
Ventricular Septal Defect
•
Welsh Mountain Ponies*, Standardbreds and
Arabs
•
Presentation can range from incidental
finding to congestive heart failure
•
•
Cases with small VSD can be useful and safe
for lower level careers
•
•
Depends on size of defect
Often inappropriate to recommend
purchase or continued use due to age of
likely riders
Avoid breeding
*7 of 121 ponies WMP assessed by auscultation only, unpublished
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©cmarr2008
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Differentiating causes of bilateral
systolic murmurs
Relative
Pulmonic
Stenosis
IC3
IC4
IC3
IC4
VSD
IC5
IC5
Mitral
regurgitation
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Tricuspid
regurgitation
Additional Murmur:
aortic regurgitation
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Location of defect
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Prognostic Indicators
• Size of defect
•
< 2.5 cm Thoroughbreds and
Standardbreds
•
< 1/3 of aortic diameter - other
breeds
18 month-old TB
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11 year-old Riding horse
Application of the Bernoulli
equation
•
The velocity of the shunt can be used to estimate
the pressure difference between the right and left
ventricle
•
With a large defect, RV pressure rises and the
shunt velocity falls
•
With a small (restrictive) defect, the large pressure
difference between the ventricles is maintained
and the shunt velocity is high
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VSD Shunt Velocity: indicator of
RV pressure increase
∆P = 4v2; > 4 m/s > 64 mmHg
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Left ventricular volume overload
• L>R shunt
• Concurrent AR
• Other cardiac
pathology
© cmarr, 2013
RV
IVS
PA
AO
PA
Care: VSD is part of many complex defects
© cmarr, 2013
Complex Cardiac Defects
•
Clinical signs are usually
consistent with severe
cardiac compromise
•
Diagnostic aids may allow
specific anomaly to be
characterised
•
Echocardiography, including
contrast and colour-flow
studies
•
•
•
Radiography
Cardiac catheterization
Prognosis is hopeless
© cmarr 2013
©cmarr,2013
ACKNOWLEDGEMENT
• Congenital malformations of the
heart
• Drs Robert Rushmer and Richard
Blandau, University of Washington,
1951
•
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http://www.youtube.com/watch?v=5DIUk9IXUaI
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Tetralogy of Fallot
• perimembranous VSD,
• overriding aorta,
• RVOT obstruction
• RV hypertrophy.
©cmarr,2013
30 months, mild ill thrift
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Common Differentials for a diastolic
murmur on the left and/or right
VENTRICULAR FILLING
AORTIC REGURGITATION
PULMONIC REGURGITATION
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Diastolic murmurs associated with
forward flow
•
Early, late or mid
•
Loudest over left or right
heart base
•
Localised
•
Soft to moderate
•
Decresendo
•
Squeaky or creaky
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Aortic Regurgitation
MURMUR CHARACTERISTICS
•
•
•
•
•
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Grade 1 - 6/6
Early or holodiastolic
Decrescendo
Left heart base
Radiating caudoventrally
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Aortic insufficiency
Diastole - increased left ventricular filling
Hyperkinetic
pulse
Normal
pulse
Systole - cardiac output maintained or increased
© cmarr 2013
Aortic Regurgitation: pathology
DEGENERATIVE
• Middle-aged or older horses -
typically not severe until in late
teens
• Frequently an incidental finding
INFECTIVE ENDOCARDITIS
• Fever, vague malaise, shifting
lameness
• Congestive heart failure
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© cmarr 2013
<7yr
8-12yr
14-23 yr
>24 yr
1972, 4(1) 1-8
Aortic valve lesions 311/1557 i.e. 20%
Aortic
Regurgitation
• There is a higher prevalence of ventricular arrhythmias
in horses with aortic regurgitation compared with
other forms of valvular insufficiency
• AR cases with VPD are more likely to progress
clinically within 2 years compared to those without*
• Incidental finding?
• Concurrent myocardial and endocardial pathology?
• Catecholamine-induced?
• Altered coronary artery blood flow?
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* Horn, PhD thesis, 2002
© cmarr 2013
Clinical decision making with AR
INDICATIONS FOR FURTHER INVESTIGATION
•
•
•
•
•
•
•
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Hyperkinetic pulses
18
Murmur grade > 3/6
14
Holo or pan-diastolic
10
16
12
8
6
Young horse
4
2
Old horse still in work
0
AR
MR
Multiple
TR
Flow
Concurrent murmurs or arrhythmias
Note: this is a slowly progressive condition: regular reexamination (q 1 or 2 years) are indicated while in work
© cmarr 2013
Summary of guidelines for assessing murmurs
Location & timing
Differentials
Characteristics prompting further investigation
Left, systolic
Aortic Flow
murmur
If loud, prolonged or widespread suspect MR
Mitral
regurgitation
Grade 3 or louder, pre-cordial thrill
Concurrent Arrhythmia
Long high-level career ahead
Ventricular
septal defect
Also murmur on the left side
Mostly non-athletic breeds or juveniles
Tricuspid
regurgitation
Grade 4 or louder
Pre-cordial thrill
Concurrent Arrhythmia
Non-athlete: suspect VSD
Ventricular
filling
Loud, prolonged or widespread suspect AR
Right, systolic
Diastolic
Aortic
Regurgitation
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Young horse
Grade 4 or louder, pre-cordial thrill
Concurrent Arrhythmia
Prospective purchaser should know this is
progressive, although often slowly
© cmarr 2013
Differentials for a continuous murmur
MITRAL & AORTIC REGURGITATION
PATENT DUCTUS ARTERIOSUS
AORTOCARDIAC FISTULA
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DVD includes 70 cases contributed by 17 authors
If you buy this book also buy a stethoscope
speaker pad:
www.blaufuss.org
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