Page 1015 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

990 CHAPTER 8

VetBooks.ir murmurs associated with valve prolapse are uncom- Management
No treatment is indicated unless clinical signs of
mon. More intense murmurs are likely to be associ-
ated with larger defects. A murmur of intensity 3/6
or higher is generally clinically significant. AF is less congestive heart failure develop.
commonly associated with right AV valve insuffi- Prognosis
ciency than with left AV valve insufficiency, but it may The prognosis is excellent and clinical signs, includ-
develop in the face of atrial dilatation. Right-sided ing performance effects, are uncommon. Mild to
congestive heart failure may develop in severe cases. moderate regurgitation has been documented in
animals that were performing well.
Differential diagnosis
Endocarditis and functional murmurs may produce AORTIC VALVE DISEASE
similar signs.
Definition/overview
Diagnosis Valvular pathology in the horse is most commonly
The murmur is typically identified during routine found at the aortic valve. Degenerative changes
auscultation. Location and characteristics of the consisting of nodules, fenestrations and valve-cusp
murmur can be suggestive of right AV insufficiency, thickening are common. Fenestrations may be seen
but echocardiography is required for confirma- in normal animals. Aortic insufficiency is most com-
tion (Fig. 8.24). 2-D echocardiography is of value monly diagnosed in older animals.
in determining the extent of the regurgitation,
assessing any valvular changes and assessing cardiac Aetiology/pathophysiology
chamber dilatation. Colour-flow Doppler analysis With aortic insufficiency, the aortic valve fails to
is valuable for assessing the regurgitant jet. Right- close completely and blood flows backwards into the
sided chamber dimensions are difficult to evaluate. left ventricle during diastole. If extensive, left ven-
Evidence of right AV valvular regurgitation is more tricular volume overload may result.
common than are associated murmurs.
There are no characteristic radiographic or elec- Clinical presentation
trocardiographic changes associated with right AV Clinical signs associated with aortic valve insuf-
valve disease in the horse. AF in association with evi- ficiency are commonly limited to the presence of a
dence of moderate to severe right AV valvular insuf- diastolic heart murmur.
ficiency may indicate right atrial dilatation.

8.24

Fig. 8.24 Right atrioventricular (AV) (tricuspid)
valvular regurgitation. Right-heart long-axis view
taken from the right 4th ICS, highlighting the AV
valve. This horse had a history of poor performance,
AF and a grade 2/6 right-sided holosystolic murmur.
Colour-flow Doppler echocardiography reveals
high-velocity regurgitant flow in green. RV =
right ventricle; RA = right atrium; Ao = aorta;
PA = pulmonary artery.