Page 1016 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Cardiovascular system 991

VetBooks.ir Differential diagnosis (Table 8.4). The effects of this treatment are not well
documented. Signs of heart failure indicate a poor
Diastolic flow murmur is the most common differ-
ential diagnosis. A similar murmur can occur with
clinical signs.
pulmonic valvular regurgitation but is very rare. prognosis and treatment only temporarily alleviates
Diagnosis BACTERIAL ENDOCARDITIS
The presence of a holodiastolic murmur should be
considered an indication of aortic regurgitation until Definition/overview
proven otherwise. This murmur is usually crescendo– Bacterial endocarditis is an uncommon acute or
decrescendo in character, although musical or ‘honk- chronic disease associated with bacterial colonisa-
ing’ murmurs have also been described. With severe tion and development of vegetative lesions either
regurgitation the peripheral pulse becomes bounding on the valves or on the non-valvular endocardium.
in character because of the rapid diastolic drop-off in In the horse, the aortic valve is most commonly
pressure. The intensity of the murmur does not cor- affected, followed by the left AV valve and then the
relate well with the severity of regurgitation. AF may right AV valve. Involvement of the pulmonic valve is
develop as a result of volume overload of the left heart uncommon.
and subsequent chamber enlargement.
There are no characteristic radiographic or elec- Aetiology/pathophysiology
trocardiographic findings associated with aortic It is speculated that bacterial infection follows
insufficiency in the horse. Echocardiography is used trauma to the valve, such as in cases of valvular
to confirm the diagnosis. Valvular regurgitation on insufficiency or VSD, where turbulent blood flow
echocardiography is more common than the associ- develops. Injury to the endocardium has been docu-
ated murmur (Fig. 8.25). mented in stressed pigs and may also occur in other
animal species when stressed. Endocarditis has been
Management/prognosis initiated experimentally by the inoculation of bacte-
There is no treatment for aortic valvular insuffi- ria in animals with no evidence of prior endocardial
ciency. In most cases the prognosis is good, both for damage. Damage to the valve may be such that even
performance and for survival. Aortic insufficiency if the infection is eliminated, the valve is no longer
does tend to progress, therefore repeated evalua- capable of normal function due to deformation. The
tions are indicated. The use of angiotensin convert- source of infection is often unknown. Jugular vein
ing enzyme (ACE) inhibitors, such as enalapril, has thrombosis has been reported as a predisposing fac-
been proposed. This is an attempt to slow progres- tor. There appears to be no age or breed predilection.
sion and allow the animal to continue performance An increased incidence in males has been reported.

8.25

Fig. 8.25 Aortic regurgitation. Right heart long-
axis view highlighting the aortic valve taken from the
right 4th ICS. Colour-flow Doppler echocardiography
reveals aortic regurgitation as a red flame-like flow
present during diastole. No murmurs were associated
with this finding. RV = right ventricle; RA = right
atrium; LV = left ventricle; Ao = aorta.