SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
although occasionally they are detected as incidental findings in horses with no
clinical signs. When the aortic sinus of Valsalva aneurysm or aortic root ruptures into
the right side of the heart, an aortic cardiac fistula is created. This rupture is life
threatening, with most affected horses living < 1 year following rupture. The affected
animals are not safe to use as the risk of sudden cardiac death is high.
The murmur associated with an aorticocardiac fistula is usually grade 4-6/6 (although
can be lower in intensity), is continuous and machinery or musical with its point of
maximal intensity on the right side of the chest in the tricuspid valve area. This
murmur usually radiates apically on the right as well as cranially on the left and out
the aorta. The arterial pulses are bounding in horses with an aorticocardiac fistula,
unless the shunt from the aorta into the heart is small.
An intact sinus of Valsalva aneurysm appears as a thin membrane at the right
coronary sinus of Valsalva, continuous with the right wall of the aortic root that
bulges into the right atrium, right ventricle or tricuspid valve. When the aortic sinus of
Valsalva aneurysm ruptures into the right atrium, right ventricle, through the tricuspid
valve, or dissects down into the interventricular septum, an aortocardiac fistula is
created. Aortic root rupture at the right sinus of Valsalva can also occur without a
pre-existing aneurysm. In these horses a defect is imaged in the wall of the aorta at
the right sinus of Valsalva, with no other pre-existing aortic root abnormalities.
Aortic cardiac fistula
Depending upon the site of rupture, abnormalities of the tricuspid or mitral valve
leaflets, such as a ruptured chorda tendineae, may also be imaged. If blood is
dissecting down the interventricular septum, an anechoic fluid space will be imaged
between the endocardium and the myocardium that originates from the right sinus of
Valsalva. These subendocardial dissections can subsequently rupture into the right
or left ventricle. Detecting the high velocity turbulent blood flow associated with the
aortocardiac fistula is easiest with color flow Doppler echocardiography. The size of
the aortocardiac shunt and its hemodynamic significance should be determined, if
possible, at the time the rupture is diagnosed.
Arrhythmias
Atrial Fibrillation
Atrial fibrillation (AF) is a common arrhythmia in horses and is most frequently
associated with exercise intolerance. There is some evidence for a genetic
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