Description
Narrowing of the outflow channel between the left ventricle and the main
artery of the body, the aorta, is called aortic stenosis.
The narrowing can occur at three sites :
At the level of the aortic valve (valvular)
"Above" the aortic valve , in the aorta (supravalvular) - rare
(has been caused by vitamin D supplementation in pregnant bitches)
"Below" the aortic valve, in the ventricle (subvalvular) - most
common (90% of cases)
Breed Occurrence
There is reported to be an increased risk of developing aortic stenosis in
Boxers (50% of cases reported in the UK), English Bull Terriers, German Shepherd
Dogs, German Short-haired Pointers, Golden Retrievers, Newfoundlands and
Samoyeds It has also been seen in smaller breeds such as terriers.
Aortic stenosis is uncommon in cats.
Diagnosis
X-rays - often no abnormality is seen. May see a "bulge" in the
aorta on the dorsoventral view.
ECG - Often no evidence of left ventricular enlargement. Severely affected
animals develop ventricular tachydysrhythmias.
Echocardiography - can be useful in severe cases, but Doppler
echocardiography is the best method to identify the lesion -because there
is an obvious increase in the velocity of blood flow as it passes through the
narrowed area of stenosis.
Catheterisation and angiography - a direct left ventricular angiogram is
best, but lesions will show up with non-selective angiography.
Treatment
Most cases do not require treatment.
Usually treatment is aimed at improving cardiac output and controlling
abnormal heart rhythms (dysrhythmias). b -blockers
(e.g. propranolol at a dose rate of 0.25-0.5mg/kg tid) or calcium channel
blockers (e.g. diltiazem) have been used successfully. Procainamide has been
used to control ventricular dysrhythmias
Dilatation of the stenosis using balloon catheters has not yet proved
successful.