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PET OWNER EDUCATIONAL ATLAS. CARDIORESPIRATORY SYSTEM
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Subaortic stenosis Congenital narrowing of the outflow tract of the left ventricle, generally caused by a subvalvular fibrous ring. The obstruction causes an accelerated and turbulent blood flow into the aorta, which produces an audible heart murmur on auscultation. The heart responds to the resistance with hypertrophy of the left ventricle, which is proportional to the degree of stenosis. The appearance of ventricular arrhythmias often complicates this condition.
Clinical signs It is more common in large-breed dogs: the Terranova, Golden Retriever, Rottweiler and Boxer are among the most represented breeds. It is very rare in cats.
Normal aortic valve
■■ Mild
or moderate cases may be asymptomatic. ■■ Severely affected animals may show fatigue or intolerance to exercise and syncope. ■■ Cases of sudden death with no previous signs are common.
Diagnosis ■■ Echocardiography
shows left ventricular hypertrophy and a turbulent outflow. ■■ The severity of the stenosis is estimated with spectral Doppler to calculate the increase in the blood flow velocity through the obstruction.
Subvalvular fibrous ring
Hypertrophy of the right ventricle
In the most affected breeds, an early detection programme (auscultation, echocardiography) should be established and breeding of affected animals should be prevented.
Treatment ■■ Valvuloplasty ■■ In
(dilatation) of the stenosis using a balloon has not resulted in improvements in the survival rates. severe cases, the use of beta blockers is recommended to try to prevent sudden death.
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