Introduction
- Congenital narrowing of left ventricular outflow tract. Represents 7% of feline congenital cardiac anomalies.
- Cause : developmental malformation. Lesion is most commonly supravalvular in the cat, but may be valvular or subvalvular.
- Signs : asymptomatic, systolic murmur, weakness, lethargy, syncope, sudden death; left-sided congestive heart failure (CHF)
. - Diagnosis : history, clinical signs, radiography, angiocardiography, electrocardiography, ultrasonography.
- Treatment : for mild cases none indicated; to treat CHF and arrythmias use beta-blockers, calcium channel blockers; diuretics, anti-arryhthmics and rest.
- Prognosis : generally poor, most develop CHF, but some cases remain asymptomatic.
Diagnosis
Clinical signs
- Systolic ejection murmur, maximal at left heart base, intensity usually proportional to severity, ie murmur in mild disease is low grade and localized.
There is less variation in the degrees of severity seen in the cat than in the dog.
- Murmur radiating to right heart base.
- Murmur heard at thoracic inlet (carotid arteries).
- Signs of forward cardiac failure; occasionally reduced pulse strength.
- Dyspnea if left-sided CHF.
Diagnosis
Differential diagnosis
Systolic murmurs- Atrioventricular valve dysplasia .
- Pulmonic stenosis.
- Ventricular septal defect (VSD) .
- Hypertrophic cardiomyopathy with dynamic left ventricular outflow tract obstruction .
- Innocent 'flow' murmur .
- Tetralogy of Fallot .
Sequelae
Prognosis
- Mild : guarded.
- Severe : poor.
Expected response to treatment
- Improvement in signs.
Reasons for treatment failure
- Too severe.
- Progressive deterioration.
Sources
Publications
Refereed papers
- Schrope D Pet al(1995)Effects of electrocardiograph frequency filters on P-QRS-T amplitudes of the feline electrocardiogram.Am J Vet Res56(11), 1534-1540.
- Liu S Ket al(1980)Animal models of primary myocardial diseases.Yale J Biol Med53(3), 191-211.
- Liu S K (1977)Pathology of feline heart diseases.Vet Clin North Am7(2), 323-339.
