Congenital mitral valve dysplasia in young cats
1-year-old cat with tachypnoea and pulmonary oedema on radiographs. Grade 4/6 holosystolic murmur at the left apex. Echocardiography: thickened, poorly mobile mitral leaflets, short chordae tendineae, papillary muscles fused to the septum, severe mitral regurgitation and a markedly enlarged left atrium. Left ventricular walls 5 mm in diastole.
What is the most likely diagnosis?
chevron_right Show answer and explanation
A. Hypertrophic cardiomyopathy with systolic anterior motion of the mitral valve
HCM is diagnosed by a diastolic wall thickness ≥ 6 mm. Here the walls measure 5 mm and the lesions are in the valve itself, not the myocardium.
B. Mitral valve dysplasia
Correct. Abnormalities of the whole valve apparatus (leaflets, chordae and papillary muscles) in a young cat with normal ventricular walls indicate congenital mitral dysplasia, one of the most common congenital heart defects in cats.
C. Endomyocardial restrictive cardiomyopathy
The endomyocardial form shows scars or bands distorting the left ventricle, with atrial enlargement but without the valve malformations described.
D. Myxomatous mitral valve disease
Myxomatous degeneration is typical of middle-aged to older small-breed dogs; in cats it is rare and does not explain short chordae and fused papillary muscles in a one-year-old.
lightbulb Key takeaway
In cats, atrioventricular dysplasias (mitral and tricuspid) are among the most common congenital heart defects. In dogs, mitral dysplasia is described in Bull Terriers (sometimes with mitral stenosis), German Shepherds and Great Danes. Treatment is that of congestive heart failure; prognosis depends on the severity of regurgitation.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.