Feline restrictive cardiomyopathy: echocardiographic diagnosis
12-year-old cat with pleural effusion. Echocardiogram: LV wall thickness of 4.5 mm, LV cavity not dilated, fractional shortening of 32%, both atria markedly enlarged and a thick echogenic band joining the septum to the LV free wall. Mitral Doppler shows a tall E wave with a short deceleration time.
What is the most likely diagnosis?
chevron_right Show answer and explanation
A. Hypertrophic cardiomyopathy
Wall thickness is normal (< 6 mm). End-stage HCM may thin some segments, but the fibrous band and normal cavity fit another phenotype.
B. Dilated cardiomyopathy
In DCM the LV is dilated with markedly reduced systolic function. Here the cavity is not dilated and fractional shortening is normal.
C. Restrictive cardiomyopathy, endomyocardial form
Correct. Markedly enlarged atria with an LV of normal thickness and size and a restrictive filling pattern define RCM. The endomyocardial band or scar bridging septum and free wall characterises the endomyocardial form under the 2020 ACVIM consensus.
D. Nonspecific (unclassified) phenotype cardiomyopathy
This category is for phenotypes that fit no other. This case meets the criteria for the endomyocardial form of RCM, so it should be classified as such.
lightbulb Key takeaway
In cats, very large atria with a normal-looking LV should make you think of RCM. Treatment is that of CHF (diuretic) plus thromboprophylaxis because of the enlarged atrium; prognosis in stage C is guarded.
References: ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats (2020)
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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.