Pulmonary thromboembolism in the cat: echocardiography
2-year-old domestic shorthair cat on treatment for immune-mediated haemolytic anaemia that suddenly develops marked tachypnoea and dyspnoea without coughing. Echocardiography: right parasternal long-axis view (left) and right parasternal short-axis view at ventricular level (right):
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The right atrium and ventricle are dilated and, in the short-axis view, the interventricular septum is flattened with a small LV. What do these findings indicate in this context?
chevron_right Show answer and explanation
A. Pulmonary hypertension due to thromboembolism
Correct. Right-sided dilation with septal flattening indicates RV pressure overload (pulmonary hypertension). In a cat with IMHA and acute dyspnoea, the most likely cause is pulmonary thromboembolism.
B. Hypertrophic cardiomyopathy with heart failure
HCM causes LV thickening and left atrial enlargement. Here the LV is small and it is the right chambers that are dilated.
C. Decompensated congenital tricuspid dysplasia
Tricuspid dysplasia is congenital, with an abnormal valve and chronic regurgitation. It does not explain an acute picture in a cat with IMHA.
D. Arrhythmogenic right ventricular cardiomyopathy
Arrhythmogenic cardiomyopathy dilates the right chambers, but it is a chronic myocardial disease with arrhythmias. The IMHA setting and sudden onset point to thromboembolism.
lightbulb Key takeaway
Acute dyspnoea with unremarkable radiographs in a patient with IMHA, sepsis, neoplasia or hypercortisolism should make you think of pulmonary thromboembolism. Echocardiography supports it (right-sided dilation, flattened septum, sometimes the thrombus) and CT angiography confirms it; in IMHA, thromboprophylaxis is part of the treatment.
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Updated: November 1, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.