Resolution of a right heart, intracardiac thrombus in a dog

The patient here is a 7 y.o. Bull Terrier with a several-week history of progressive diarrhoea and malaise.  She is markedly hypoalbuminaemic and her duodenum looks like this:

In the course of routine ultrasonography she also turned out to have this rather alarming oscillating intracardiac mass attached to the chordae of the tricuspid valve.

There was no sonographic evidence of pulmonary thromboembolism in the lungs themselves.  The right ventricle is arguably somewhat dilated and the septum is probably somewhat flattened to the right but it’s difficult to know whether some of this might be due to the effect of the visible thrombus on haemodynamics.

I can find very little in the veterinary literature relating to the management of intracardiac thrombi in dogs generally -whether right – or left-sided.  They appear to be rarely-reported although, I guess, potentially under-diagnosed.   Hypoproteinaemia due to presumed protein-losing enteropathy is, obviously, a very plausible predisposing factor in thrombogenesis.

Even in human medicine there is very little evidence on which to base treatment.  Primarily on grounds of convenience and safety we went with oral clopidogrel 10mg/Kg on day one followed by 2mg/Kg s.i.d. thereafter.  The enteropathy was managed with a single protein source diet and oral prednisolone 2mg/Kg.

At re-examination 3 weeks later the thrombus was no longer visible in the heart and no clinical signs or sonographic evidence of pulmonary thromboembolism were evident.  The right ventricle is distinctly dilated (judged in ratio to the left ventricle) and the septum remains suspiciously pushed rightwards.  There was no appreciable tricuspid regurgitation whose velocity could be measured to confirm/deny pulmonary hypertension.  The two possibilities here are 1) that the thrombus detached and ended up in the lungs as a ‘silent’ PTE or 2) it resorbed.

Asymptomatic PTE appears to be common in people: I suspect that this is the most likely scenario.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1352639/

Asymptomatic pulmonary embolism. A common event in high risk patients.

https://www.ncbi.nlm.nih.gov/pubmed/26992758

Risk of asymptomatic pulmonary embolism in patients with deep venous thrombosis.