31/05/2026
We had an elderly dog present for collapse episodes, and on exam he had thready pulses and a very fast heart rate. He was lethargic and had no history of any heart disease previously. His physical exam was otherwise normal.
His ECG was normal except for a dangerously high heart rate, indicating it was initiated from the normal pathways, and not from an abnormal arrhythmia.
When we ultrasounded his chest and heart, we found a tumour within the right atrial wall, close to where the pacemaker node for the heart is, as well as fluid around the heart compressing the heart (pericardial effusion and cardiac tamponade). When we froze the frames we can see a breach in the atrial wall adjacent to the tumour meaning that the fluid around the heart is most likely blood from the heart itself.
Draining this fluid to relieve the pressure on the heart is fraught with problems, because as the pressure within the sac equalises with the heart, it stops blood flowing into the sac. If we drain it we drop the pressure and encourage blood to continue to flow into the sac and we're back where we started. If the heart can survive the pressure sometimes these can heal over (at least temporarily) but, because this one is associated with a tumour, the prognosis is grave.
We also weren't sure if the abnormally high heart rate was from the stressed heart, or from the tumour at this stage but tests on heart muscle stress were highly abnormal. Either way, we couldn't easily remove the stress from the heart, and if the tumour was the cause we couldn't change that either.
Unfortunately the outcome wasn't good for this sweet old man, but it does highlight how heart issues aren't always obvious, and can be quite silent until they are quite advanced.
