This is not something that you want to ignore. I should hope by now you have conacted your doctor. Take care, Ally
I agree with Kenkeith, have it looked at by a professional. If a clot has formed this can be very dangerous should some of it break free.
Sometimes the site of the vessel entry for the cath can cause a problem.....clot or infection. See your cardiologist for a followup visit to rule out any problem from that procedure
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Have they put you on any "water pills' diuretics?