What is their primary concern; a possible embolism? I'm not a professional, but I can't imagine that a 3.3 meter tank would pose any risk at all. It's good they're looking out for your safety, but I think their concerns are unnecessary, especially as far out from your procedure as you are.
Interestingly, I received no instructions for an aspirin regeime following my ablation other than watch for tingling or cold legs. I did receive an unspecified amount of Heparin during the procedure, but that anti-coagulant is quickly metabolized and is gone within a day.