What Causes Swelling In Tongue And Swelling In Face And Legs?

My mother , age 60 years old under went mitral valve replacement surgery- metal valve & also a pacemaker in Jan 10. Now she is fine but sometimes she feeels heaviness in her tongue & hence cannot speak properly . Also her face & legs are swollen sometimes (rarely). She is currently taking Acitrom 1 mg everyday & we do the Prothrombin time test in every 8 days.
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