Hi & Welcome. I can understand your concern for your beloved mother. Basically used to treat breast cancer in postmenopausal women, Anaztrazole can cause the following side effects like bone (back, joint) pain or muscle pains diarrhea, hot flushes, & edema (responsible for weight gain). Edema develops due to accumulation of fluids in the body tissue and this may cause volume overload and thus heart may not function properly. You are advised to consult her treating oncologist for proper evaluation, she may need to discontinue the treatment with Anastrazole or its dosage reduction may be advised. Hope this answers your query.