Kathleen,

Thanks for your posting, which poses several questions concerning your Mother.  First of all, the catheterization is necessary to assess her coronary artery situation.  It sounds as though she had a stress test, probably pharmacologic rather than treadmill, which was abnormal.  Hopefully, any blockage they might find can be taken care of during the procedure with angioplasty and stent placement.  This would optimize her cardiac situation and significantly lower her risk for surgery.  Catheterizations and interventions (stent placements) have an extremely low complication rate, and the benefits of the procedure far outweigh the risk. 

Why look at her heart now?  The knee-replacement surgery(s) is a major procedure with a long recovery phase that involves prolonged physical therapy.  Good cardiac function is necessary to tolerate the surgery and the post-operative phases.  The thing to keep in mind is: this surgery is elective (optional), and doctors will hesitate if there is an underlying problem that raises a patient's risk above acceptable levels.  On the other hand, the bladder surgery sounds like a necessary procedure rather than elective, and hence the cardiac evaluation and treatment.  This procedure, like all surgeries, also carries risk, and this risk should be decreased if/when her cardiac situation is improved.

I hope this has been helpful.

Martin Cane, M.D.