Hi there..serum creatinine upto 1.5 is considered safe to do angiogram, some take upto 2 as limit... during angiography contrast dye wil be injected which wil be later excreted out of body by kidneys, so if there is chronic kidney disease or creatinine more than 2 then risk of getting contrast induced nephropathy is high so they won't do angio.. If the block in the vessel is less than 50-60% then medical management is done by giving blood thinners.. if block is more then angioplasty ie stent is placed.. hope this helped you...