my daughter is a carrier of sickle cell and as a child we were told that surgery with general anasthetic was dangerouse and could leave her in a coma. she had a hernia repair at 4 yrs and it was worrying , now she has a cyst in her throat and she needs surgery surgeon said no problem . do's he know ? is he guessing ? was the other surgeon years ago wrong? im worried .
general anaesthesia  presents risk and certain danger to anyone, in particular to those with chronic health problems.  a carrier of the sickle cell trait isn't really a chronic health problem and i would have to agree with your surgeon......he knows best.  but if you are that concerned, get another opionion, say with a hemotologist, specializing in blood disorders.
He is probably have an angiogram tomorrow.  They will not do angioplasty unless it is necessary.  He probably had a nuc. test that showed the shades regions.  Why was he getting the test in the first place.  If he went to the doc w/ problems then yes, he needs to have the angiogram.  That is simply the study of his vessels with dye.  An angioplasty is the opening of the blockages with balloons and or stent.