My Mom Is 83. She Fell March 8th And Broke

My mom is 83. She fell March 8th and broke her pelvis, was in hospital 7 days and In nursing home/rehab for 8 weeks. Continued with in home health care/rehab. Currently walks with walker. Began blacking out in early April without any certain pattern. Maybe once a week, last week it was everyday. Had whooping cough May 30. She always complains of chest tightness, gets light headed and blacks out. They only way to wake her up is to slap her on the cheeks. Her lips, tongue, fingers, feet are numb when she comes to. Doctors have ran dozens of blood work, she wore a heart monitor for 7 days, left caraterated artery was cleaned out, had chest CTs, MRIs, EEG, heart CT. They find nothing.