AFTER ANGIOPLASTY IN JULY 2007 E.F OF MY DAD AT 62 YRS NOW THEN IMPROVED TO NEARLY 44PERCENT. NOW A FEW DAYS BACK IT ALARMINGLY STARTED DROPPING AND CAME TO NEARLY 35 P.C. AGAIN CONSULTATIONS LED TO A NEW ANGIOGRAPHY WHICH REVEALED NORMALCY IN STENT AND ARTERIES . AN ECHO TEST TOLD IVS 2 BE NEARLY HALF BLOCKED. NOW DOC. SAY NO TO BETA BLOCKERS AND ARE STATING THEM TO BE RESPONSIBLE FOR EF DROPPINGS. WHAT DOES THIS IMPLY AND WHAT IS THE CURRENT RISK.