Heart attack. Viable option right now?

My father had a heart attack recently and still in hospital. He had a bypass 4 years ago. original vessel is 100% blocked and bypass LIMA one 90% which is only 2mm wide. His Right side vessel is also 95% blocked. First doc recommended we should go for angioplasty and try to open original vessel which is 100% blocked and put stent into it but chances or re-opening it are less cos its blocked for very long time. So can try into bypass LIMA one which is only 2mm wide and 90% blocked already. So doc changed his opinion and said we should go with right side vessel which is 95% blocked and it is much easier, safer and straightforward to do angioplasty on it. It is 3.5mm wide. My concern is can we leave left side blockage as it is and only do angioplasty onto right side. Is it the only viable option right now? Look forward for consultations from experienced surgeons.