No, medicine can unfortunately not cure it.
The 30% blockage is not a real problem but the two 90% will need treatment.
Normally they place stents at the location of the blockages to open them up (angioplasty). This procedure is very easy for the patient.
Sometimes the blockages are however at locations where stents can not be placed and bypass surgery is the only option.
Ask the cardiologist why angioplasty is not an option, but probably he/she has weighed the advantages/disadvantages and concluded the surgery is the preferred treatment.