Heart Disease and Heart Attack Forum - Inducible Ischemia- Is Angiogram Needed?

My father is living in vayanad district kerala.He is 65.He is very stable hard working in the field, his blood pressure is 90/140 and weight 60kgs.He is a vegetarian,having chloestrol and sugar well with in control. Two years back he complains of guddiness.He came to chennai and my family doctor found an irregular heart beat and advices to take ecg in which irregular rhythm was found (6 vpc's per strip). Immediately he was admitted in a heart centre and monitored a whole night.All the tests were taken in tmt result it was found positive for inducible ischemia, and in echo result it reads grade I diastolic dysfunction,
doctors adviced for cag.And later they decided to go with medicines betaloc,storvas,imdur,ecosprin and clopigrel were given.He was doing good up to last week.
Last week he felt slight gudiness after taking the tablets.We went to the heart centre again tests were taken now ecg strip shows 4 vpc's and in tmt result it was found positive for inducible ischemia, no doppler was done. Now doctors adviced to take cag next week. My question is is it really needed, cant it be cured with medicines. If we have to undergo cag what is the procedure? And how reliable it is? Is my father has to be admitted for the test? Kindly guide me.