my Dad is 67 years old and had memory loss ,slurred speech due to two little block in brain and blockage in internal carotid artery . The doppler study and MRI A angiogram showed 100% blockage of left internal carotid artery. The right artery had 30% 40% of block. His colateral blood is normal. he had diabeties and Bp for the past 1 1/2 years. he got blood supply through right arteries.. He never had any health problems before, he doesn't smoke, doesn't drink, he undergone treatment, what is my doubt is, is this lead to any lifethreat. how to prevent it. Does he needs an angiogram every year? What are the chances to happen again? Thank you , lalitha.