I am very sad after getting the news about the death of your grandfather on 22nd of January 2012. I am shocked to hear that he passed away due to a cardiac arrest compared to the healthy lifestyle he had.
I believe that you must be in a state of shock after his demise as he was very close to you. I have always seen him leading a healthy lifestyle. He never had any bad habit and used to exercise regularly. So it is strange that a healthy person like him had a cardiac arrest. He was always very cheerful and full of life.
I understand that it is a difficult time that you are going through but you have to be strong and take care of your family. In case if you need any help please do let me.