I'm so very sorry to hear of your loss of your grandson.
Congenital heart disease in a newborn baby is not usually detected during pregnancy unless a fetal echocardiogram is done. After birth, it is usually detected by a heart murmur. It would be very unusual for an ASD alone to cause the death of a newborn, and in fact, it is uncommon for an ASD even to cause severe symptoms in babies or young children. ASD's are typically closed after the child is two to five years old, if they don't close on their own. But you mention "and Congenital Heart Disease" so there may have been more serious heart abnormalities, in addition to the ASD.
Is it possible for you to talk further with the pediatrician and let her know you need to understand the exact causes of your grandson's death? You also can request his hospital records or the physician's records who pronounced his death, which will show the cause of death. I don't know much about coroner reports, but I'd think you would be able to get those, too. You don't mention if autopsy was performed, but if so, that would give you definitive answers.
I hope knowing more will help you. Please keep in mind that knowing why your dear grandson died may not resolve your feelings about the actuality of your grandson's death or the loss of someone you will always love. I'd encourage you to talk with a grief counselor if you can. The loss of a child is an especially difficult type of grief, and there are resources on the Internet that may help, such as Grief Haven, Compassionate Friends and the American Association for Marriage and Family Therapy.
I wish you well and let us know how you do.
Sue Salisbury Maui Hawaii
57 y/o ASD/VSD repair 47 yrs ago. Also a nurse. You didn't mention what the congenital heart disease was if there was more going on than just the ASD or was there more. The problem with feeding and newborns / infants who have congenital heart disease many times the heart is for more enlarged than it would normally be and it crowds out the lungs and makes it difficult to both breathe and suck / eat. The other issue is that when you eat and your stomach gets full of formula / food, it will push up on your lungs and heart which will in turn make it more difficult to breathe it gives you a feeling that you just cannot hold another thing in your chest and the human body if given the choice to either breathe or eat it will breathe. You also did not say whether the coroner did any genetic testing because the other possibility is that the ASD / congenital heart disease may have gone along with or been secondary to a genetic defect which may not have been apparent physically. Some of those genetic / chromosomal defects are incompatible with life. But we don't know whether that was the case with your grandson. My suggestion to you is to celebrate the life he did have, however short. And celebrate the fact that you got to meet him and hold him which is more than many parents and grandparents of children born with congenital defects ever get. The memory in your heart of your grandson can never be taken from you. Please allow yourself to grieve fully so that you can move on in your life and with your memories