Heart problem - ARSA. Avg 500 ml/day!

Hi, My son was diagnosed with Aberrant origin of right subclavian artery (ARSA) during 2nd tri semester. He was normal delivered baby (3.5 month old). Initially he was feeding well for a month and suddenly he started sleeping 8 ~10 hour continuously. Having feared we took him to hosp where he was admitted on suspicious of infection/sephalis. During the five days he was fed mothers milk collected in bottle. At the end reports ruled out any infections.. At this same time my wife had reduced secretion and that doctor had to put him on Formula drink. He used to sleep for 18~20 hours a day till 3 months (6~8 hours continuously). Now the sleep have reduced to 16 hours.. but still we could hear his breathing to be little fast during feeding and his having latching problem. My question: Is my son having difficulty swallowing (cons above situation)or is it normal. Do 100% of ARSA suffering kids have problem swallowing or is there any exemptions to it. Between my kid drinks avg 500 ml/day