Go through these in order and stop at the first one that applies. If you are reading this for someone else, answer for them.
1
Is any of this happening now?
Call 911
Call emergency services if a baby, child, or adult has:
Severe difficulty breathing, gasping, or pauses in breathing
New, worsening, or severe blue or grey lips or tongue
Collapse, fainting, or difficulty waking
Sudden severe weakness or confusion
Chest pain with fainting, severe breathlessness, or a very fast heartbeat
Follow any emergency plan provided by the congenital heart team.
Other emergency signs, for anyone
Someone who is struggling to breathe, gasping, choking, or cannot get words out
Someone who has chest pain, tightness or pressure lasting more than a few minutes
Someone who has sudden weakness or drooping on one side of the face or body, slurred speech, or sudden confusion
Someone who is unconscious, or cannot be woken
Someone who is bleeding heavily and it will not stop with firm pressure
Someone who has had a seizure that will not stop, or does not wake up afterwards
Someone who has lips or skin that look pale, blue, grey or blotchy
Someone who you believe has taken an overdose or swallowed something poisonous
2
Is any of this happening?
Be seen today
Seek prompt medical advice for increased breathing rate, feeding difficulty, sweating during feeds, reduced urine output, new swelling, worsening tiredness, poor weight gain, or a new or persistent fever.
3
Does any of this apply?
Book an appointment
Keep all routine follow-up appointments even when there are no symptoms.
The article also says
Contact the congenital heart team soon about new palpitations, reduced exercise ability, dizziness, increasing breathlessness, or swelling.
Every sign above is quoted from the sofidex article on Double outlet right ventricle. If you are not sure, err upward — it is always reasonable to be checked.