A consultant paediatric cardiologist at Our Lady's Children's Hospital in Crumlin has said some of her public outpatients will be waiting two years for an appointment.
Speaking on RTÉ's Morning Ireland, Dr Orla Franklin said more staff are required to run the extra clinics that are needed to reduce waiting lists.
She said three new posts have been approved by the Health Service Executive and are ready to be advertised.
Dr Franklin said: "The reason for this waiting list is not because our clinics are not running at absolutely full capacity 46 weeks of the year.
"It is essentially because the volume of referrals is absolutely huge."
She continued: "The volume of referrals is increasing year-on-year as parents are particularly increasingly alarmed by the sudden death of children undertaking sporting activities and wish their otherwise healthy children to be screened."
