Paramedics should have warned A&E staff that a severely ill woman, who later died from sepsis, was on her way to hospital, an inquest has heard.
Samantha Brousas, 49, from Gresford, near Wrexham, died on 23 February 2018, two days after being taken to Wrexham Maelor Hospital.
She had waited three hours in an ambulance before being admitted.
Consultant paramedic Duncan Robertson said the ward should have been informed under existing guidelines.
The inquest also heard from Dr Kate Clark, consultant in emergency medicine, who revealed coroners had issued a total of six "regulation 28" reports aimed at preventing future deaths involving ambulances having to queue outside hospitals in north Wales.
Mr Robertson, the regional clinical lead for the Welsh Ambulance Service Trust, referred to guidance from the Joint Royal Colleges Ambulance Liaison Committee.
"Sam should have been pre-alerted to the emergency department," he told the inquest in Ruthin.
The court previously heard from the paramedics in question, who raised questions about the efficacy of the pre-alerting process.
Paramedic Steffan Jarvis had told the court ambulance staff knew the hospital was so busy it was "dangerous and unsafe" and had not pre-alerted the hospital, despite having assessed Ms Brousas as "high-risk, critically ill".
Mr Robertson also told the hearing the number of hours lost by ambulances waiting for emergency admissions at Wrexham Maelor had seen a steady fall since Ms Brousas died.
At the time, 450-500 hours were lost per week by delays at A&E, but by the beginning of November fewer than 40 hours per week were being lost.