There was a "gross failure" in the care of a women who died from sepsis after a three hour ambulance wait outside A&E, an inquest has found.
Samantha Brousas, 49, from Gresford, Wrexham, died on 23 February 2018, two days after she was forced to wait outside Wrexham Maelor Hospital.
Coroner Joanne Lees issued a prevention of future deaths report to the Welsh Ambulance Service.
But she said the failings did not cause Ms Brousas's death.
Ms Lees recorded a narrative verdict at the inquest in Ruthin.
A spokesman for Betsi Cadwaladr University Health Board (BCUHB) said "lessons must be learnt" from Ms Brousas's death.
The inquest previously heard Ms Brousas had been suffering from a common cold over the New Year period of 2017, but her condition deteriorated around 19 February 2018.
The next day, she went to see her GP and said she felt as if she was going to die.
On 21 February, she was assessed at home and taken to hospital by ambulance, but she was forced to wait outside for three hours after being told there were no hospital beds and that the A&E department was "under siege".
Ms Brousas's daughter, a fourth year medical student at the time, said no staff came out to see her and she was not given antibiotics.
Sepsis, sometimes called septicaemia or blood poisoning, happens when the body's immune system goes into overdrive in response to an infection.
Prof Solomon Almond, an expert witness to the inquest, said Ms Brousas was already "desperately sick" by the time she was taken to hospital.
He said she was "destined to die" and the "point of no return" had been reached prior to her calling an ambulance on the afternoon of 21 February.
The inquest was previously told paramedics should have pre-alerted A&E staff that a severely ill woman was on her way to hospital under the guidelines.
Paramedic Steffan Jarvis told the hearing 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".
The inquest also heard from Dr Kate Clark, a 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.
Concluding the inquest on Friday, Ms Lees said she had seen some improvements to the Wrexham Maelor A&E department, but issued a regulation 28 report to the Welsh Ambulance Service Trust citing issues regarding pre-alert policy, whether paramedics can issue antibiotics and "absence of a meaningful escalation policy".
In an interview with BBC Wales, Ms Brousas's long-term partner Simon Goacher said: "They immediately recognised how ill she was and that she had sepsis.
"It isn't a case they simply don't diagnose it quickly enough, they did diagnose it straight away they just didn't treat it at all, let alone effectively.
"I didn't realise how bad it was... I knew it was dangerous but I still thought 'they can't think it's that bad otherwise they would have got her in to hospital, they wouldn't be leaving her in the back of an ambulance, they'd be treating her'.
"It's impossible to describe it if you've not been through it. It's just a nightmare. To have to be there and watch someone you love go through that is just indescribable."
Her daughter, Sophie Brousas, said: "As soon as I saw her I was just shocked at how ill she looked. Mum was quite a glamorous, well put-together lady and she looked about 20 years older, she was grey - I was really just shocked by the sight of her."
She said there was "no sense of urgency" in trying to treat her mother.
"The most frustrating thing is it wasn't a misdiagnosis. Everyone knew how ill she was and still no action was taken. I just don't understand how that could happen."
Stephen Jones, clinical negligence solicitor at law firm Leigh Day, added: "The evidence that we have heard over the course of the inquest has been truly shocking.
"The absolute tragedy of this case is that all those healthcare professionals who came into contact with Sam on 21 February recognised at the time that she had sepsis and understood that sepsis is a potentially fatal time critical condition."
Dr Brendan Lloyd of the Welsh Ambulance Service said: "Our ambulance service exists to preserve life so it was with a heavy heart that we learned of the death of Miss Brousas."
He said there were lessons to be learned for the service and health board and they had been working to reduce the risk of anything similar happening again.
A number of steps have already been taken, including giving advice for paramedics to pre-alert a hospital to a patient's condition.
"We accept the conclusions of the coroner and would once again extend our thoughts and sympathies to the family of Miss Brousas," he added.
A spokesman for Betsi Cadwaladr University Health Board said: "We fully accept the coroner's verdict today and we would like to extend our deepest condolences to Miss Brousas's family.
"We know that lessons must be learnt. Over the past 18 months we have worked with our partners in the ambulance service to improve the way patients are transferred when they arrive at hospital.
"This has already brought about significant improvements."