A pensioner died 16 hours after his wife dialed 999, an inquest was told.
Joseph Edge had been ill from a stomach bug, had banged his head and complained of feeling dizzy with low blood pressure in December, 2019.
His wife Carole called out-of-hours who classed him as "critically unwell" and urged her to call 999 for an ambulance immediately.
But the 74-year-old from Llandegla, Denbighshire was deemed as a "green" call among the lowest category of urgency.
Gill Pleming, utilisation manager for the Welsh Ambulance Service in North Wales, told the hearing in Ruthin the demand for ambulances at the time was "quite unprecedented."
One hundred extra 999 calls had been received in 24 hours on top of the average 350 calls.
Instead of a 15-minute patient handover at A&E at Glan Clwyd Hospital, ambulances waited an average of six hours.
The inquest heard the first emergency call by Mrs Edge was at 1.24pm on December 28 but no ambulance was available for Mr Edge.
Welfare calls were made by the control centre. In the early evening the call was re-prioritised as an "amber two."
However, Mrs Pleming said: "There were other higher category calls waiting in the system. The demand was quite unprecedented in this particular 24 hours."
Mr Edge's widow - married for 52 years to the former plumber and mechanic who had a heart attack at the age of 48 and then suffered a stroke - said he'd been unwell and had a stomach bug. At 5am on December 28 she heard her husband in the bathroom and he was bleeding from a bang to the head.
Later that morning he complained of feeling dizzy and his blood pressure was very low. Mrs Edge rang NHS Direct but got no answer so called her surgery.
An out-of-hours service contacted her and advised that she dial 999.
She was unable to take her husband to hospital. During phone calls with the ambulance service she had been reassured that an ambulance would be sent "but they were very busy". At 5.15am the next day she went upstairs to see her husband and he was cold and unresponsive.
Mrs Edge dialled 999 again and a paramedic arrived in a car.
"Clearly the service I have received isn't acceptable," she said in a statement.
"I am very upset and annoyed about what has happened."
Elizabeth Dudley-Jones, assistant coroner for North Wales east and central, recorded a conclusion that the death occurred due to natural causes.
She said Mr Edge could have died at any time because of his health but "Joe was denied the opportunity to receive medical treatment which may have made a difference".
The coroner said efforts were being made by the ambulance service to address a "massive problem."
She added: "Unfortunately on December 28-29 there were unprecedented calls coming into the system.
"I'm not going to issue a prevention of future deaths (report) in this case because I don't consider that a great deal more could be done than is being done.
"This case has concerned me. On the face of it, it's an incredible delay. But it seems that has been properly acknowledged by the service."
After the inquest Mrs Edge said: "The coroner was very fair. She highlighted our concerns."
A police investigation had been launched into a possible case of corporate manslaughter but the inquiry was closed. Home Office pathologist Dr Brian Rodgers found Mr Edge had ischemic heart disease.
