Miller, who lived in Delaware, Ont., was 17 in early 2003 when he fell ill with what looked to his parents like a bad case of the flu.
When he started throwing up every 45 minutes, Tim and Theresa Miller thought he had gastroenteritis. But when he wasn't getting better, his parents took him to a hospital.
Though the teenager had an unusually high heart rate, doctors too thought he had a stomach bug. He was given intravenous fluids and sent home.
It was the wrong diagnosis and the wrong treatment. Two days later he was back in the emergency department and then admitted to hospital. The high school senior had heart failure, brought on by myocarditis — an infection in his heart muscle.
His parents watched helplessness as their formerly healthy son died of heart failure, which, had it been spotted earlier, may have been treatable.
He became noticeably ill on Saturday and was dead by Thursday.
"You never want to live through that, that's for sure," Theresa Miller says of the loss of her son and his final days.
Heart failure is common in the elderly. But doctors often don't think about it in young, healthy kids — a fact of life Dr. Paul Kantor and some colleagues are hoping to change.
Kantor, who is the head of pediatric cardiology at Stollery Children's Hospital in Edmonton, chaired a working group that has drawn up guidelines to help doctors spot a condition that is too often mistaken for a stomach infection, hepatitis or even asthma.
The guidelines are being presented Tuesday at the Canadian Cardiovascular Congress, a scientific conference jointly hosted by the Canadian Cardiovascular Society and the Heart and Stroke Foundation.
"(It's) truly a devastating thing to find out that your child has a heart condition at all. And when you find out the extreme severity of it, it's even worse," said Kantor, whose specialty is pediatric heart failure.
"But I think there's a special degree of helplessness that strikes parents who feel that they've done what they could do to access the medical system, but unfortunately the medical system was not able to recognize the true nature of the problem and deal with it effectively."
There aren't good figures on how many children suffer heart failure in Canada. Kantor says data from the U.S. suggests that about 3,000 children a year in North America are hospitalized with heart failure and survive to be discharged.
Those — plus the children who don't make it — are the most severe cases. Many others have milder cases of heart failure and go unnoticed, Kantor said.
Heart failure in children can be caused by genetic abnormalities, or the result of an infection like influenza where something goes wrong.
Sometimes a respiratory virus moves out of the lungs to infect the heart muscle. Sometimes the body's immune response to the initial infection leads to excess inflammation, which weakens the heart muscle to the point where it cannot pump blood properly.
"They may be breathless, they may have grunting type of breathing. Often in teenagers they vomit and have serious abdominal pain and are misinterpreted to have gastroenteritis," Kantor said.
Caught early enough, heart failure is reversible with the right treatment. But if it becomes advanced, only about 50 per cent of children will still be alive five years later, Kantor said. And those that survive may need a heart transplant.
The aim of the guidelines is to prompt emergency room physicians and family doctors to put heart failure on the list of possible diagnoses when they are faced with sick children who have vague symptoms.
"If the heart rate is very fast and there's no good explanation as to why that is and the blood pressure is low, an ECG can be done. Blood tests can also be done to indicate whether there is damage to heart muscle," Kantor said, suggesting that at that point a pediatric cardiologist should be consulted if possible.
"A specialist who considers this would not have much difficulty deciding that a child has myocarditis."
In addition to giving doctors the tools needed to spot heart failure, the guidelines tell physicians how to treat it. Rather than giving fluids, as was done with Dan Miller, diuretics should be used to drain excess fluid from the body that is making the heart's job even tougher.
Severe cases may need to be put on machines that take over for the heart, to give it time to recover.
Theresa Miller is lending her voice to the effort to bring the new guidelines to the attention of the medical community, saying she wished someone had thought to explore the state of her son's heart when he first went to hospital.
"We're so appreciative of the work that's been done around these guidelines and just hope they get out there to every Canadian ER," she said.
"When you go through this, that's all you're left with, is that hope that, well, whatever we could do so someone else wouldn't go down this road."