
Mapping a new future of congenital heart disease
Dr. Ariane Marelli is close to predicting and preventing complications before they occur
Chapter 1 Future: unknown
Dr. Ariane Marelli is determined to see children and adults with congenital heart disease live longer, fuller lives. In her view, “we're in the heart of what I would call a period of accelerated progress.”
Earlier in the 20th century, surgical techniques to repair tiny newborn hearts were developed. This changed everything for babies born with serious heart defects. Instead of dying within days or weeks of birth, most could now survive through childhood and beyond.
But what would it take to keep their hearts beating for a lifetime? Nobody knew.
That’s where Dr. Marelli, a cardiologist and professor of medicine at McGill University, saw a problem she wanted to solve.
She was inspired by a patient she met at the Montreal Heart Institute during her medical training. He had been born with a complex heart defect that kept his body from getting enough oxygen. Then in his mid-20s — the same age as Dr. Marelli at the time — he was bedridden, waiting for a heart transplant.
He died before he could receive a new heart. But Dr. Marelli was moved by his spirit and determination to live a full life. “He already had a wife; he had three children, and he was just such a beautiful person.”
She completed her cardiology training, specializing in adult congenital heart disease. At the McGill University Health Centre, she founded the adult congenital heart disease unit.
With support from Heart & Stroke donors, she embarked on research that could change the future for people living with congenital heart disease.
Chapter 2 Moving beyond survival
Congenital heart disease (CHD) occurs when abnormalities in the structure of the heart are present before birth. One in every 80-100 babies in Canada is born with CHD. Some heart defects are minor and cause few or no symptoms; some even heal without treatment.

Dr. Marelli’s research will show which complications tend to arise, when and for whom, and how various interventions could change that course.
More complex defects, such as transposition of the great arteries – a critical birth defect in the heart where two main arteries are switched – make up about one in 10 CHD cases. Repairing them can require multiple surgeries, often shortly after birth.
“I think in the early days, we were happy that people were surviving,” Dr. Marelli says. “Now we've learned that as these patients become adults, they acquire a lot of cardiovascular complications, such as arrhythmias, heart failure and premature stroke in some cases.”
She’s determined to reduce those complications and help people stay healthy. “The fundamental question we're asking is, how do we measure outcomes decades later? And how early can we intervene to change those outcomes?”
Chapter 3 A new frontier for CHD
Dr. Marelli’s team is working to map trajectories for adults living with CHD. They’re using databases to track about 450,000 people in Canada, integrating healthcare records with biological and clinical information.
“It was a lot of data cleaning and auditing and developing algorithms, which we have automated with deep learning and different types of AI methodologies,” Dr. Marelli says. Some of the patients are the first with their type of CHD to reach their 50s and 60s. “So, we're learning as we go.”
Using this data, they will develop models showing which complications tend to arise, when and for whom, and how various interventions could change that course.
Eventually, doctors will use this tool to look into an individual patient’s future and determine what treatments might help them — and, crucially, when. For example, Dr. Marelli says, “I could say to that person, ‘OK, if I change this valve now, this is what you might look like in three decades. If I wait five years to change the valve, this is what you might look like.’”
That’s the new normal she envisions: using data to make better, earlier decisions on treatment. “If we wait for patients to become symptomatic, it's often too late.”
The work will take time and collaboration across many disciplines — including computer science, data science, biochemistry and genetics. Dr. Marelli is grateful to Heart & Stroke for funding her research starting in 2008. And she’s thrilled that Heart & Stroke has worked with Brain Canada and the Canadian Institutes of Health Research to establish new team grants on congenital heart disease.
Since her appointment as Scientific Director of the Institute of Circulatory and Respiratory Health at the Canadian Institutes of Health Research (CIHR) in April 2024, she has been providing scientific leadership to support research priorities and inform strategic funding decisions.
“Science is a team sport more than ever,” she says. “Research has become much more complex. It needs resources. It needs excellence. It needs imagination.”
It’s clear we’re progressing, but there’s still work to be done. Now, donors have another chance to help fund research that could change the future for children (and adults) living with congenital heart disease, thanks to Dr. Marelli.
- Learn more about recovering from heart disease
- See how your donation is impacting lives

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