Nordic Cooperation Boosts Heart Transplant Survival Rates

The study in brief:

• 597 children were listed for heart transplantation in the Nordic countries between 1986 and 2023, and 461 children (77%) underwent heart transplantation.
• Mortality among children on the waiting list for heart transplantation fell from 22.8% (1986-1998) to 6.8% (2012-2023)
• The long-term survival rate after transplantation was 78% after 10 years. Of the children who have had the opportunity to live 30 years with their new heart, more than half are alive today.
• Just over 40% of hearts used for paediatric heart transplantation in Sweden come from donors in other Nordic countries.

The study published in the Journal of Heart and Lung Transplantation is the first of its kind to look at all paediatric heart transplants performed in the Nordic countries, within the framework of the Nordic Scandiatransplant collaboration. The researchers looked at both survival while waiting for transplantation and survival after transplantation.

"The Scandiatransplant countries all have relatively small populations and perform only a small number of paediatric heart transplants each year. We realised that there had never been an overview of the results within Scandiatransplant before, and we were particularly interested in mapping how the results have changed over time and how they fare in an international context, where the comparison is made with larger countries and centres that perform significantly more transplants every year," says Oscar van der Have, researcher at Lund University and medical registrar at the Children's Heart Centre at Skåne University Hospital and first author of the study.

A previous retrospective study published in 2009 outlined the outcomes after 20 years of heart transplantation practice in Sweden. The current study is an overview of the last 38 years and includes the entire Nordic region divided into three time periods, 1986-1998, 1999-2011 and 2012-2023, to compare outcomes over time. The result that stands out is a significant reduction in mortality while waiting for a new organ, despite the increase in waiting time.

"What is clear from the study is that more children on the waiting list now make it to a heart transplant. In the first time period, 22.8 per cent of children on the waiting list died while waiting for a new heart. In the most recent period, this figure is 6.8 per cent. At the same time, the median waiting time for a new heart has almost doubled - from 38 to 63 days - but despite the longer waiting time, more children are surviving until transplantation," says Oscar van der Have.

The researchers believe that more children are surviving despite longer waiting times because of technological advances in transplantation care in recent years.

"This is largely down to having better and more advanced technology today. We have short and long-term circulatory support, such as ECMO and mechanical heart pumps, such as the Berlin Heart, which can help children survive the waiting period," says Karin Tran-Lundmark, researcher and associate professor at Lund University and senior consultant at the Children's Heart Centre at Skåne University Hospital.

Longer waiting times for a new heart and better survival rates may also be partly due to children being put on the waiting list earlier in the course of the disease.

"Another aspect is that we are likely to list the children a little earlier, before they become too ill. This means they have to wait longer - but with better conditions. It is probably an increased awareness: to make the decision earlier, which also allows for improved support during the waiting time," says Michal Odermarsky, researcher at Lund University and consultant at the Children's Heart Centre at Skåne University Hospital.

Despite the advancements, challenges remain. Long-term survival after transplantation is very good within Scandiatransplant. Despite being small centers with few transplants per year, the outcomes are comparable to much larger centres in, for example, the US, but long-term survival has not improved at the same rate as waiting list survival.

"Unfortunately, lifelong immunosuppressive treatment is needed after a heart transplantation, which carries risks. We need to get even better at detecting and treating complications such as rejection, infections and malignancies. It is important that we follow, and do our best to contribute to, the development of diagnostic methods and medicines," says Karin Tran-Lundmark.

More knowledge is also needed on how to improve care for the single ventricle patient group:

"We are very interested in the single ventricle patient group, a group of children with severe congenital heart defects. This is our most challenging patient group, where the liver can fail over time due to the heart defect. It can be difficult to decide when it is time to transplant, and whether it is sufficient to replace the heart or whether the liver also needs to be transplanted. There is a lot to consider. It is a small group, but a very complex one," says Michal Odermarsky.

Another challenge is the availability of organs for the very youngest patients, where mortality on the waiting list remains the highest.

"We also need better solutions for the youngest children. It is difficult to find donors at that age, as, thankfully, we have a low infant mortality rate in the Nordic countries. Increased awareness of the existence of children awaiting transplants may encourage more relatives to donate, and even better heart pumps may also help more patients survive," Karin Tran-Lundmark suggests.