Although Kovalainen is not suffering from any symptoms and can carry on with his day-to-day life without any issues, the Finn has decided against competing in rallying until he has made a full recovery.

Kovalainen was set to return to the Japanese Rally Championship in 2024 with Rally Team AICELLO, which has switched from Skoda machinery to a Toyota GR Yaris Rally2 entry this year. The 42-year-old was again due to team up with Sae Kitagawa, the driver with which he won back-to-back titles in 2022 and ‘23.

But ahead of the opening round of the championship on 16 February, the Rally Mikana, it was announced that Kovalainen will be replaced by Katsuhiko Taguchi in the team’s line-up.

At that time, a simple medical examination had revealed that he needed a thorough investigation.

With all the medical tests now complete, it has been found that Kovalainen is suffering from ascending aortic aneurysm, a bulge in the artery closest to the heart.

An aneurysm is a weak spot in a blood vessel wall and can tear or rupture, causing severe, life-threatening internal bleeding.

In a statement issued by the team, Kovalainen revealed his intention to get a surgery done in Finland before returning to rallying at a later point

“I was diagnosed with ascending aortic aneurysm in a medical check-up recently and I was told not to be able to participate in rallies due to increased risk of aortic rupture," he said. "I have no symptoms and I’m currently feeling good, and we are now making a plan on how to solve this issue. 

"An open-heart surgery is our favourable solution at the moment and we are preparing for that. We hope to get an operation done and start the recovery as soon as possible.

"My aim is of course to return to the Japanese Rally Championship with Rally Team AICELLO. I was planning to participate in the rallies until the end of January, but after careful consideration with my team of doctors I’ve decided to try and fix this issue instead.

"I’m sorry for all our team partners and fans for this problem and many thanks for all the encouragement and support regarding this."

Team representative Hironobu Makino commented: “When I heard this story from Heikki just before the start of the season, I was extremely shocked. Considering Heikki's feelings, who was looking forward to this season's activities more than anyone else, and the concerns of his family, I had no choice but to make the decision. 

“Although there was a period of hesitation, Rally Team AICELLO decided to continue participating in the race in order to fully support Heikki's return, and to deepen his understanding and maturity of the new machine together with Katsuhiko Taguchi.

“We apologise for the great concern this may cause to everyone, but we ask for your understanding and support as we work towards Heikki's recovery and return.''

Kovalainen has been actively competing in Japan since he first joined SUPER GT in 2015, winning the GT500 title in only his second season of competition with Kohei Hirate in a Lexus LC500.

In 2022, he made a full switch to the country’s national rallying championship and found instant success in the JN1 class, the highest level in the All-Japan Rally Championship. He also took part in the Finnish Rally Championship last year.