The 27-year-old Denmark international joined the Toffees in 2020 before leaving last summer and then joining American side Portland Thorns.
In November, the Thorns said Sevecke would not be returning to the National Women's Soccer League club in 2024.
"The past months I've had some tests done," wrote Sevecke in a social media post.
"I recently got the results back which says that I have a heart condition.
"This means that I'm not allowed to continue playing professional football and I've therefore been forced to stop playing immediately."
Sevecke was part of Denmark's squad at the 2023 Women's World Cup.
"Being part of the national team and representing my country for many more years is also something I won't be able to do any more and it makes me sad," added Sevecke.
"I'm surrounded by the best people and I will get through this."
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