Earlier this week, he said he felt “fine” and was staying in hospital for some examinations.
“After Christian has been through different heart examinations it has been decided that he should have an ICD (heart starter). This device is necessary after a cardiac attack due to rhythmic disturbances,” national team doctor Morten Boesen said.
“Christian has accepted the solution and the plan has moreover been confirmed by specialists nationally and internationally who all recommend the same treatment. We encourage everybody to give Christian and his family peace and privacy the following time.”
It is connected to the heart with thin wires and is able to regulate abnormal heart rhythms through electrical shocks.
Denmark, which lost 1-0 to Finland after Saturday’s game was resumed following Eriksen’s collapse, plays Belgium in its second game of Euro 2020 on Thursday.
Lukaku has also said that he wants to visit his Inter Milan teammate in hospital.
On Wednesday, players from Finland and Russia wore “Get well Christian!” T-shirts as they warmed up for their game, which Russia went on to win 1-0.