Aguero will remain under the supervision of medical professionals for at least two more days to undergo cardiology tests, according to Marca.

Aguero will only return to the training ground when it is safe to do so and the Catalan giants will publish a statement with the results of his heart tests when they are released.

The report adds Barcelona will take no risks with the Manchester City legend given the uncommon nature of the issue.

Aguero will only return to the training ground when it is safe to do so and the Catalan giants will publish a statement with the results of his heart tests when they are released.

Sport claims initial examinations found arrhythmia, whereby the heart beats with an irregular rhythm.

Sergi Barjuan is serving as Barcelona’s interim manager until Koeman’s successor is appointed and he recalled the moment of Aguero’s substitution in his post-match interview.

“I asked him and he told me he was dizzy,” said Barjuan of Aguero. “I was told he went to the hospital. I don’t know anything else.”

Aguero was making just his fifth appearance for Barcelona having missed the start of the season with a calf injury.

The former Atletico Madrid striker arrived at Camp Nou on a free transfer this summer after his contract with City expired.

Aguero has scored one goal for the club, who have slumped to ninth in the table after a dismal start to the season.