Lucas made 247 Premier League appearances during a 10-year spell with Liverpool, scoring just one goal in the competition, before joining Serie A giants Lazio in 2017.
The former Brazil international then re-joined Gremio – the club where he began his career – after leaving Italy at the end of the 2021-22 campaign.
On Tuesday, Lucas tweeted a statement from the Gremio's medical department, announcing he would sit out the team's pre-season preparations while undergoing assessment.
The statement read: "The Gremio medical department communicates that the athlete Lucas Leiva presented, in pre-season routine exams, a picture of having an altered cardiac rhythm.
"Consequently, he is removed from physical activities until the conclusion of complementary exams and treatment of the condition."
Gremio – who have won the joint-most Copa Libertadores titles of any Brazilian club (three) – won promotion from Brazil's second tier in 2022 after finishing second.
Liverpool and Barcelona great Suarez joined Gremio in January, having helped his boyhood club Nacional to the Uruguayan Primera Division title on his return to South America last year.
Suarez has scored four goals in 12 appearances in the Brazilian top flight this campaign, but his future is in doubt amid reports he is Miami's next big-name target.
Miami have already signed Suarez's former Barca team-mates Messi, Busquets and Alba, and Sunday brought confirmation they had traded with the San Jose Earthquakes to gain another international registration slot.
That move has heightened speculation regarding a move for Suarez, and while Lucas understands the draw of MLS, he hopes Gremio can keep the striker.
Asked about Suarez's future, Lucas – who retired in March after being diagnosed with a heart issue – said: "He made a fantastic impact here in Brazil at Gremio.
"I think made the right move. Luis is a world-class player, we don't need to speak about his qualities and what he's doing here in Brazil.
"He's been linked, but I just hope he can stay at Gremio because it's my club and he's my neighbour here!
"I hope he stays a bit longer but MLS is getting attention from every player and from the fans. It's normal that he will be linked with big teams like Inter Miami."
After Messi marked his Miami debut with a dramatic free-kick winner against Cruz Azul in the Leagues Cup, there has arguably never been a more compelling time to follow MLS.
Lucas is among those excited by the league's potential, adding: "MLS is growing every year, people are watching more MLS. If you look back maybe 10 years, nobody would have expected that.
"Americans know how to do these things, so well done to them. Messi going there will just attract a lot of fans and people who will be following the league, so it's great.
"It's great because football should be everywhere in the world because it is a fantastic sport that people love to watch.
"We can see him in another league, not in Europe. In America, it's a great thing for the fans that love football. It's a league that is improving and is growing and getting better every season."
