One of the three people who died at Burning Man this year had been dealing with heart problems before attending the festival … TMZ has learned.

Armando Ramirez‘s mom and sister tell TMZ … he had gone to the emergency room twice for heart-related issues in the weeks leading up to Burning Man and had a doctor’s appointment scheduled for November.

His friends noticed he was having difficulty breathing while helping set up a tent after arriving at the festival.

We’re told medics resuscitated Armando once before he was airlifted to a hospital, but he died before reaching it. His family suspects he suffered a heart attack, but toxicology results are still pending.

Asked whether Armando used drugs or whether they believed drugs played a role in his death, his family had no comment … saying they were not with him at the time.

Armando’s family tells us this was not his first time attending Burning Man.

The Pershing County Sheriff’s Office says no foul play is suspected in his death.

As we reported … two other festivalgoers, Sampson Tshombe and Craig Mann, also died during the event. Officials say autopsy and toxicology results in those cases could take 6 to 8 weeks.