Chris Pratt's Stunt Double Tony McFarr's Cause of Death Revealed

Tony McFarr -- a stuntman who served as a double for big Hollywood stars like Chris Pratt -- died from a heart issue likely brought on by acute alcohol poisoning from prolonged heavy drinking.

In new documents, obtained by TMZ, the Orange County Medical Examiner in Florida officially declared Tony's death the result of an irregular heartbeat due to an issue with his heart valves.

The ME says contributing factors in Tony's death include alcohol poisoning and chronic obstructive pulmonary disease ... also known as COPD, a common lung disease that restricts airflow and causes breathing problems.

Tony's autopsy notes he had a history of binge alcohol abuse ... and there's info on what his BAC was when his body was examined ... the ME notes a concentration of 0.29 percent. For reference, the legal BAC limit for driving is .08 in most states.

TMZ broke the story ... Tony died back in May , and his mother Donna told us her son's passing was unexpected and shocking.

The ME says the daredevil was found dead in his home, and it sounds like he had been there for some time, because his body was already decomposing.

The ME is officially classifying his death as an accident. Tony was only 47.

Chris and Tony worked on a bunch of movies together ... including the 'Guardians of the Galaxy' and 'Jurassic World' franchises.