According to the Medical Examiner Office's report, obtained by TMZ, the "General Hospital" star's official cause of death is being listed as positional asphyxia due to acute alcohol intoxication. There's a contributing condition cited ... coronary artery atherosclerosis.

In layman's terms, Tyler suffocated to death because of how he was positioned when he died -- and the ME here is saying booze played in a part in him ending up that way. The latter description is basically plaque build-up in his arteries. His death was accidental.

We broke the story ... Tyler's friend found him deceased at his San Diego apartment -- this after trying and failing to get a hold of him for a while. His pal discovered his body in his bedroom ... and called 911 shortly thereafter.

Tyler's one-time costar, Maurice Benard, broke the news about his passing ... calling him a "truly talented individual that lit up the screen in every scene he performed and relished bringing joy to his loyal fans through his acting."

He'd been on 'General Hospital' for a very long time, starring in over 1,100 episodes. TC was only 50.