The Clark County Coroner tells TMZ that Vinnie died of dilated cardiomyopathy -- an enlarged heart -- as well as severe coronary artery disease -- a heart condition. We're told he died of natural causes.

As we reported ... Vinnie died in his sleep this past June at his Las Vegas home. His body was going to be buried in Texas next to his mom and his late brother, "Dimebag" Darrell Abbott -- who was tragically murdered on stage during a show.

Like we told you ... Vinnie was laid to rest in a custom KISS casket, identical to the one his brother was buried in. Gene Simmons and co. provided the casket as a gift to Vinnie's family. He was buried in some of his own clothes -- including his hat, shoes and flannel ... among other items.

A free public memorial concert was also held for him in Dallas at 3:33 PM to recognize his brother, Darrell. Pantera was a huge heavy metal band in the '90s -- having been nominated for Grammys in 1995 and 2001. Their album, "Far Beyond Driven," hit #1 in 1994.