There were reports the actor croaked thanks to a bum ticker -- but while his heart may have been a contributing factor in his demise ... the official cause of death is listed as "sequelae of right hip fracture."

For those who don't know ... sequela is doctor-speak for a pathological condition that stems from a previous injury -- in this case, a broken hip.

According to the death cert, Farentino broke his hip in December after falling out of his bed. The nature of the complication that eventually killed him last month is unclear.