Del Rosario fell into a coma after the heart attack, which was likely the result of a congenital disorder, his manager, Jason House, said doctors told his family.
He died Monday at Hoag Memorial Presbyterian Hospital in Newport Beach, Calif., the Chicago Tribune reported.
The UFC issued a statement saying it "mourns the loss" of the fighter.
"The entire organization sends its deepest condolences to Shane's family and friends," the statement said.
Del Rosario began his fighting career with Muay Thai, a combat style from Thailand, and moved his way up the professional mixed martial arts ladder, the Tribune said.
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UPI Sports Results for September 19, 2014