The Iowa medical examiner’s office has concluded that the death of a Spencer High School wrestler who collapsed at a December match was likely caused by a congenital heart defect.

The Sioux City Journal reports that Dr. Michele Catellier, who performed an autopsy on 18-year-old Austin Roberts’ body Dec. 22 determined the cause of death.

The medical examiner’s office also listed “probable dehydration” and “other significance” in his death. The manner of his death will be certified as natural causes.

Roberts, at 220 pounds, collapsed at a tournament Dec. 19 in Spencer after taking injury time when he couldn’t catch his breath. He was pronounced dead at a local hospital later that day.

He was ranked sixth in the state in Class 3A at the time of his death.