Three-time world champion surfer Andy Irons died of a heart attack and drugs in his system according to an autopsy report provided to The New York Times.

The Times reported that Irons, 32, who was found dead in his Texas hotel room on November 2 last year, died primarily of a heart attack related to coronary artery disease, with the secondary cause listed as "acute mixed drug ingestion".

The death of triple world surfing champion Andy Irons shocked the sporting world. Credit:AP

But the Irons family has reportedly disputed the official autopsy findings, enlisting Texan forensic pathologist Vincent Di Maio to review the findings and explain his results to the family.

His review of the autopsy differed significantly from the official report, concluding that Irons died of a heart attack due to focal severe coronary atherosclerosis, or hardening of the arteries.