Bernard Tomic feared for a spectator's life after his Australian Open clash with Denis Istomin was delayed for more than 20 minutes because of a medical issue.

Tomic was often put under the pump by Istomin on Tuesday night but rallied when required to prevail 6-7 (4-7) 6-4 6-4 6-4 in three hours.

The top-ranked local hope was rattled by an incident in the fourth set, when a fan was taken from Hisense Arena on a stretcher.