The I.S.T.D. book indicates that the heel pivot is "acceptable" for examinations, which means that it won't be a part of the oral or written exam, but can be used during a freestyle demonstration if desired.

More and more U.S. competitions are providing step lists these days as a guide for competitors. In the International style, the list usually outlines the ISTD syllabus, not including the "named variations" such as the heel pivot. For this reason, I would tend to avoid using it during a competition. You could probably get away with it, but it's not really worth the risk.

We created our step checklist for the purpose of helping teachers and students to monitor their progress with syllabus figures. We included the named variations simply to give people the option to include them, since they do exist in the syllabus (even if most people don't use them).

Sincerely,
Jonathan Atkinson www.ballroomdancers.com