This is the 7" version of the Pet Shop Boys' 70s-tinged "Heart", which is only available on "Discography". Both "Actually" and "PopArt" contain the album version, and this 7" edit wasn't even included on the "Heart" CD single. This is the version that went to #1 in the UK. It's subtly (yet noticeably) different to the album version; it flows better and feels faster.
It remains to be seen which version the new compilation Ultimate contains, but either way this is the definitive - and by far the best - version of a PSB classic.