I just came across this publication (link below) in the AHA journal. it has a summary/abstract of the research but no link to the full research paper. Would anyone be able to explain the reasoning behind this.
There's no full paper associated to that abstract, because it's a conference abstract, not a paper abstract. If you go up one level from that link you'll find:
That is a collection of the abstracts of the works presented at that conference. This is common in some conferences: authors submit only a short description of their work, typically half or one page long. In the past, these submission were typically collected in a book of abstracts which was given to the participants at the beginning of the conference. Nowadays, abstracts are more commonly distributed in electronic form.