You are never going to become an expert cardiologist overnight anyway, so your best bet is to start with the speaker's published corpus, if he has one. If he represents an organization, familiarize yourself with its institutional platform and activities, particularly the aspects that have something to do with your topic.

Read the accessible documents and/or collect a set of works representative of the position that the conference titles suggest, print them out, and highlight the terminology specific to them. List the terms as they appear, along with cryptic sentences or phrases. Make a separate list of proper names and significant numbers -- this will be the subject of separate study. Next, alphabetize your list of terms, print out two copies, and jot down your initial definitions on one of them.

Choose your validation tools: a field-specific bilingual dictionary (or two, for cross-checking), a general bilingual dictionary, an authoritative monolingual dictionary in the source language -- the importance of this should never be underestimated -- and, say, a good encyclopedia in target. Basically, the next task is measuring how familiar you already are with these concepts. If you are the over-nervous, defensive type, you will probably find during this process that half your list needs weeding: i.e., some of what you have listed is not terminology, may be found in the general dictionary, can be presumed safely covered already (be careful here, since what you thought was alright may well be improved), or is a stylistic idiosyncracy, for which you just may have to formulate something appropriate.

Print out your short list with the authoritative definitions and whatever definitions of your own that you have validated against expert opinion. Your next task is now to reconcile the term and make it consistent, with the target audience in mind. Oxford may have said one thing and Ernst another, but Smith, who translated this author's most significant book, or wrote an authoritative work on the subject, used ___________. In a nutshell, check out the authorities with corpus context, and decide on the best solution.

Ironic as it sounds, this last reductive step is the one that will mark the session. Don't be reluctant to give up the false feeling of security that comes from having many options. Rather, go for appropriate register. Physically, you'll see a reduced, much thinner glossary -- but the job won't leave much time for more, anyway. Two pared-down, precision-researched sheets are better equipment than twenty beating about the bush and distracting your listener because of the rustle of turning pages. Print them out in case your notebook fails.