It means a discussion of matters of great importance. In this instance, heady would be defined as "having strong effect".

I think your original interpretation is correct. Heady is more commonly used to refer to "exciting" and "fast-paced" events that happened many years ago, like "those heady days". Talking or acting in a big, excitable way without caution or fear. There is an online etymology dictionary for English on the internet, which gives lots of meanings and origins of words.