Saw in this article about breakfast sandwiches, this term "velocity time integral" as a measurement of blood vessel healthy function.

How Unhealthy Are Breakfast Sandwiches? - Prevention.com

I am wondering if anyone can provide more enlightenment on this parameter and what it means ? Also, I am curious of the short-term and immediate negative effects noted are due to the carbs, fat, or combination of both, in this presumably high carb and high fat conventional breakfast sandwich, and whether there are any studies linking the typical low carb, high fat Primal way of eating to these same (claimed) negative effects on blood vessel performance ?