How is DTI calculated on HELOCs?

[Gonzalo Escobar]

I have a 210K interest only HELOC untapped with a $0 balance and a rate @ 3.75 and I'm looking to do a refinance on some of my other properties and wanted to get a sense of how that would factor in to my DTI.

For qualification  purposes on the HELOC even though the line was undrawn they counted against me the what I would have to pay if it was fully drawn. This makes sense to me, but they also took into account a surge pricing if the interest rate had tripled or something. 

I get this, but I somewhat dont. In any case moving on I want to know when other lenders underwrite me from peoples past experience did they also do this surge possibility on the HELOC or is that only when they are originating.