1♣ = 11-13 bal or 17+ any
3♦ = Hearts, INV+ opposite 11-13 bal
I couldn't find much in the notes except that bidding their suit at the 3-level asks for a stopper, which doesn't seem to be an option here.
It would seem to me that both 3♥ and 4♥ show the weak balanced hand, 3♠ and 4♣ should be NAT GF, leaving 4♦ and 4NT as strong heart raises. Does that sound right?
If that sounds right to you, would you bid 4♦ here or 4NT? If you bid 4♦ and partner bids 4♥, do you give up?