It looks like just a round tip that was used. We did this in one of the Wilton classes (the first one, I think). Just use a small round tip, squeeze and pull down for half the heart, then squeeze and pull down for the other half. HTH!
it looks like just a plain round tip like a 3 or 4. You pipe a simple circle blob and pull it down to get a tail and then do a second one next to it mirroring the fist and continue the tail down to the cake base. The icing looks fairly loose so the two heart halves flow together.
I agree with Starkie. There is als a tip that will make the heart shape. But I think Starkie is right, because of the lines.
I have a heart tip and the round tips actually work better for a heart.
There is a heart tip... I have it but haven't used it yet.
I just love my online cake friends. Virtual high five to you all