If you like the look, I'd just cut out any dead growth and it will fill in quickly. It is on the invasive list in the PNW, and is a real problem when it escapes into wooded parks. But, since you already have it established, you may just monitor it to be sure it doesn't spread. As Sue notes, when the leaves change to more of a heart shape, it is getting ready to flower and fruit. At that point, you may want to cut it back as the birds will eat the fruit and spread the seed. Here's an article you might be interested in.
http://extension.oregonstate.e...
