Hi yerbamate,
Treat your Passiflora to a good thick protective mulch this autumn and wait til spring.
If you are in a mild area with little frost and a have it in a sunny south facing asspect, just prune out any dead, diseased or weak growth and try and maintain an open frame-work, where you have it trained.
In colder areas where frost is a problem its often a good bet to prune it harder, even to almost ground level and it should shoot again from the base. Good Luck Tbird+