Loris Follador from Casa Coste Piane explains the pruning techniques they use in their Prosecco Valdobbiadene vineyards:
The technique is to attach two branches together, pull them up so they don't get disorganized, but as such that they cover all the branches, without covering the grapes. From there your can form them.
The branches shouldn't have serious health problems, like Botrytis, for example. Hail is another natural hazard that can seriously damage the vines.