importantly

from WordNet (r) 3.0 (2006)

importantly
    adv 1: in an important way or to an important degree; "more
           importantly, Weber held that the manifold meaning
           attached to the event by the social scientist could alter
           his definition of the concrete event itself" [syn:
           {importantly}, {significantly}]
    2: in an important way; "for centuries jellies have figured
       importantly among English desserts, particularly upon festive
       occasion"

from The Collaborative International Dictionary of English v.0.48

Importantly \Im*por"tant*ly\, adv.
   In an important manner.
   [1913 Webster]