revdep-rebuild -X --soname libqt-mt.so.3 -p
Configuring search environment for revdep-rebuild

Environment mismatch from previous run, deleting temporary files...

Checking reverse dependencies...

Packages containing binaries and libraries using libqt-mt.so.3
will be emerged.

Collecting system binaries and libraries... done.
  (/root/.revdep-rebuild.1_files)

Checking dynamic linking...
  found /usr/kde/3.4/lib/libqtmcop.so.1.0.0
  found /usr/qt/3/bin/assistant
  found /usr/qt/3/bin/designer
  found /usr/qt/3/bin/linguist
  found /usr/qt/3/bin/lrelease
  found /usr/qt/3/bin/lupdate
  found /usr/qt/3/bin/msg2qm
  found /usr/qt/3/bin/qm2ts
  found /usr/qt/3/bin/qtconfig
  found /usr/qt/3/bin/uic
  found /usr/qt/3/lib/libqui.so.1.0.0
 done.
  (/root/.revdep-rebuild_af85ec6a.3_rebuild)

Assigning files to packages...
  /usr/kde/3.4/lib/libqtmcop.so.1.0.0 -> kde-base/arts
  /usr/qt/3/bin/assistant -> x11-libs/qt
  /usr/qt/3/bin/designer -> x11-libs/qt
  /usr/qt/3/bin/linguist -> x11-libs/qt
  /usr/qt/3/bin/lrelease -> x11-libs/qt
  /usr/qt/3/bin/lupdate -> x11-libs/qt
  /usr/qt/3/bin/msg2qm -> x11-libs/qt
  /usr/qt/3/bin/qm2ts -> x11-libs/qt
  /usr/qt/3/bin/qtconfig -> x11-libs/qt
  /usr/qt/3/bin/uic -> x11-libs/qt
  /usr/qt/3/lib/libqui.so.1.0.0 -> x11-libs/qt
 done.
  (/root/.revdep-rebuild_af85ec6a.4_packages_raw, /root/.revdep-rebuild_af85ec6a.4_package_owners)

Cleaning list of packages to rebuild... done.
  (/root/.revdep-rebuild_af85ec6a.4_packages)

Assigning packages to ebuilds... done.
  (/root/.revdep-rebuild_af85ec6a.4_ebuilds)

Evaluating package order... done.
  (/root/.revdep-rebuild_af85ec6a.5_order)

All prepared. Starting rebuild...
emerge --oneshot -p =x11-libs/qt-3.3.4-r8 =kde-base/arts-3.4.3

These are the packages that I would merge, in order:

Calculating dependencies ...done!
[ebuild   R   ] x11-libs/qt-3.3.4-r8  USE="mysql* -cups*"
[ebuild   R   ] kde-base/arts-3.4.3
Now you can remove -p (or --pretend) from arguments and re-run revdep-rebuild.