perfusion scans allow the distinction to be made between primary pulmonary
hypertension and obstructive causes of pulmonary hypertension such as CTEPH.
When V/Q scan results are inconclusive, or in cases where information about
the technical operability is required, pulmonary arteriography is the
procedure of choice.
Ventilation perfusion (V/Q)
scans and pulmonary arteriograms are advocated as providing the most useful
information in the diagnosis of, and subsequent decisions about, the
operability of cases of CTEPH.