Purpose Currently best clinical practice for the investigation of pulmonary hypertension (raised pulmonary pressures) involves patients attending the catheter laboratory and catheters being passed under fluoroscopic guidance via the femoral vein to measure right heart pressures (and generally also via the femoral artery and aorta to measure left sided pressures). Wave intensity analysis using simultaneous pressure and flow measurements gives additional information about the upstream and downstream effects on haemodynamics, and we propose will lead to a more detailed assessment of the influences both causing and exacerbating pulmonary hypertension. Until recently it has not been possible to assess these effects formally: the standard technique measures only local pressure.