Non-invasive stroke volume assessment in patients with pulmonary arterial hypertension: left-sided data mandatory

Thirty-four PAH patients underwent both CMR and right-sided heart catheterisation. CMR-derived SV was measured by PA flow, left (LV) and right ventricular (RV) volumes, and, in a subset of nine patients also by aortic flow. These SV values were compared to the SV obtained by invasive Fick method.For SV by PA flow versus Fick, r = 0.71, mean difference was -4.2 ml with limits of agreement 26.8 and -18.3 ml. For SV by LV volumes versus Fick, r = 0.95, mean difference was -0.8 ml with limits of agreement of 8.7 and -10.4 ml. For SV by RV volumes versus Fick, r = 0.73, mean difference -0.75 ml with limits of agreement 21.8 and -23.3 ml. In the subset of nine patients, SV by aorta flow versus Fick yielded r = 0.95, while in this subset SV by pulmonary flow versus Fick yielded r = 0.76. For all regression analyses, p < 0.0001.In conclusion, SV from PA flow has limited accuracy in PAH patients. LV volumes and aorta flow are to be preferred for the measurement of SV.In pulmonary arterial hypertension (PAH), cardiovascular magnetic resonance (CMR) has been proposed as a standard for the assessment of right ventricular function and characteristics of the pulmonary vascular bed [1,2]. Accurate assessment of stroke volume (SV) by CMR is critical in this respect, since earlier studies revealed that SV is closely related to prognosis and that a change in SV reflects treatment effects [3,4]. Since most of the CMR protocols used in PAH [5,6] measured pulmonary artery flow, SV can be assessed by measuring flow in the main pulmonary artery (PA).Previous studies have shown that this method is accurate to measure SV from PA flow in healthy subjects [7-9]. Whether this also holds true in PAH is questionable, since the velocity profile in PAH is non-laminar, in contrast to the profile in healthy subjects [10-13].For this test of accuracy, a clinical standard is required. This standard is provided by the measurement of SV by the direct Fick principle during right heart catheterisation (RH