Table 2 4D flow and cardiopulmonary exercise test (CPET) parameters in healthy controls and pulmonary arterial hypertension (PAH)

LV 4D flow

 Direct flow, %

34 (10)

31 (12)

0.474

 Retained inflow, %

17 (5)

17 (8)

0.607

 Delayed ejection flow, %

17 (5)

16 (7)

0.020

 Residual volume, %

33 (6)

36 (10)

0.042

 Peak systolic KEI_EDV, µJ/ml

16.1 (5.1)

19.3 (15.0)

0.012

 Average systolic KEI_EDV, µJ/ml

8.9 (3.1)

11.5 (8.0)

0.025

 Peak E–wave KEI_EDV, µJ/ml

27.0 (12.0)

19.0 (17.4)

0.002

RV 4D flow

 Direct flow, %

37 (7)

24 (16)

< 0.001

 Retained inflow, %

16 (6)

16 (5)

0.956

 Delayed ejection flow, %

17 (5)

14 (6)

0.017

 Residual volume, %

29 (10)

44 (16)

< 0.001

 Peak systolic KEI_EDV, µJ/ml

21.2 (8.5)

19.4 (18.3)

0.521

 Average systolic KEI_EDV, µJ/ml

12.2 (4.5)

10.4 (6.9)

0.070

 Peak E–wave KEI_EDV, µJ/ml

13.9 (7.6)

8.4 (6.3)

< 0.001

 KE discordance

1.30 (0.53)

0.94 (0.66)

< 0.001

 Fractional flow ratio

1.24 (0.60)

0.51 (0.40)

< 0.001

CPET

 Peak VO₂, ml/kg/min

22.6 (10.5)

13.2 (4.4)

< 0.001

 % predicted peak VO₂, %

87 (33)

48 (23)

< 0.001

 VE/VCO₂ slope

27 (4)

41 (10)

< 0.001