Forward stepwise regression analysis of clinical variables, resting haemodynamics parameters and 6-min walk test characteristics assessed at baseline in idiopathic and nonidiopathic pulmonary arterial hypertension (PAH)
| Regression coefficient | se | p-value | R2 change % | |
| Idiopathic PAH# | ||||
| ΔHR | 3.62 | 0.50 | <0.0001 | 31 |
| SV | 3.07 | 0.44 | <0.0001 | 36 |
| Nonidiopathic PAH¶ | ||||
| SV | 2.46 | 0.47 | <0.0001 | 42 |
| ΔHR | 3.69 | 0.96 | 0.0005 | 18 |
ΔHR: Δ heart rate, i.e. chronotropic response (HRpeak–HRrest); SV: stroke volume. Only statistically significant variables are presented. #: n = 46, multiple R2 = 0.67; ¶: n = 37, multiple R2 = 0.60.