Exercise-Induced Pulmonary Arterial Hypertension

Background-The clinical relevance of exercise-induced pulmonary arterial hypertension (PAH) is uncertain, and its existence has never been well studied by direct measurements of central hemodynamics. Using invasive cardiopulmonary exercise testing, we hypothesized that exercise-induced PAH represents a symptomatic stage of PAH, physiologically intermediate between resting pulmonary arterial hypertension and normal. Methods and Results-A total of 406 consecutive clinically indicated cardiopulmonary exercise tests with radial and pulmonary arterial catheters and radionuclide ventriculographic scanning were analyzed. The invasive hemodynamic phenotype of exercise-induced PAH (n = 78) was compared with resting PAH (n = 15) and normals (n = 16). Log-log plots of mean pulmonary artery pressure versus oxygen uptake ((V)over dotO(2)) were obtained, and a "join-point" for a least residual sum of squares for 2 straight-line segments (slopes m1, m2) was determined; m2<m1 = "plateau," and m2>m1 = "takeoff" pattern. At maximum exercise, (V) over dotO(2) (55.8 +/- 20.3% versus 66.5 +/- 16.3% versus 91.7 +/- 13.7% predicted) was lowest in resting PAH, intermediate in exercise-induced PAH, and highest in normals, whereas mean pulmonary artery pressure (48.4 +/- 11.1 versus 36.6 +/- 5.7 versus 27.4 + 3.7 mm Hg) and pulmonary vascular resistance (294 +/- 158 versus 161 +/- 60 versus 62 +/- 20 dyne . s . cm(-5), respectively; P<0.05) followed an opposite pattern. An exercise-induced PAH plateau (n = 32) was associated with lower (V) over dotO(2)max (60.6 +/- 15.1% versus 72.0 +/- 16.1% predicted) and maximum cardiac output (78.2 +/- 17.1% versus 87.8 +/- 18.3% predicted) and a higher resting pulmonary vascular resistance (247 +/- 101 versus 199 +/- 56 dyne . s . cm(-5); P<0.05) than takeoff (n = 40). The plateau pattern was most common in resting PAH, and the takeoff pattern was present in nearly all normals. Conclusions-Exercise-induced PAH is an early, mild, and clinically relevant phase of the PAH spectrum. (Circulation. 2008; 118: 2183-2189.)