Pre- and postcapillary exercise contributions to pulmonary hypertension in adults > 45 yr

Clinical differentiation of pre- vs. postcapillary pulmonary hypertension can be challenging in older patients with risk factors for both pathophysiologies. The use of exercise pressure-flow relationships during hemodynamic assessment is now recommended when resting pulmonary artery wedge pressure is proximate to a threshold of 15 mmHg. In this study, we examined relationships between resting pulmonary artery wedge pressure and the balance of pre- and postcapillary contributions to exercise pulmonary hypertension. Patients > 45 yr suspected of precapillary pulmonary hypertension (n = 29, 72 ± 10 yr, 52% Female) with risk factors for left-heart disease were prospectively recruited to undergo semiupright cycle-ergometry at the time of diagnostic right-heart catheterization. Hemodynamic data, including pressure-flow slopes and contributions of transpulmonary gradient and pulmonary artery wedge pressure to mean pulmonary artery pressure, were analyzed to evaluate pre- and postcapillary contributions, respectively, at rest and during exercise. Exercise pressure-flow slopes indicated 62% with postcapillary contributions to pulmonary hypertension, and 31% with solely precapillary contributions. Of patients with pulmonary artery wedge pressure <12 mmHg, 67% had postcapillary contributions to exercise pulmonary hypertension. Conversely, 50% of patients with pulmonary artery wedge pressure >15 mmHg had precapillary contributions to exercise pulmonary hypertension. Exercise-associated increases in pulmonary artery pressures were more strongly associated with precapillary contributions, regardless of postcapillary contributions or the value of resting pulmonary artery wedge pressure. In conclusion, in this population, postcapillary contributions to exercise pulmonary hypertension were commonly disclosed over a range of resting pulmonary artery wedge pressure, including <12 mmHg. The severity of exercise pulmonary hypertension was determined by the precapillary contributions.NEW & NOTEWORTHY Exercise is recommended in patients with pulmonary artery wedge pressure (PAWP) between 12 and 15 mmHg and risk factors for left-heart disease to differentiate pre- versus postcapillary contributions to pulmonary hypertension (PH). However, our prospective experience shows resting PAWP does not reliably predict exercise postcapillary PH, which remains common even at lower PAWP ranges (<12 mmHg). Our findings suggest that exercise may retain utility to elicit postcapillary PH across a broad range of resting PAWP.