Pre- and post-capillary exercise contributions to pulmonary hypertension in older adults

BackgroundDiagnosing pulmonary arterial hypertension (PAH) versus pulmonary hypertension associated with left hear disease (PH-LHD) can be challenging in patients with risk factors for both conditions. When resting pulmonary artery wedge pressure (PAWP) is proximate to a threshold of 15mmHg, exercise has been recommended to differentiate pre- versus post-capillary contributions to PH. To improve our understanding of this practice recommendation, we studied relationships between resting PAWP and the balance of pre- and post-capillary contributions to exercise PH. MethodsPatients suspected of PAH (n=29, 72{+/-}2y, 52% F) with risk factors for LHD were prospectively recruited to undergo cycle ergometry at time of diagnostic right-heart catheterization. Hemodynamic data, including pressure-flow slopes and contributions of transpulmonary gradient (TPG) and PAWP to mPAP, were analyzed to evaluate pre- and post-capillary contributions, respectively, at rest and during exercise. ResultsPAWP ranged from 0 to 20 mmHg. Exercise pressure-flow slopes demonstrated 62% with post-capillary PH, and 31% with pre-capillary PH only. The relationship between resting PAWP and the pre- versus post-capillary contributions to exercise PH was not straightforward. Of patients with PAWP<12mmHg, 67% had post-capillary contributions to exercise PH. Conversely, 50% of patients with PAWP>15mmHg had pre-capillary contributions to exercise PH. Exercise-associated increases in pulmonary artery pressures were more strongly associated with pre-capillary contributions regardless of post-capillary contributions or the value of resting PAWP. ConclusionIn this population, post-capillary contributions to exercise PH were commonly disclosed over a range of resting PAWP, including <12mmHg. The severity of exercise PH was determined by the pre-capillary contributions.