Temporal Patterns of Pulmonary Vascular Loading during Exercise in Patients with Pre versus Post Capillary Pulmonary Hypertension

Abstract

<h3>Purpose</h3> In healthy humans, pulmonary artery pressures (PAP) increase modestly and equilibrate rapidly in response to constant intensity exercise. PAP increase markedly in pre- or post-capillary pulmonary hypertension (pre-cap or post-cap PH), but the time course is unclear. We studied pulse (PP) and diastolic (PADP) PAP as indices of pulsatile load and pulmonary vascular outflow pressure, respectively, and explored whether the magnitude and time course of their response to exercise differs in pre-cap or post-cap PH. <h3>Methods</h3> Patients underwent right heart catheterization with cycle-ergometry (25/40W, F/M), and were classified by their exercise hemodynamic responses: 1) Normal 2) pre-cap PH and 3) post-cap PH. PAP were recorded continuously and analyzed offline. Changes from Control, 2 min, and 7 min were examined. <h3>Results</h3> We studied 76 patients (47% F; 59±15 years); groups comprised 32 Normal, 22 pre-cap PH, and 22 post-cap PH. After exercise onset in the Normal group, PADP increased at 2 min (∆5±3mmHg). This increase was less than both pre-cap PH (∆9±4mmHg, p<0.01) and post-cap PH (∆8±6mmHg, p=0.1), which did not differ (p=0.99). While PADP did not increase further at 7 min in Normal and post-cap PH groups, it did in the pre-cap PH group (∆3±5mmHg, p=0.04, Fig. 1). In the Normal group, PP increased at 2 min (∆5±4mmHg). PP increases at 2 min were greater in pre-cap PH (∆13±8mmHg) than post-cap PH (∆7±4mmHg, p<0.01) and Normal (p<0.01). Although PP increased further at 7 min in the Normal group (∆2±3mmHg, p<0.01), the increases in pre-cap PH (∆6±5mmHg, p<0.01) and post-cap PH (∆6±6mmHg, p<0.01) were both greater compared to Normal (pre-cap PH: p<0.01 post-cap PH: p=0.02, Fig. 1). <h3>Conclusion</h3> During exercise, patients with pre-cap or post-cap PH demonstrate differences in both the magnitude and temporality of change in PAP. Despite constant work-rate, the pulmonary vascular load continues to increase in both pre-cap and post-cap PH.