PULMONARY TO SYSTEMIC PULSATILE AND RESISTIVE VASCULAR RESPONSES TO EXERCISE IN PATIENTS WITH PULMONARY HYPERTENSION SECONDARY TO LEFT HEART DISEASE (HFPEF)

Systemic and pulmonary arterial stiffening with age are said to be linked, and contribute towards the development of pulmonary hypertension (PH) with age. Systemic arterial stiffening may contribute to the development of PH due to left heart disease (PH-LHD). However, the relationships between the systemic and pulmonary circuit have not been as well described in populations with pulmonary hypertension. Exercise during right heart catheterization (RHC) is used to discriminate between PH-LHD and pulmonary arterial hypertension (PAH). In this study we aimed to describe the relationships between pulmonary and systemic compliance (a measure of vascular stiffening, also referred to as pulsatile loading) and vascular resistance (a measure of resistive loading) at rest and during exercise RHC, in patients with normal hemodynamics, PH-LHD and PAH. We hypothesized that systemic and pulmonary arterial stiffening would be linked in PH-LHD but not PAH.

A retrospective hemodynamic analysis was conducted using data from 80 individuals (50% female, 59±15 years) with dyspnea and/or suspected pulmonary hypertension who underwent RHC and a bout of semi-upright submaximal cycling. Exercise hemodynamic classifications were as follows: Normal – change in mean pulmonary artery pressure (mPAP) over cardiac output (CO)(ΔmPAP/ΔCO ≥3.2 woods units (WU)), Exercise PAH - ΔmPAP/ΔCO >3.2WU and exercise pulmonary arterial wedge pressure (PAWP) < 20mmHg, and Exercise PH-LHD - ΔmPAP/ΔCO >3.2WU and PAWP >20mmHg with exercise. Proportional relationships between pulsatile load in the pulmonary vs. systemic circuit are displayed in Table 1. There was a significantly greater increase in the pulmonary pulse pressure (PPP) to systemic pulse pressure (SPP) (73±40% to 93±51% vs. 51±29% to 63±36%, p < 0.001) and pulmonary vascular resistance (PVR) to systemic vascular resistance (SVR) (26±16% to 39±27% vs. 14±11% to 25±18%, p < 0.01) from rest to exercise in the PAH group when compared to PH-LHD. Otherwise, there were no differences in the total pulmonary resistance (TPulmR) to total peripheral resistance (TPR) ratio. There was a significant correlation between pulmonary (PulmCp) and systemic compliance (SysCp), both at rest (r2=0.33, p < 0.01) and during exercise (r2=0.16, p=0.05), in the PH-LHD group (Figure 1).

The proportional vascular loads between the pulmonary and systemic circulations differ as expected between PAH and PH-LHD. However, the net proportional resistive load (TPulmR/TPR) was very similar. There was a significant relationship between systemic and pulmonary stiffening (pulsatile load) at rest and exercise only in the PH-LHD group, which provides support for the hypothesis that systemic arterial stiffening is a mechanism that promotes the development of PH-LHD.