Background Systemic sclerosis associated pulmonary artery hypertension (SScPAH) has a worse prognosis compared to idiopathic pulmonary arterial hypertension (IPAH), with a median survival of 3 years after diagnosis often due to right ventricular (RV) failure. We tested if SScPAH or systemic sclerosis related pulmonary hypertension with interstitial lung disease (SSc-ILD-PH) imposes a greater pulmonary vascular load than IPAH and/or leads to worse RV contractile function. Methods and Results We analyzed pulmonary artery pressures and mean flow in 282 patients with pulmonary hypertension (166 SScPAH, 49 SSc-ILD-PH, 67 IPAH). An inverse relation between pulmonary resistance (RPA) and compliance (CPA) was similar for all three groups, with a near constant resistance × compliance product. RV pressure-volume loops were measured in a subset, IPAH (n=5) and SScPAH (n=7) as well as SSc without PH (SSc-no-PH, n=7) to derive contractile indexes (end-systolic elastance [Ees] and preload recruitable stroke work [Msw]), measures of right ventricular load (arterial elastance [Ea]), and RV-pulmonary artery coupling (Ees/Ea). RV afterload was similar in SScPAH and IPAH (RPA=7.0±4.5 vs. 7.9±4.3 Wood units; Ea=0.9±0.4 vs. 1.2±0.5 mmHg/mL; CPA=2.4±1.5 vs. 1.7±1.1 mL/mmHg; p>0.3 for each). Though SScPAH did not have greater vascular stiffening compared to IPAH, RV contractility was more depressed (Ees=0.8±0.3 vs. 2.3±1.1, p<0.01; Msw=21±11 vs. 45±16, p=0.01), with differential RV-PA uncoupling (Ees/Ea=1.0±0.5 vs. 2.1±1.0, p=.03). This ratio was higher in SSc-no-PH (Ees/Ea = 2.3±1.2, p=0.02 vs. SScPAH). Conclusions RV dysfunction is worse in SScPAH compared to IPAH at similar afterload, and may be due to intrinsic systolic function rather than enhanced pulmonary vascular resistive and/or pulsatile loading.

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Background Right ventricular (RV) functional reserve affects functional capacity and prognosis in patients with pulmonary arterial hypertension (PAH). PAH associated with systemic sclerosis (SSc-PAH) has a substantially worse prognosis as compared to idiopathic PAH (IPAH), even though many measures of resting RV function and pulmonary vascular load are similar. We therefore tested the hypothesis that RV functional reserve is depressed in SSc-PAH patients. Methods and Results RV pressure-volume relations were prospectively measured in IPAH (n=9) and SSc-PAH (n=15) patients at rest and during incremental atrial pacing or supine bicycle ergometry. Systolic and lusitropic function increased at faster heart rates in IPAH patients, but were markedly blunted in SSc-PAH. The recirculation fraction, which indexes intracellular calcium recycling, was also depressed in SSc-PAH (0.32±0.05 versus 0.50±0.05; p=0.039). At matched exercise (25 Watts), SSc-PAH patients failed to augment contractility (end-systolic elastance) whereas IPAH did (p<0.001). RV afterload assessed by effective arterial elastance rose similarly in both groups; thus, ventricular-vascular coupling declined in SSc-PAH. Both end-systolic and end-diastolic RV volumes increased in SSc-PAH patients to offset contractile deficits, whereas chamber dilation was absent in IPAH (+37±10% versus +1±8%, p=0.004, and +19±4% versus −1±6%, p<0.001, respectively). Exercise-associated RV dilation also strongly correlated with resting ventricular-vascular coupling in a larger cohort. Conclusions RV contractile reserve is depressed in SSc-PAH versus IPAH subjects, associated with reduced calcium recycling. During exercise, this results in ventricular-pulmonary vascular uncoupling and acute RV dilation. RV dilation during exercise can predict adverse ventricular-vascular coupling in PAH patients.