Complex Pathophysiology of Pulmonary Hypertension Associated with Systemic Sclerosis: Potential Unfavorable Effects of Vasodilators

The multifaceted problem of pulmonary arterial hypertension in systemic sclerosis

Cardiopulmonary complications are a leading cause of death in systemic sclerosis. Pulmonary hypertension in particular carries a high mortality and morbidity burden. Patients with systemic sclerosis can suffer from all of the clinical groups of pulmonary hypertension, particularly pulmonary arterial hypertension and pulmonary hypertension related to interstitial lung disease. Despite a similar pathogenetic background with idiopathic pulmonary arterial hypertension, different mechanisms determine a worse prognostic outcome for patients with systemic sclerosis. In this Viewpoint, we will consider the link between pathogenetic and potential therapeutic targets for the treatment of pulmonary hypertension in the context of systemic sclerosis, with a focus on the current unmet needs, such as the importance of early screening and detection, the absence of agreed criteria to distinguish pulmonary arterial hypertension with interstitial lung disease from pulmonary hypertension due to lung fibrosis, and the need for a holistic treatment approach to target all the vascular, immunological, and inflammatory components of the disease.

Two patients with mixed connective tissue disease complicated by pulmonary arterial hypertension showing contrasting responses to pulmonary vasodilators

Mixed connective tissue disease (MCTD) involves various clinical manifestations, and pulmonary hypertension (PH) is an important organ dysfunction defining the prognosis of MCTD. The pathology of PH is heterogeneous. Here, we present 2 cases of MCTD complicated by PH that had contrasting clinical courses. The first case involved a 54-year-old woman with Raynaud's phenomenon and dyspnoea on exertion. She was diagnosed with MCTD accompanied by pulmonary arterial hypertension (PAH) and was treated with ambrisentan and tadalafil in addition to high-dose glucocorticoid (GC) therapy and rituximab therapy. After treatment, her PH resolved. The second case involved a 64-year-old woman with Raynaud's phenomenon and dyspnoea on exertion. She was similarly diagnosed with MCTD accompanied by PAH and was treated with ambrisentan and tadalafil in addition to high-dose GC therapy and cyclophosphamide pulse therapy. However, she showed exacerbation of her respiratory condition and manifestation of pulmonary veno-occlusive disease (PVOD). Thus, the treatment was discontinued, and subsequently, her condition improved and eventually returned to that before treatment. The findings suggest that the presence or absence of latent PVOD might be an important factor for predicting the therapeutic responsiveness of MCTD-associated PH. Evaluation of chest radiography findings, computed tomography findings, percent vital capacity, and percent carbon monoxide diffusion capacity might be useful for predicting prognosis and might aid in treatment. PVOD could be underlying in patients with CTD-PH. When the complication of PVOD is suggested by chest CT or pulmonary function test, we need a careful introduction with pulmonary vasodilators. So, combination therapy of pulmonary vasodilators should not be applied in all patients with CTD-PH since underlying PVOD could deteriorate the patient's condition.

Initial combination therapy of ambrisentan and tadalafil in connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) in the modified intention-to-treat population of the AMBITION study: post hoc analysis

OBJECTIVES

To evaluate initial combination therapy with ambrisentan plus tadalafil (COMB) compared with monotherapy of either agent (MONO), and the utility of baseline characteristics and risk stratification in predicting outcomes, in patients with connective tissue disease-associated pulmonary arterial hypertension (CTD-PAH) and the systemic sclerosis (SSc)-pulmonary arterial hypertension (PAH) subpopulation.

METHODS

This post hoc analysis of the Ambrisentan and Tadalafil in Patients with Pulmonary Arterial Hypertension (AMBITION) study included patients with CTD-PAH from the modified intention-to-treat population. Time to clinical failure (TtCF) was assessed by baseline characteristics, treatment assignment and risk group (low, intermediate and high) at baseline and week 16. TtCF was compared between groups using Kaplan-Meier curves and Cox proportional hazards regression modelling.

RESULTS

The analysis included 216 patients (COMB, n=117; MONO, n=99). The risk of clinical failure was lower with COMB versus MONO (risk reduction: CTD-PAH 51.7%, SSc-PAH 53.7%), particularly in patients with haemodynamic parameters characteristic of typical PAH without features of left heart disease and/or restrictive lung disease at baseline. The risk of clinical failure was lower with COMB versus MONO in the baseline low-risk group (HR not calculated due to no events in COMB), baseline intermediate-risk group (HR 0.519, 95% CI 0.297 to 0.905) and in the week 16 low-risk group (HR 0.069, 95% CI 0.009 to 0.548).

CONCLUSIONS

The benefit of COMB over MONO was demonstrated in patients with CTD-PAH, particularly in those with typical PAH haemodynamic characteristics at baseline. COMB is appropriate for patients categorised as low risk and intermediate risk at baseline and low risk at follow-up.

TRIAL REGISTRATION NUMBER

NCT01178073.

Early treatment with ambrisentan of mildly elevated mean pulmonary arterial pressure associated with systemic sclerosis: a randomized, controlled, double-blind, parallel group study (EDITA study)

Objective

The objective of this randomized, placebo-controlled, double-blind, parallel group, trial was to assess the effect of ambrisentan on mean pulmonary arterial pressure (mPAP) in patients with systemic sclerosis (SSc) and mildly elevated pulmonary hypertension (PH).

Methods

Thirty-eight SSc patients with mildly elevated mPAP at rest between 21 and 24 mmHg and/or > 30 mmHg during low-dose exercise were randomly assigned to treatment with either ambrisentan 5–10 mg/day or placebo. Right heart catheterization and further clinical parameters were assessed at baseline and after 6 months. The primary endpoint was the difference of mPAP change at rest between groups.

Results

After 6 months, the two groups did not differ in the primary endpoint (ambrisentan mPAP − 1 ± 6.4 mmHg vs. placebo − 0.73 ± 3.59 mmHg at rest, p = 0.884). However, three patients from the placebo group but none of the ambrisentan group progressed to SSc-associated pulmonary arterial hypertension. Furthermore, ambrisentan treatment showed significant improvements in the secondary endpoints cardiac index (CI) and pulmonary vascular resistance (PVR) at rest (CI 0.36 ± 0.66 l/min/m² vs. − 0.31 ± 0.71 l/min/m², p = 0.010; PVR − 0.70 ± 0.78 WU vs. 0.01 ± 0.71 WU, p = 0.012) and during exercise (CI 0.7 ± 0.81 l/min/m² vs. − 0.45 ± 1.36 l/min/m², p = 0.015; PVR − 0.84 ± 0.48 WU vs. − 0.0032 ± 0.34 WU, p < 0.0001).

Conclusion

This is the first randomized, double-blind, placebo-controlled study testing the effect of ambrisentan in patients with mildly elevated mPAP and/or exercise PH. The primary endpoint change in mPAP did only tendentially improve in the ambrisentan group, but the significant improvement of other hemodynamic parameters points to a possible benefit of ambrisentan and will be helpful to design future trials.

Trial registration

www.ClinicalTrials.gov, unique identifier NCT: NCT02290613, registered 14^th of November 2014.