Pulmonary hypertension (PH) has been linked to worse outcomes in chronic lung diseases. The presence of PH in the setting of underlying Interstitial Lung Disease (ILD) is strongly associated with decreased exercise and functional capacity, an increased risk of hospitalizations and death. Examining the scope of this issue and its impact on patients is the first step in trying to define a roadmap to facilitate and encourage future research in this area. The aim of our working group is to strengthen the communities understanding of PH due to lung diseases and to improve the care and quality of life of affected patients. This introductory statement provides a broad overview and lays the foundation for further in‐depth papers on specific topics pertaining to PH‐ILD.

The adaptation of right ventricular (RV) systolic function to afterload is a major determinant of outcome in pulmonary hypertension (PH) [1]. The gold standard measurement of RV-pulmonary arterial (PA) coupling is the ratio of end-systolic to arterial elastances (Ees/Ea) which is optimal for RV flow output at minimal energy cost at values between 1.5 and 2 [2]. Progressive RV-PA uncoupling is associated with maintained RV dimensions down to Ees/Ea values of around 0.8 [3]. Thus, the evaluation of RV-PA coupling would theoretically allow monitoring of the transition from compensated to decompensated RV function in PH. However, measuring RV-PA coupling at the bedside is technically demanding and invasive. Therefore, simpler imaging surrogates are being evaluated. One of those is the ratio of tricuspid annular plane systolic excursion (TAPSE) as a surrogate of contractility and systolic pulmonary artery pressure (PASP) as a surrogate of afterload, both measured using echocardiography (M-mode for TAPSE and Doppler assessment of the maximum velocity of tricuspid regurgitation for PASP) [4]. The TAPSE/PASP ratio has emerged as a potent predictor of outcome in heart failure [5] as well as in pulmonary arterial hypertension (PAH) [6].

Pulmonary hypertension (PH) is characterized by severe exercise limitation mainly attributed to the impairment of right ventricular function resulting from a concomitant elevation of pulmonary vascular resistance and pressure. The unquestioned cornerstone in the management of patients with pulmonary arterial hypertension (PAH) is specific vasoactive medical therapy to improve pulmonary hemodynamics and strengthen right ventricular function. Nevertheless, evidence for a beneficial effect of exercise training (ET) on pulmonary hemodynamics and functional capacity in patients with PH has been growing during the past decade. Beneficial effects of ET on regulating factors, inflammation, and metabolism have also been described. Small case‐control studies and randomized clinical trials in larger populations of patients with PH demonstrated substantial improvements in functional capacity after ET. These findings were accompanied by several studies that suggested an effect of ET on inflammation, although a direct link between this effect and the therapeutic benefit of ET in PH has not yet been demonstrated. On this background, the aim of the present review is to describe current concepts regarding the effects of exercise on the pulmonary circulation and pathophysiological limitations, as well as the clinical and mechanistic effects of exercise in patients with PH.

We have read with interest the article from Unlu and co-workers exploring right ventricular (RV) mechanics using the ratio between RV strain and systolic pulmonary artery pressure (PASP) as a surrogate of RV to pulmonary arterial (PA) coupling.¹ The gold-standard measure of RV-PA coupling is the ratio of RV contractility [end-systolic elastance (Ees)] to its load [arterial elastance (Ea)], obtained by conductance catheterization.² Recently, the ratio of tricuspidal annular plane excursion (TAPSE) to PASP was validated as a non-invasive surrogate³ and has proved its prognostic relevance.⁴ However, this index is not without limitation and especially TAPSE is influenced by various condition and might not be the most robust or sensitive parameter to reflect RV contractility. The idea of Unlo and co-workers to replace TAPSE with a more sensitive echocardiographic parameter, such as RV free-wall longitudinal strain (FWLS), appears plausible, since the ratio of RV strain/PASP might also represent the length/force relationship and overcome certain limitations. However, the relationship of RV strain/PASP has not yet been validated. It is debatable whether proposed surrogates should be presented as measures of RV-PA coupling without any validation against the gold standard. Therefore, we think that it is of crucial importance to validate the proposed method and to assess its relation to gold standard method.