Pulmonary Vascular and Right Ventricular Burden During Exercise in Interstitial Lung Disease

BACKGROUND: Pulmonary hypertension (PH) adversely affects patient’s exercise capacity in interstitial lung disease (ILD). The impact of pulmonary vascular and right ventricular (RV) dysfunction, however, has traditionally been believed to be mild and clinically relevant principally in advanced lung disease states. RESEARCH QUESTION: The aim of this study was to evaluate the relative contributions of pulmonary mechanics, pulmonary vascular function, and RV function to the ILD exercise limit. STUDY DESIGN AND METHODS: Forty-nine patients with ILD who underwent resting right heart catheterization followed by invasive exercise testing were evaluated. Patients with PH at rest (ILD + rPH) and with PH diagnosed exclusively during exercise (ILD + ePH) were contrasted with ILD patients without PH (ILD non-PH). RESULTS: Peak oxygen consumption was reduced in ILD + rPH (61 ± 10% predicted) and ILD + ePH (67 ± 13% predicted) compared with ILD non-PH (81 ± 16% predicted; P < .001 and P = .016, respectively). Each ILD hemodynamic phenotype presented distinct patterns of dynamic changes of pulmonary vascular compliance relative to pulmonary vascular resistance from rest to peak exercise. Peak RV stroke work index was increased in ILD + ePH (24.7 ± 8.2 g/m(2) per beat) and ILD + rPH (30.9 ± 6.1 g/m(2) per beat) compared with ILD non-PH (18.3 ± 6.4 g/m(2) per beat; P = .020 and P = .014). Ventilatory reserve was reduced in ILD + rPH compared with the other groups at the anaerobic threshold, but it was similar between ILD + ePH and ILD non-PH at the anaerobic threshold (0.32 ± 0.13 vs 0.30 ± 0.11; P = .921) and at peak exercise (0.70 ± 0.17 vs 0.73 ± 0.24; P = .872). INTERPRETATION: ILD with resting and exercise PH is associated with increased exercise RV work, reduced pulmonary vascular reserve, and reduced peak oxygen consumption. The findings highlight the role of pulmonary vascular and RV burden to ILD exercise limit.