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Abstract
Background and Goals: Pulmonary hypertension (PH) is common in patients with interstitial lung disease (ILD), and is associated with increased short-term mortality. We hypothesise that in advanced ILD, short-term mortality is related to the severity of pulmonary vascular disease, rather than the severity of pulmonary fibrosis, or the underlying ILD diagnosis. We suggest that markers of established pulmonary vascular disease are associated with short-term mortality, whereas markers of early pulmonary vascular disease are linked to longer-term mortality. This thesis is concerned with the relationship between markers of pulmonary vascular disease to early and overall mortality across the ILD population. A secondary goal of this thesis is to explore the relationship between invasive and non-invasive markers of pulmonary vascular disease.
Results: Early mortality was strongly associated with increased pulmonary vascular resistance (PVR), as measured on right heart catheter, independent of the ILD severity, or specific ILD diagnosis. Early mortality was also linked to non-invasive markers including: right ventricular (RV) dilatation, six-month decline in KCO, six-minute walk test (6MWT) oxygen desaturation, and impaired cardiac index (CI, InnocorTM).
Longer-term mortality was strongly linked to elevated brain natriuretic peptide (BNP) levels, maximal exercise dead space/tidal volume ratio (VD/VT), nocturnal desaturation index (DI), and maximal exercise oxygen desaturation, and moderate-severe PH on echocardiography. Longer-term mortality was also associated with increased PVR, RV dilatation, six-month decline in KCO and the diagnosis of idiopathic pulmonary fibrosis.
PH on echocardiography was associated with: increased BNP levels, maximal exercise VD/VT, maximal exercise and 6MWT oxygen desaturation and increased nocturnal DI. Six-month decline in KCO strongly predicted the development of PH at follow-up. However, no non-invasive variable was able to identify PH at RHC
Conclusions: Pulmonary vascular disease is closely related to mortality across the ILD population. Markers of established pulmonary vascular disease (including elevated PVR, right ventricular dilatation, reduced CI and 6MWT oxygen desaturation) are associated with increased short-term mortality. In contrast, markers of earlier pulmonary vascular disease (including elevated BNP, increased maximal exercise VD/VT, maximal exercise oxygen desaturation and increased nocturnal DI) are linked to longer-term mortality. These findings directly impact the prognostic assessment of ILD patients.