Rationale: Pulmonary hypertension (PH) is associated with a poor prognosis in diffuse lung disease (DLD). We compare the prognostic significance of invasive and non-invasive parameters in patients with DLD and suspected PH.
Methods: Hospital records of consecutive DLD patients undergoing right heart catheterisation (RHC) were reviewed (n=66). Mean pulmonary artery pressure (mPAP), pulmonary vascular resistance (PVR) and non-invasive variables were examined against early (within 12months) and overall mortality. A priori thresholds were examined against early mortality. Relationships between mPAP, PVR and non-invasive markers were assessed.
Results: Fifty patients had PH on RHC (mean ± SD; mPAP 33.5±11.8mmHg; PVR 5.9±4.3 Wood units (WU)). Elevated PVR was strongly associated with early mortality (Odds ratio (OR) 1.30; 95% Confidence Interval (CI) 1.11, 1.52; p=0.001), with PVR ≥6.23 WU being the optimal threshold after adjustment for age, gender, composite physiologic index (CPI) and diagnosis of idiopathic pulmonary fibrosis (OR 11.09; CI 2.54, 48.36; p=0.001). Early mortality was linked, albeit less strongly, to right ventricular dilation at echocardiography, but not to other non-invasive variables or mPAP. Overall mortality was most strongly associated with increasing CPI levels. Correlations between PVR and non-invasive variables were moderate (R2<0.32), improving little following construction of a multivariate index, which did not itself, predict mortality.
Conclusion: In severe DLD, early mortality is strongly linked to increased PVR , but not to other RHC or non-invasive variables. These findings suggest that the threshold for RHC in severe DLD should be low, enabling prioritisation of aggressive therapy, including lung transplantation.