Idiopathic pulmonary arterial hypertension and pulmonary hypertension due to chronic lung disease can be difficult to differentiate, but new research suggests descriptions of lung parenchyma in routine CT scans may prove useful.
Identifying patients with idiopathic pulmonary arterial hypertension (IPAH) versus pulmonary hypertension due to chronic lung disease and/or hypoxia (PH-CLD) can be difficult, but it is crucial in accurate prognostication and treatment decisions. A recent study found that descriptions of lung parenchyma in chest computed tomography (CT) imaging may help predict outcomes for IPAH and PH-CLD.
There are 5 classification groups of pulmonary hypertension (PH), including IPAH and PH-CLD, all of which have similar clinical and pathological manifestations. PH overall is progressive, incurable, and linked to morbidity and mortality. Patients with PH-CLD generally have mild to moderate PH, while those with IPAH typically have more severe PH. But in practice, it is not always clear-cut.
For example, based on 6th World Symposium on PH task force recommendations, patients who meet criteria for IPAH but only have minor lung disease may still be diagnosed with IPAH. And those with mild lung disease but severely abnormal pulmonary hemodynamics have been described as not part of the OPAH continuum and similar to PH-CLD instead in recent research, according to the study. The prognostic utility of parenchymal features in CT imaging was unknown at the time of the current study.
The analysis included 660 patients who met inclusion criteria out of 5643 patients diagnosed with all forms of PH between 2001 and 2019. A total of 335 in the main study cohort were diagnosed with IPAH and 325 with PH-CLD. Researchers assessed reports for all CT imaging 1 year ahead of diagnosis to identify any significant lung parenchymal patterns.
In the overall cohort, centrilobular ground-glass (CGG) changes and ground-glass opacification were associated with improved survival (hazard ratio [HR], 0.29 and 0.53, respectively). On the other hand, honeycombing, emphysema, and fibrosis predicted worse survival with HRs of 2.79, 2.09, and 2.38, respectively.
In the IPAH subgroup, patients without reported parenchymal lung disease (IPAH-noLD) had an 85% 2-year survival rate, compared with 60% in patients who had IPAH and CT lung disease and 46% in PH-CLD patients. In the IPAH-noLD cohort, patients with and without CGG changes did not have significantly different survival rates.
Independent of other factors, fibrosis was predictive of outcomes, with an HR of 1.37. In the PH-CLD subgroup, those with fibrosis had worse survival rates than patients with emphysema.
Overall, the study found that routine radiological reporting of CT scans in patients with potential IPAH or PH-CLD can have significant utility in clinical practice, especially when emphysema or fibrosis are present.
The findings are also in line with recent suggestions that there is a distinct subgroup of patients assigned a diagnosis of IPAH whose disease is phenotypically closer to PH-CLD. In the study, patients diagnosed with IPAH who had fibrosis or emphysema showed worse survival than those who did not, and the extent of emphysema or fibrosis in reports was associated with prognosis.
Further studies are needed to do more in-depth analysis, but this study presents real-world data suggesting lung features identified in clinical radiological reports can help refine diagnostic and prognostic processes for subtypes of PH that have historically been difficult to diagnose.
Dwivedi K, Condliffe R, Sharkey M, et al. Computed tomography lung parenchymal descriptions in routine radiological reporting have diagnostic and prognostic utility in patients with idiopathic pulmonary arterial hypertension and pulmonary hypertension associated with lung disease. ERJ Open Res. Published online January 24, 2022. doi:10.1183/23120541.00549-2021