Clinical significance of lung cross‐sectional area measured by computed tomography in chronic thromboembolic pulmonary hypertension: The correlation with pulmonary hemodynamics and the limitations

The percentage cross‐sectional area of the lung under five (%CSA(<5)) is the percentage of pulmonary vessels with <5 mm(2) area relative to the total lung area on computed tomography (CT). The extent that %CSA(<5) is related to pulmonary hemodynamics in patients with chronic thromboembolic pulmonary hypertension (CTEPH) is unclear, as is the effect of pulmonary endarterectomy (PEA) on %CSA(<5). Therefore, we aimed to evaluate the clinical significance of %CSA(<5) in patients with CTEPH. We studied 98 patients (64 females, mean age 62.5 ± 11.9 years), who underwent CT with %CSA(<5) measurement and right heart catheterization (RHC). Patients were classified into groups based on eligibility for PEA. We compared the %CSA(<5) with pulmonary hemodynamics measured by RHC in various groups. In 38 patients who underwent PEA, the relationship between %CSA(<5) and pulmonary hemodynamics was also evaluated before and after PEA. Significant correlations between %CSA(<5) and pulmonary vascular resistance, and compliance, and pulmonary artery pulse pressure were observed in all patients. Pulmonary hemodynamics in the patients who underwent or were eligible for PEA showed a significant correlation with %CSA(<5). Additionally, %CSA(<5) was significantly lower in the postoperative than in the preoperative group. There was no correlation between changes in %CSA(<5) and pulmonary hemodynamics before and after PEA. Furthermore, %CSA(<5) did not correlate significantly with prognosis. %CSA(<5) may reflect pulmonary hemodynamics in CTEPH with central thrombosis. Furthermore, %CSA(<5) was reduced by PEA postoperatively. However, %CSA(<5) is not a prognostic indicator, its clinical usefulness in CTEPH patients is limited, and further validation is required.