Abstract 13796: Quantitative Measurement of Cross sectional Area of Small Pulmonary Vessels Using High-resolution Ct in Chronic Thromboembolic Pulmonary Hypertension

Background: It is generally recognized that there is narrowing and diminution of the small vessels on pulmonary angiography in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Previous studies have shown that these vascular alterations could be assessed by the cross-sectional area of small pulmonary vessels (CSA) on high-resolution CT (HRCT) in patients with COPD. However, it is unknown whether there is a correlation between CSA and hemodynamics in patients with CTEPH. Aims: We retrospectively evaluated the relationship between the CSA on HRCT and hemodynamics measured by right heart catheterization (RHC). Materials and Methods: 61 patients (61±12 yrs, 13 male) with proven CTEPH underwent non-enhanced 64-slice HRCT (Aquilion ONE, Toshiba) and RHC. The HRCT images with 0.5 mm section thickness and 10 mm spacing were selected from all of the CT images in each patient. Using a semiautomatic image-processing program (Image J), CSA less than 5mm2 and 5-10mm2 , and total lung area were measured, and the percentage of the total CSA less than 5mm2 and 5-10mm2 for the lung area (%CSA<5 and %CSA5-10, respectively) were calculated. The correlations of %CSA with hemodynamics measured by RHC were evaluated. Results: Mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR) from RHC were 41±9 mmHg and 8.3±3.0 Wood Units, respectively. %CSA<5 and %CSA5-10 were 1.095±0.166% and 0.447±0.093 %, respectively. The correlation coefficients of %CSA<5 with mPAP and PVR were -0.45 (P<0.001) and -0.64 (P<0.001), respectively. The correlation coefficients of %CSA5-10 with mPAP and PVR were -0.20 (P=0.1) and -0.38 (P=0.002), respectively. Conclusions: This study suggests that %CSA<5 measured on HRCT is inversely correlated with PVR and can be used to evaluate hemodynamics in CTEPH subjects.