[The role of CT pulmonary angiography in the diagnosis and prognosis of pulmonary embolism and correlation with blood gas values].

OBJECTIVE: To analyze the value of CT pulmonary angiography (CTPA) in assessing the severity of pulmonary embolism (PE), and to investigate the correlations of the parameters from CTPA with blood gas values. METHODS: Forty-four PE patients were classified into 19 critical and 25 non-critical patients, and 37 subjects without PE were defined as control group. Right ventricular (RV) and left ventricular (LV) maximal short axis, RV to LV (RV/LV), superior vena cava and pulmonary artery diameter, obstruction index, leftward bowing of interventricular septum, reflux of contrast medium into inferior vena cava were compared among the 3 groups. The correlations of these parameters with blood gas values were investigated. RESULTS: There were significant differences in RV, LV, RV/LV, superior vena cava and pulmonary artery diameter, leftward bowing of interventricular septum, reflux of contrast medium into inferior vena cava when compared among 3 groups (P < 0.05). However, significant differences were detected in RV, LV and RV/LV between critical [(53 ± 8) mm, (35 ± 6) mm, 1.56 ± 0.50] and non-critical group [(45 ± 7) mm, (43 ± 9) mm, 1.09 ± 0.31] (RV: t = 3.44, P < 0.05; LV: t = 3.08, P < 0.05; RV/LV: t = 4.62, P < 0.05), critical group and group without PE [(40 ± 7) mm, (43 ± 9) mm, 0.96 ± 0.23] (RV: t = 5.76, P < 0.05; LV: t = 3.40, P < 0.05; RV/LV: t = 6.33, P < 0.05). Superior vena cava diameter and pulmonary artery diameter were significantly different between critical group [(24 ± 4) mm, (33 ± 4) mm] and group without PE [(21 ± 4) mm, (29 ± 4) mm] (t = 2.80, P < 0.05; t = 3.98, P < 0.05). Pulmonary artery diameter in non-critical group (31 ± 5) mm was significantly different from group without PE (t = 2.59, P = 0.03). Reflux of contrast medium into inferior vena cava showed significant difference between critical group and group without PE (χ(2) = 5.54, P = 0.02). There was significant difference in obstruction index between critical (76 ± 24)% and non-critical group (52 ± 34)% (t = -2.75, P = 0.01). Obstruction index and RV/LV were negatively correlated with PaO(2) (r = -0.525, -0.502), while positively correlated with P((A-a))O(2) (r = 0.753, 0.630). Blood gas values differed significantly between above and below the 60%, 70% and 80% cutoff values of obstruction index. CONCLUSION: Superior vena cava and pulmonary artery diameter, reflux of contrast medium into inferior vena cava can be used as indirect evidence in the diagnosis of PE, while obstruction index, RV, LV, RV/LV and leftward bowing of interventricular septum can be applied as indicators of severity of PE. The severity of the obstruction index and RV/LV assessed using CTPA are significantly correlated to the blood gas values.