MDCT Pulmonary Angiography Assessment of Severity of Acute Pulmonary Embolism: Pulmonary Artery Obstruction Index Compared With Right Ventricle to Left Ventricular Diameter Ratio

Abstract

AIMS AND OBJECTIVES To investigate the relation between pulmonary artery obstruction index (PAOI) and right ventricle to left ventricle diameter ratio in patients with acute pulmonary embolism. MATERIALS AND METHODS The study population comprised of patients with definite diagnosis of pulmonary thromboembolism based on their CTPA. PAOI was calculated from the size of embolus and the location of thrombus on CT images according to a study by Qanadli et al and compared with the right to left ventricular diameter ratio. Quantitative variables were expressed in terms of mean, standard deviation with confidence interval of 95%. PAOI was compared with RV/LV ratio using Spearman correlation test, p<0.005 was considered statically significant. RESULTS Total of 32 patients with pulmonary embolism, mean PAOI was 38.9 ± 17.7%. The mean RV/LV ratio was 1.14 ± 0.37; twenty two patients (69%) had an RV/LV ratio of more than 1; ten patients (31%) had an RV/LV ratio of less than 1. There was a statistically significant correlation between PAOI and RV/LV ratio (p < 0.0001; rho=0.75). The mean PAOI of patients with RV/LV ratio >1 was significantly higher than that of patients with RV/LV ratio <1 (46.2% vs. 18.0%; p < 0.0001). CONCLUSION Quantification of a clot at CTPA is an important predictor of right heart failure and determines patient's outcome in the setting of pulmonary thromboembolism.