Original Article Hypoxia as an independent predictor of adverse outcomes in pulmonary embolism Muthiah Subramanian, Srinivasan Ramadurai, Preetam Arthur and Sowmya Gopalan Abstract Background: The purpose of this study was to investigate the correlation between the computed tomography pul- monary artery obstruction index and parameters of functional lung impairment in acute pulmonary embolism, and establish the value of these parameters in prognosticating right ventricular dysfunction and 30-day mortality. Methods: This study included 322 consecutive patients (mean age 45.6  13.2 years, 46.9% male) with acute pulmonary embolism, free of other cardiopulmonary disease, who underwent computed tomography pulmonary angiography. Correlations of arterial CO 2 ,O 2 , and alveolar-arterial oxygen gradient with the computed tomography pulmonary artery obstruction index, measured using the Qanadli score, were analyzed. Logistic regression was used to identify independent predictors of right ventricular dysfunction and 30-day mortality. Results: Of the 322 patients, 196 (60.9%) had right ventricular dysfunction, and 58 (18.0%) died within 30 days. The pulmonary artery obstruction index had a significant correlation with partial pressures of arterial O 2 (r ¼0.887, p < 0.001) and CO 2 (r ¼0.618, p ¼ 0.019) and alveolar-arterial oxygen gradient (r ¼þ0.874, p < 0.001). Arterial O 2 pressure had a good predictive accuracy and discriminative power for both right ventricular dysfunction (sensitivity 80.6%, specificity 85.1%, area under the curve 0.91) and 30-day mortality (sensitivity 77.8%, specificity 82.0%, area under the curve 0.89). Conclusions: In patients with acute pulmonary embolism, free of other cardiopulmonary disease, parameters of func- tional impairment have a strong correlation with computed tomography pulmonary artery obstruction index. Hypoxia is an independent predictor of both right ventricular dysfunction and 30-day mortality in these patients. Keywords Blood gas analysis, Computed tomography angiography, Hypoxia, Pulmonary embolism, Ventricular dysfunction, right Introduction Reliable identification of the factors determining prog- nosis in patients with acute pulmonary embolism (PE) would be extremely valuable in choosing between ambulatory and in-hospital management. Acute PE impairs the efficient transfer of oxygen and carbon dioxide across the lung; hypoxemia, determined by par- tial pressure of oxygen (PaO 2 ), and an increase in the alveolar-arterial oxygen tension gradient are the most common gas exchange abnormalities. 1 Clot burden assessment by computed tomography (CT) pulmonary angiography (CTPA) has been suggested as a predictor of right ventricular (RV) dysfunction and short-term mortality, enabling more-accurate risk stratification in patients with acute PE. 2–4 Previous studies have sug- gested that in patients with acute PE (without other underlying cardiopulmonary disease), the severity of the pulmonary artery obstruction index (PAOI) correl- ates significantly with blood gas values. 5 Simple Asian Cardiovascular & Thoracic Annals 0(0) 1–6 ß The Author(s) 2017 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492317746252 journals.sagepub.com/home/aan Department of General Medicine, Sri Ramachandra University, Porur, Chennai, India Corresponding author: Muthiah Subramanian, Amrita Institute of Medical Sciences, Ponekkara, Kochi, Kerala 682041, India. Email: muthiah727@yahoo.com