Risk stratification in submassive pulmonary embolism via alveolar-arterial oxygen gradient

This study investigated the utility of the alveolar-arterial (AaDO2) gradient in predicting the short-term prognosis of submassive pulmonary embolism (PE).

This study retrospectively enrolled 124 patients with acute submassive PE. During the first 24 h of admission, all patients had initial artery blood gas collected under room air. Cardiac troponin T (cTn-T) was measured and on spiral computed tomography pulmonary angiography (CTPA) and echocardiography both right ventricle diameter and left ventricle diameter was calculated (RV/LV ratio). Patients who did not have objectively confirmed submassive PE and who had curative anticoagulant treatment for more than 24 hours and had a life expectancy less than 3 months were excluded from the study.

The best cut-off value for AaDO2 was 42.38 mmHg and using this, fourteen of 15 patients who died had AaO2 ≥ 42.38 and 71 of 109 patients who survived had a AaO2 lower than 42.38 with a sensitivity, specificity and negative predictive value (NPV) for overall deaths were 93.3%, 65.1% and 98.6% respectively. In addition, AaDO2 < 42.38 showed significant survival benefit for overall mortality rates. In this study, having high cTn-T and PaO2/ PaCO2 < 1.83 and pulmonary artery pressure > 47.5 were also an indicator of poor prognosis for patients with submasssive PE.

The AaDO2 measurement is a highly useful and simple measurement for predicting short-term prognosis in patients with submassive PE. It may be used in risk stratification of patients with submassive PE. Aggressive thrombolytic treatment strategies may be considered for patients who have AaO2 < 42.38. Hippokratia 2014; 18 (4): 333-339.