CT Pulmonary Angiography for Risk Stratification of Patients with Nonmassive Acute Pulmonary Embolism

Purpose: To investigate the prognostic value of an integrative approach combining clinical variables and the Qanadli CT obstruction index (CTOI) in patients with nonmassive acute pulmonary embolism (PE). Materials and Methods: This retrospective study included 705 consecutive patients (mean age, 63 years; range, 18-95 years) with proven PE. Clot burden was quantified using the CTOI, which reflects the ratio of fully or partially obstructed pulmonary arteries to normal arteries. Patients were subdivided into two groups according to the presence (group A) or absence (group B) of preexisting cardiopulmonary disease. Thirty-day and 3-month mortality was evaluated. CTOI thresholds of 20% and 40% were used to stratify patients regarding outcome (low, intermediate, and high risk). The predictive value of CTOI was assessed through logistic regression analysis. Results: Analysis included 690 patients (mean age, 63.3 years +/- 18 [standard deviation]) with complete follow-up data: 247 (36%) in group A and 443 (64%) in group B. The mean CTOI was 23% +/- 19, 30-day mortality was 9.7%, and 3-month mortality was 11.6%. Three-month mortality was higher in group A than in group B (17.8% and 8.1%, respectively; P = .001). Within group B, CTOI predicted outcome and allowed stratification: significantly higher mortality with CTOI greater than 40% (P < .001) and lower mortality with CTOI less than 20% (P = .05). CTOI did not predict outcome in group A. Age was an independent mortality risk factor (P = .04). Conclusion: CTOI predicted outcome in this cohort of patients with PE and no cardiopulmonary disease, and it may provide a simple single-examinationbased approach for risk stratification in this subset of patients. (c) RSNA, 2020 Summary: In patients with pulmonary embolism but without concomitant cardiopulmonary disease, the CT obstruction index can identify low-risk patients who may benefit from outpatient treatment as well as high-risk patients who may need more aggressive therapy.