The prognosis of acute pulmonary embolism (PE) is highly variable [1, 2], and various clinical and radiological parameters have been evaluated to help physicians to risk stratify patients with acute PE [3–5]. Given that computed tomography pulmonary angiography (CTPA) has become the method of choice for diagnosing acute PE, risk stratification based on initial imaging would combine diagnosis and prognostic assessment into a single test. To assess short-term prognosis in patients with PE, several CTPA findings have been evaluated for their predictive value [6–9]. The best-validated scoring system taking into account the embolic burden assessed by CTPA is the computed tomography obstruction index (CTOI) . The CTOI is calculated by adding the number of occluded segmental arteries after assigning a weighting factor depending on the degree of obstruction to each occluded artery . Several studies evaluated the score for its prognostic ability with controversial results [11–16]. Most validation studies were limited by retrospective or single-center design [11–13], or small sample size [14, 15].