Acute Low-Risk Pulmonary Embolism and Concerning CT Findings

Quick Takes

  • Concerning computed tomography (CT) findings in acute, low-risk acute pulmonary embolisms are not associated with short-term adverse clinical outcomes.
  • Concerning CT findings are associated with increased hospitalization and resource utilization in this population.

Study Questions:

Are concerning computed tomography (CT) findings among patients seen in the emergency department (ED) with acute, low-risk pulmonary embolism (PE) associated with differences in treatment received and/or clinical outcomes?


This cohort study was conducted using a registry for all acute PEs diagnosed in the ED at an academic medical center from October 2016 to December 2019. Patients with acute PE were divided into low- or high-risk groups using the PE Severity Index (PESI) score, which was abstracted from the medical records or calculated using available data. The low-risk group was further divided based on the PE protocol computed tomography (CTPE) findings as having or not concerning imaging findings if one or more were present: 1) bilateral embolus described as saddle or located in main pulmonary arteries, 2) right ventricle-to-left ventricle (RV-LV) ratio >1, 3) right ventricular (RV) enlargement, 4) septal abnormalities consistent with RV pressure overload, or 5) pulmonary infarction. The primary outcome was all-cause mortality at 7 and 30 days. Secondary outcomes included hospitalization, length of stay, need for intensive care, use of cardiac point-of-care ultrasonography (POCUS) and/or transthoracic echocardiography (TTE), and activation of the PE response team (PERT).


A total of 817 acute PEs were included in the registry with 331 (40.5%) deemed to be low risk (PESI class I or class II). Low-risk acute PE patients were a median age of 46 (34-57) years old and were predominately white (72.5%) females (54.1%). This group was further divided based on the absence (54.3%) or presence (46.7%) of one or more concerning CTPE findings.

There were no deaths at 7 days in either low-risk group, whereas 7-day mortality was 6.8% in the high-risk group. At 30 days, mortality remained low in both low-risk groups (with or without CTPE concerning findings) vs. 18.1% mortality in the high-risk group. Even low-risk acute PEs with three concerning findings of bilateral, central emboli with an RV-LV ratio >1 and septal abnormalities, had no deaths at 30 days.

There was a higher rate of outpatient treatment in low-risk patients in the absence of concerning CTPE findings versus those with concerning CTPE findings (7.8% vs. 2.0%; p = 0.01). The length of stay was similar in low-risk patients in the absence of concerning CTPE findings versus those with concerning CTPE findings (2.3 ± 1.9 vs. 2.6 ± 3.5 days; p = 0.32). Both cardiac POCUS and TTE were performed more frequently in low-risk cases with than without concerning CTPE findings: 23.2% vs. 8.3% for POCUS (p < 0.001) and 57.6% vs. 27.2% for TTE (p < 0.001). Similarly, the multidisciplinary PERT was activated in 22.5% of low-risk cases with concerning CTPE findings vs. 6.1% without (p < 0.001).


ED patients diagnosed with acute low-risk PE had similar short-term clinical outcomes irrespective of CTPE results. Nonetheless, concerning CTPE findings were associated with increased resource utilization and hospitalization of these patients.


Acute PE accounts for approximately 250,000 patient diagnoses in the ED each year. Most of these patients are hospitalized despite evidence from multiple studies and society-based guidelines recommending consideration for discharge for those patients with low-risk stratification scores. A potential barrier to outpatient management may be clinician concern about findings in CTPE that are perceived as high risk for adverse clinical outcomes but are not incorporated in commonly used risk stratification scores.

The results of the current study show that CTPE findings—including bilateral pulmonary embolus described as saddle or in main pulmonary arteries, RV dilation, septal abnormalities consistent with pressure overload and pulmonary infarctions—are not associated with increased short-term mortality; however, they are associated with increased hospitalization and resource utilization in the ED. These findings suggest not only that outpatient management may be considered for low-risk acute PE patients seen in the ED, but that concerning CTPE findings represent an important barrier to discharge.

Clinical Topics: Noninvasive Imaging, Prevention, Vascular Medicine, Computed Tomography, Echocardiography/Ultrasound, Nuclear Imaging

Keywords: Diagnostic Imaging, Echocardiography, Emergency Service, Hospital, Intensive Care, Length of Stay, Outpatients, Patient Discharge, Pulmonary Embolism, Pulmonary Infarction, Risk, Secondary Prevention, Tomography, X-Ray Computed, Ultrasonography, Vascular Diseases

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