The prevalence of symptomatic and coincidental pulmonary embolism on computed tomography

Detection of Incidental Pulmonary Embolism on Conventional Contrast-Enhanced Chest CT: Comparison of an Artificial Intelligence Algorithm and Clinical Reports

BACKGROUND. Artificial intelligence (AI) algorithms have shown strong performance for detection of pulmonary embolism (PE) on CT examinations performed using a dedicated protocol for PE detection. AI performance is less well studied for detecting PE on examinations ordered for reasons other than suspected PE (i.e., incidental PE [iPE]). OBJECTIVE. The purpose of this study was to assess the diagnostic performance of an AI algorithm for detection of iPE on conventional contrast-enhanced chest CT examinations. METHODS. This retrospective study included 2555 patients (mean age, 53.2 ± 14.5 [SD] years; 1340 women, 1215 men) who underwent 3003 conventional contrast-enhanced chest CT examinations (i.e., not using pulmonary CTA protocols) between September 2019 and February 2020. A commercial AI algorithm was applied to the images to detect acute iPE. A vendor-supplied natural language processing (NLP) algorithm was applied to the clinical reports to identify examinations interpreted as positive for iPE. For all examinations that were positive by the AI-based image review or by NLP-based report review, a multireader adjudication process was implemented to establish a reference standard for iPE. Images were also reviewed to identify explanations of AI misclassifications. RESULTS. On the basis of the adjudication process, the frequency of iPE was 1.3% (40/3003). AI detected four iPEs missed by clinical reports, and clinical reports detected seven iPEs missed by AI. AI, compared with clinical reports, exhibited significantly lower PPV (86.8% vs 97.3%, p = .03) and specificity (99.8% vs 100.0%, p = .045). Differences in sensitivity (82.5% vs 90.0%, p = .37) and NPV (99.8% vs 99.9%, p = .36) were not significant. For AI, neither sensitivity nor specificity varied significantly in association with age, sex, patient status, or cancer-related clinical scenario (all p > .05). Explanations of false-positives by AI included metastatic lymph nodes and pulmonary venous filling defect, and explanations of false-negatives by AI included surgically altered anatomy and small-caliber subsegmental vessels. CONCLUSION. AI had high NPV and moderate PPV for iPE detection, detecting some iPEs missed by radiologists. CLINICAL IMPACT. Potential applications of the AI tool include serving as a second reader to help detect additional iPEs or as a worklist triage tool to allow earlier iPE detection and intervention. Various explanations of AI misclassifications may provide targets for model improvement.

Pulmonary embolisms in patients with COVID-19: A prevalence study in a tertiary hospital

Introduction

Objective

Methods

Results

Conclusions

Pulmonary embolisms in patients with COVID-19: a prevalence study in a tertiary hospital

INTRODUCTION

SARS-CoV-2, the virus responsible for the current pandemic, predominantly affects the respiratory tract, and a growing number of publications report the predisposition of patients with COVID-19 to develop thrombotic phenomena.

OBJECTIVE

To determine the prevalence of pulmonary embolism in patients with COVID-19; to determine the possible relationship between the severity of pulmonary involvement and D-dimer levels; to analyze the location of pulmonary embolisms in patients with COVID-19 and to compare it with the location in patients without COVID-19.

METHODS

This retrospective study analyzed all CT angiograms of the pulmonary arteries done in patients with suspected pulmonary embolisms between March 15 and April 30, 2020 and compared them with studies done in the same period one year earlier.

RESULTS

We included 492 pulmonary CT angiograms (342 (69.9%) in patients with COVID-19 and 147 (30.1%) in patients without COVID-19). The prevalence of pulmonary embolisms was higher in patients with COVID-19 (26% vs. 16.3% in patients without COVID-19, p=0.0197; relative risk=1.6). The prevalence of pulmonary embolisms in the same period in 2019 was 13.2%, similar to that of the group of COVID-19-negative patients in 2020 (p=0.43). There were no significant differences in D-dimer levels or the location of pulmonary embolisms between the two groups. CT showed moderate or severe pulmonary involvement in 78.7% of the patients with COVID-19.

CONCLUSIONS

Patients with COVID-19 have an increased prevalence of pulmonary embolisms (26%), and most (78.7%) have moderate or severe lung involvement on CT studies. The location of pulmonary embolisms and the degree of elevation of D-dimer levels does not differ between patients with COVID-19 and those without.

Incidental venous thromboembolism: is anticoagulation indicated?

Patients with cancer have a high risk of venous thromboembolism (VTE) and about one-half of these events are incidentally detected. The prognosis of incidental VTE appears to be similar to symptomatic events, with comparably high rates of recurrent VTE in this patient population. In the absence of major contraindications, anticoagulant treatment with low-molecular-weight heparin for 3 to 6 months is generally recommended for incidental proximal deep vein thrombosis as well as for incidental pulmonary embolism that involves multiple subsegmental or more proximal pulmonary arteries. The decision of whether to extend treatment beyond 3 to 6 months should be evaluated on a case-by-case basis after periodic reassessment of the risks factors for bleeding and recurrent VTE while also taking into account patient preferences. The clinical relevance of a single incidental subsegmental pulmonary embolism without concomitant deep vein thrombosis is uncertain and either a watchful approach or a shorter course of anticoagulation to minimize the bleeding risk may also be considered. Preliminary evidence suggests that anticoagulation treatment may be beneficial for cancer patients with incidental distal deep vein thrombosis or incidental splanchnic vein thrombosis.

Management of incidental pulmonary embolism

Incidental pulmonary embolism (PE) is a frequent finding on routine computed tomography (CT) scans of the chest, occurring in 1.1% of coronary CT scans and 3.6% of oncological CT scans. Despite this high frequency, optimal management of incidental PE has not been addressed in clinical trials and remains the subject of debate. Although these CT scans have not been performed with a dedicated PE protocol and have suboptimal contrast enhancement, diagnosis of incidental PE has been shown to be accurate up to the segmental and subsegmental arteries. The embolic load in incidental PE is lower than that in symptomatic PE. Even so, observational studies suggest that the natural course of incidental PE is similar to that of symptomatic PE with regard to the risk of recurrent venous thrombotic disease and mortality. Interestingly, the increased use of more advanced CT technology has coincided with an increase in the rate of incidental subsegmental PE, as is the case for symptomatic subsegmental PE. Although clinical trials are lacking, and observational data are limited to cancer-associated incidental PE, the consensus is that the management of incidental PE is identical to that of symptomatic PE, including the choice of optimal drug class, outpatient treatment and total duration of treatment.

Frequency of Deep Vein Thrombosis and/or Pulmonary Embolism After Coronary Artery Bypass Grafting Investigation Regardless of Clinical Suspicion

Venous thromboembolism (VTE) includes deep vein thrombosis (DVT) and/or pulmonary embolism (PE). Many surgeons and clinicians believe that VTE after coronary artery bypass grafting (CABG) has little clinical significance because it is seldom diagnosed. This study aimed to identify VTE after CABG, independent of clinical suspicion. In this prospective, observational, single-center study, 100 patients underwent computed tomographic pulmonary angiography (multidetector-64) and lower extremity venous compressive ultrasound after elective CABG. Patients with high risk for VTE were excluded. Aspirin was maintained throughout the preoperative and postoperative periods, and early ambulation was encouraged. Postoperatively, no mechanical or heparin prophylaxis was used in any patients. At the discretion of the surgeons, 83 surgeries were on-pump, and 17 were off-pump. On average, tomography and ultrasound were performed 7 ± 3 days after CABG. Isolated PE was observed in 13 of 100 patients (13%), simultaneous PE and DVT in 8 of 100 (8%), and isolated DVT in 4 of 100 (4%), thus totaling 25/100 VTEs (25%). Of the 21 PEs, 3 of 21 (14%) involved subsegmental, 15 of 21 (71%) segmental, 1 of 21 (5%) lobar, and 2 of 21 (10%) central pulmonary arteries. Of the 12 DVTs, all were distal (below the popliteal vein), and 2 of 12 (17%) were also proximal; 5 of 12 (42%) were unilateral, of which 3 of 5 (60%) on the contralateral saphenous vein-harvested leg. No VTE caused hemodynamic instability, and none was clinically suspected. In conclusion, VTEs were frequent, some extensive proximal VTEs occurred, but most were distally localized. Many patients in this series would have been discharged without diagnosis of and treatment for PE and/or DVT.

Improving appropriate use of pulmonary computed tomography angiography by increasing the serum D-dimer threshold and assessing clinical probability

OBJECTIVE

To determine whether the implementation of an increased D-dimer threshold value and clinical probability assessment increases the prevalence of pulmonary embolism (PE) in patients undergoing pulmonary computed tomography angiography (PCTA) in an Emergency Department setting.

METHODS

A retrospective review of all patients undergoing PCTA during 2 separate 12-month intervals, 1 before the implementation of an increased D-dimer threshold and recommendation for formal clinical probability assessment and the other after regional implementation. The primary outcome measure was the prevalence of acute PE in each of the samples.

RESULTS

After the implementation of the increased D-dimer threshold and recommendation for formal clinical probability assessment, the prevalence of PE detected by PCTA increased from 4.7% to 11.7% (p < 0.001). Among all PCTAs performed after the new guidelines were promulgated, 8.6% were still performed on patients who had serum D-dimer values lower than the threshold of 1.0 µg/mL. Despite the recommendation for formal clinical probability assessment before ordering a PCTA, only 4% of patients had a formal clinical probability assessment recorded in their electronic medical record.

CONCLUSION

The implementation of an increased D-dimer threshold value increased the prevalence of PE in patients undergoing PCTA in an Emergency Department setting, but more consistent application of clinical probability assessment remains an elusive target.

Cancer-associated unsuspected pulmonary embolism

Clinically unsuspected pulmonary embolism (UPE) is frequently diagnosed in cancer patients undergoing routine computed tomography scans for staging purposes or treatment response evaluation. The reported incidence of UPE ranges from 1% to 5% which probably represents an underestimation. A significant proportion of cancer patients with UPE actually do have pulmonary embolism (PE) related symptoms. However, these can erroneously be attributed to the cancer itself or to cancer therapy leading to a delayed or missed diagnosis. The incidence of UPE is likely to increase further with the improvements of imaging techniques. Radiologic features of UPE appear similar to symptomatic PE with nearly half of the UPE located in central pulmonary arteries and one third involving both lungs. UPE in cancer patients is not a benign condition with rates of recurrent venous thromboembolic events, bleeding and a mortality rate comparable to cancer patients with symptomatic PE. Current guidelines suggest that UPE should receive similar initial and long-term anticoagulant treatment as for symptomatic PE. However, direct evidence regarding the treatment of UPE is scarce and treatment indications are largely derived from studies performed in cancer patients with symptomatic venous thromboembolism. Selected subgroups of cancer patients with UPE such as those with sub-segmental UPE may be treated conservatively by withholding anticoagulation and avoiding the associated bleeding risk, although this requires further evaluation.

Pulmonary embolism in oncologic patients: frequency and embolus burden of symptomatic and unsuspected events

BACKGROUND

Pulmonary embolism (PE) is a common cause of morbidity and mortality in oncologic patients. Furthermore, PE is an unsuspected finding in many cases.

PURPOSE

To determine the frequency and embolus burden of PE in a consecutive oncologic patient group including symptomatic as well as incidental and initially unreported events.

MATERIAL AND METHODS

In a retrospective, single-center study from June 2005 to January 2010 all patients with an oncologic disease (ICD-10 code C00 to C96) that received at least one contrast-enhanced computed tomography (CT) examination of the chest were reviewed. The study group included 3270 patients with 6780 examinations. A validated pulmonary artery obstruction index (Mastora score) was used to assess embolus burden.

RESULTS

PE was found in 240 of 3270 (7.3%) oncologic patients. The frequency was highly variable among different malignancies ranging from 0% to 25%. In the present study about half of all PE were unsuspected. The mean embolus burden was significantly higher in symptomatic PE than in unsuspected PE (P <0.001). The risk of developing a PE was 1.5 times higher in patients with metastases compared to patients without metastases (P <0.005). Age and sex had no influence on PE risk and embolus burden.

CONCLUSION

PE is a frequent unsuspected finding in staging examinations: particularly in patients with malignancies of the ovary, brain, and pancreas, and in patients with metastases. Therefore, the status of the pulmonary vasculature should be assessed in every staging examination that includes the chest. The effect of therapeutic actions on PE events and the unsuspected finding of PE in follow-up CT examinations require further prospective studies.

Management dilemmas in acute pulmonary embolism

Background

Physicians treating acute pulmonary embolism (PE) are faced with difficult management decisions while specific guidance from recent guidelines may be absent.

Methods

Fourteen clinical dilemmas were identified by physicians and haematologists with specific interests in acute and chronic PE. Current evidence was reviewed and a practical approach suggested.

Results

Management dilemmas discussed include: sub-massive PE, PE following recent stroke or surgery, thrombolysis dosing and use in cardiac arrest, surgical or catheter-based therapy, failure to respond to initial thrombolysis, PE in pregnancy, right atrial thrombus, role of caval filter insertion, incidental and sub-segmental PE, differentiating acute from chronic PE, early discharge and novel oral anticoagulants.

Conclusion

The suggested approaches are based on a review of the available evidence and guidelines and on our clinical experience. Management in an individual patient requires clinical assessment of risks and benefits and also depends on local availability of therapeutic interventions.

Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

This article addresses the treatment of VTE disease.

METHODS

We generated strong (Grade 1) and weak (Grade 2) recommendations based on high-quality (Grade A), moderate-quality (Grade B), and low-quality (Grade C) evidence.

RESULTS

For acute DVT or pulmonary embolism (PE), we recommend initial parenteral anticoagulant therapy (Grade 1B) or anticoagulation with rivaroxaban. We suggest low-molecular-weight heparin (LMWH) or fondaparinux over IV unfractionated heparin (Grade 2C) or subcutaneous unfractionated heparin (Grade 2B). We suggest thrombolytic therapy for PE with hypotension (Grade 2C). For proximal DVT or PE, we recommend treatment of 3 months over shorter periods (Grade 1B). For a first proximal DVT or PE that is provoked by surgery or by a nonsurgical transient risk factor, we recommend 3 months of therapy (Grade 1B; Grade 2B if provoked by a nonsurgical risk factor and low or moderate bleeding risk); that is unprovoked, we suggest extended therapy if bleeding risk is low or moderate (Grade 2B) and recommend 3 months of therapy if bleeding risk is high (Grade 1B); and that is associated with active cancer, we recommend extended therapy (Grade 1B; Grade 2B if high bleeding risk) and suggest LMWH over vitamin K antagonists (Grade 2B). We suggest vitamin K antagonists or LMWH over dabigatran or rivaroxaban (Grade 2B). We suggest compression stockings to prevent the postthrombotic syndrome (Grade 2B). For extensive superficial vein thrombosis, we suggest prophylactic-dose fondaparinux or LMWH over no anticoagulation (Grade 2B), and suggest fondaparinux over LMWH (Grade 2C).

CONCLUSION

Strong recommendations apply to most patients, whereas weak recommendations are sensitive to differences among patients, including their preferences.

Thoracic complications and emergencies in oncologic patients

Oncology patients often experience urgent or emergent medical complications that are a direct or indirect result of the underlying malignant condition and are first identified or clarified on radiologic imaging studies. The aim of this review is to identify, discuss, and illustrate some of the major thoracic complications in patients with primary intrathoracic or extrathoracic neoplasms; particular focus is placed on issues in which radiologic imaging may have a significant impact on patient management, including superior vena cava (SVC) syndrome, post-obstructive pneumonia, diaphragmatic paralysis, pleural effusions, pericardial disease, tracheo-esophageal fistula, deep venous thrombosis, and pulmonary embolism.