Multidetector computed tomographic pulmonary angiography in patients with a high clinical probability of pulmonary embolism

The History of Diagnosing Venous Thromboembolism

An accurate and prompt diagnosis of deep vein thrombosis and/or pulmonary embolism is important to prevent serious complications and mortality. Because the clinical presentation of venous thromboembolism (VTE) is often nonspecific, objective testing by means of radiological imaging is required to confirm the diagnosis. Historically, a diagnosis of VTE involved invasive imaging techniques like contrast venography or conventional pulmonary angiography. Technological developments toward more accurate and less invasive diagnostics have driven the implementation of a variety of newer technologies over the past decades, as well as the derivation and validation of clinical decision rules (CDRs) that can be used to rule out VTE in combination with D-dimer blood tests. In this narrative review, we provide a historical overview of the most notable developments in the imaging techniques and CDRs for VTE diagnosis.

Diagnostic accuracy of multiorgan point-of-care ultrasound compared with pulmonary computed tomographic angiogram in critically ill patients with suspected pulmonary embolism

BACKGROUND

Critically ill patients have a higher incidence of pulmonary embolism (PE) than non-critically ill patients, yet no diagnostic algorithm has been validated in this population, leading to the overuse of pulmonary artery computed tomographic angiogram (CTA). This study aimed to comparatively evaluate the diagnostic accuracy of point-of-care ultrasound (POCUS) combined with laboratory data versus CTA in predicting PE in critically ill patients.

METHODS

A prospective diagnostic accuracy study. Critically ill patients with suspected acute PE undergoing CTA were prospectively enrolled. Demographic and clinical data were collected from electronic medical records. Blood samples were collected, and the Wells and revised Geneva scores were calculated. Standardized multiorgan POCUS and CTA were performed. The discriminatory power of multiorgan POCUS combined with biochemical markers was tested using ROC curves, and multivariate analysis was performed.

RESULTS

A total of 88 patients were included, and 37 (42%) had PE. Multivariate analysis showed a relative risk (RR) of PE of 2.79 (95% CI, 1.61-4.84) for the presence of right ventricular (RV) dysfunction, of 2.54 (95% CI, 0.89-7.20) for D-dimer levels >1000 ng/mL, and of 1.69 (95% CI, 1.12-2.63) for the absence of an alternative diagnosis to PE on lung POCUS or chest radiograph. The combination with the highest diagnostic accuracy for PE included the following variables: 1- POCUS transthoracic echocardiography with evidence of RV dysfunction; 2- lung POCUS or chest radiograph without an alternative diagnosis to PE; and 3- plasma D-dimer levels >1000 ng/mL. Combining these three findings resulted in an area under the curve of 0.85 (95% CI, 0.77-0.94), with 50% sensitivity and 96% specificity.

CONCLUSIONS

Multiorgan POCUS combined with laboratory data has acceptable diagnostic accuracy for PE compared with CTA. The combined use of these methods might reduce CTA overuse in critically ill patients.

Contemporary management of acute pulmonary embolism

This review examines the recent progress in the initial management of pulmonary embolism (PE). Diagnostic strategies allowing the safe decrease of imaging testing have been proposed. New modalities of catheter-based interventions have emerged for hemodynamically unstable PE patients. For normotensive PE patients, direct oral anticoagulant treatment has become the new norm and a large proportion of patients are eligible for home treatment.

Systematic review and meta-analysis of test accuracy for the diagnosis of suspected pulmonary embolism

Pulmonary embolism (PE) is a common, potentially life-threatening yet treatable condition. Prompt diagnosis and expeditious therapeutic intervention is of paramount importance for optimal patient management. Our objective was to systematically review the accuracy of D-dimer assay, compression ultrasonography (CUS), computed tomography pulmonary angiography (CTPA), and ventilation-perfusion (V/Q) scanning for the diagnosis of suspected first and recurrent PE. We searched Cochrane Central, MEDLINE, and EMBASE for eligible studies, reference lists of relevant reviews, registered trials, and relevant conference proceedings. 2 investigators screened and abstracted data. Risk of bias was assessed using Quality Assessment of Diagnostic Accuracy Studies-2 and certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation framework. We pooled estimates of sensitivity and specificity. The review included 61 studies. The pooled estimates for D-dimer sensitivity and specificity were 0.97 (95% confidence interval [CI], 0.96-0.98) and 0.41 (95% CI, 0.36-0.46) respectively, whereas CTPA sensitivity and specificity were 0.94 (95% CI, 0.89-0.97) and 0.98 (95% CI, 0.97-0.99), respectively, and CUS sensitivity and specificity were 0.49 (95% CI, 0.31-0.66) and 0.96 (95% CI, 0.95-0.98), respectively. Three variations of pooled estimates for sensitivity and specificity of V/Q scan were carried out, based on interpretation of test results. D-dimer had the highest sensitivity when compared with imaging. CTPA and V/Q scans (high probability scan as a positive and low/non-diagnostic/normal scan as negative) both had the highest specificity. This systematic review was registered on PROSPERO as CRD42018084669.

Acute pulmonary embolism: appropriateness of emergency department management according to clinical guidelines

BACKGROUND AND AIMS

To evaluate the frequency of acute pulmonary embolism, the use of clinical probability scores, and the appropriateness of the management of patients for whom computed tomography angiography (CTA) was requested from the emergency department for suspected acute pulmonary embolism.

MATERIALS AND METHODS

This was a retrospective observational study of CTA studies requested from the emergency department to rule out acute pulmonary embolism. We analyzed clinical variables and the explicit use of clinical probability scores. We determined the appropriateness of management according to the Wells Score and Geneva Score and the simplified versions of these two scores, calculated retrospectively.

RESULTS

We included 534 patients (52.8% women; mean age, 73 years). The frequency of acute pulmonary embolism was 23.0% and the Wells Score was explicitly used in 15.2%. The appropriateness of the management varied depending on the clinical probability score used to assess it (54.5%-75.8%) and on whether the standard D-dimer or age-adjusted D-dimer was used.

CONCLUSIONS

The failure to use the Wells Scores in all cases does not necessarily imply inappropriate management, and the performance of global clinical judgment can be similar to that of clinical probability scores; however, specific studies are necessary to confirm this hypothesis.

EANM guideline for ventilation/perfusion single-photon emission computed tomography (SPECT) for diagnosis of pulmonary embolism and beyond

These guidelines update the previous EANM 2009 guidelines on the diagnosis of pulmonary embolism (PE). Relevant new aspects are related to (a) quantification of PE and other ventilation/perfusion defects; (b) follow-up of patients with PE; (c) chronic PE; and (d) description of additional pulmonary physiological changes leading to diagnoses of left ventricular heart failure (HF), chronic obstructive pulmonary disease (COPD) and pneumonia. The diagnosis of PE should be reported when a mismatch of one segment or two subsegments is found. For ventilation, Technegas or krypton gas is preferred over diethylene triamine pentaacetic acid (DTPA) in patients with COPD. Tomographic imaging with V/PSPECT has higher sensitivity and specificity for PE compared with planar imaging. Absence of contraindications makes V/PSPECT an essential method for the diagnosis of PE. When V/PSPECT is combined with a low-dose CT, the specificity of the test can be further improved, especially in patients with other lung diseases. Pitfalls in V/PSPECT interpretation are discussed. In conclusion, V/PSPECT is strongly recommended as it accurately establishes the diagnosis of PE even in the presence of diseases like COPD, HF and pneumonia and has no contraindications.

Definitions, adjudication, and reporting of pulmonary embolism-related death in clinical studies: A systematic review

BACKGROUND

Pulmonary embolism (PE)-related death is a component of the primary outcome in many venous thromboembolism (VTE) studies. The absence of a standardized definition for PE-related death hampers study outcome evaluation and between-study comparisons.

OBJECTIVES

To summarize definitions for PE-related death used in recent VTE studies and to assess the PE-related death rate.

PATIENTS/METHODS

A systematic literature search was conducted on 26 April 2018 from 1 January 2014 up to the search date in MEDLINE, Embase, and CENTRAL. Cohort studies and randomized trials in which PE-related death was included in the primary outcome were eligible. Screening of titles, abstracts, and full-text articles, and data extraction were independently performed in duplicate by two authors. Study outcomes included the definition for PE-related death, VTE case-fatality rate, and death due to PE rate. Descriptive statistics were used to analyze the data.

RESULTS

Of the 6807 identified citations, 83 studies were included of which 27% were randomized trials, 31% were prospective, and 42% retrospective cohort studies. Thirty-five studies (42%) had a central adjudication committee. Thirty-eight (46%) reported a definition for PE-related death of which the most frequently used components were "autopsy-confirmed PE" (50%), "objectively confirmed PE before death" (55%), and "unexplained death" (58%). Median VTE case-fatality rate was 1.8% (interquartile range, 0.0-13).

CONCLUSIONS

Only half of the included studies reported definitions for PE-related death, which were very heterogeneous. Case-fatality rate of VTE events varied widely across studies. Standardization of the definition and guidance on adjudication and reporting of PE-related death is needed.

Outcomes following a negative computed tomography pulmonary angiography according to pulmonary embolism prevalence: a meta-analysis of the management outcome studies

Essentials Computed tomographic pulmonary angiography (CTPA) is used to exclude pulmonary embolism. This meta-analysis explores the occurrence of venous thromboembolic events (VTE) after a CTPA. Occurrence of VTE after a negative CTPA is ˜8% in study subgroups with a prevalence of PE ≥ 40%. CTPA may be insufficient to safely rule out VTE as a stand-alone diagnostic test for this subgroup.

SUMMARY

Background Outcome studies have reported the safety of computed tomographic pulmonary angiography (CTPA) as a stand-alone imaging technique to rule out pulmonary embolism (PE). Whether this can be applied to all clinical probabilities remains controversial. Objectives We performed a meta-analysis to determine the proportion of patients with venous thromboembolic events (VTE) despite a negative CTPA according to pretest PE prevalence. Methods We searched MEDLINE, EMBASE and the Cochrane Library (January 1990 to May 2017) for outcome studies recruiting patients with suspected PE using CTPA as a diagnostic strategy. The primary outcome was the cumulative occurrence of VTE at 3 months following a negative CTPA. Results Twenty-two different studies were identified. VTE was confirmed in 2.4% of patients (95% CI, 1.3-3.8%) either at the time of the index event or in the 3 months follow-up. Subgroup analyses suggested that the cumulative occurrence of VTE was related to pretest prevalence of PE, as VTE occurred in 1.8% (95% CI, 0.5-3.7%), 1.4% (95% CI, 0.7-2.3%), 1.0% (95% CI, 0.5-1.8%) and 8.1% (95% CI, 3.5-14.5%) of subgroups of patients with a PE prevalence < 20%, 20-29%, 30-39% and ≥ 40%, respectively. This was further confirmed using meta-regression analysis. Conclusions The negative predictive value of CTPA for VTE varies according to pretest prevalence of PE, and is likely to be insufficient to safely rule out VTE as a stand-alone diagnostic test amongst patients at the highest pretest probability of VTE. Prospective studies are required to validate the appropriate diagnostic algorithm for this subgroup of patients.

Ruling out Pulmonary Embolism in Patients with High Pretest Probability

Introduction

The American College of Emergency Physicians guidelines recommend more aggressive workup beyond imaging alone in patients with a high pretest probability (PTP) of pulmonary embolism (PE). However, the ability of multiple tests to safely rule out PE in high PTP patients is not known. We sought to measure the ability of negative computed tomography pulmonary angiography (CTPA) along with negative D-dimer to rule out PE in these high-risk patients.

Methods

We analyzed data from a previous prospective observational study conducted in 12 emergency departments (ED). Wells score criteria were entered by providers before final PE testing. PE was diagnosed by imaging on the index ED visit, or within 45 days, demonstrating either PE or deep vein thrombosis (DVT), or if the patient died of PE during the 45-day, follow-up period. Testing threshold was set at 1.8%.

Results

A total of 7,940 patients were enrolled and tested for PE, and 257 had high PTP (Wells >6). Sixteen of these high-risk patients had negative CTPA and negative D-dimer, of whom two were positive for PE (12.5% [95% confidence interval {2.2%–40.0%}]). One of these patients had a DVT on CT venogram and the other was diagnosed at follow-up.

Conclusion

Our analysis suggests that in patients with high PTP of PE, neither negative CTPA by itself nor a negative CTPA plus a negative D-dimer are sufficient to rule out PE. More aggressive workup strategies may be required for these patients.

To immunosuppress or not: Behcet's syndrome presenting as an eosinophilic pleural effusion

Etiologic diagnosis of an eosinophilic pleural effusion (EPE) presents a diagnostic challenge when intrapleural air and blood have been ruled out as its proximate causes. Among the causes of EPE, those that require immunosuppression for the underlying disease include connective tissue diseases, sarcoidosis, vasculitis, and eosinophilic pneumonia. We present a case of clinically suspected Behcet's syndrome based on a 10-year history of recurrent multiple oral ulcers and human leukocyte antigen-B51 positivity who presented with only an EPE. Computed tomography pulmonary angiogram ruled out central thoracic vein thrombosis but was inconclusive in ruling out a subsegmental pulmonary embolism. The patient declined immunosuppressants and while on follow-up developed bilateral extensive acute lower limb deep venous thrombosis and pulmonary embolism. Upper infrarenal inferior vena cava demonstrated chronic thrombosis suggestive of its antecedent role in pulmonary embolism-related EPE during the first instance. Behcet's syndrome-related EPE can be associated with venous thromboembolism, and immunosuppressive therapy prevents the subsequent thrombotic episodes.

Safety of multidetector computed tomography pulmonary angiography to exclude pulmonary embolism in patients with a likely pretest clinical probability

Essentials Safety of computed tomography (CTPA) to exclude pulmonary embolism (PE) in all patients is debated. We analysed the outcome of PE-likely outpatients left untreated after negative CTPA alone. The 3-month venous thromboembolic risk in these patients was very low (0.6%; 95% CI 0.2-2.3). Multidetector CTPA alone safely excludes PE in patients with likely clinical probability.

SUMMARY

Background In patients with suspected pulmonary embolism (PE) classified as having a likely or high pretest clinical probability, the need to perform additional testing after a negative multidetector computed tomography pulmonary angiography (CTPA) finding remains a matter of debate. Objectives To assess the safety of excluding PE by CTPA without additional imaging in patients with a likely pretest probability of PE. Patients/Methods We retrospectively analyzed patients included in two multicenter management outcome studies that assessed diagnostic algorithms for PE diagnosis. Results Two thousand five hundred and twenty-two outpatients with suspected PE were available for analysis. Of these 2522 patients, 845 had a likely clinical probability as assessed by use of the simplified revised Geneva score. Of all of these patients, 314 had the diagnosis of PE excluded by a negative CTPA finding alone without additional testing, and were left without anticoagulant treatment and followed up for 3 months. Two patients presented with a venous thromboembolism (VTE) during follow-up. Therefore, the 3-month VTE risk in likely-probability patients after a negative CTPA finding alone was 2/314 (0.6%; 95% confidence interval [CI] 0.2-2.3%). Conclusions In outpatients with suspected PE and a likely clinical probability as assessed by use of the simplified revised Geneva score, CTPA alone seems to be able to safely exclude PE, with a low 3-month VTE rate, which is similar to the VTE rate following the gold standard, i.e. pulmonary angiography.

Diagnosis of acute pulmonary embolism

Advances in the management of patients with suspected pulmonary embolism (PE) have improved diagnostic accuracy and made management algorithms safer, easier to use, and well standardized. These diagnostic algorithms are mainly based on the assessment of clinical pretest probability, D-dimer measurement, and imaging tests-predominantly computed tomography pulmonary angiography. These diagnostic algorithms allow safe and cost-effective diagnosis for most patients with suspected PE. In this review, we summarize signs and symptoms of PE, current existing evidence for PE diagnosis, and focus on the challenge of diagnosing PE in special patient populations, such as pregnant women, or patients with a prior VTE. We also discuss novel imaging tests for PE diagnosis and highlight some of the additional challenges that might require adjustments to current diagnostic strategies, such as the reduced clinical suspicion threshold, resulting in a lower proportion of PE among suspected patients as well as the overdiagnosis of subsegmental PE.

Is CT angiography of the pulmonary arteries indicated in patients with high clinical probability of pulmonary embolism?

When a diagnostic test confirms clinical suspicion, the indicated treatment can be administered. A problem arises when the diagnostic test does not confirm the initially suspected diagnosis; when the suspicion is grounded in clinically validated predictive rules and is high, the problem is even worse. This situation arises in up to 40% of patients with high suspicion for acute pulmonary embolism, raising the question of whether CT angiography of the pulmonary arteries should be done systematically. This paper reviews the literature about this issue and lays out the best evidence about the relevant recommendations for patients with high clinical suspicion of acute pulmonary embolism and negative findings on CT angiography. It also explains the probabilistic concepts derived from Bayes' theorem that can be useful for ascertaining the most appropriate approach in these patients.

Variations of Postresuscitation Lung Function after Thrombolysis Therapy in a Cardiac Arrest Porcine Model Caused by Pulmonary Thromboembolism

BACKGROUND

Study of lung function in survivor from cardiac arrest (CA) caused by pulmonary thromboembolism (PTE) was rare. The aim of this study was to investigate the variations of postresuscitation lung function after thrombolysis treatment in a CA porcine model caused by PTE.

METHODS

After 2 min of untreated CA, pigs of 10-12 weeks with a weight of 30 ± 2 kg (n = 24) were treated with recombinant human tissue plasminogen activator (50 mg). Cardiopulmonary resuscitation (CPR) and ventilation were initiated after drug administration. Pulmonary function and arterial blood gas parameters were measured at baseline, return of spontaneous circulation (ROSC) immediately, and 1 h, 2 h, 4 h, and 6 h after ROSC.

RESULTS

The dynamic lung compliance decreased significantly at ROSC immediately and 1 h after ROSC compared to baseline (21.86 ± 2.00 vs. 26.72 ± 2.20 ml/mmHg and 20.38 ± 1.31 vs. 26.72 ± 2.20 ml/mmHg, respectively; P < 0.05; 1 mmHg = 0.133 kPa). Compared with baseline, airway resistance increased significantly at ROSC immediately and 1 h after ROSC (P < 0.05). Respiratory index also increased after ROSC and showed significant differences among baseline, ROSC immediately, and 2 h after ROSC (P < 0.05). Oxygen delivery decreased at ROSC immediately compared to baseline (P < 0.05). The oxygenation index decreased significantly at any time after ROSC compared to baseline (P < 0.05). Extravascular lung water index and pulmonary vascular permeability index (PVPI) showed significant differences at ROSC immediately compared to baseline and 1 h after ROSC (P < 0.05); PVPI at ROSC immediately was also different from 6 h after ROSC (P < 0.05). Ventilation/perfusion ratios increased after ROSC (P < 0.05). Histopathology showed fibrin effusion, bleeding in alveoli, and hemagglutination in pulmonary artery.

CONCLUSIONS

Lung function remains abnormal even after CPR with thrombolysis therapy; it is essential to continue anticoagulation and symptomatic treatment after ROSC.

Is a normal computed tomography pulmonary angiography safe to rule out acute pulmonary embolism in patients with a likely clinical probability? A patient-level meta-analysis

A normal computed tomography pulmonary angiography (CTPA) remains a controversial criterion for ruling out acute pulmonary embolism (PE) in patients with a likely clinical probability. We set out to determine the risk of VTE and fatal PE after a normal CTPA in this patient category and compare these risk to those after a normal pulmonary angiogram of 1.7 % (95 %CI 1.0-2.7 %) and 0.3 % (95 %CI 0.02-0.7 %). A patient-level meta-analysis from 4 prospective diagnostic management studies that sequentially applied the Wells rule, D-dimer tests and CTPA to consecutive patients with clinically suspected acute PE. The primary outcome was the 3-month VTE incidence after a normal CTPA. A total of 6,148 patients were included with an overall PE prevalence of 24 %. The 3-month VTE incidence in all 4,421 patients in whom PE was excluded at baseline was 1.2 % (95 %CI 0.48-2.6) and the risk of fatal PE was 0.11 % (95 %CI 0.02-0.70). In patients with a likely clinical probability the 3-month incidences of VTE and fatal PE were 2.0 % (95 %CI 1.0-4.1 %) and 0.48 % (95 %CI 0.20-1.1 %) after a normal CTPA. The 3-month incidence of VTE was 6.3 % (95 %CI 3.0-12) in patients with a Wells rule >6 points. In conclusion, this study suggests that a normal CTPA may be considered as a valid diagnostic criterion to rule out PE in the majority of patients with a likely clinical probability, although the risk of VTE is higher in subgroups such as patients with a Wells rule >6 points for which a closer follow-up should be considered.

Prevalence of Deep Vein Thrombosis in Hospitalized Patients With Suspected Pulmonary Embolism Ruled Out by Multislice CT Angiography

Current evidence suggests that for outpatients with suspected pulmonary embolism (PE), multislice computed tomographic angiography (CTPA) is sufficient to rule out PE. However, the accuracy of CTPA alone has not been established for hospitalized patients. Our goal was to determine the prevalence of deep vein thrombosis (DVT) in hospitalized patients who had PE ruled out by CTPA. We conducted a prospective cohort study of patients who developed symptoms indicative of PE, after being admitted to the hospital for any reason other than PE and were evaluated with multislice CTPA. The main outcome was proximal DVT. Between November 2011 and December 2014, 191 hospitalized patients were screened. A total of 99 patients satisfied our inclusion criteria. The average length of hospitalization for this group was 14 days (range: 2-127 days). While hospitalized, 54 (28%) patients underwent a major surgical procedure and 80 (79%) were receiving thromboprophylaxis. Of the 99 patients included, 7 (7.07%; 95% confidence intervals [CIs]: 3.4-13.8) were diagnosed with a proximal DVT. The likelihood of developing a proximal DVT was higher for those with subtle and nonspontaneously reported symptoms of DVT, odds ratio [OR] was 50.93 (95% CI: 5.35-2572) and for those classified as PE likely OR was 37.54 (95% CI: 4.05-186.1). Given the prevalence of DVT in hospitalized patients with suspected PE ruled out by a negative multislice CTPA, our study suggests that compression ultrasonography would, in fact, be justified for patients with these characteristics.