Diagnostic management of clinically suspected acute pulmonary embolism

Summary.  Current diagnostic management of hemodynamically stable patients with clinically suspected acute pulmonary embolism (PE) consists of the accurate and rapid distinction between the approximate 20–25% of patients who have acute PE and require anticoagulant treatment, and the overall majority of patients who do not have the disease in question. Clinical outcome studies have demonstrated that, using algorithms with sequential diagnostic tests, PE can be safely ruled out in patients with a clinical probability indicating PE to be unlikely and a normal D-dimer test result. This obviates the need for additional radiological imaging tests in 20–40% of patients. CT pulmonary angiography (CTPA) has become the first line tool to confirm or exclude the diagnosis of PE in patients with a likely probability of PE or an elevated D-dimer blood concentration. While single-row-detector technology CTPA has a low sensitivity for PE and bilateral compression ultrasound (CUS) of the lower limbs is considered necessary to rule out PE, multi-row-detector CTPA is safe to exclude PE without the confirmatory use of CUS.     

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.

     

Management of suspected pulmonary embolism (PE) by D-dimer and multi-slice computed tomography in outpatients: an outcome study

OBJECTIVES: A prospective outcome study designed to evaluate a simple strategy for the management of outpatients with suspected pulmonary embolism (PE), based on clinical probability, D-dimer, and multi-slice computed tomography (MSCT). METHODS: A cohort of 432 consecutive patients admitted to the emergency department with suspected PE was managed by sequential non-invasive testing. Patients in whom PE was ruled out were not given anticoagulants, but were followed-up for 3 months. RESULTS: Normal D-dimer and low-intermediate clinical probability ruled out PE in 103 patients [24% (95% CI 20-28)]. Seventeen patients had normal D-dimer, but high clinical probability and proceeded to MSCT. All patients proved negative for PE. A total of 329 (76%) patients underwent MSCT examination. Pulmonary embolism was diagnosed in 93 patients [21.5% (95% CI 18-26)] and was ruled out by negative MSCT in 221 patients [51% (95% CI 46-56)]. MSCT scans were determined as inconclusive in 15 (4.5%) patients. No patient developed objectively verified venous thromboembolism (VTE) during the 3-month follow-up period. However, the cause of death was adjudicated as possibly related to PE in two patients, resulting in an overall 3-month VTE risk of 0.6% (95% CI 0-2.2%). The diagnostic algorithm yielded a definite diagnosis in 96.5% of the patients. CONCLUSIONS: This simple and non-invasive strategy combining clinical probability, D-dimer, and MSCT for the management of outpatients with suspected PE appears to be safe and effective.     

Subsegmental pulmonary embolism diagnosed by computed tomography: incidence and clinical implications. A systematic review and meta‐analysis of the management outcome studies

Summary. Background: Multiple‐detectors computed tomographic pulmonary angiography (CTPA) has a higher sensitivity for pulmonary embolism (PE) within the subsegmental pulmonary arteries as compared with single‐detector CTPA. Multiple‐detectors CTPA might increase the rate of subsegmental PE diagnosis. The clinical significance of subsegmental PE is unknown. We sought to summarize the proportion of subsegmental PE diagnosed with single‐ and multiple‐detectors CTPA and assess the safety of diagnostic strategies based on single‐ or multiple‐detectors CTPA to exclude PE. Patients and methods: A systematic literature search strategy was conducted using MEDLINE, EMBASE and the Cochrane Register of Controlled Trials. We selected 22 articles (20 prospective cohort studies and two randomized controlled trials) that included patients with suspected PE who underwent a CTPA and reported the rate of subsegmental PE. Two reviewers independently extracted data onto standardized forms. Results: The rate of subsegmental PE diagnosis was 4.7% [95% confidence interval (CI): 2.5–7.6] and 9.4 (95% CI: 5.5–14.2) in patients that underwent a single‐ and multiple‐detectors CTPA, respectively. The 3‐month thromboembolic risks in patients with suspected PE and who were left untreated based on a diagnostic algorithm including a negative CTPA was 0.9% (95% CI: 0.4–1.4) and 1.1% (95% CI: 0.7–1.4) for single‐ and multiple‐detectors CTPA, respectively. Conclusion: Multiple‐detectors CTPA seems to increase the proportion of patients diagnosed with subsegmental PE without lowering the 3‐month risk of thromboembolism suggesting that subsegmental PE may not be clinically relevant.     

Symptomatic subsegmental pulmonary embolism: what is the next step?

Summary. The introduction of computed tomography pulmonary angiography (CTPA) has led to an increase in the incidence of pulmonary embolism (PE) diagnosis. However, the case fatality rate is lower and the mortality rates of PE have remained unchanged, suggesting a lower severity of illness. Specifically, the multiple‐detector CTPA increased the rate of subsegmental filling defect reported in patients with suspected PE. Whether these filling defects reported on CTPA would correlate with true subsegmental PE (SSPE) on pulmonary angiography or are actually artifacts is unknown. The inter‐observer agreement for SSPE diagnosis among radiologists with varied levels of experience is low (κ of 0.38; 95% CI, 0.0–0.89). Furthermore, the clinical importance of a symptomatic SSPE diagnosed by CTPA is unclear. SSPE are frequent on pulmonary angiography in patients with a low probability ventilation‐perfusion (V/Q) scan for suspected PE. Several prospective management cohort studies have demonstrated that patients with low or intermediate V/Q scan results can be safely managed without anticoagulation by combining the scan results with the pretest probability (PTP) of PE and compression ultrasonography. Although clinical equipoise exists, the majority of patients diagnosed with SSPE on CTPA are currently treated with anticoagulant therapy. Only a small number of patients with SSPE diagnosed by CTPA and without DVT who did not receive anticoagulation treatment have been reported in the literature. None of these patients suffered recurrent symptomatic VTE (PE or DVT) during the 3‐month follow‐up period (0%; 95% CI, 0–7.4%), suggesting that SSPE might be clinically unimportant. These conclusions are only hypothesis generating and need to be confirmed in prospective clinical management studies before changing clinical practice.     

Contribution of indirect computed tomography venography to computed tomography angiography of the chest for the diagnosis of thromboembolic disease in two United States emergency departments

Summary.  Recent reports suggest that physicians in non-ambulatory settings can use indirect CT venography (CTV) of the lower extremities immediately following spiral CT angiography (CTA) of the chest to identify patients with a negative CTA who have thromboembolic disease identified on CTV. We sought to determine the frequency of isolated deep venous thrombosis (DVT) discovered on CTV in emergency department (ED) patients with complaints suggestive of pulmonary embolism (PE) yet having a negative CTA. This study was conducted in a suburban and urban ED where patients with symptoms suspicious for PE were primarily evaluated with CTA and CTV. A total of 800 patients were studied, including 360 from the suburban ED and 440 from the urban ED. 88 (11%) patients were diagnosed with thromboembolic disease by CTA, or CTV, or both. Seventy-three patients had a CTA of the chest that was positive for PE, 42 (5.2%) of whom had evidence of both PE on CTA and DVT on CTV. Fifteen patients (2%, 95% CI = 1–3%) had a negative CTA and were subsequently found to have isolated DVT on CTV, all of whom received anticoagulation therapy. These data suggest that indirect CT venography of immediately following CT angiography of the chest significantly increased the frequency of diagnosed thromboembolic disease requiring anticoagulation in ED patients with suspected PE.     

Computed tomography pulmonary angiography in the diagnosis of acute pulmonary embolism in the emergency department

This study was undertaken to evaluate the use of computed tomography pulmonary angiography (CTPA) in patients with pulmonary embolism (PE) who were followed in the emergency department (ED). The files and computer records of 850 patients older than 16 years of age who were seen in the Hacettepe University Hospital ED between April 10, 2001, and December 1, 2005, and who required CTPA for PE prediagnosis and/or another diagnosis, were studied retrospectively. PE was identified by CTPA in 9.4% of 416 women and in 5.8% of 434 men. A significant difference (P< .05) was noted in the women and men in whom PE was detected. The mean age of the patients was 58.13±17.88 y (range, 16–100 y). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for clinical susceptibility to PE among patients who underwent CTPA were assessed at 95.3%, 48.2%, 13%, and 99.2%, respectively. CTPA was done for different reasons: aortic aneurysm dissection (n=1), cough distinctive diagnosis (n=1), dyspnea distinctive diagnosis (n=6), chest pain distinctive diagnosis (n=3), PE prediagnosis (n=51), and other reasons (n=2). Also, sensitivity, specificity, PPV, and NPV were found to be 95.4%, 16.2%, 14.4%, and 96%, respectively, for D-dimer. CTPA, which is accessible on a 24-h basis in the ED, is a valuable tool for the diagnosis of PE.     

Accuracy of clinical decision rule, D-dimer and spiral computed tomography in patients with malignancy, previous venous thromboembolism, COPD or heart failure and in older patients with suspected pulmonary embolism

BACKGROUND: The diagnostic work-up of patients with suspected pulmonary embolism (PE) has been optimized and simplified by the use of clinical decision rules (CDR), D-dimer (DD) testing and spiral computed tomography (s-CT). Whether this strategy is equally safe and efficient in specific subgroups of patients is evaluated in this study. METHODS: A diagnostic strategy including a CDR, DD test and s-CT was evaluated in patients with malignancy, previous venous thromboembolism (VTE), chronic obstructive pulmonary disease or heart failure and in older patients. PE was ruled out by either an unlikely CDR and a normal DD or a s-CT negative for PE. The safety of these tests was assessed by the 3-month incidence rate of symptomatic VTE in those without PE at baseline. The efficiency was evaluated by calculating the numbers needed to test for the different subgroups. RESULTS: The venous thromboembolic incidence rate after the combination of an unlikely CDR and a normal DD varied from 0% (95% CI: 0-7.9%) in the 482 patients older than 75 years of age to 2% (95% CI: 0.05-10.9%) in the 474 patients with a malignancy. For s-CT these incidences varied from 0.3% to 1.8%. The number needed to test in order to rule out one patient from PE with the studied strategy was highest in cancer patients and in the elderly patients (approximately 10). CONCLUSION: It appears to be safe to rule out PE by either the combination of an unlikely CDR and a normal DD or by a negative s-CT in various subgroups of patients with suspected PE. However, the clinical usefulness of the CDR in combination with the DD as the initial step in the diagnostic process varied among these patient groups.     

Safety of outpatient treatment in acute pulmonary embolism

See also Baglin T. Fifty per cent of patients with pulmonary embolism can be treated as outpatients. This issue, pp 2404–5; Kovacs MJ, Hawel JD, Rekman JF, Lazo‐Langner A. Ambulatory management of pulmonary embolism: a pragmatic evaluation. This issue, pp 2406–11. Summary. Introduction: Data regarding outpatient treatment of pulmonary embolism (PE) is scarce. This study evaluates the safety of outpatient management of acute PE. Methods: This is a retrospective cohort study of consecutive patients presenting at the Ottawa Hospital with acute PE diagnosed between 1 January 2007 and 31 December 2008. PE was defined as an arterial filling defect on CTPA or a high probability V/Q scan. Patients were managed as outpatients if they were hemodynamically stable, did not require supplemental oxygenation and did not have contraindications to low‐molecular‐weight heparin therapy. Results: In this cohort of 473 patients with acute PE, 260 (55.0%) were treated as outpatients and 213 (45.0%) were admitted to the hospital. The majority of the patients were admitted because of severe comorbidities (45.5%) or hypoxia (22.1%). No outpatient died of fatal PE during the 3‐month follow‐up period. At the end of follow‐up, the overall mortality was 5.0% (95% CI, 2.7–8.4%). The rates of recurrent venous thromboembolism (VTE) in outpatients were 0.4% (95% CI, 0.0–2.1%) and 3.8% (95% CI, 1.9–7.0%) within 14 days and 3 months, respectively. The rates of major bleeding episodes were 0% (95% CI, 0–1.4%) and 1.5% (95% CI, 0.4–3.9%) within 14 days and 3 months, respectively. Four (1.5%) outpatients were admitted to the hospital within 14 days. Conclusions: A majority of patients with acute PE can be managed as outpatients with a low risk of mortality, recurrent VTE and major bleeding episodes.     

Incidence of symptomatic venous thromboembolism following hematopoietic stem cell transplantation

Summary.  Background: The incidence of symptomatic venous thromboembolism (VTE) following hematopoietic stem cell transplantation (HSCT) is not well described, particularly with increased use of ambulatory care in the transplant setting. Methods: A retrospective analysis involving 589 patients (382 autologous HSCT, 207 allogeneic HSCT) undergoing transplantation between 2000 and 2005 in a single Canadian institution was undertaken to identify the incidence of proximal deep vein thrombosis (DVT) or pulmonary embolism (PE) in HSCT patients. Results: The total 1-year incidence of symptomatic VTE was 3.7% [95% confidence interval (CI) 2.5–5.6]. Among the HSCT patients, 7/589 (1.2%, 95% CI  0.6–2.4) developed symptomatic non-catheter-related VTE following HSCT (four PE and three DVT). All VTE events occurred after hematopoietic engraftment. Patients undergoing autologous HSCT did not receive thromboprophylaxis, whereas most patients undergoing allogeneic HSCT (79.7%) received enoxaparin 20 mg daily for the prevention of veno-occlusive disease of the liver, starting 6 ± 3 days before transplantation for a mean of 22 ± 14 days. Conclusion: HSCT patients have a high incidence of VTE. Thromboprophylaxis should potentially be considered in these patients. However, future studies assessing the risk and benefits of thromboprophylaxis are needed in this specific population.     

Real-time risk stratification of patients with acute pulmonary embolism by grading the reflux of contrast into the inferior vena cava on computerized tomographic pulmonary angiography

Summary.  Objective: To investigate whether fast grading of reflux of contrast to the inferior vena cava (IVC) on computerized tomographic pulmonary angiography (CTPA) is a potential biomarker for real-time risk stratification. Methods: We retrospectively identified 343 patients investigated for possible pulmonary embolism (PE) by CTPA at our medical center between September 2004 and March 2006. A total of 145 consecutive patients with PE (age 67 ± 19 years) and 168 consecutive ones with negative CTPAs (age 64 ± 20 years) fulfilled entry criteria. CTPAs were evaluated for retrograde reflux of contrast to the IVC by fast visual grading from 1 to 6 using the original axial images. Pulmonary obstruction index, the diameters of right and left ventricles and pulmonary artery, and patient survival data were recorded as well. Results: Twenty-nine (20.0%) patients with positive CTs and 23 (13.7%) patients with negative CTs had substantial degrees (≥4) of reflux of contrast to the IVC ( P  = 0.14). The Kaplan–Meier 30-day survival curves demonstrated significant reduction in survival in individuals with PE and grade ≥4 reflux of contrast to the IVC compared with lower grades ( P  = 0.008), but not in patients with grade ≥4 and no PE on CTPA ( P  = 0.26). The other cardiovascular parameters showed no significant correlation with survival in patients with and without PE. Conclusion: Substantial grades of reflux of contrast to the IVC during CTPA could predict early mortality in patients with acute PE. Rapid grading of reflux of contrast from the original axial CTPA images can be used for real-time risk stratification in patients with acute PE.     

Thromboembolic risk after lumbar spine surgery: a cohort study on 325 000 French patients

Essentials

• The risk of venous thromboembolism (VTE) after lumbar spine surgery (LBS) is not precisely known.
• More than 320 000 patients who underwent LBS in France between 2009 and 2014 were followed‐up.
• The overall risk of VTE after LBS is less than 1% but modulated by patient and procedural factors.
• Surgical device implantation, anterior approach and complex surgery increase the risk of VTE.

Summary

Background

Postoperative venous thromboembolism (VTE) is a severe complication, the risk of which after lumbar spine surgery (LBS) is not precisely known.

Objective

To estimate the incidence of VTE after LBS, and to identify individual and surgical risk factors.

Methods

All patients aged >18 years who underwent LBS in France between 2009 and 2014 were identified. Among 477 024 patients screened, exclusions concerned recent VTE or surgery, and multiple surgeries during the same hospital stay.

Results

In 323 737 patients (mean age 52.9 years, 51.4% male), we observed 2911 events (0.91%) after a median time of 12 days (Q1–Q3: 5–72 days). The multivariate adjusted Cox model showed increased risks associated with age (4% per year of age; 95% confidence interval [CI] 3.8–4.3), obesity (hazard ratio [HR] 1.32, 95% CI 1.18–1.46), active cancer (HR 1.65, 95% CI 1.5–1.82), previous thromboembolism (HR 5.41, 95% CI 4.74–6.17), severe paralysis (HR 1.47, 95% CI 1.17–1.84), renal disease (HR 1.28, 95% CI 1.04–1.6), psychiatric disease (HR 1.21, 95% CI 1.1–1.32), use of antidepressants (HR 1.13, 95% CI 1.03–1.24), use of contraceptives (HR 1.56, 95% CI 1.19–2.03), extended surgery for scoliosis (HR 3.61, 95% CI 2.96–4.4), implantation of pedicular screws with a ‘dose–effect’ association, and an anterior approach (HR 1.97, 95% CI 1.6–2.43) or a combined approach (HR 2.03, 95% CI 1.44–2.84).

Conclusions

The overall VTE risk after LBS is moderate (< 1%) but is widely modulated by several easily identifiable risk factors. The surgical community should be aware of this heterogeneity, adapt prevention according to patients and to the procedure, and use drug prophylaxis in the event of a high risk being present.

     

Contemporary diagnostics of pulmonary arterial embolism

Nowadays, computed tomography along with pulmonary angiography (CTPA) is a recognized method of assumed pulmonary embolism (PE) diagnostics; however, even in experienced centers, CTPA sensitivity varies between 58 and 95%. Computed tomography with contrast venography and femoral scanning aimed at the diagnostics of profound venous thromboembolism, is a useful addition to CTPA. Besides these methods, some other well-known diagnostic techniques may be used in complex PE diagnostics: ventilation-perfusion pulmonary scanning, the evaluation of PE probability by clinical manifestations (P. Wells method), and digital subtraction angiography.     

Subjective assessment of right ventricle enlargement from computed tomography pulmonary angiography images

To retrospectively evaluate prognostic accuracy of subjective assessment of right ventricle (RV) enlargement on CT pulmonary angiography (CTPA) images in comparison with objective measures of RV enlargement in patients with acute pulmonary embolism (PE). For 200 consecutive patients with acute PE, two readers blinded to patient outcomes subjectively determined whether the maximum RV diameter was greater than that of the left ventricle (LV) using axial CTPA images. For the objective measurements, RV/LV diameter ratios were calculated using axial images and 4-chamber reformatted images. For all assessments, sensitivities and specificities for predicting PE-related death within 30-days and a composite outcome including PE-related death or the need for intensive therapies were compared. The agreement between two readers was 91.5% (kappa = 0.83) and all other assessments had pair-wise agreement over 75% (kappa = 0.53–0.72). There was no significant difference in sensitivity between the subjective and objective methods for predicting both outcomes. The specificity for subjective RV enlargement (55.4–67.7%) was significantly higher than objective measures (45.8–53.1%), except for the 4-chamber views where, for one reader, the specificity of the subjective evaluation was higher but did not reach statistical significance. Complex measurements of RV/LV diameter ratios may not be needed to maximize the prognostic value from CTPA. The radiologist who interprets the CTPA images should report RV enlargement when the RV diameter subjectively appears larger than the LV.     

Likelihood ratios increase diagnostic certainty in pulmonary embolism

Pulmonary embolism (PE) is a difficult diagnosis to confirm. The choice of tests has led to a myriad of algorithms. Diagnostic uncertainty can be quantified by the application of the tests' likelihood ratios (LR). Positive and negative LR enable the conversion of a pretest to a post-test probability, given a positive and negative test result, respectively. Thus, a pretest probability of <17% and a negative D-dimer with a negative LR of 0.05 (sensitivity 98%, specificity 40%) lead to a post-test probability of PE of <1%. Ventilation perfusion (V/Q) scans with a normal, very low, low, intermediate and high probability result have an LR of 0, 0.125, 0.25, 1 and 17, respectively. Also, patients with a V/Q scan result other than normal or high probability still have a post-test probability of PE from 3 to 65%. Positive and negative computed tomography pulmonary angiograms (CTPA) have an LR of 8.6 and 0.06, respectively (sensitivity 95%, specificity 89%). Patients with a high pretest probability and negative CTPA again still have a post-test probability of more than 10%. However, as the post-test probability after one test becomes the pretest probability for the next, test results used cumulatively progressively narrow the gap to a final diagnosis. The post-test probability after a D-dimer, V/Q scan, CTPA, leg ultrasound or pulmonary angiography, alone or in any combination or in any order, can be calculated using their LR. Use of LR thus assists in the precise interpretation of test results, such as in complex algorithms for PE.     

光谱CT肺动脉成像定性诊断肺动脉栓塞及定量评估肺组织灌注

目的 观察光谱CT肺动脉成像(SCTPA)定性诊断肺动脉栓塞(PE)和定量评估肺组织灌注的价值。方法 回顾性分析37例临床诊断PE患者的CTPA资料,观察常规CTPA及SCTPA后处理图像,后者包括40 keV虚拟单能量图(VMI_{40 keV})、碘密度图(IDI)与有效原子序数(Z-eff)图的融合图及电子密度图(EDI);记录2种图像中肺段动脉、肺亚段及以下动脉内的栓子数量和位置,对比其中相应肺灌注缺损区与对侧相应正常肺实质区常规CT值、碘密度(ID)、Z-eff及电子密度(ED)的差异;针对差异有统计学意义的sCTPA参数绘制受试者工作特征(ROC)曲线,计算曲线下面积(AUC),评估其区分PE肺灌注缺损区与正常肺实质的效能。结果 37例中,仅以常规CTPA检出37个栓子,其中26个位于肺段动脉、11 个位于肺亚段及以下动脉;之后结合SCTPA后处理图像额外检出1个肺段动脉和2个肺亚段以下动脉内栓子。全部40个栓子对应肺灌注缺损区常规CT值高于、ID及Z-eff均低于对侧正常肺实质区(P均<0.01),而ED与正常肺实质区差异无统计学意义(P=0.54)。以常规CT值区分肺灌注缺损区与正常肺实质区的敏感度、特异度分别为42.50%及87.50%,以ID及Z-eff区分的敏感度分别为95.00%、97.50%,特异度均为100%。ID及Z-eff的AUC均为0.99,均高于常规CT值(0.65,Z=5.56、5.53,P均<0.01),而 ID与Z-eff的AUC差异无统计学意义(Z=0.71,P=0.48)。结论 利用SCTPA可提高PE检出率及定量评估肺组织灌注;根据ID及Z-eff可有效区分肺灌注缺损区与正常肺实质。     

Prospective multicenter evaluation of the pulmonary embolism rule-out criteria

Summary.  Backgound:  Over-investigation of low-risk patients with suspected pulmonary embolism (PE) represents a growing problem. The combination of gestalt estimate of low suspicion for PE, together with the PE rule-out criteria [PERC(−): age < 50 years, pulse < 100 beats min⁻¹, SaO₂ ≥ 95%, no hemoptysis, no estrogen use, no surgery/trauma requiring hospitalization within 4 weeks, no prior venous thromboembolism (VTE), and no unilateral leg swelling], may reduce speculative testing for PE. We hypothesized that low suspicion and PERC(−) would predict a post-test probability of VTE(+) or death below 2.0%. Methods:  We enrolled outpatients with suspected PE in 13 emergency departments. Clinicians completed a 72-field, web-based data form at the time of test order. Low suspicion required a gestalt pretest probability estimate of <15%. The main outcome was the composite of image-proven VTE(+) or death from any cause within 45 days. Results:  We enrolled 8138 patients, 85% of whom had a chief complaint of either dyspnea or chest pain. Clinicians reported a low suspicion for PE, together with PERC(−), in 1666 patients (20%). At initial testing and within 45 days, 561 patients (6.9%, 95% confidence interval 6.5–7.6) were VTE(+), and 56 others died. Among the low suspicion and PERC(−) patients, 15 were VTE(+) and one other patient died, yielding a false-negative rate of 16/1666 (1.0%, 0.6–1.6%). As a diagnostic test, low suspicion and PERC(−) had a sensitivity of 97.4% (95.8–98.5%) and a specificity of 21.9% (21.0–22.9%). Conclusions:  The combination of gestalt estimate of low suspicion for PE and PERC(−) reduces the probability of VTE to below 2% in about 20% of outpatients with suspected PE.     

Complete venous ultrasound in outpatients with suspected pulmonary embolism

Summary.  Background: Compression ultrasonography (US) confined to the proximal veins is usually performed to detect deep vein thrombosis (DVT) in patients with suspected pulmonary embolism (PE). Recent studies suggested a limited yield of proximal US when multislice computed tomography (MSCT) was used. Objectives: To assess whether performing an additional distal vein US would increase the diagnostic yield of the test. Patients and methods: Data of 855 consecutive outpatients included in a multicenter randomized controlled trial were analyzed. Patients were investigated by a sequential diagnostic strategy including clinical probability assessment, D-dimer measurement, proximal US and MSCT. Proximal US was completed by an examination of the distal veins, the result of which was not disclosed to the physician in charge of the patient. Results: US was positive in 21% of patients, of whom 10% (53/541) had proximal DVT and 11% (59/541) isolated distal DVT. Of the 59 patients with distal DVT, 21 (36%) had no PE on MSCT. Twenty of those 21 patients were not given anticoagulant therapy and had an uneventful follow-up. The diagnostic performance of distal US for the diagnosis of PE was as follows: sensitivity 22% [95% confidence interval (CI) 17–29]; specificity 94% (95% CI  91–96); positive likelihood ratio 3.9 (95% CI  2.4–6.4). Conclusions: In patients with suspected PE, distal US has limited diagnostic performance, and its additional use only modestly increases the yield of US. Moreover, it carries a high false-positive rate, impeding the use of distal US as a confirmatory test for PE.     

Combined computed tomography venography and pulmonary angiography for the diagnosis PE and DVT in the ED

The purpose of this study is to evaluate the usefulness of combined computed tomography venography and pulmonary angiography (CTVPA) in the diagnosis of venous thromboembolic (VTE) disease in the emergency department (ED). CTVPA images and clinical data of 73 nonselected patients with suspected pulmonary embolism (PE) and/or deep venous thrombosis (DVT) were retrospectively assessed. CTVPA correctly identified 33 of 34 patients with VTE disease, including 7 patients with PE alone, 11 patients with DVT alone, and 16 patients with both PE and DVT. Among the 27 patients with DVT, CTVPA disclosed thrombosis involving the abdominal and pelvic veins in 4 patients, and isolating to the inferior vena cava and iliac vein in one patient. CTVPA showed high accuracy in the diagnosis of both PE and DVT, in comparison with lower extremity venous sonography and ventilation-perfusion scintigraphy. In 26 (66%) of the 39 patients without of evidence VTE, CTVPA provided important ancillary information that suggests additional or alternative diagnoses. CTVPA is therefore an appropriate single diagnostic tool for evaluation VTE disease in the ED.     

Detection of central pulmonary embolism on non-contrast computed tomography: a case control study

The purpose of our study was to evaluate detection of central pulmonary embolism (PE) on non-contrast CT. The unenhanced series (PA localizer, 5 mm slice thickness) of 180 CT pulmonary angiograms (CTPA) [90 consecutive CTPA positive for central and proximal interlobar PE taken from 3,161 consecutive CTPA (2.85 % prevalence) mixed with 90 randomly selected negative controls] were independently reviewed by two radiologists (R1 and R2). This was subsequently followed by concluding validation from a third radiologist with access to contrast-enhanced CTPA images and official reports. Six suboptimal studies were excluded. Patient age, gender, hemoglobin value and clot location were recorded. Interobserver agreement, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were determined. Sensitivity, specificity, PPV and NPV were 65 % [95 % confidence interval (CI) 54–75 %, 57/88], 49 % (95 % CI 38–60 %, 42/86), 3.6 % (95 % CI 2.8–4.6 %),97.9 % (95 % CI 97.1–98.6 %) for R1, and 55 % (95 % CI 44–65 %, 48/88), 76 % (95 % CI 65–84 %, 65/86), 6.2 % (95 % CI 4.3–9.3 %), 98.3 % (95 % CI 97.8–98.7 %) for R2. Patient age, sex and hemoglobin value were found to have no impact on PE detection. For strictly central PE, sensitivity was 80 % (45/56) (R1) and 70 % (39/56) (R2), while for bilateral PE, sensitivity was 74 % (48/65) (R1) and 66 % (43/65) (R2). For truly positive PE, interobserver agreement was 67 % (59/88) with a moderate Cohen’s kappa of 0.41 (95 % CI 0.24–0.57). In conclusion, non-contrast CT shows high NPV for central PE identification, however it is neither sensitive nor specific enough to accurately detect it.