Pulmonary embolism: making sense of the diagnostic evaluation

Comparison of helical and axial mode indirect computed tomographic venography in patients with pulmonary thromboembolism

OBJECTIVE

To compare the helical and axial modes of indirect computed tomographic (CT) venography (CTV) for accuracy for diagnosing deep venous thrombosis (DVT) of the lower extremities as well as for their radiation burden in patients proven to have pulmonary thromboembolism (PTE) on CT pulmonary angiography (CTPA).

SUBJECTS AND METHODS

Of patients evaluated with CTPA for suspected acute PE, 20 of patients who were found to have PTE underwent both indirect CTV of the lower extremities and color Doppler examination. For indirect CTV, patients were randomly assigned to helical and axial modes. The CTV and Doppler findings were interpreted by two experienced radiologists who were blinded to the results of each other.

RESULTS

Out of total of 260 venous segments analyzed (130 venous segments each by helical or axial CTV), thrombi were seen in 43 venous segments (15 and 28 each by helical or axial CTV respectively). On comparison with Doppler, helical CTV had 82.35% sensitivity and 99.11% specificity, whereas axial CTV had 96.6% sensitivity and 100% specificity. The mean radiation dose was significantly higher for helical (1153.57 mgy.cm) as compared to axial mode CTV (806.28 mgy.cm) with P value of <0.0001.

CONCLUSION

Axial CTV results in decreased radiation dose without significant change in the accuracy, as compared to helical CTV in the evaluation of DVT.

Pulmonary embolism

Pulmonary embolism (PE) remains one of the most challenging medical diseases in the emergency department. PE is a potentially life threatening diagnosis that is seen in patients with chest pain and/or dyspnea but can span the clinical spectrum of medical presentations. In addition, it does not have any particular clinical feature, laboratory test, or diagnostic modality that can independently and confidently exclude its possibility. This article offers a review of PE in the emergency department. It emphasizes the appropriate determination of pretest probability, the approach to diagnosis and management, and special considerations related to pregnancy and radiation exposure.

Utilization and yield of chest computed tomographic angiography associated with low positive D-dimer levels

BACKGROUND

It is unclear to what degree broadly applied D-dimer testing combined with a low threshold for imaging with even minimally positive results may be contributing to the utilization of chest computed tomographic angiography (CTA).

STUDY OBJECTIVES

To determine what proportion of chest CTAs for suspected pulmonary embolism (PE) were performed in the setting of minimally elevated D-dimer levels, and to determine the prevalence of PE in those patients when stratified by clinical risk.

METHODS

Retrospective chart review of all patients who had chest CTA for the evaluation of suspected PE during the years 2002-2006 in a suburban community teaching hospital emergency department.

RESULTS

There were 1136 eligible patient visits, of which 353 (31.1%) were found to have D-dimer levels in the low positive range (0.5-0.99 μg/mL). Of these 353 patients, 9 (2.6%; 95% confidence interval [CI] 0.9-4.2%) were diagnosed with PE. There were also 109 patients (9.6%) who had normal D-dimer levels (<0.5 μg/mL). Two of these 109 (1.8%; 95% CI 0-4.2%) were diagnosed with PE. When stratified by the Pulmonary Embolism Rule-out Criteria, 99 of 353 patients with low positive D-dimer levels (28.0%; 95% CI 23.4-32.7%), and 14 of 109 with normal D-dimer levels (12.8%; 95% CI 6.6-19.1%) were classified as low risk, none of whom had PE.

CONCLUSIONS

Nearly one-third of all chest CTAs were done for patients with minimally elevated D-dimer levels, and another 9.6% for patients with normal D-dimer levels with very low yield. Further research to define clinical criteria identifying patients with minimal risk of PE despite low positive D-dimer levels represents an opportunity to improve both patient safety and utilization efficiency of chest CTA.

A diagnostic dilemma of syncope: a patient with chronic pulmonary embolism

In the present report, the case of a 60-year-old man who presented with syncope secondary to chronic thromboemboli of the main pulmonary arteries and pulmonary arterioles is described.

A study of pulmonary embolism after abdominal surgery in patients undergoing prophylaxis

AIM: To determine risk factors for pulmonary embolism and estimate effects and benefits of prophylaxis.

METHODS: We included 78 patients who died subsequently to a pulmonary embolism after major abdominal surgery from 1985 to 2003. A first, retrospective analysis involved 41 patients who underwent elective surgery between 1985 and 1990 without receiving any prophylaxis. In the prospectively evaluated subgroup, 37 patients undergoing major surgery between 1991 and 2003 were enrolled: all of them had received a prophylaxis consisting in low-molecular weight heparin, given subcutaneously at a dose of 2850 IU AXa/0.3 mL (body weight < 50 kg) or 5700 IU AXa/0.6 mL (body weight ≥ 50 kg).

RESULTS: A higher incidence of thromboembolism (43.9% and 46.34% in the two groups, respectively) was found in older patients (> 60 years). The incidence of pulmonary embolism after major abdominal surgery in patients who had received the prophylaxis was significantly lower compared to the subjects with the same condition who had not received any prophylaxis (P < 0.001, OR = 2.825; 95% CI, 1.811-4.408). Furthermore, the incidence of pulmonary embolism after colorectal cancer surgery was significantly higher compared to incidence of pulmonary embolism after other abdominal surgical procedures. Finally, the incidence of pulmonary embolism after colorectal cancer surgery among the patients who had received the prophylaxis (11/4316, 0.26%) was significantly lower compared to subjects undergoing a surgical procedure for the same indication but without prophylaxis (10/1562, 0.64%) (P < 0.05, OR = 2.522; 95% CI, 1.069-5.949).

CONCLUSION: Prophylaxis with low molecular weight heparin is highly recommended during the preoperative period in patients with diagnosis of colorectal cancer due to high risk of pulmonary embolism after elective surgery.

Prospective multicenter evaluation of the pulmonary embolism rule-out criteria

BACKGROUND

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), SaO(2) >or= 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.

Diagnostic accuracy of the Triage® D-dimer test for exclusion of venous thromboembolism in outpatients

BACKGROUND

We evaluated the diagnostic performance of the Triage D-dimer test, a new fast quantitative point-of-care whole blood D-dimer assay and compared it with the Vidas D-dimer assay.

MATERIALS AND METHODS

The study population comprised 319 outpatients for whom D-dimer testing was requested in order to rule out venous thromboembolism (VTE). Routine testing consisted of a plasma ELISA D-dimer analysis (Vidas). For all included patients, an additional EDTA whole blood D-dimer test (Triage) was performed. Patients were classified by reference imaging or by follow-up of the medical record. Accuracy indices, receiver operating characteristics and the kappa coefficient for agreement were calculated using the cutoff values recommended by the manufacturer.

RESULTS

Prevalence of VTE was 14%. Sensitivity and specificity for VTE were 98% (95%CI: 88-100) and 34% (95%CI: 28-40) for Vidas and 91% (95%CI: 78-97) and 42% (95%CI: 36-48) for Triage, respectively. The differences in sensitivity and specificity between both D-dimer assays were statistically significant (McNemar, p<0.0001). ROC-curve analysis yielded an area under the curve of 0.83 (95%CI: 0.76-0.89) for the Vidas and 0.81 (95%CI: 0.74-0.88) for the Triage (p=0.396). The kappa coefficient for agreement between Vidas and Triage was 0.75 (95%CI: 0.68-0.79).

CONCLUSIONS

The Triage and Vidas D-dimer tests show comparable diagnostic accuracy. Vidas showed a significant higher sensitivity. Our findings strongly suggest lowering the cutoff for the Triage D-dimer test from 400 to 350 ng/mL. In this way specificity lowers from 42 to 38%, but, more importantly, sensitivity increases from 91 to 95%.

Initial approach to the patient who has chest pain

The last decade has seen extraordinary advances in the cardiovascular arena, particularly in the evaluation and management of the patient who has acute coronary syndromes. From bedside markers of myocardial damage to drug-eluting stents, technical advances are proliferating. Efforts in developing an international registry for acute aortic dissection have helped elucidate the acute presentation, management, and prognosis of this uncommon but lethal disease. Finally, the multiple research efforts in coordinating clinical decision-making with serologic markers and advanced imaging for the diagnosis of pulmonary embolism is changing the approach to the patient at risk for thromboembolic disease.

Trombose venosa profunda e suspeita de tromboembolismo pulmonar: avaliação simultânea por meio de angiotomografia pulmonar e venotomografia combinadas

OBJETIVO: Avaliar a ocorrência e a correlação de tromboembolismo pulmonar (TEP) e trombose venosa profunda (TVP) por meio de um protocolo único de angiotomografia computadorizada. MATERIAIS E MÉTODOS: Estudo prospectivo realizado de julho de 2003 a junho de 2004 no Hospital Copa D'Or, Rio de Janeiro, RJ. Foram analisadas 116 angiotomografias de pacientes com suspeita clínica de TEP. Após o estudo do tórax, com um intervalo de três minutos e sem injeção adicional de contraste, foram obtidos cortes do diafragma até os joelhos, a fim de pesquisar TVP. RESULTADOS: De 116 pacientes, 23 (19,8%) cursaram com TEP, 24 com TVP (20,7%), 15 (12,9%) apresentaram tanto TEP quanto TVP e 9 (7,8%) apresentaram TVP na ausência de TEP. Dos 23 casos positivos de TEP, 15 apresentaram concomitantemente TVP (65,2%), enquanto em 8 (34,8%) foi visto apenas TEP. Dos 24 casos positivos de TVP, 15 (62,5%) apresentaram TEP associado, enquanto em 9 (37,5%) foi encontrada TVP isolada. CONCLUSÃO: Os resultados demonstraram a forte relação entre TEP e TVP, a importância de pesquisar TVP nos casos com suspeita de TEP e a utilidade do uso combinado da angiotomografia de tórax e da venotomografia como alternativa de único exame de investigação de TEP e TVP simultaneamente.

Initial Evaluation of Chest Pain

Chest pain is among the most frequently evaluated presenting complaints in the emergency department (ED). Diagnostic etiologies range from benign to life-threatening. Failure to diagnose the life-threatening chest emergencies-specifically acute coronary syndrome, aortic dissection, and pulmonary embolism-can lead to catastrophic medical and legal outcomes for the patient and physician respectively. This article focuses on clinical and risk management strategies to minimize misdiagnosis and produce favorable medical and medicolegal outcomes.

Optimized image reconstruction for detection of deep venous thrombosis at multidetector-row CT venography

The aims of this study were to optimize image quality for indirect CT venography (sequential versus spiral), and to evaluate different image reconstruction parameters for patients with suspected deep venous thrombosis (DVT). Fifty-one patients (26/25 with/without DVT) were prospectively evaluated for pulmonary embolism (PE) with standard multidetector-row computed tomography (MDCT) protocols. Retrospective image reconstruction was done with different slice thicknesses and reconstruction increments in sequential and spiral modes. All reconstructions were read for depiction of DVT and to evaluate best reconstruction parameters in comparison with the thinnest reconstruction ("gold standard"). Image noise and venous enhancement were measured as objective criteria for image quality. Subjective image quality was rated on a four-point scale. Effective dose was estimated for all reconstructions. In sequential 10/50 reconstruction DVT was completely detected in 13/26 cases, partially in 10/26 cases and was not detected at all in 3/26 cases, and 15/26, 9/26 and 2/26 cases for the 10/20 reconstruction, respectively. DVT was completely detected in all spiral reconstructions. Image noise ranged between 14.8-29.1 HU. Median image quality was 2. Estimated effective dose ranged between 2.3 mSv and 11.8 mSv. Gaps in sequential protocols may lead to false negative results. Therefore, spiral scanning protocols for complete depiction of DVT are mandatory.

The mortality of untreated pulmonary embolism in emergency department patients

Much of the literature on pulmonary embolism that is commonly referenced by emergency physicians begins with statistics concerning how often the diagnosis is missed and the lethality of pulmonary embolism if undiagnosed and untreated. It is likely that many emergency physicians continue to pursue an aggressive diagnostic strategy even in low-risk patients because of concerns about the potential for poor patient outcome and the medicolegal consequences of a missed diagnosis. The believed and often-quoted mortality and recurrence rates for untreated or missed pulmonary embolism are 26% to 30%. However, these figures originate from investigations that have little relevance to modern emergency medicine, which include studies dating to the 1940s, many of which have significant methodologic pitfalls. These data are also based primarily on either inpatient or autopsy populations, neither of which is representative of patients treated in the emergency department (ED). Analysis of untreated or missed pulmonary embolism in ambulatory patients reveals mortality and recurrence rates of less than 5%. This article discusses the background of commonly quoted pulmonary embolism statistics and highlights the need for future investigations enrolling ED patients that focus on disease outcome in this population.

Prospective validation of wells criteria in the evaluation of patients with suspected pulmonary embolism

STUDY OBJECTIVE

The literature suggests that the d -dimer is useful in patients suspected of having pulmonary embolism and who have a low pretest probability of disease. A previously defined clinical decision rule, the Wells Criteria, may provide a reliable and reproducible means of determining this pretest probability. We evaluate the interrater agreement and external validity of Wells Criteria in determining pretest probability in patients suspected of having pulmonary embolism.

METHODS

This was a prospective observational study. Trained research assistants enrolled patients during 120 random 8-hour shifts. Patients who underwent imaging for pulmonary embolism after a medical history, physical examination, and chest radiograph were enrolled. Treating providers and research assistants determined pretest probability according to Wells Criteria in a blinded fashion. Two d -dimer assays were run. Three-month follow-up for the diagnosis of pulmonary embolism was performed. Interrater agreement tables were created. kappa Values, sensitivities, and specificities were determined.

RESULTS

Of the 153 eligible patients, 3 patients were missed, 16 patients declined, and 134 (88%) patients were enrolled. Sixteen (12%) patients were diagnosed with pulmonary embolism. The kappa values for Wells Criteria were 0.54 and 0.72 for the trichotomized and dichotomized scorings, respectively. When Wells Criteria were trichotomized into low pretest probability (n=59, 44%), moderate pretest probability (n=61, 46%), or high pretest probability (n=14, 10%), the pulmonary embolism prevalence was 2%, 15%, and 43%, respectively. When Wells Criteria were dichotomized into pulmonary embolism-unlikely (n=88, 66%) or pulmonary embolism-likely (n=46, 34%), the prevalence was 3% and 28%, respectively. The immunoturbidimetric and rapid enzyme-linked immunosorbent assay d -dimer assays had similar sensitivities (94%) and specificities (45% versus 46%).

CONCLUSION

Wells Criteria have a moderate to substantial interrater agreement and reliably risk stratify pretest probability in patients with suspected pulmonary embolism.

Pulmonary embolism: an unsuspected killer

The presentation of PE is often subtle and may mimic other diseases. Many pulmonary emboli invariably preclude diagnosis by their occult nature or by leading to rapid death from cardiopulmonary arrest. In patients who do manifest symptoms from PE, accurate diagnosis is essential. Often it is difficult to distinguish the vague symptoms of PE from other diagnoses, such as acute coronary syndrome, pneumonia, COPD, CHF,aortic dissection, myocarditis or pericarditis, pneumothorax, and musculo-skeletal or gastrointestinal causes. Regardless of the presentation, the most fundamental step in making the diagnosis of PE is first to consider it. Historical clues and risk factors should raise the clinician's suspicion.PE is an unsuspected killer with a nebulous presentation and high mortality. In all likelihood, PE will remain an elusive diagnosis despite advances in technology and a wealth of research. A high index of suspicion is required, but no amount of suspicion would eliminate all missed cases. Patients with significant underlying cardiopulmonary disease seem to be the most challenging. Patients with significant comorbidity have poor reserve and are likely to have poor outcomes, especially if the diagnosis is not made and anticoagulation is not initiated early. Controversy exists over the best diagnostic approach to PE. A battery of diagnostic studies is available, with few providing definitive answers. Studies such as CT may be helpful at some institutions but offer poor predictive value at others. Other diagnostic tests are not universally available. It is hoped that further research and improvements in current diagnostic modalities will clear some of the current confusion and controversy of this ubiquitous and deadly disease.

CT venography in suspected pulmonary thromboembolism

Pulmonary embolism (PE) and deep venous thrombosis (DVT) are a continuum and are difficult to diagnose clinically. Combined CT venography and pulmonary angiography (CTVPA) is a single examination that combines multidetector CT pulmonary angiography (CTPA) and CT venography (CTV) of the abdomen, pelvis, and lower extremities, providing "one-stop shopping" for venous thromboembolism without additional venipuncture or i.v. contrast, and it adds only a few additional minutes to scanning time. CTVPA rapidly and accurately examines the deep veins, reveals the presence, absence, and extent of deep venous thrombosis, serves as a baseline, and helps guide patient management. Multiple investigators have reported a high degree of accuracy when CTV is compared with venous ultrasound. There are some pitfalls in image interpretation, especially with regard to mixing artifacts, and there are continuing controversies as to exactly which parts of the abdomen, pelvis, and legs should be scanned routinely, the ideal timing of CTV acquisition relative to contrast injection, and the slice thickness and gap, if any, that should be used.

Efficacy of alteplase thrombolysis for ED treatment of pulmonary embolism with shock

Our objective was to assess efficacy and tolerance of thrombolysis using 0.6 mg/kg of Alteplase in patients with massive pulmonary embolism defined as the association of a pulmonary embolism with shock. We retrospectively included 21 patients presenting with a massive pulmonary embolism confirmed by either scintigraphy or spiral computed tomography. Patients were treated on the basis of a standard rationale followed by thrombolysis with 0.6 mg/kg Alteplase over a period of 15 minutes. Hospital mortality, vital signs before and 2 hours after thrombolysis, and incidence of hemorrhagic events were recorded. Five patients (23.8%) died, 4 of these deaths occurred during the first 4 hours after hospital admission. Systolic and diastolic blood pressure (Sp02) were significantly improved 2 hours after the beginning of thrombolysis. Five minor hemorrhagic events occurred. This study demonstrates that for patients with pulmonary embolism and shock, a bolus treatment with Alteplase is potentially effective and well tolerated.

Turbidimetric D-Dimer Test in the Diagnosis of Pulmonary Embolism: A Metaanalysis

Background: Clinicians in outpatient clinics and emergency departments desire an accurate quantitative D-dimer assay. The study objective was to evaluate the diagnostic performance characteristics of the latex turbidimetric D-dimer test in the diagnosis of pulmonary embolism (PE) in the emergency department population.

Methods: We conducted a search of MEDLINE, EMBASE, and bibliographies of previous systematic reviews with no language restriction. Experts in the field of PE research were contacted to identify unpublished studies. Prospective investigations involving predominately outpatient populations with suspected PE that used a turbidimetric D-dimer test were included. Two authors extracted data independently and assessed study quality based on the composition of the patient spectrum and the reference standard used. Consensus was reached by conference. The analysis was based on a summary ROC curve and combining sensitivity and specificity independently across studies using a random-effects model.

Results: The search yielded 264 publications and 2 unpublished studies. Nine studies met the inclusion criteria and provided a sample of 1901 individuals. Eight of the nine studies were homogeneous in terms of both sensitivity and specificity. One study had similar sensitivity but higher specificity. Combining the studies yielded an overall sensitivity of 0.93 (95% confidence interval, 0.89–0.96) and an overall specificity of 0.51 (95% confidence interval, 0.42–0.59).

Conclusions: The turbidimetric D-dimer test is sensitive but nonspecific for the detection of PE in the emergency department setting. D-Dimer tests using latex turbidimetric methods appear to have test characteristics comparable to those for ELISA methods.

Misdiagnosis of pulmonary embolism in patients with allergic reaction — The importance of prior probability of disease

Because pulmonary embolism (PE) and its treatment carry substantial risk of morbidity and mortality, accurate diagnosis is essential. We report two cases with allergic reactions, in which PE was suggested by routine ECG and D-dimer elevation and strengthened by spiral CT. Therapy with low-molecular-weight heparin was initiated and long-term anticoagulation was considered. As their histories did not reveal any predisposing factor to PE, the cases were re-evaluated. Elevation of D-dimer was now attributed to allergic reaction, ECG abnormalities were considered as constitutional, and findings from spiral CT attributed to breathing artifacts and partial-volume effects. The diagnosis of PE was therefore rejected and anticoagulant treatment discontinued without sequelae. These cases show the importance of determining clinical probability before ordering further diagnostic tests and critical interpretation of test results suggestive of PE, based on prior probability of the disease.

Comparison of diagnostic accuracies in outpatients and hospitalized patients of D-dimer testing for the evaluation of suspected pulmonary embolism

BACKGROUND

The ability of various D-dimer assays to exclude the diagnosis of thromboembolic diseases is controversial. We examined the diagnostic accuracy of two D-dimer methods in hospitalized patients and outpatients.

METHODS

We studied consecutive patients for whom D-dimer testing was ordered for investigation of suspected pulmonary embolism. We measured D-dimer by an ELISA (VIDAS D-dimer) and an enhanced microlatex immunoassay method (Diagnostica Stago STA Liatest D-di). Patient diagnoses were based on imaging studies or, when these were not performed, on follow-up by review of medical records 3 months later.

RESULTS

We examined 233 hospitalized patients and 234 outpatients with a mean age of 58 years (range, 1-92 years) and a female-to-male ratio of 1.4 to 1. Thromboembolism was present in 8% of outpatients and 12% of hospitalized patients. In outpatients, the negative predictive values were 98% [95% confidence interval (CI), 93-100%] and 99% (94-100%) for the microlatex and ELISA methods, respectively, at the recommended cutoffs. Areas under the ROC curves were similar for the two methods [0.77 (95% CI, 0.67-0.87) and 0.81 (0.73-0.89), respectively]. By contrast, in hospitalized patients, the confidence intervals for the areas under the ROC curves included 0.5 [0.60 (95% CI, 0.50-0.71) and 0.56 (0.44-0.67)].

CONCLUSIONS

For hospitalized patients, in contrast to outpatients, the diagnostic accuracy of D-dimer testing for pulmonary embolism is poor in a tertiary care setting, presumably reflecting thrombosis and comorbidities, other than pulmonary embolism, that increase the D-dimer concentrations in these patients. The patient population studied appears more important than assay method in studies of the diagnostic accuracy of D-dimer testing.

Role of fibrin D-dimer testing in emergency medicine

OBJECTIVES

Systemic values of the fibrinolytic plasma marker fibrin D-dimer are raised in a variety of acute clinical conditions. D-dimer values can now be rapidly determined and used to aid diagnosis in emergency medicine. However, despite clinical guidelines, inappropriate and unnecessary measurement of D-dimer values is a significant clinical problem. An understanding of the pathophysiological basis and limitations of the value of D-dimer values may help reduce this problem. This review discusses the pathophysiology of the fibrinolytic system. The currently used assays, clinical indications, and limitations of D-dimer measurement are reviewed. Finally, the potential future clinical indications for measurement of D-dimer values in emergency medicine are discussed.

METHODS

Literature on D-dimer was identified from Medline, along with cross referencing from the reference lists of major articles on the subject

RESULTS

and conclusions: Systemic D-dimer values aids diagnosis, and is potentially a prognostic indicator, in a variety of clinical conditions in emergency medicine. However, it has limited specificity in patients with comorbid conditions. Although, currently, there is no standard D-dimer assay, immunoturbidimetric assays are the most suitable for use in emergency medicine

Modulation and roles of the endothelins in the pathophysiology of pulmonary embolism

Recent research on the endothelins (ETs) and their pathways in acute pulmonary embolism (APE) has led to significant advances in the understanding of this disease. ETs are potent vasoconstrictors and bronchoconstrictors found abundantly in the lung and can be released by stimuli such as endothelial injury, hypoxia, or thrombin, a key product in the coagulation cascade. Many studies using different approaches and methods of inducing pulmonary embolization, both in vitro and in vivo in various species, have mostly shown that ETs play an important role in the pathophysiology of APE. These results were obtained by comparing the hemodynamic data in the presence or absence of various ETs inhibitors, but also by assessing the modulation of the ET-related elements of this system by molecular, cell biology, and pharmacological methods. Based on the current understanding, a mechanism involving the ET pathway in the pathophysiology of APE is proposed for the reader's considerations. We postulate that ETs are primary mediators in APE based on the following: (i) their source from pulmonary endothelial cells where the primary injury takes place; (ii) their direct vasconstrictive, bronchoconstrictive, and promitogenic effects via distinct ET receptors; and (iii) their indirect effects associated with the secondary release of thromboxane and other mediators, which are released from inflammatory cells and platelets, which together can potentiate the overall hemodynamic response, most specifically the pulmonary vascular bed. Such combined effects of ETs on bronchomotor and vasomotor tone in the lung can adversely affect ventilation perfusion matching and lead to severe hypoxemia without causing significant changes in the chest X-ray of these patients. Thus, we may consider ET inhibitors as future current therapeutic agents in patients with PE.

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

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.

Clinical policy: critical issues in the evaluation and management of adult patients presenting with suspected pulmonary embolism

This clinical policy focuses on critical issues in the evaluation and management of patients with signs or symptoms of pulmonary embolism (PE). A MEDLINE search for clinical trials published from January 1995 through April 2001 was performed using the key words "pulmonary embolus" with limits of "clinical investigations" and "clinical policies." Subcommittee members and expert peer reviewers also supplied articles with direct bearing on the policy. This policy focuses on 2 major areas of current interest and/or controversy: (1) diagnostic: utility of D -dimer, ventilation-perfusion scanning, and spiral computed tomography angiogram in the evaluation of PE; and (2) therapeutic: indications for fibrinolytic therapy. Recommendations for patient management are provided for each 1 of these topics based on strength of evidence (Level A, B, or C). Level A recommendations represent patient management principles that reflect a high degree of clinical certainty; Level B recommendations represent patient management principles that reflect moderate clinical certainty; and Level C recommendations represent other patient management strategies based on preliminary, inconclusive, or conflicting evidence, or based on panel consensus. This guideline is intended for physicians working in emergency departments or chest pain evaluation units.

Predicting the presence of acute pulmonary embolism: a comparative analysis of the artificial neural network, logistic regression, and threshold models

OBJECTIVE

The objective of this study was to determine whether an artificial neural network, a new data analysis method, offers increased performance over conventional logistic regression in predicting the presence of a pulmonary embolism for patients in a well-known data set.

MATERIALS AND METHODS

Data from the 1064 patients who received an angiographically based diagnosis of pulmonary embolism in the Prospective Investigation of Pulmonary Embolism Diagnosis study were encoded using a previously described method. The 21 input variables represented abnormalities identified on each patient's ventilation-perfusion scan and chest radiograph. Two methods-an artificial neural network with one hidden layer and a multivariate logistic regression-were compared for accuracy in predicting the presence or absence of pulmonary embolism on subsequent pulmonary arteriography.

RESULTS

No significant difference was observed between the two methods. Areas under the receiver operating characteristic curves +/- standard deviation were 0.78 +/- 0.02 for the artificial neural network model and 0.79 +/- 0.02 for the logistic regression model. Furthermore, use of these two methods resulted in no more diagnostic accuracy than did the use of a simple threshold model based only on the number of subsegmental perfusion defects, which was the dominant input variable.

CONCLUSION

In the study population, the usefulness of data from ventilation-perfusion scans as predictors of the presence of a pulmonary embolism was similar for the three analytic methods, a finding that reinforces the importance of making comparisons to simpler or more established methods when performing studies involving complex analytic models, such as artificial neural networks.

Combined CT venography and pulmonary angiography: a comprehensive review

The combination of computed tomographic (CT) venography and pulmonary angiography (CTVPA) was initially described in 1998 as a single comprehensive noninvasive imaging examination for suspected thromboembolic disease. It allowed the identification of pulmonary embolism as well as deep venous thrombosis (DVT) in the abdomen, pelvis, thighs, and calves. The venographic portion of CTVPA has now been studied by multiple researchers and has been shown to be an accurate imaging study for the thigh veins in comparison with lower extremity sonography. In contrast to sonography, however, CTVPA readily and rapidly permits evaluation of the inferior vena cava, the pelvic veins, the calf veins, and all of the superficial venous system. Complex venous anatomy can be surveyed, an additional sonographic study is not required, and only a few extra minutes and images are required over and above CT pulmonary angiography. A review of 957 recent cases of suspected pulmonary embolism examined with CTVPA revealed an overall 10.5% frequency of DVT, with a nearly equal distribution of thrombosis at the common femoral, superficial femoral, popliteal, and deep calf veins. Although a variety of protocols for CTVPA may be implemented, including a contiguous helical acquisition, obtaining 5- or 10-mm-thick images every 4 cm provides a high degree of accuracy and decreases overall radiation dose.

The accuracy of the enzyme-linked immunosorbent assay D-dimer test in the diagnosis of pulmonary embolism: a meta-analysis

STUDY OBJECTIVE

We sought to determine the sensitivity and specificity of the enzyme-linked immunosorbent assay (ELISA) D -dimer test in the diagnosis of pulmonary embolism (PE) in the adult emergency department population.

METHODS

A search of MEDLINE, EMBASE, and bibliographies of previous systematic reviews was conducted, with no language restriction. Experts in the field of PE research were contacted to identify unpublished studies. Prospective investigations involving a predominately outpatient population suspected of PE that used ELISA D -dimer tests were included. Two authors extracted data independently and assessed study quality on the basis of the patient spectrum and reference standard. Consensus was reached by means of conference. The analysis was based on a summary receiver operating characteristic curve and pooled estimates for sensitivity and specificity by using a random-effects model.

RESULTS

The search yielded 52 publications. No unpublished studies were found. Eleven studies met the inclusion criteria and provided a sample of 2,126 patients. The summary receiver operating characteristic curve analysis found significant heterogeneity among the 11 studies. Subgroup analysis of the 9 studies that used traditional ELISA D -dimer methods yielded the most valid pooled estimates, with a sensitivity of 0.94 (95% confidence interval [CI] 0.88 to 0.97) and a specificity of 0.45 (95% CI 0.36 to 0.55). Advanced age resulted in a lower specificity. A prolonged duration of symptoms decreased the sensitivity and specificity.

CONCLUSION

The ELISA D -dimer test is highly sensitive but nonspecific for the detection of PE in the clinical setting. This test might help clinicians safely rule out PE, especially in the face of low and low-to-moderate pretest probabilities.

Variable diagnostic approach to suspected pulmonary embolism in the ED of a major academic tertiary care center

The purpose of this study is to retrospectively examine the patterns of diagnostic modality utilization in the setting of suspected acute pulmonary embolism (PE) by physicians in the emergency department (ED) of a major academic tertiary care center. All patients (n=180) with a hospital discharge diagnosis of PE that were admitted through the ED during 1997 to 1999 were included. Overall test frequency and distribution, ancillary testing used when the initial ventilation-perfusion (V/Q) scan or spiral computed tomography (sCT) angiogram was nondiagnostic, concordance of V/Q and sCT, and sensitivities of D-dimer assays, arterial blood gas analysis, and deep venous imaging were assessed. There was a wide discrepancy in practice, most pronounced when first-line radiological studies were nondiagnostic. There was a poor correlation of PE detection between sCT and V/Q. D-dimer assay, arterial blood gas analysis, and deep venous imaging are insensitive tests for PE, and "gold standard" pulmonary angiography is rarely used.