Diagnostic accuracy of lung ultrasound for pulmonary embolism: a systematic review and meta-analysis

Emergency Thoracic US: The Essentials

Acute thoracic symptoms are common among adults visiting emergency departments in the United States. Adults with these symptoms constitute a large burden on the overall resources used in the emergency department. The wide range of possible causes can make a definitive diagnosis challenging, even after clinical evaluation and initial laboratory testing. In addition to radiography and computed tomography, thoracic ultrasonography (US) is an alternative imaging modality that can be readily performed in real time at the patient's bedside to help diagnose many thoracic diseases manifesting acutely and in the trauma setting. Advantages of US include availability, relatively low cost, and lack of ionizing radiation. Emergency thoracic US consists of two main parts, lung and pleura US and focused cardiac US, which are closely related. Acoustic mismatches among aerated lungs, pleura, chest wall, and pathologic conditions produce artifacts useful for diagnosis of pneumothorax and pulmonary edema and help in detection of subpleural, pleural, and chest wall pathologic conditions such as pneumonia, pleural effusion, and fractures. Visual assessment of cardiac contractility and detection of right ventricular dilatation and pericardial effusion at focused cardiac US are critical in patients presenting with acute dyspnea and trauma. Additional US examinations of the inferior vena cava for noninvasive volume assessment and of the groin areas for detection of deep venous thrombosis are often performed at the same time. This multiorgan US approach can provide valuable information for emergency treatment of both traumatic and nontraumatic thoracic diseases involving the lungs, pleura, chest wall, heart, and vascular system. Online supplemental material is available for this article. (©)RSNA, 2016.

Role of Transthoracic Lung Ultrasonography in the Diagnosis of Pulmonary Embolism: A Systematic Review and Meta-Analysis

Background

Pulmonary embolism (PE) is a potentially life-threatening condition. Although computed tomography pulmonary angiography (CTPA) is the reference standard for diagnosis, its early diagnosis remains a challenge, and the concerns about the radiation exposures further limit the general use of CTPA. The primary aim of this meta-analysis was to evaluate the overall diagnostic accuracy of transthoracic lung ultrasound (TLS) in the diagnosis of PE.

Methods

PubMed, Web of science, OvidSP, ProQuest, EBSCO, Cochrane Library and Clinicaltrial.gov were searched systematically. The quality of included studies was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. The sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR) and hierarchical summary receiver operating characteristic (HSROC) curves were used to examine the TS performance. The Bayes analysis was used to calculate the post-test probability of PE. Publication bias was assessed with Deeks funnel plot.

Results

The results indicated that the sensitivity, specificity, PLR and NLR were 0.85 (95% confidence interval (CI), 0.78 to 0.90), and 0.83 (95% CI, 0.73 to 0.90). And the DOR and HSROC were 28.82 (95% CI, 17.60 to 47.21), 0.91(95% CI, 0.88, 0.93).

Conclusions

The present meta-analysis suggested that transthoracic lung ultrasonography is helpful in diagnosing pulmonary embolism. Although the application of transthoracic lung ultrasound may change some patients’ diagnostic processes, it is inappropriate to generally use transthoracic ultrasonography in diagnosing pulmonary embolism currently.

Point-of-care ultrasound in the diagnosis of pulmonary embolism

The best diagnostic strategy to confirm or exclude pulmonary embolism (PE) suspicion needs an appropriate combination of clinical assessment, plasma D-dimer measurement, and computed tomographic pulmonary angiography (CTPA). CTPA should be used with caution in some patient groups, such as patients with known allergy to contrast media, those with severe renal insufficiency, and pregnant women, and could be not immediately available in case of unstable patients. In the emergency setting, alternative diagnostic strategies should be implemented to overcome CTPA limitations. Ultrasonography is certainly a valuable alternative diagnostic tool. In addition to echocardiography and lower limb compressive venous ultrasonography, lung ultrasound (US) may play an important role in selected patients’ subgroups. Recent data on the diagnostic performance of a triple point-of-care US (lung, heart, and leg vein US) are discussed in the present paper, and pros and cons of triple point-of-care US are compared with those of standard diagnostic approaches.

Acute pulmonary embolism: risk assessment, risk stratification and treatment options

INTRODUCTION

Pulmonary embolism (PE) is a potentially life-threatening cardiovascular emergency with a high mortality rate. Rapid diagnosis and treatment are important in optimising clinical outcomes in patients with PE, and anticoagulants are the mainstay of treatment. Traditionally, anticoagulant therapy involves parenteral anticoagulants, overlapping with and followed by oral vitamin K antagonists. Direct oral anticoagulants (DOACs), including the factor Xa inhibitors rivaroxaban, apixaban and edoxaban, and the direct thrombin inhibitor dabigatran etexilate, have been developed to address limitations associated with traditional anticoagulant therapy. Apixaban, dabigatran and rivaroxaban have recently been approved for the treatment of acute deep vein thrombosis (DVT) and PE and prevention of recurrent DVT or PE. Edoxaban is approved in the United States but not currently in the European Union for the treatment of DVT and PE; approval of edoxaban in Europe is anticipated in the near future.

OBJECTIVE

To summarise the management of patients with suspected PE in accordance with recent guidelines, and to discuss the evidence behind the recent approvals of the DOACs for the treatment of PE.

DISCUSSION

Diagnosis and treatment of PE is guided by clinical probability scoring systems and tools for prognostic stratification and early mortality risk evaluation. Anticoagulants remain the mainstay of treatment. Successful phase III trials have demonstrated the efficacy of the DOACs for the treatment of DVT and PE, with a potentially improved safety profile, leading to their recent approval in this indication, and giving the clinician greater choice of anticoagulant therapies in this setting.

CONCLUSIONS

DOACs offer an alternative and potentially simplified option for anticoagulation therapy in patients with PE compared with traditional anticoagulants and are likely to assist physicians in optimising management of patients with PE and improve clinical outcomes.

Ultrasound of the pleurae and lungs

The value of ultrasound techniques in examination of the pleurae and lungs has been underestimated over recent decades. One explanation for this is the assumption that the ventilated lungs and the bones of the rib cage constitute impermeable obstacles to ultrasound. However, a variety of pathologies of the chest wall, pleurae and lungs result in altered tissue composition, providing substantially increased access and visibility for ultrasound examination. It is a great benefit that the pleurae and lungs can be non-invasively imaged repeatedly without discomfort or radiation exposure for the patient. Ultrasound is thus particularly valuable in follow-up of disease, differential diagnosis and detection of complications. Diagnostic and therapeutic interventions in patients with pathologic pleural and pulmonary findings can tolerably be performed under real-time ultrasound guidance. In this article, an updated overview is given presenting not only the benefits and indications, but also the limitations of pleural and pulmonary ultrasound.

A Young Man Presenting with Pleuritic Chest Pain and Fever after Electrophysiological Study and Implantable Cardioverter-Defibrillator Placement: Diagnostic Difficulties and Value of Bedside Thoracic Sonography

We describe the case of a 23-year-old man presenting with recurrent pleuritic chest pain and prolonged fever after electrophysiology testing and placement of an implantable cardioverter-defibrillator because of a suspected arrhythmogenic right ventricular dysplasia. The clinical suspicion was initially directed toward pneumonia with pleural effusion and later toward an infection of the cardiac device complicated by septic pulmonary embolism. The definitive diagnosis of pulmonary embolism and infarction was suggested by a point-of-care thoracic sonography, performed at the bedside by a clinician caring for the patient, and then confirmed by contrast enhanced computed tomography, which also showed thrombosis of the left iliofemoral vein, site of percutaneous puncture for cardiac catheterization. Prolonged fever was attributable to a concomitant Epstein-Barr virus primary infection that acted as confounding factor. The present report confirms the value of bedside thoracic sonography in the diagnostic evaluation of patients with nonspecific respiratory symptoms.

Emergency ultrasound of the chest

Thoracic ultrasound is a noninvasive and portable diagnostic tool which is highly indicated for an initial workup of thoracic emergencies. The suspicion of a pneumothorax, pneumonia, pulmonary embolism or a lung contusion after trauma can be quickly assessed using ultrasound. Main advantages are its good availability and the steep learning curve. Another advantage of thoracic sonography is that this rapid, symptom-based examination has a high sensitivity and specificity. However, a disadvantage is that only pleura-affecting lesions or lesions visible through a sound window, e.g. an effusion or a subpleural consolidation, can be reached.

Pulmonary ultrasound examination for edema, effusion, and thromboembolism

Bedside, or point-of-care, ultrasound (US) has increasingly been used in various clinical settings to provide clinicians with rapid clinical information without the use of ionizing radiation. Lung US has been demonstrated as a valuable tool in the diagnosis and evaluation of pulmonary edema, pleural effusions, and pulmonary thromboembolism. Lung US enables the clinician to more quickly identify and initiate treatment for these potentially life-threatening conditions without the need for patient transportation to the radiology suite. Additionally, lung US can repeatedly be implemented to assess clinical changes without concern for repeated radiation exposure and is cost-effective given its ability to decrease the need for additional radiological and laboratory testing to confirm a suspected diagnosis. This review focuses on the application of lung US in the evaluation and management of pulmonary edema, pleural effusions, and pulmonary thromboembolism.