Triage for suspected acute Pulmonary Embolism: Think before opening Pandora's Box

Diagnosis of Pulmonary Embolism in Pregnancy

Pulmonary embolism (PE) is a significant cause of obstetric morbidity and mortality. However, overdiagnosis related to excessive use of diagnostic testing is also associated with long-term major health issues, including impact on future pregnancies and subsequent health care. Accurate diagnosis of PE depends on the knowledge of prevalence of PE in the pregnant population, the a priori probability of a PE based on specific findings in a given patient, and understanding of the accuracy of computed tomography pulmonary angiography (CTPA), the dominant diagnostic modality employed for this diagnosis. Venous thromboembolism is widely considered to be more common in pregnancy. However, this term includes both deep venous thrombosis as well as PE. While the former appears to be more common, published data on the prevalence of PE in pregnancy show little or no increase relative to the general population. Given the published data on the sensitivity and specificity of CTPA, a positive reading is more likely to be a false positive unless the probability of a PE in a given patient is at least 5% (a 200-fold increase from baseline). Doubling the probability to 10% (a 400-fold increase) only improves the positive predictive value to approximately 67%. Strategies to refine the a priori probability of a PE in a given patient are detailed, including scoring systems and D-dimer measurements. A careful history and physical examination and thoughtful development of a differential diagnosis are key elements of clinical practice and should include both the likelihood of each possible diagnosis and the accuracy of diagnostic modalities. This approach should precede the application of a given algorithm. Such a structured approach can decrease utilization and limit false positive diagnoses without increasing morbidity or mortality. KEY POINTS: · Incidence of PE is lower than assumed.. · Incidence is critical for assessing predictive value of a test.. · Computed tomography angiography is likely overused in pregnancy.. · Clinical scoring and D-dimer have a role in PE diagnosis..

Effectiveness of Manchester Triage System in risk prioritisation of patients with pulmonary embolism who present dyspnoea, chest pain or collapse

BACKGROUND

Recognising patients with pulmonary embolism continues to be a clinical challenge. In the Emergency Department, up to 50% of patients with pulmonary embolism can be delayed or even misdiagnosed. The ability of a triage system to correctly prioritise suspected embolism in these patients is fundamental for determining diagnostic-therapeutic procedures.

AIM

To verify the effectiveness of the Manchester Triage System in risk prioritisation of patients with pulmonary embolism who present with dyspnoea, chest pain, or collapse.

METHODS

In this observational, retrospective, study the sensitivity, specificity, and positive and negative predictive values of the Manchester Triage System were calculated using the triage classification for these patients, and their established diagnoses. The analysis included baseline characteristics and triage evaluations.

RESULTS

During the two-year study period, 7055 patients were enrolled. Pulmonary embolism episodes were 2.1% of all cases, while severe pulmonary embolisms were 0.8%. The estimated specificity of the Manchester Triage System was 72.5% (CI 95%, 71.5-73.6), and the negative predictive value was 98.1% (CI 95%, 97.7-98.5). The results suggest that clinical characteristics leading to a high Manchester Triage System priority are similar to those characterising a pulmonary embolism episode.

CONCLUSIONS

Although pulmonary embolism is difficult to diagnose, the Manchester Triage System is an effective tool for prioritising patients with symptoms of this disease.

Diagnosis of pulmonary embolism: Following the evidence from suspicion to certainty

Accurate, timely and cost-effective identification of pulmonary embolism remains a diagnostic challenge. This article reviews the pulmonary embolism diagnostic process with a focus on the best practice advice from the American College of Physicians. Benefits and risks of each diagnostic step are discussed. Emerging diagnostic tools, not included in the algorithm, are briefly reviewed.

Value of MRI in medicine: More than just another test?

There is increasing scrutiny from healthcare organizations towards the utility and associated costs of imaging. MRI has traditionally been used as a high-end modality, and although shown extremely important for many types of clinical scenarios, it has been suggested as too expensive by some. This editorial will try and explain how value should be addressed and gives some insights and practical examples of how value of MRI can be increased. It requires a global effort to increase accessibility, value for money, and impact on patient management. We hope this editorial sheds some light and gives some indications of where the field may wish to address some of its research to proactively demonstrate the value of MRI. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;49:e14-e25.

Magnetic resonance angiography for the primary diagnosis of pulmonary embolism: A review from the international workshop for pulmonary functional imaging

Pulmonary contrast enhanced magnetic resonance angiography (CE-MRA) is useful for the primary diagnosis of pulmonary embolism (PE). Many sites have chosen not to use CE-MRA as a first line of diagnostic tool for PE because of the speed and higher efficacy of computerized tomographic angiography (CTA). In this review, we discuss the strengths and weaknesses of CE-MRA and the appropriate imaging scenarios for the primary diagnosis of PE derived from our unique multi-institutional experience in this area. The optimal patient for this test has a low to intermediate suspicion for PE based on clinical decision rules. Patients in extremis are not candidates for this test. Younger women (< 35 years of age) and patients with iodinated contrast allergies are best served by using this modality We discuss the history of the use of this test, recent technical innovations, artifacts, direct and indirect findings for PE, ancillary findings, and the effectiveness (patient outcomes) of CE-MRA for the exclusion of PE. Current outcomes data shows that CE-MRA and NM V/Q scans are effective alternative tests to CTA for the primary diagnosis of PE.

Magnetic Resonance Imaging of Pulmonary Embolism: Diagnostic Accuracy of Unenhanced MR and Influence in Mortality Rates

OBJECTIVES

We evaluated the diagnostic value for pulmonary embolism (PE) of the True fast imaging with steady-state precession (TrueFISP) MRI, a method that allows the visualization of pulmonary vasculature without breath holding or intravenous contrast.

METHODS

This is a prospective investigation including 93 patients with suspected PE. All patients underwent TrueFISP MRI after undergoing CT pulmonary angiography (CTPA). Two independent readers evaluated each MR study, and consensus was obtained. CTPA results were analysed by a third independent reviewer and these results served as the reference standard. A fourth radiologist was responsible for evaluating if lesions found on MRI for both analysis were the same and if these were the correspondent lesions on the CTPA. Sensitivity, specificity, predictive values and accuracy were calculated. Evidence for death from PE within the 1-year follow-up was also assessed.

RESULTS

Two patients could not undergo the real-time MRI and were excluded from the study. PE prevalence was 22%. During the 1-year follow-up period, eight patients died, whereas PE was responsible for 12.5% of cases. Between patients who developed PE, only 5% died due to this condition. There were no differences between MR and CT embolism detection in these subjects. MR sequences had a sensitivity of 85%, specificity was 98.6% and accuracy was 95.6%. Agreement between readers was high (κ= 0.87).

CONCLUSIONS

Compared with contrast-enhanced CT, unenhanced MR sequences demonstrate good accuracy and no differences in the mortality rates in 1 year were detected.

Imaging techniques used in the diagnostic workup of acute venous thromboembolic disease

Early diagnosis is one of the most important factors affecting the prognosis of pulmonary embolism (PE); however, the clinical presentation of PE is often very unspecific and it can simulate other diseases. For these reasons, imaging tests, especially computed tomography angiography (CTA) of the pulmonary arteries, have become the keystone in the diagnostic workup of PE. The wide availability and high diagnostic performance of pulmonary CTA has led to an increase in the number of examinations done and a consequent increase in the population's exposure to radiation and iodinated contrast material. Thus, other techniques such as scintigraphy and venous ultrasonography of the lower limbs, although less accurate, continue to be used in certain circumstances, and optimized protocols have been developed for CTA to reduce the dose of radiation (by decreasing the kilovoltage) and the dose of contrast agents. We describe the technical characteristics and interpretation of the findings for each imaging technique used to diagnose PE and discuss their advantages and limitations; this knowledge will help the best technique to be chosen for each case. Finally, we comment on some data about the increased use of CTA, its clinical repercussions, its "overuse", and doubts about its cost-effectiveness.

Incidence of actionable findings on contrast enhanced magnetic resonance angiography ordered for pulmonary embolism evaluation

PURPOSE

To determine the incidence of actionable findings on contrast-enhanced magnetic resonance angiography (MRA) scans performed for the primary diagnosis of pulmonary embolism (PE).

MATERIALS AND METHODS

This was a HIPAA-compliant and IRB-approved single center, retrospective study of consecutive series of patients evaluated with contrast-enhanced MRA for PE. The final radiology report of each MRA was reviewed. All technically adequate negative exams were included in the analysis. The findings were divided into three types: those requiring further action (actionable-Type 1) those not requiring follow-up (non-actionable-Type 2) and normal exams. We compared our results with the literature regarding the use of computed tomographic angiography (CTA) in this scenario using Fisher's exact test.

RESULTS

580 MRA scans for PE were performed. There were 561/580 (97%) technically adequate exams. Of these, 514/580 (89%) were negative and 47/580 (8%) were positive for PE. In the PE negative group of 514 exams, Type 1 findings were identified in 85/514 (17%), 188/514 (36%) cases were Type 2 and 241/514 (47.0%) were Type 3. There was no significant difference between the incidence of Type 1 and the combination of Type 2 and Type 3 findings on MRA and the reported incidence of actionable findings derived from CTA negative exams for PE (p<0.5).

CONCLUSION

MRA as a first-line test for PE can identify actionable findings in those patients without PE, with an incidence similar to that reported in the literature for CTA.

Contrast enhanced pulmonary magnetic resonance angiography for pulmonary embolism: Building a successful program

The performance of contrast enhanced pulmonary magnetic resonance angiography (MRA) for the diagnosis of pulmonary embolism (PE) is an effective non-ionizing alternative to contrast enhanced computed tomography and nuclear medicine ventilation/perfusion scanning. However, the technical success of these exams is very dependent on careful attention to the details of the MRA acquisition protocol and requires reader familiarity with MRI and its artifacts. Most practicing radiologists are very comfortable with the performance and interpretation of computed tomographic angiography (CTA) performed to detect pulmonary embolism but not all are as comfortable with the use of MRA in this setting. The purpose of this review is to provide the general radiologist with the tools necessary to build a successful pulmonary embolism MRA program. This review will cover in detail image acquisition, image interpretation, and some key elements of outreach that help to frame the role of MRA to consulting clinicians and hospital administrators. It is our aim that this resource will help build successful clinical pulmonary embolism MRA programs that are well received by patients and physicians, reduce the burden of medical imaging radiation, and maintain good patient outcomes.