Presentation on theme: "Diagnosis of Pulmonary Embolism"— Presentation transcript:
1Diagnosis of Pulmonary Embolism Presented By: Safa Omran.PharmD , Gp5.Supervised by : Dr. Seham Hafz.
2Diagnosis of PEDiagnosis is challenging, because symptoms and signs are nonspecific and diagnostic tests are either imperfect or invasive (NO SINGLE NONINVASIVE TEST for pulmonary embolism is both sensitive and specific).Failure to diagnose pulmonary embolism is associated with high mortality, and incorrect diagnosis of the condition unnecessarily exposes patients to the risks of anticoagulant therapy.
3Diagnosis of PE Includes: Clinical assessment ( Clinical presentation),Assessment of clinical probability.Diagnostic tests:D-dimer blood testing.ventillation perfusion lung scanning.Computed tomography (CT).pulmonary angiography.Echocardiography.combination of diagnostic tests for PE.Tests for deep vein thrombosis (DVT).
4Clinical assessment ( Clinical presentation) Evaluating the likelihood of PE in an individual patient accordingto the clinical presentation is of utmost importance in theinterpretation of diagnostic test results & selection of anAppropriate diagnostic strategy.Clinical assessment is considered here within the frameworkof diagnostic tests that influence the probability ofpulmonary embolism.in 90% of cases : suspicion of PE is raised by clinical symptoms.but individual clinical signs & symptoms are not very helpfulas they are neither sensitive nor specific.
6Clinical assessment ( Clinical presentation) in summary :clinical signs , symptoms & routinelab tests do not allow the exclusion orconfirmation of acute PE ,but increasethe index of its suspicion.
7Assessment of clinical probability: Despite the limited sensitivity & Specificity of individualsymptoms, signs & common tests , the combination ofthese variables either implicitly by the clinician orby the use of a prediction rule, makes it possible todiscriminate suspected PE patients in categories ofclinical or pretest probability corresponding to anincreasing prevalence of PE.This has become a key step in all diagnosticalgorithms for PE.
8Assessment of clinical probability (Cont.): Prediction rules:Canadian rule ,By Wells et al.The revised Geneva rule. (Europe).
9Assessment of clinical probability (Cont.): In summary:clinical evaluation makes it possible to classify patientsinto probability categories corresponding to anincreasing prevalence of PE , whether assessed byimplicit clinical judgment or by a validatedprediction rule.
10Diagnostic tests; Ventilation perfusion lung scanning. D-dimer blood testing.Ventilation perfusion lung scanning.Computed tomography (CT).Pulmonary angiography.Echocardiography.combination of diagnostic tests for PETests for deep vein thrombosis (DVT).
11D-dimer blood testingD-dimer is formed when cross-linked fibrin is lysed by plasmin, and elevated levels usually occur with pulmonary embolism.However, because elevations of D-dimer arenonspecific (e.g., increased by aging, inflammation,cancer),an abnormal result has a low positive predictive value.The value of D-dimer is that a negative result can help to exclude pulmonary embolism.
12D-dimer blood testing Very highly sensitive D-dimer tests There are a wide variety of D-dimer assays, some of whichare not suitable as diagnostic tests for pulmonary embolismbecause they have such poor operating characteristics(i.e., they are inaccurate).D-dimer assays that have beenvalidated as tests for pulmonary embolism vary in theirsensitivity and specificity, partly because of differences intheir accuracy.D-dimer assays that are valid diagnostic tests for pulmonaryembolism can be divided into: 2 categories.Very highly sensitive D-dimer testsModerate-to-highly sensitive D-dimer tests
13D-dimer blood testing Very highly sensitive D-dimer tests These D-dimer assays have a sensitivity for venousthromboembolism of about 98% or higher.Their negative likelihood ratio is high enough to “rule out”pulmonary embolism in all patients and, consequently,these assays can be used as a “stand-alone” test for theexclusion of pulmonary embolism.However, these assays generally have a low specificity(about 40%) and a high frequency of false-positiveresults (e.g., 53%), which reduces their clinical usefulness.
14D-dimer blood testing 2-Moderate-to-highly sensitive D-dimer tests These D-dimer assays have a sensitivity for venous thromboembolism of about 85%–98%.The negative likelihood ratio and predictive value with these tests are not high enough to rule out pulmonary embolism in consecutive patients.
15D-dimer blood testing 2-Moderate-to-highly sensitive D-dimer tests Consequently, a normal result needs to be combined with another assessment that identifies patients as having a lower pretest probability for pulmonary embolism (e.g., low clinical probability, nondiagnostic lung scan, high alveolar dead space fraction).Such D-dimer assays are more specific than very sensitiveD-dimer assays and, therefore, generate fewer false-positiveresults (e.g., 32%).A whole-blood D-dimer assay (SimpliRED, Agen Biomedical, Brisbane, Australia), which can be performed at the bedside in minutes, is one such test that has been extensively evaluated (approximate sensitivity 85%, approximate specificity 70%).
16Test results that effectively confirm orexclude the presenceof pulmonaryembolism
17Ventilation–perfusion lung scanning Ventilation–perfusion lung scanning has been the usual initial investigation in patients with suspected pulmonary embolism.A normal perfusion scan excludes pulmonaryembolism, but is found in a minority (about 25%) of patients.Perfusion defects are nonspecific, however, with only about one-third of patients with defects having pulmonary embolism.The probability that perfusion defects are due to pulmonary embolism increases with increasing size and number, the presence of a wedged shape and the presence of a normal ventilation scan (“mismatched” defect).
18Computed tomographyTraditional computed tomography (CT) is not suitablefor evaluating suspected pulmonary embolism, because it isnot feasible to opacify the pulmonary arteries with radiographiccontrast for the time required to complete imaging(about 3 minutes) and, even if this could be achieved,motion artifact would interfere with image quality.These problems are overcome by helical CT (also known as spiralor continuous volume CT).Although helical CT is widely used in clinicalpractice, 2 recent systematic reviews of studies that evaluatedthe accuracy of helical CT for the diagnosis of pulmonaryembolism concluded that the technique has beeninadequately evaluated for this purpose.
19Magnetic resonance imaging (MRI) has been less well evaluated than helical CT for the diagnosis of pulmonary embolism; however, it appears to have similar accuracy.Both helical CT and MRI have the advantagethat they may reveal an alternative pulmonary diagnosis,and both examinations may be extended to look for concomitant deep vein thrombosis. MRI also avoids exposure to radiation and radiographic contrast.It is anticipated that the diagnosis of pulmonary embolism by CT and MRI will continue to improve, and modern scanners may already be more accurate than those used in published studies using older technology.
21Pulmonary angiography Pulmonary angiography is the criterion standard for thediagnosis of pulmonary embolism, but it is associatedWith serious side effects(e.g., mortality of about 0.5%), is technicallydemanding to perform, may be difficult to interpretand is costly. It is contraindicated in patientswith renal impairment and may not be feasible inthe sickest patients.
22EchocardiographyEchocardiography is valuable in differentiating betweenmassive pulmonary embolism and other causes ofhemodynamic compromise.In conjunction with clinical assessment and theresults of other noninvasive tests(e.g., venous ultrasonography), echocardiography mayenable pulmonary embolism to be diagnosed, orAnticoagulants to be withheld, in severely ill patients,at least until it becomes feasible to performadditional testing.
23Tests for deep vein thrombosis Detection of asymptomatic deep vein thrombosis is an indirect way to diagnose pulmonary embolism. In the presence of acute pulmonary embolism, deep vein thrombosis is detectable by bilateral ascending venography in about 75% of patients and by compression ultrasonography of the proximal veins in about 50% of patients(i.e., sensitivity for pulmonary embolism of 75% and 50% respectively).
24Combinations of diagnostic tests for pulmonary embolism When individual tests are nondiagnostic, it may be possible to combine their results to confirm or exclude pulmonary Embolism.Some of the better studied combinations Are:Clinical assessment and ventilation–perfusion lung Scanning.Clinical assessment and negative D-dimer testingNondiagnostic lung scanning and negative D-dimer testingNondiagnostic lung scanning and normal ultrasoundtesting for proximal deep vein thrombosis.Helical CT scanning in combination with other tests
25Algorithms for the diagnosis of pulmonary Embolism There are many valuable tests (including clinical assessment) that may be used, singly or in combination, to confirm or exclude the presence of pulmonary embolism with a high degree of confidence. Availability of testing and differences among patient presentations will influence the diagnostic approach used.A number of prospectively validated algorithms have been published that emphasize the use of different initial noninvasive tests in conjunction with ventilation–perfusion lung scanning. These include structured clinical assessment and serial venous ultrasonography; sensitive D-dimer assay, clinical assessment and venous ultrasonography at presentation only.