2014ESC急性肺栓塞诊断和管理指南(英文版)(6)

Mobile right heart thrombi are detected by transthoracic or trans-oesophageal echocardiography(or by CT angiography)in less than 4%of unselected patients with PE,183–185but their prevalence may reach18%in the intensive care setting.185Mobile right heart thrombi essentially con?rm the diagnosis of PE and their presence is associated with RV dysfunction and high early mortality.184,186,187 Consequently,transoesophageal echocardiography may be consid-ered when searching for emboli in the main pulmonary arteries in speci?c clinical situations,188,189and it can be of diagnostic value in haemodynamically unstable patients due to the high prevalence of bilateral central pulmonary emboli in most of these cases.190

In some patients with suspected acute PE,echocardiography may detect increased RV wall thickness and/or tricuspid insuf?ciency jet velocity beyond values compatible with acute RV pressure overload. In these cases,chronic pulmonary hypertension,and CTEPH in par-ticular,should be included in the differential diagnosis.

3.9Compression venous ultrasonography In the majority of cases,PE originates from DVT in a lower limb.In a study using venography,DVT was found in70%of patients with proven PE.191Nowadays,lower limb CUS has largely replaced venog-raphy for diagnosing DVT.CUS has a sensitivity.90%and a speci?-city of approximately95%for symptomatic DVT.192,193CUS shows a DVT in30–50%of patients with PE,116,192,193and?nding a proximal DVT in patients suspected of having PE is considered suf?cient to warrant anticoagulant treatment without further testing.194

In the setting of suspected PE,CUS can be limited to a simple four-point examination(groin and popliteal fossa).The only validated diag-nostic criterion for DVT is incomplete compressibility of the vein, which indicates the presence of a clot,whereas?ow measurements are unreliable.The diagnostic yield of CUS in suspected PE may be increased further by performing complete ultrasonography,which includes the distal veins.Two recent studies assessed the proportion of patients with suspected PE and a positive D-dimer result,in whom a DVT could be detected by complete CUS.195,196The diagnostic yield of complete CUS was almost twice that of proximal CUS,but a high proportion(26–36%)of patients with distal DVT had no PE on thoracic MDCT.In contrast,a positive proximal CUS result has a high positive predictive value for PE,as con?rmed by data from a large pro-spective outcome study,in which524patients underwent both MDCT and CUS.The sensitivity of CUS for the presence of PE on MDCT was 39%and its speci?city was99%.194The probability of a positive prox-imal CUS in suspected PE is higher in patients with signs and symptoms related to the leg veins than in asymptomatic patients.192,193

3.10Diagnostic strategies

The prevalence of con?rmed PE in patients undergoing diagnostic work-up because of suspicion of disease has been rather low(10–35%)in large series.99,100,113,116,197Hence,the use of diagnostic algo-rithms is warranted,and various combinations of clinical assessment, plasma D-dimer measurement,and imaging tests have been pro-posed and validated.These strategies were tested in patients present-ing with suspected PE in the emergency ward,99,113,114,116,197during the hospital stay and more recently in the primary care setting.118,126 Failure to comply with evidence-based diagnostic strategies when withholding anticoagulation was associated with a signi?cant increase in the number of VTE episodes and sudden cardiac death at three-month follow-up.198The most straightforward diagnostic algorithms for suspected PE—with and without shock or hypotension—are pre-sented in Figures3and4,respectively;however,it is recognized that the diagnostic approach to suspected PE may vary,depending on the availability of—and expertise in—speci?c tests in various hospi-tals and clinical settings.Accordingly,Table6provides the necessary evidence for alternative evidence-based diagnostic algorithms. The diagnostic strategy for suspected acute PE in pregnancy is dis-cussed in Section8.1.

3.10.1Suspected pulmonary embolism with shock

or hypotension

The proposed strategy is shown in Figure3.Suspected high-risk PE is an immediately life-threatening situation,and patients presenting with shock or hypotension present a distinct clinical problem.The clinical probability is usually high,and the differential diagnosis includes acute valvular dysfunction,tamponade,acute coronary syndrome(ACS), and aortic dissection.The most useful initial test in this situation is bedside transthoracic echocardiography,which will yield evidence of acute pulmonary hypertension and RV dysfunction if acute PE is the cause of the patient’s haemodynamic decompensation.In a highly un-stable patient,echocardiographic evidence of RV dysfunction is suf?-cient to prompt immediate reperfusion without further testing.This decision may be strengthened by the(rare)visualization of right heart thrombi.184,199,200Ancillary bedside imaging tests include transoeso-phageal echocardiography which,if available,may allow direct visualiza-tion of thrombi in the pulmonary artery and its main branches,188,190,201 and bedside CUS,which can detect proximal DVT.As soon as the patient can be stabilized by supportive treatment,?nal con?rmation of the diagnosis by CT angiography should be sought.

For unstable patients admitted directly to the catheterization la-boratory with suspected ACS,pulmonary angiography may be con-sidered as a diagnostic procedure after the ACS has been excluded, provided that PE is a probable diagnostic alternative and particularly if percutaneous catheter-directed treatment is a therapeutic option.

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3.10.2Suspected pulmonary embolism without shock

or hypotension

Strategy based on computed tomographic angiography(Figure4) Computed tomographic angiography has become the main thor-acic imaging test for investigating suspected PE but,since most patients with suspected PE do not have the disease,CT should not be the?rst-line test.

In patients admitted to the emergency department,plasma D-dimer measurement,combined with clinical probability assess-ment,is the logical?rst step and allows PE to be ruled out in around30%of patients,with a three-month thromboembolic risk in patients left untreated of,1%.D-dimer should not be measured in patients with a high clinical probability,owing to a low negative pre-dictive value in this population.202It is also less useful in hospitalized patients because the number needed to test to obtain a clinically rele-vant negative result is high.

In most centres,MDCT angiography is the second-line test in patients with an elevated D-dimer level and the?rst-line test in patients with a high clinical probability.CT angiography is considered to be diagnostic of PE when it shows a clot at least at the segmental level of the pulmonary arterial tree.False-negative results of MDCT have been reported in patients with a high clinical probability of PE;134however,this situation is infrequent,and the three-month thromboembolic risk was low in these cases.99Therefore,both the necessity of performing further tests and the nature of these tests in such patients remain controversial.

Value of lower limb compression ultrasonography

Under certain circumstances,CUS can still be useful in the diagnostic work-up of suspected PE.CUS shows a DVT in30–50% of patients with PE,116,192,193and?nding proximal DVT in a patient suspected of PE is suf?cient to warrant anticoagulant treatment without further testing.194Hence,performing CUS before CT may be an option in patients with relative contraindications for CT such as in renal failure,allergy to contrast dye,or pregnancy.195,196 Value of ventilation–perfusion scintigraphy

In centres in which V/Q scintigraphy is readily available,it remains a valid option for patients with an elevated D-dimer and a

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contraindication to CT.Also,V/Q scintigraphy may be preferred over CT to avoid unnecessary radiation,particularly in younger and female patients in whom thoracic CT may raise the lifetime risk of breast cancer.139V/Q lung scintigraphy is diagnostic(with either normal or high-probability?ndings)in approximately30–50%of emergency ward patients with suspected PE.83,94,135,203The proportion of diag-nostic V/Q scans is higher in patients with a normal chest X-ray,and this supports the recommendation to use V/Q scan as the?rst-line imaging test for PE in younger patients.204

The number of patients with inconclusive?ndings may also be reduced by taking into account clinical probability.94Thus,patients with a non-diagnostic lung scan and low clinical probability of PE have a low prevalence of con?rmed PE.94,157,203The negative predict-ive value of this combination is further increased by the absence of a DVT on lower-limb CUS.If a high-probability lung scan is obtained from a patient with low clinical probability of PE,con?rmation by other tests may be considered on a case-by-case basis.

3.11Areas of uncertainty

Despite considerable progress in the diagnosis of PE,several areas of uncertainty persist.The diagnostic value and clinical signi?cance of sub-segmental defects on MDCT are still under debate.136,137A recent retrospective analysis of two patient cohorts with suspected PE showed similar outcomes(in terms of three-month recurrence and mortality rates)between patients with sub-segmental and more proximal PE;outcomes were largely determined by comorbid-ities.205The de?nition of sub-segmental PE has yet to be standardized and a single sub-segmental defect probably does not have the same clinical relevance as multiple,sub-segmental thrombi.

There is also growing evidence suggesting over-diagnosis of PE.206A randomized comparison showed that,although CT detected PE more frequently than V/Q scanning,three-month out-comes were similar,regardless of the diagnostic method used.135 Data from the United States show an80%rise in the apparent in-cidence of PE after the introduction of CT,without a signi?cant impact on mortality.207,208

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