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Pulmonary Embolism: Difference between revisions
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;Non-invasive imaging | ;Non-invasive imaging | ||
[[CT pulmonary angiogram|CT pulmonary angiography]] (CTPA) is a [[pulmonary angiogram]] obtained using [[computed tomography]] (CT) with [[radiocontrast]] rather than right heart catheterization. Its advantages are clinical equivalence, its non-invasive nature, its greater availability to patients, and the possibility of identifying other lung disorders from the [[differential diagnosis]] in case there is no pulmonary embolism. Assessing the accuracy of CT pulmonary angiography is hindered by the rapid changes in the number of rows of detectors available in multidetector CT (MDCT) machines.< | [[CT pulmonary angiogram|CT pulmonary angiography]] (CTPA) is a [[pulmonary angiogram]] obtained using [[computed tomography]] (CT) with [[radiocontrast]] rather than right heart catheterization. Its advantages are clinical equivalence, its non-invasive nature, its greater availability to patients, and the possibility of identifying other lung disorders from the [[differential diagnosis]] in case there is no pulmonary embolism. Assessing the accuracy of CT pulmonary angiography is hindered by the rapid changes in the number of rows of detectors available in multidetector CT (MDCT) machines. <cite>REFNAME16</cite> According to a [[cohort study]], single-slice [[spiral CT]] may help diagnose detection among patients with suspected pulmonary embolism. <cite>REFNAME17</cite> In this study, the [[sensitivity (tests)|sensitivity]] was 69% and [[specificity (tests)|specificity]] was 84%. In this study which had a prevalence of detection was 32%, the [[positive predictive value]] of 67.0% and [[negative predictive value]] of 85.2% ([http://medinformatics.uthscsa.edu/calculator/calc.shtml?calc_dx_SnSp.shtml?prevalence=32&sensitivity=69&specificity=84 click here] to adjust these results for patients at higher or lower risk of detection). However, this study's results may be biased due to possible incorporation bias, since the CT scan was the final diagnostic tool in patients with pulmonary embolism. The authors noted that a negative single slice CT scan is insufficient to rule out pulmonary embolism on its own. A separate study with a mixture of 4 slice and 16 slice scanners reported a [[sensitivity (tests)|sensitivity]] of 83% and a [[specificity (tests)|specificity]] of 96%. This study noted that additional testing is necessary when the clinical probability is inconsistent with the imaging results. <cite>REFNAME18</cite> CTPA is non-inferior to VQ scanning, and identifies more emboli (without necessarily improving the outcome) compared to VQ scanning. <cite>Anderson2007</cite> | ||
''[[Ventilation/perfusion scan]]'' (or ''V/Q scan'' or ''lung [[scintigraphy]]''), which shows that some areas of the lung are being [[Ventilation (physiology)|ventilated]] but not [[Perfusion|perfused]] with blood (due to obstruction by a clot). This type of examination is used less often because of the more widespread availability of CT technology, however, it may be useful in patients who have an allergy to [[iodinated contrast]] or in [[pregnancy]] due to lower radiation exposure than CT.< | ''[[Ventilation/perfusion scan]]'' (or ''V/Q scan'' or ''lung [[scintigraphy]]''), which shows that some areas of the lung are being [[Ventilation (physiology)|ventilated]] but not [[Perfusion|perfused]] with blood (due to obstruction by a clot). This type of examination is used less often because of the more widespread availability of CT technology, however, it may be useful in patients who have an allergy to [[iodinated contrast]] or in [[pregnancy]] due to lower radiation exposure than CT. <cite>REFNAME19</cite> | ||
;Low probability diagnostic tests/non-diagnostic tests | ;Low probability diagnostic tests/non-diagnostic tests | ||
Tests that are frequently done that are not [[sensitivity (tests)|sensitive]] for PE, but can be diagnostic. | Tests that are frequently done that are not [[sensitivity (tests)|sensitive]] for PE, but can be diagnostic. | ||
*''[[Chest X-ray]]s'' are often done on patients with shortness of breath to help rule-out other causes, such as [[congestive heart failure]] and [[rib fracture]]. Chest X-rays in PE are rarely normal,< | *''[[Chest X-ray]]s'' are often done on patients with shortness of breath to help rule-out other causes, such as [[congestive heart failure]] and [[rib fracture]]. Chest X-rays in PE are rarely normal, <cite>REFNAME20</cite> but usually lack [[radiologic sign|sign]]s that suggest the diagnosis of PE (e.g. [[Westermark sign]], [[Hampton's hump]]). | ||
*''[[medical ultrasound|Ultrasonography]] of the legs'', also known as ''leg doppler'', in search of [[deep venous thrombosis]] (DVT). The presence of [[deep venous thrombosis|DVT]], as shown on [[ultrasonography]] of the legs, is in itself enough to warrant anticoagulation, without requiring the V/Q or spiral CT scans (because of the strong association between DVT and PE). This may be valid approach in [[pregnancy]], in which the other modalities would increase the risk of birth defects in the unborn child. However, a negative scan does not rule out PE, and low-radiation dose scanning may be required if the mother is deemed at high risk of having pulmonary embolism. {{Citation needed|date=August 2011}} | *''[[medical ultrasound|Ultrasonography]] of the legs'', also known as ''leg doppler'', in search of [[deep venous thrombosis]] (DVT). The presence of [[deep venous thrombosis|DVT]], as shown on [[ultrasonography]] of the legs, is in itself enough to warrant anticoagulation, without requiring the V/Q or spiral CT scans (because of the strong association between DVT and PE). This may be valid approach in [[pregnancy]], in which the other modalities would increase the risk of birth defects in the unborn child. However, a negative scan does not rule out PE, and low-radiation dose scanning may be required if the mother is deemed at high risk of having pulmonary embolism. {{Citation needed|date=August 2011}} | ||
===Electrocardiogram=== | ===Electrocardiogram=== | ||
[[File:Pulmonary embolism ECG.jpg|thumb|Electrocardiogram of a patient with pulmonary embolism showing [[sinus tachycardia]] of approximately 150 beats per minute and [[right bundle branch block]].]] | [[File:Pulmonary embolism ECG.jpg|thumb|Electrocardiogram of a patient with pulmonary embolism showing [[sinus tachycardia]] of approximately 150 beats per minute and [[right bundle branch block]].]] | ||
An [[electrocardiogram]] (ECG) is routinely done on patients with chest pain to quickly diagnose [[myocardial infarction]]s (heart attacks). An ECG may show signs of right heart strain or acute ''[[cor pulmonale]]'' in cases of large PEs - the classic signs are a large S wave in lead I, a large Q wave in lead III and an inverted [[T wave]] in lead III ("S1Q3T3").<ref>{{cite journal |author=McGinn S, [[Paul Dudley White|White PD]] | title=Acute cor pulmonale resulting from pulmonary embolism |journal=J Am Med Assoc |year=1935 |volume=104 | pages=1473–80}}</ref> This is occasionally (up to 20%) present, but may also occur in other acute lung conditions and has therefore limited diagnostic value. The most commonly seen signs in the ECG is [[sinus tachycardia]], right axis deviation and [[right bundle branch block]].< | An [[electrocardiogram]] (ECG) is routinely done on patients with chest pain to quickly diagnose [[myocardial infarction]]s (heart attacks). An ECG may show signs of right heart strain or acute ''[[cor pulmonale]]'' in cases of large PEs - the classic signs are a large S wave in lead I, a large Q wave in lead III and an inverted [[T wave]] in lead III ("S1Q3T3").<ref>{{cite journal |author=McGinn S, [[Paul Dudley White|White PD]] | title=Acute cor pulmonale resulting from pulmonary embolism |journal=J Am Med Assoc |year=1935 |volume=104 | pages=1473–80}}</ref> This is occasionally (up to 20%) present, but may also occur in other acute lung conditions and has therefore limited diagnostic value. The most commonly seen signs in the ECG is [[sinus tachycardia]], right axis deviation and [[right bundle branch block]]. <cite>REFNAME21</cite> Sinus tachycardia was however still only found in 8 - 69% of people with PE. <cite>REFNAME22</cite> | ||
===Echocardiography=== | ===Echocardiography=== | ||
In massive and submassive PE, dysfunction of the right side of the heart can be seen on [[echocardiography]], an indication that the [[pulmonary artery]] is severely obstructed and the heart is unable to match the pressure. Some studies (see below) suggest that this finding may be an indication for [[thrombolysis]]. Not every patient with a (suspected) pulmonary embolism requires an echocardiogram, but elevations in [[troponin|cardiac troponins]] or [[brain natriuretic peptide]] may indicate heart strain and warrant an echocardiogram.< | In massive and submassive PE, dysfunction of the right side of the heart can be seen on [[echocardiography]], an indication that the [[pulmonary artery]] is severely obstructed and the heart is unable to match the pressure. Some studies (see below) suggest that this finding may be an indication for [[thrombolysis]]. Not every patient with a (suspected) pulmonary embolism requires an echocardiogram, but elevations in [[troponin|cardiac troponins]] or [[brain natriuretic peptide]] may indicate heart strain and warrant an echocardiogram. <cite>REFNAME23</cite> | ||
The specific appearance of the right ventricle on echocardiography is referred to as the ''McConnell's sign''. This is the finding of akinesia of the mid-free wall but normal motion of the apex. This phenomenon has a 77% sensitivity and a 94% specificity for the diagnosis of acute pulmonary embolism in the setting of right ventricular dysfunction.< | The specific appearance of the right ventricle on echocardiography is referred to as the ''McConnell's sign''. This is the finding of akinesia of the mid-free wall but normal motion of the apex. This phenomenon has a 77% sensitivity and a 94% specificity for the diagnosis of acute pulmonary embolism in the setting of right ventricular dysfunction. <cite>REFNAME24</cite> | ||
===Algorithms=== | ===Algorithms=== | ||
Recent recommendations for a diagnostic algorithm have been published by the PIOPED investigators; however, these recommendations do not reflect research using 64 slice MDCT.< | Recent recommendations for a diagnostic algorithm have been published by the PIOPED investigators; however, these recommendations do not reflect research using 64 slice MDCT. <cite>REFNAME25</cite> These investigators recommended: | ||
* Low clinical probability. If negative D-dimer, PE is excluded. If positive D-dimer, obtain MDCT and based treatment on results. | * Low clinical probability. If negative D-dimer, PE is excluded. If positive D-dimer, obtain MDCT and based treatment on results. | ||
* Moderate clinical probability. If negative D-dimer, PE is excluded. ''However'', the authors were not concerned that a negative MDCT with negative D-dimer in this setting has an 5% probability of being false. Presumably, the 5% error rate will fall as 64 slice MDCT is more commonly used. If positive D-dimer, obtain MDCT and based treatment on results. | * Moderate clinical probability. If negative D-dimer, PE is excluded. ''However'', the authors were not concerned that a negative MDCT with negative D-dimer in this setting has an 5% probability of being false. Presumably, the 5% error rate will fall as 64 slice MDCT is more commonly used. If positive D-dimer, obtain MDCT and based treatment on results. | ||
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The Pulmonary Embolism Rule-out Criteria, or PERC rule, helps assess people in whom pulmonary embolism is suspected, but unlikely. Unlike the Wells Score and Geneva score, which are clinical prediction rules intended to risk stratify patients with suspected PE, the PERC rule is designed to rule out risk of PE in patients when the physician has already stratified them into a low-risk category. | The Pulmonary Embolism Rule-out Criteria, or PERC rule, helps assess people in whom pulmonary embolism is suspected, but unlikely. Unlike the Wells Score and Geneva score, which are clinical prediction rules intended to risk stratify patients with suspected PE, the PERC rule is designed to rule out risk of PE in patients when the physician has already stratified them into a low-risk category. | ||
Patients in this low risk category without any of these criteria may undergo no further diagnostic testing for PE: Hypoxia - Sa0<sub>2</sub> <95%, unilateral leg swelling, hemoptysis, prior DVT or PE, recent surgery or trauma, age >50, hormone use, tachycardia. The rationale behind this decision is that further testing (specifically CT angiogram of the chest) may cause more harm (from radiation exposure and contrast dye) than the risk of PE.< | Patients in this low risk category without any of these criteria may undergo no further diagnostic testing for PE: Hypoxia - Sa0<sub>2</sub> <95%, unilateral leg swelling, hemoptysis, prior DVT or PE, recent surgery or trauma, age >50, hormone use, tachycardia. The rationale behind this decision is that further testing (specifically CT angiogram of the chest) may cause more harm (from radiation exposure and contrast dye) than the risk of PE. <cite>REFNAME26</cite> The PERC rule has a sensitivity of 97.4% and specificity of 21.9% with a false negative rate of 1.0% (16/1666). <cite>REFNAME27</cite> | ||
==Treatment== | ==Treatment== | ||
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===Anticoagulation=== | ===Anticoagulation=== | ||
{{main|anticoagulant}} | {{main|anticoagulant}} | ||
In most cases, [[anticoagulant]] therapy is the mainstay of treatment. [[Heparin]], [[low molecular weight heparin]]s (such as [[enoxaparin]] and [[dalteparin]]), or [[fondaparinux]] is administered initially, while [[warfarin]], [[acenocoumarol]], or [[phenprocoumon]] therapy is commenced (this may take several days, usually while the patient is in the hospital). [[Low molecular weight heparin]] may reduce bleeding among patients with pulmonary embolism as compared to heparin according to a [[systematic review]] of [[randomized controlled trial]]s by the [[Cochrane Collaboration]].< | In most cases, [[anticoagulant]] therapy is the mainstay of treatment. [[Heparin]], [[low molecular weight heparin]]s (such as [[enoxaparin]] and [[dalteparin]]), or [[fondaparinux]] is administered initially, while [[warfarin]], [[acenocoumarol]], or [[phenprocoumon]] therapy is commenced (this may take several days, usually while the patient is in the hospital). [[Low molecular weight heparin]] may reduce bleeding among patients with pulmonary embolism as compared to heparin according to a [[systematic review]] of [[randomized controlled trial]]s by the [[Cochrane Collaboration]]. <cite>REFNAME28</cite> The [[relative risk reduction]] was 40.0%. For patients at similar risk to those in this study (2.0% had bleeding when not treated with low molecular weight heparin), this leads to an [[absolute risk reduction]] of 0.8%. 125.0 patients [[number needed to treat|must be treated for one to benefit]]. | ||
It is possible to treat low risk patients (risk class I or class II) as [[Patient#Outpatients_and_inpatients|outpatients]].<ref name="Aujesky2011">{{cite journal | It is possible to treat low risk patients (risk class I or class II) as [[Patient#Outpatients_and_inpatients|outpatients]].<ref name="Aujesky2011">{{cite journal | ||
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| format= | | format= | ||
| date = January 22, 2007 | | date = January 22, 2007 | ||
| accessdate = July 4, 2011}}</ref> This confirms the findings of an earlier [[systematic review]] of [[observational study|observational studies]].< | | accessdate = July 4, 2011}}</ref> This confirms the findings of an earlier [[systematic review]] of [[observational study|observational studies]]. <cite>REFNAME29</cite> | ||
Warfarin therapy often requires frequent dose adjustment and monitoring of the [[international normalized ratio|INR]]. In PE, INRs between 2.0 and 3.0 are generally considered ideal. If another episode of PE occurs under warfarin treatment, the INR window may be increased to e.g. 2.5-3.5 (unless there are contraindications) or anticoagulation may be changed to a different anticoagulant e.g. [[low molecular weight heparin]]. In patients with an underlying malignancy, therapy with a course of [[low molecular weight heparin]] may be favored over warfarin based on the results of the CLOT trial.< | Warfarin therapy often requires frequent dose adjustment and monitoring of the [[international normalized ratio|INR]]. In PE, INRs between 2.0 and 3.0 are generally considered ideal. If another episode of PE occurs under warfarin treatment, the INR window may be increased to e.g. 2.5-3.5 (unless there are contraindications) or anticoagulation may be changed to a different anticoagulant e.g. [[low molecular weight heparin]]. In patients with an underlying malignancy, therapy with a course of [[low molecular weight heparin]] may be favored over warfarin based on the results of the CLOT trial. <cite>REFNAME30</cite> | ||
Similarly, pregnant women are often maintained on low molecular weight heparin to avoid the known [[teratogenic]] effects of warfarin, especially in the early stages of pregnancy. {{Citation needed|date=August 2011}} | Similarly, pregnant women are often maintained on low molecular weight heparin to avoid the known [[teratogenic]] effects of warfarin, especially in the early stages of pregnancy. {{Citation needed|date=August 2011}} | ||
People are usually admitted to hospital in the early stages of treatment, and tend to remain under inpatient care until INR has reached therapeutic levels. Increasingly, low-risk cases are managed on an outpatient basis in a fashion already common in the treatment of DVT.< | People are usually admitted to hospital in the early stages of treatment, and tend to remain under inpatient care until INR has reached therapeutic levels. Increasingly, low-risk cases are managed on an outpatient basis in a fashion already common in the treatment of DVT. <cite>REFNAME31</cite> | ||
Warfarin therapy is usually continued for 3–6 months, or "lifelong" if there have been previous DVTs or PEs, or none of the usual risk factors is present. An abnormal [[D-dimer]] level at the end of treatment might signal the need for continued treatment among patients with a first unprovoked pulmonary embolus.< | Warfarin therapy is usually continued for 3–6 months, or "lifelong" if there have been previous DVTs or PEs, or none of the usual risk factors is present. An abnormal [[D-dimer]] level at the end of treatment might signal the need for continued treatment among patients with a first unprovoked pulmonary embolus. <cite>REFNAME32</cite> | ||
===Thrombolysis=== | ===Thrombolysis=== | ||