Pulmonary Embolism Workup

  • Author: Daniel R Ouellette, MD, FCCP; Chief Editor: Zab Mosenifar, MD   more...
 
Updated: May 15, 2012
 

Approach Considerations

Clinical signs and symptoms for pulmonary embolism are nonspecific; therefore, patients suspected of having pulmonary embolism—because of unexplained dyspnea, tachypnea, or chest pain or the presence of risk factors for pulmonary embolism—must undergo diagnostic tests until the diagnosis is ascertained or eliminated or an alternative diagnosis is confirmed. Further, routine laboratory findings are nonspecific and are not helpful in pulmonary embolism, although they may suggest another diagnosis.

A hypercoagulation workup should be performed if no obvious cause for embolic disease is apparent. This may include screening for conditions such as the following:

  • Antithrombin III deficiency
  • Protein C or protein S deficiency
  • Lupus anticoagulant
  • Homocystinuria
  • Occult neoplasm
  • Connective tissue disorders

No particular strategy appears to be superior to another at present for the diagnosis of pulmonary embolism. More clinical studies are needed to evaluate the utility of new approaches to the condition’s diagnosis. The availability of diagnostic tests, as well as cost-effectiveness analysis, local traditions, and the expertise of radiologists involved in the diagnosis, appears to be the considerations in the workup of a patient suspected of having pulmonary embolism.

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Clinical Scoring Systems

Evidence-based literature supports the practice of determining the clinical probability of pulmonary embolism before proceeding with testing.[17] A clinical practice guideline from the American Academy of Family Physicians (AAFP) and the American College of Physicians (ACP) recommends that validated clinical prediction rules be used to estimate pretest probability of pulmonary embolism and to interpret test results.[40, 41] The guideline, Current Diagnosis of Venous Thromboembolism in Primary Care, advocates use of the Wells prediction rule for this purpose but notes that the Wells rule performs better in younger patients without comorbidities or a history of venous thromboembolism than in other patients.

One study assessed the performance of 4 clinical decision rules in addition to D-dimer testing to exclude acute PE. All 4 rules, Wells rule, simplified Wells rule, revised Geneva score, and simplified revised Geneva score, showed similar performance for excluding acute PE when combined with a normal D-dimer result.[42]

To see complete information on Pulmonary Embolism Clinical Scoring Systems, please go to the main article by clicking here.

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D-Dimer Follow-Up on Low-to-Moderate Pretest Probability

When clinical prediction rule results indicate that the patient has a low or moderate pretest probability of pulmonary embolism, D-dimer testing is the usual next step.[17]

D-Dimer, a degradation product produced by plasmin-mediated proteases of cross-linked fibrin, is measured by a variety of assay types, including quantitative, semiquantitative, and qualitative rapid enzyme-linked immunosorbent assays (ELISAs); quantitative and semiquantitative latex; and whole-blood assays. A systematic review of prospective studies of high methodologic quality concluded that the ELISAs—especially the quantitative rapid ELISA—dominate the comparative ranking among the D-dimer assays for sensitivity and negative likelihood ratio.[43] The quantitative rapid ELISA has a sensitivity of 0.95 and negative likelihood ratio of 0.13; the latter is similar to that for a normal to near-normal lung scan in patients with suspected pulmonary embolism.

Negative results on a high-sensitivity D-dimer test in a patient with a low pretest probability of pulmonary embolism indicate a low likelihood of venous thromboembolism and reliably exclude pulmonary embolism. A large, prospective, randomized trial found that in patients with a low probability of pulmonary embolism who had negative D-dimer results, forgoing additional diagnostic testing was not associated with an increased frequency of symptomatic venous thromboembolism during the subsequent 6 months.[44]

D-dimer testing is most reliable for excluding pulmonary embolism in younger patients who have no associated comorbidity or history of venous thromboembolism and whose symptoms are of short duration.[41] However, it is of questionable value in patients who are older than 80 years, who are hospitalized, who have cancer, or who are pregnant, because nonspecific elevation of D-dimer concentrations is common in such patients.

D-dimer testing should not be used when the clinical probability of pulmonary embolism is high, because the test has low negative predictive value in such cases.[45]

Combining D-dimer results with measurement of the exhaled end-tidal ratio of carbon dioxide to oxygen (etCO2/O2) can be useful for diagnosis of pulmonary embolism. Kline et al found that, in moderate-risk patients with a positive D-dimer (>499 ng/mL), an etCO2/O2 < 0.28 significantly increased the probability of finding segmental or larger pulmonary embolism on computed tomography multidetector-row pulmonary angiography, while an etCO2/O2) >0.45 predicted the absence of segmental or larger pulmonary embolism.[46]

Because of the poor specificity, positive D-dimer measurements are generally not helpful in diagnosis. In addition, the use of D-dimers in children is not well studied. A small pediatric series reported that D-dimers findings are negative in 40% of patients.[24] A retrospective series reported an elevated D-dimer in 86% of patients at presentation.[11]

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Ischemia-Modified Albumin levels

A potential alternative to D-dimer testing is assessment of the ischemia-modified albumin (IMA) level, which data suggest is 93% sensitive and 75% specific for pulmonary embolism.[47] Notably, in a study comparing the prognostic value of IMA to D-dimer testing, IMA assessment in combination with Wells and Geneva probability scores appeared to positively impact overall sensitivity and negative predictive value.[47] The positive predictive value of IMA, in particular, is better than D-dimer. However, it should not be used alone.[48]

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White Blood Cell Count

The white blood cell (WBC) count may be normal or elevated in patients with pulmonary embolism, with a WBC count as high as 20,000 being not uncommon in patients with this condition.

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Arterial Blood Gases

Arterial blood gas determinations characteristically reveal hypoxemia, hypocapnia, and respiratory alkalosis; however, the predictive value of hypoxemia is quite low. The PaO2 and the calculation of alveolar-arterial oxygen gradient contribute to the diagnosis in a general population thought to have pulmonary embolism. Nonetheless, in high-risk settings such as patients in postoperative states in whom other respiratory conditions can be ruled out, a low PaO2 in conjunction with dyspnea may have a strong positive predictive value.

The PO2 on arterial blood gases analysis (ABG) has a zero or even negative predictive value in a typical population of patients in whom pulmonary embolism is suspected clinically. This is contrary to what has been taught in many textbooks, and even though it seems counterintuitive, it is demonstrably true. This is because other etiologies that masquerade as pulmonary embolism are more likely to lower the PO2 than pulmonary embolism. In fact, because other diseases that may masquerade as pulmonary embolism (eg, chronic obstructive pulmonary disease [COPD], pneumonia, CHF) affect oxygen exchange more than does pulmonary embolism, the blood oxygen level often has an inverse predictive value for pulmonary embolism.

In most settings, fewer than half of all patients with symptoms suggestive of pulmonary embolism actually turn out to have pulmonary embolism as their diagnosis. In such a population, if any reasonable level of PaO2 is chosen as a dividing line, the incidence of pulmonary embolism will be higher in the group with a PaO2 above the dividing line than in the group whose PaO2 is below the divider. This is a specific example of a general truth that may be demonstrated mathematically for any test finding with a Gaussian distribution and a population incidence of less than 50%.

Conversely, in a patient population with a very high incidence of pulmonary embolism and a lower incidence of other respiratory ailments (eg, postoperative orthopedic patients with sudden onset of shortness of breath), a low PO2 has a strongly positive predictive value for pulmonary embolism.

The discussion above holds true not only for arterial PO2 but also for the alveolar-arterial oxygen gradient and for the oxygen saturation level as measured by pulse oximetry. In particular, pulse oximetry is extremely insensitive, is normal in the majority of patients with pulmonary embolism, and should not be used to direct a diagnostic workup.

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Troponin levels

Serum troponin levels can be elevated in up to 50% of patients with a moderate to large pulmonary embolism, presumptively due to acute right ventricular myocardial stretch.[45]

Although troponin assessment is not currently recommended as part of the diagnostic workup, studies have shown that elevated troponin levels in the setting of pulmonary embolism correlate with increased mortality.[49] However, further studies need to be performed to identify subsets of patients with pulmonary embolism who might benefit from this testing.

A meta-analysis by Jimenez et al suggested that in acute symptomatic pulmonary embolism, elevated troponin levels do not distinguish between patients who are at high risk for death and those who are at low risk. Pooled results from studies including 1366 normotensive patients with acute symptomatic pulmonary embolism showed that elevated troponin levels were associated with a 4.26-fold increased odds of overall mortality (95% confidence interval [CI], 2.13-8.50; heterogeneity chi2 = 12.64; degrees of freedom = 8; P = .125). Summary receiver operating characteristic curve analysis showed a relationship between the sensitivity and specificity of troponin levels to predict overall mortality (Spearman rank correlation coefficient = 0.68; P = .046). Pooled likelihood ratios (LRs) were not extreme (negative LR, 0.59 [95% CI, 0.39-0.88]; positive LR, 2.26 [95% CI,1.66-3.07]).[50]

Serum troponin, although seemingly marginal for purposes of diagnosis of pulmonary embolism, may contribute significantly to the ability to stratify patients by risk for short-term death or adverse outcome events when they reach the ED. In patients with pulmonary embolism and normal blood pressure specifically, elevated serum troponin level has been associated with right ventricular overload.[49, 51, 52, 53]

Leptin is another cardiovascular risk factor that may be associated with outcome in acute pulmonary embolism. Dellas et al conducted a prospective analysis of 264 patients with acute pulmonary embolus and found that serum leptin levels were inversely associated with the risk of adverse outcomes. Further study will be needed to confirm these findings and determine the clinical utility of leptin measurement.[54]

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Brain Natriuretic Peptide

Although brain natriuretic peptide (BNP) tests are neither sensitive nor specific, patients with pulmonary embolism tend to have higher BNP levels. BNP testing had a sensitivity and specificity of only 60% and 62%, respectively, in a case-control study of 2213 hemodynamically stable patients with suspected acute pulmonary embolism.[55]

Elevated levels of BNP or of its precursor, N -terminal pro-brain natriuretic peptide (NT-proBNP), do correlate with an increased risk of subsequent complications and mortality in patients with acute pulmonary embolism. One meta-analysis revealed that patients with a BNP level greater than 100 pg/mL or an NT-proBNP level greater than 600 ng/L had an all-cause in-hospital mortality rate 6- and 16-fold higher than those below these cutoffs, respectively.[31] In a second smaller observational study, serum BNP levels greater than 90 pg/mL were associated with a higher rate of complications, such as the need for cardiopulmonary resuscitation, need for mechanical ventilation, need for vasopressor therapy, and death.[56]

BNP testing is not currently recommended as part of the standard evaluation of acute pulmonary embolism, and future studies may aid in defining its role in this setting.

Elevated levels of brain-type natriuretic peptides (BNP) may also provide prognostic information.[52] A meta-analysis demonstrated a significant association between elevated N-terminal–pro-BNP (NT-pro-BNP) and right ventricular function in patients with pulmonary embolism (P < .001), leading to an increased risk for complicated in-hospital course (odds ratio [OR] 6.8; 95% confidence interval [CI], 9.0-13) and 30-day mortality (OR 7.6; 95% CI, 3.4-17).[57] Importantly, increased NT-pro-BNP alone does not justify more invasive treatment.

A recent study by Scherz et al analyzed a large sample of patients hospitalized with acute pulmonary embolism. Hyponatremia at presentation was common and was associated with a higher risk of 30-day mortality and readmission.[58]

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Venography

Venography is the criterion standard for diagnosing DVT. With the advent of noninvasive imaging, it has become less common in pediatric and adult practice.

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Angiography

Pulmonary angiography remains the criterion standard for the diagnosis of pulmonary embolism. Following injection of iodinated contrast, anteroposterior, lateral, and oblique studies are performed on each lung. Positive results consist of a filling defect or sharp cutoff of the affected artery (as shown in the image below). Nonocclusive emboli are described as having a tram-track appearance. Abnormal findings on V/Q scans performed prior to angiography guide the operator to focus on abnormal areas. Angiography generally is a safe procedure. The mortality rate for patients undergoing this procedure is less than 0.5%, and the morbidity rate is less than 5%. Patients who have long-standing pulmonary arterial hypertension and right ventricular failure are considered high-risk patients. Negative pulmonary angiogram findings, even if false negative, exclude clinically relevant pulmonary embolism.

A pulmonary angiogram shows the abrupt terminationA pulmonary angiogram shows the abrupt termination of the ascending branch of the right upper-lobe artery, confirming the diagnosis of pulmonary embolism.

If multidetector-row computed tomography angiography (MDCTA) is unavailable, conduct pulmonary angiography. Long the criterion standard for pulmonary embolism diagnosis, pulmonary angiography is nevertheless more invasive and harder to perform than MDCTA, and for these reasons, it is rapidly being replaced. However, pulmonary angiography remains a useful diagnostic modality when MDCTA cannot be performed.

When pulmonary angiography has been performed carefully and completely, a positive result provides virtually a 100% certainty that an obstruction to pulmonary arterial blood flow exists. A negative pulmonary angiogram provides a greater than 90% certainty for the exclusion of pulmonary embolism.

A positive angiogram is an acceptable endpoint no matter how abbreviated the study. However, a complete negative study requires the visualization of the entire pulmonary tree bilaterally. This is accomplished via selective cannulation of each branch of the pulmonary artery and injection of contrast material into each branch, with multiple views of each area. Even then, emboli in vessels smaller than third order or lobular arteries are not seen.

Small emboli cannot be seen angiographically, yet embolic obstruction of these smaller pulmonary vessels is very common when postmortem examination follows a negative angiogram. These small emboli can produce pleuritic chest pain and a small sterile effusion even though the patient has a normal V/Q scan and a normal pulmonary angiogram.

In most patients, however, pulmonary embolism is a disease of multiple recurrences, with large and small emboli already present by the time the diagnosis is suspected. Under these circumstances, the V/Q scan and the angiogram are likely to detect at least some of the emboli.

Pulmonary angiography demonstrates subsegmental vessels in more detail than does CT scanning, although the superimposition of the small vessels remains a limiting factor. As a result, the interobserver agreement rate for isolated subsegmental pulmonary embolism is only 45%.

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Computed Tomography Scanning

Technical advances in CT scanning, including the development of multidetector-array scanners, have led to the emergence of CT scanning as an important diagnostic technique in suspected pulmonary embolism.[38, 17] Contrast-enhanced CT scanning is increasingly used as the initial radiologic study in the diagnosis of pulmonary embolism, especially in patients with abnormal chest radiographs in whom scintigraphic results are more likely to be nondiagnostic.

Computed tomography angiography (CTA) is[59, 60, 61] the initial imaging modality of choice for stable patients with suspected pulmonary embolism. The American College of Radiology (ACR) considers chest CTA to be the current standard of care for the detection of pulmonary embolism.[62] A study by Ward et al determined that a selective strategy in which CTA is used after compression ultrasonography is cost-effective for patients with a high pretest probability of pulmonary embolism.[63] This strategy may reduce the need for CTA and help eliminate adverse effects associated with CTA.

Toward a goal of reducing unnecessary CTA and associated radiation exposure, Drescher et al studied the effect of implementing a computerized decision support system for pulmonary embolism evaluation in the ED. Before implementation, the rate of positive pulmonary embolism diagnosis for CTAs performed was 8.3%; after, the positivity rate rose to 12.7%. The positive yield would have been higher (16.7%) had emergency physicians adhered in all cases to the outcome of the decision support system; in 27% of cases they did not.[64]

Like pulmonary angiography, CT scanning shows emboli directly, but it is noninvasive, cheaper than pulmonary angiography, and widely available. CT scanning is the only test that can provide significant additional information related to alternate diagnoses[65] ; spiral (helical) CT scanning results may suggest an alternative diagnosis in up to 57% of patients. This is a clear advantage of CT scanning over pulmonary angiography or scintigraphy.

A study of multidetector computed tomography (MDCTA) for detection of right ventricular dysfunction in 457 patients with acute pulmonary embolism found reasonable correlation with echocardiography, the reference standard. The criterion selected, a right-to-left ventricular dimensional ratio of 0.9 or more at MDCTA, had 92% sensitivity for right ventricular dysfunction.[66] The combination of quantatative assessment of ventricular dimensions by CT and measurement of biomarkers may provide additional diagnostic accuracy for the presence of right ventricular dysfunction.[67]

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Chest Radiography

Chest radiographs are abnormal in most cases of pulmonary embolism, but the findings are nonspecific. Common radiographic abnormalities include atelectasis, pleural effusion, parenchymal opacities, and elevation of a hemidiaphragm. The classic radiographic findings of pulmonary infarction include a wedge-shaped, pleura-based triangular opacity with an apex pointing toward the hilus (Hampton hump) or decreased vascularity (Westermark sign). These findings are suggestive of pulmonary embolism but are infrequently observed.

A prominent central pulmonary artery (knuckle sign), cardiomegaly (especially on the right side of the heart), and pulmonary edema are other findings. In the appropriate clinical setting, these findings could be consistent with acute cor pulmonale. A normal-appearing chest radiograph in a patient with severe dyspnea and hypoxemia, but without evidence of bronchospasm or a cardiac shunt, is strongly suggestive of pulmonary embolism.

The ACR recommends chest radiography (see the images below) as the most appropriate study for ruling out other causes of chest pain in patients with suspected pulmonary embolism.[62] Initially, the chest radiographic findings are normal in most cases of pulmonary embolism. However, in later stages, radiographic signs may include a Westermark sign (dilatation of pulmonary vessels and a sharp cutoff), atelectasis, a small pleural effusion, and an elevated diaphragm. Generally, chest radiographs cannot be used to conclusively prove or exclude pulmonary embolism; however, radiography and electrocardiography may be useful for establishing alternative diagnoses. (See Electrocardiography.)

Posteroanterior and lateral chest radiograph findiPosteroanterior and lateral chest radiograph findings are normal, which is the usual finding in patients with pulmonary embolism. A chest radiograph with normal findings in a 64-yeA chest radiograph with normal findings in a 64-year-old woman who presented with worsening breathlessness. A posteroanterior chest radiograph showing a peripA posteroanterior chest radiograph showing a peripheral wedge-shaped infiltrate caused by pulmonary infarction secondary to pulmonary embolism. Hampton hump is a rare and nonspecific finding. Courtesy of Justin Wong, MD.
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Ventilation-Perfusion Scanning

V/Q scanning of the lungs is an important modality for establishing the diagnosis of pulmonary embolism. However, V/Q scanning should be used only when CT scanning is not available or if the patient has a contraindication to CT scanning or intravenous contrast material. Children generally have a more homogenous perfusion scan; thus, deficits in perfusion are more likely to represent real or significant pulmonary embolism than they are in adults.

The PIOPED II trial provided high-, intermediate-, and low-probability criteria for V/Q scanning diagnosis of pulmonary embolism (see the images of high-probability scans below).

High-probability perfusion lung scan shows segmentHigh-probability perfusion lung scan shows segmental perfusion defects in the right upper lobe and subsegmental perfusion defects in right lower lobe, left upper lobe, and left lower lobe. A normal ventilation scan will make the above-noteA normal ventilation scan will make the above-noted defects in Image 5 a mismatch and, hence, a high-probability ventilation-perfusion scan. Anterior views of perfusion and ventilation scans Anterior views of perfusion and ventilation scans are shown here. A perfusion defect is present in the left lower lobe, but perfusion to this lobe is intact, making this a high-probability scan. This perfusion scan shows bilateral perfusion defeThis perfusion scan shows bilateral perfusion defects. The ventilation scan findings were normal; therefore, these are mismatches, and this is a high-probability scan.

The high-probability criteria are as follows:

  • Two large (>75% of a segment) segmental perfusion defects without corresponding ventilation or chest radiographic abnormalities
  • One large segmental perfusion defect and 2 moderate (25-75% of a segment) segmental perfusion defects without corresponding ventilation or radiographic abnormalities
  • Four moderate segmental perfusion defects without corresponding ventilation or chest radiographic abnormalities
  • The intermediate-probability criteria are as follows:
  • One moderate to fewer than 2 large segmental perfusion defects without corresponding ventilation or chest radiographic abnormalities
  • Corresponding V/Q defects and radiographic parenchymal opacity in lower lung zone
  • Single moderate matched V/Q defects with normal chest radiographic findings
  • Corresponding V/Q and chest radiography small pleural effusion
  • Difficult to categorize as normal, low, or high probability

Low probability criteria are as follows:

  • Multiple matched V/Q defects, regardless of size, with normal chest radiographic findings
  • Corresponding V/Q defects and radiographic parenchymal opacity in upper or middle lung zone
  • Corresponding V/Q defects and large pleural effusion
  • Any perfusion defects with substantially larger radiographic abnormality
  • Defects surrounded by normally perfused lung (stripe sign)
  • More than 3 small (< 25% of a segment) segmental perfusion defects with normal chest radiographic findings
  • Nonsegmental perfusion defects (cardiomegaly, aortic impression, enlarged hila)

The normal finding is the presence of no perfusion defects and perfusion outlines the shape of the lung seen on a chest radiograph.

The very low–probability criterion is the presence of 3 small (< 25% of a segment) segmental perfusion defects with normal chest radiographic findings.

In the PIOPED II study, very low–probability V/Q scans in patients whose Wells score indicated low pretest probability of pulmonary embolism reliably excluded pulmonary embolism.[68]

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Electrocardiography

The most common ECG abnormalities in the setting of pulmonary embolism are tachycardia and nonspecific ST-T wave abnormalities. The finding of S1 Q3 T3 is nonspecific and insensitive in the absence of clinical suspicion for pulmonary embolism. The classic findings of right heart strain and acute cor pulmonale are tall, peaked P waves in lead II (P pulmonale); right axis deviation; right bundle-branch block; an S1 Q3 T3 pattern; or atrial fibrillation. Unfortunately, only 20% of patients with proven pulmonary embolism have any of these classic electrocardiographic abnormalities. If electrocardiographic abnormalities are present, they may be suggestive of pulmonary embolism, but the absence of such abnormalities has no significant predictive value.

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Magnetic Resonance Imaging

With magnetic resonance imaging (MRI), evidence of pulmonary emboli may be detected by using standard or gated spin-echo techniques. Pulmonary emboli demonstrate increased signal intensity within the pulmonary artery. By obtaining a sequence of images, this signal that is originating from slow blood flow may be distinguished from pulmonary embolism. However, this remains a problem in pulmonary hypertension.

Magnetic resonance angiography is performed following intravenous administration of gadolinium. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or magnetic resonance angiography scans.

NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

MRI has a sensitivity of 85% and specificity of 96% for central, lobar, and segmental emboli; MRI is inadequate for the diagnosis of subsegmental emboli.

Few data are available regarding the use of MRI in children suspected of having a pulmonary embolism. Its use in these patients should be considered investigational at this time.

Few investigators have reported the feasibility of MRI in the evaluation of pulmonary embolism. However, the role of MRI is mostly limited to the evaluation of patients who have impaired renal function or other contraindications for the use of iodinated contrast material.[69, 70] Newer blood-pool contrast agents and respiratory navigators may enhance the role of MRI in the diagnosis of pulmonary embolism.

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Echocardiography

This modality generally has limited accuracy in the diagnosis of pulmonary embolism. Transesophageal echocardiography may identify central pulmonary embolism, and the sensitivity for central pulmonary embolism is reported to be 82%. Overall sensitivity and specificity for central and peripheral pulmonary embolism is 59% and 77%.

Echocardiography (ECHO) provides useful information. It may allow diagnosis of other conditions that may be confused with pulmonary embolism, such as pericardial effusion. ECHO allows visualization of the right ventricle and assessment of the pulmonary artery pressure. ECHO serves a prognostic function; the mortality rate is almost 10% in the presence of right ventricular dysfunction and 0% in the absence of right ventricular dysfunction. (Vanni et al reported that a right ventricular strain pattern is associated with a worse short-term outcome.[71] ) ECHO may be used to identify the presence of right-chamber emboli.

The subcostal view is preferred at initial screening for mechanical activity and pericardial fluid and for gross assessment of global and regional abnormalities. To obtain a subcostal view, place the transducer on the left subcostal margin with the beam aimed at the left shoulder.

The parasternal view allows visualization of the aortic valve, proximal ascending aorta, and posterior pericardium and permits determination of left ventricular size. It is particularly helpful when the subcostal view is difficult to obtain. To obtain a parasternal view, place the transducer in the left parasternal area between the second and fourth intercostal spaces. The plane of the beam is parallel to a line drawn from the right shoulder to the left hip.

Several echocardiographic findings have been proposed for noninvasive diagnosis of right ventricular dysfunction at the bedside, including right ventricular enlargement and/or hypokinesis of the free wall, leftward septal shift, and evidence of pulmonary hypertension. If right ventricular dysfunction is seen on cardiac ultrasonography, the diagnosis of acute submassive or massive pulmonary embolism is supported. While the presence of right ventricular dysfunction can be used to support the clinical suspicion of pulmonary embolism, prognostic information can be obtained by assessing the severity of right ventricular dysfunction.

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Duplex Ultrasonography

The diagnosis of pulmonary embolism can be proven by demonstrating the presence of a DVT at any site. This may sometimes be accomplished noninvasively by using duplex ultrasonography. To look for DVT using ultrasonography, the ultrasonographic transducer is placed against the skin and pressed inward firmly enough to compress the vein being examined. In an area of normal veins, the veins are easily compressed completely closed, while the muscular arteries are extremely resistant to compression. Where DVT is present, the veins do not collapse completely when pressure is applied using the ultrasonographic probe.

A negative ultrasonographic scan does not rule out DVT, because many DVTs occur in areas that are inaccessible to ultrasonographic examination. Before an ultrasonographic scan can be considered negative, the entire deep venous system must be interrogated using centimeter-by-centimeter compression testing of every vessel. In two thirds of patients with pulmonary embolism, the site of DVT cannot be visualized with ultrasonography, so a negative duplex ultrasonographic scan does not markedly reduce the likelihood of pulmonary embolism.

Ultrasonographic images of thrombi are seen below.

Ultrasonogram shows the thrombus in the distal supUltrasonogram shows the thrombus in the distal superficial saphenous vein, which is under the artery. This ultrasound shows the thrombus tip in the supeThis ultrasound shows the thrombus tip in the superficial femoral vein, with a small amount of flow around it. The color flow deep into the superficial femoral vein is from the profunda femoris vein. An ultrasound shows the thrombus filling the superAn ultrasound shows the thrombus filling the superficial femoral vein; the noncompressibility further confirms the diagnosis.
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Contributor Information and Disclosures
Author

Daniel R Ouellette, MD, FCCP  Associate Professor of Medicine, Wayne State University School of Medicine; Consulting Staff, Pulmonary Disease and Critical Care Medicine Service, Henry Ford Health System

Daniel R Ouellette, MD, FCCP is a member of the following medical societies: American College of Chest Physicians and American Thoracic Society

Disclosure: Nothing to disclose.

Coauthor(s)

Gary Setnik, MD  Chair, Department of Emergency Medicine, Mount Auburn Hospital; Assistant Professor, Division of Emergency Medicine, Harvard Medical School

Gary Setnik, MD is a member of the following medical societies: American College of Emergency Physicians, National Association of EMS Physicians, and Society for Academic Emergency Medicine

Disclosure: SironaHealth Salary Management position; South Middlesex EMS Consortium Salary Management position; ProceduresConsult.com Royalty Other

Michael S Beeson, MD, MBA, FACEP  Professor of Emergency Medicine, Northeastern Ohio Universities College of Medicine and Pharmacy; Attending Faculty, Akron General Medical Center

Michael S Beeson, MD, MBA, FACEP is a member of the following medical societies: American College of Emergency Physicians, Council of Emergency Medicine Residency Directors, National Association of EMS Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Kavita Garg, MD  Professor, Department of Radiology, University of Colorado School of Medicine

Kavita Garg, MD is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, Radiological Society of North America, and Society of Thoracic Radiology

Disclosure: Nothing to disclose.

Judith K Amorosa, MD, FACR  Clinical Professor and Program Director, Department of Radiology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School; Consulting Staff, Department of Radiology, Robert Wood Johnson University Hospital

Judith K Amorosa, MD, FACR is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, Association of University Radiologists, Radiological Society of North America, and Society of Thoracic Radiology

Disclosure: Nothing to disclose.

Nader Kamangar, MD, FACP, FCCP, FCCM  Associate Professor of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, University of California, Los Angeles, David Geffen School of Medicine, Olive View-UCLA Medical Center; Associate Program Director, Pulmonary and Critical Care Multi-Campus Fellowship Program, Cedars-Sinai/West Los Angeles Veterans Affairs/Los Angeles Kaiser Permanente/Olive View-UCLA Medical Center; Site Director, Pulmonary/Critical Care Fellowship Program, Olive View-UCLA Medical Center

Nader Kamangar, MD, FACP, FCCP, FCCM is a member of the following medical societies: American Academy of Sleep Medicine, American Association of Bronchology, American College of Chest Physicians, American College of Physicians, American Lung Association, American Medical Association, American Thoracic Society, California Thoracic Society, and Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Sara F Sutherland, MD, MBA, FACEP  Assistant Professor of Emergency Medicine, University of Virginia Health System; Staff Physician, Department of Emergency Medicine, Martha Jefferson Hospital

Sara F Sutherland, MD, MBA, FACEP is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Annie Harrington, MD  Fellow in Pulmonary and Critical Care Medicine, Cedars-Sinai Medical Center

Annie Harrington, MD is a member of the following medical societies: Alpha Omega Alpha and American College of Chest Physicians

Disclosure: Nothing to disclose.

Specialty Editor Board

Gregory Tino, MD  Director of Pulmonary Outpatient Practices, Associate Professor, Department of Medicine, Division of Pulmonary, Allergy, and Critical Care, University of Pennsylvania Medical Center and Hospital

Gregory Tino, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, and American Thoracic Society

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Robert E O'Connor, MD, MPH  Professor and Chair, Department of Emergency Medicine, University of Virginia Health System

Robert E O'Connor, MD, MPH is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, American College of Physician Executives, American Heart Association, American Medical Association, Medical Society of Delaware, National Association of EMS Physicians, Society for Academic Emergency Medicine, and Wilderness Medical Society

Disclosure: Nothing to disclose.

Eugene C Lin, MD  Attending Radiologist, Teaching Coordinator for Cardiac Imaging, Radiology Residency Program, Virginia Mason Medical Center; Clinical Assistant Professor of Radiology, University of Washington School of Medicine

Eugene C Lin, MD is a member of the following medical societies: American College of Nuclear Medicine, American College of Radiology, Radiological Society of North America, and Society of Nuclear Medicine

Disclosure: Nothing to disclose.

Chief Editor

Zab Mosenifar, MD  Director, Division of Pulmonary and Critical Care Medicine, Director, Women's Guild Pulmonary Disease Institute, Professor and Executive Vice Chair, Department of Medicine, Cedars Sinai Medical Center, University of California, Los Angeles, David Geffen School of Medicine

Zab Mosenifar, MD is a member of the following medical societies: American College of Chest Physicians, American College of Physicians, American Federation for Medical Research, and American Thoracic Society

Disclosure: Nothing to disclose.

Additional Contributors

Eric J Stern, MD Professor of Radiology, Adjunct Professor of Medicine, Adjunct Professor of Medical Education and Biomedical Informatics, Adjunct Professor of Global Health, Vice-Chair, Academic Affairs, University of Washington School of Medicine

Eric J Stern, MD is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, European Society of Radiology, Radiological Society of North America, and Society of Thoracic Radiology

Disclosure: Nothing to disclose.

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A large pulmonary artery thrombus in a hospitalized patient who died suddenly.
Pulmonary embolism was identified as the cause of death in a patient who developed shortness of breath while hospitalized for hip joint surgery. This is a close-up view.
Lung infarction secondary to pulmonary embolism occurs rarely.
Posteroanterior and lateral chest radiograph findings are normal, which is the usual finding in patients with pulmonary embolism.
High-probability perfusion lung scan shows segmental perfusion defects in the right upper lobe and subsegmental perfusion defects in right lower lobe, left upper lobe, and left lower lobe.
A normal ventilation scan will make the above-noted defects in Image 5 a mismatch and, hence, a high-probability ventilation-perfusion scan.
Anterior views of perfusion and ventilation scans are shown here. A perfusion defect is present in the left lower lobe, but perfusion to this lobe is intact, making this a high-probability scan.
A segmental ventilation perfusion mismatch evident in a left anterior oblique projection.
A pulmonary angiogram shows the abrupt termination of the ascending branch of the right upper-lobe artery, confirming the diagnosis of pulmonary embolism.
A chest radiograph with normal findings in a 64-year-old woman who presented with worsening breathlessness.
This perfusion scan shows bilateral perfusion defects. The ventilation scan findings were normal; therefore, these are mismatches, and this is a high-probability scan.
Ultrasonogram shows the thrombus in the distal superficial saphenous vein, which is under the artery.
A lack of respiratory variation in the Doppler waveform of the popliteal vein.
This ultrasound shows the thrombus tip in the superficial femoral vein, with a small amount of flow around it. The color flow deep into the superficial femoral vein is from the profunda femoris vein.
An ultrasound shows the thrombus filling the superficial femoral vein; the noncompressibility further confirms the diagnosis.
A posteroanterior chest radiograph showing a peripheral wedge-shaped infiltrate caused by pulmonary infarction secondary to pulmonary embolism. Hampton hump is a rare and nonspecific finding. Courtesy of Justin Wong, MD.
Computed tomography angiogram in a 53-year-old man with acute pulmonary embolism. This image shows an intraluminal filling defect that occludes the anterior basal segmental artery of the right lower lobe. Also present is an infarction of the corresponding lung, which is indicated by a triangular, pleura-based consolidation (Hampton hump).
Computed tomography angiography in a young man who experienced acute chest pain and shortness of breath after a transcontinental flight. This image demonstrates a clot in the anterior segmental artery in the left upper lung (LA2) and a clot in the anterior segmental artery in the right upper lung (RA2).
Computed tomography angiogram in a 55-year-old man with possible pulmonary embolism. This image was obtained at the level of the lower lobes and shows perivascular segmental enlarged lymph nodes as well as prominent extraluminal soft tissue interposed between the artery and the bronchus.
Computed tomography venograms in a 65-year-old man with possible pulmonary embolism. This image shows acute deep venous thrombosis with intraluminal filling defects in the bilateral superficial femoral veins.
The pathophysiology of pulmonary embolism. Although pulmonary embolism can arise from anywhere in the body, most commonly it arises from the calf veins. The venous thrombi predominately originate in venous valve pockets (inset) and at other sites of presumed venous stasis. To reach the lungs, thromboemboli travel through the right side of the heart. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle.
A spiral CT scan shows thrombus in bilateral main pulmonary arteries.
CT scan of the same chest depicted in Image 18. Courtesy of Justin Wong, MD.
Longitudinal ultrasound image of partially recanalized thrombus in the femoral vein at mid thigh.
Sequential images demonstrate treatment of iliofemoral deep venous thrombosis due to May-Thurner (Cockett) syndrome. Far left, View of the entire pelvis demonstrates iliac occlusion. Middle left, After 12 hours of catheter-directed thrombolysis, an obstruction at the left common iliac vein is evident. Middle right, After 24 hours of thrombolysis, a bandlike obstruction is seen; this is the impression made by the overlying right common iliac artery. Far left, After stent placement, image shows wide patency and rapid flow through the previously obstructed region. Note that the patient is in the prone position in all views. (Right and left are reversed.)
Lower-extremity venogram shows outlining of an acute deep venous thrombosis in the popliteal vein with contrast enhancement.
Lower-extremity venogram shows a nonocclusive chronic thrombus. The superficial femoral vein (lateral vein) has the appearance of 2 parallel veins, when in fact, it is 1 lumen containing a chronic linear thrombus. Although the chronic clot is not obstructive after it recanalizes, it effectively causes the venous valves to adhere in an open position, predisposing the patient to reflux in the involved segment.
Pulmonary embolus.
 
 
 
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