The diagnosis of acute pulmonary embolism in patients with chronic obstructive pulmonary disease.

The clinical features and noninvasive tests, including ventilation perfusion (V/Q) lung scans, were assessed in 108 patients with chronic obstructive pulmonary disease (COPD) suspected of having pulmonary embolism (PE). Twenty-one (19 percent) of 108 patients had PE. In the majority of patients, it was impossible to distinguish between patients with and without PE by clinical assessment alone. However, when a high clinical index of suspicion was present, PE was confirmed by angiography in three of three patients, but the V/Q scan was of intermediate probability. No roentgenographic abnormalities distinguished between PE and no PE. There was no difference between the alveolar-arterial oxygen gradients in either group, nor was there evidence of a reduction in the PaCO2 in patients with PE who had prior hypercapnia. Among the 108 patients with COPD, high, intermediate, low, and normal/near normal probability scans were present in 5 percent, 60 percent, 30 percent, and 5 percent, respectively. The frequency of PE in these V/Q scan categories was five (100 percent) of five, 14 (22 percent) of 65, two (6 percent) of 33, and zero (0 percent) of five, respectively. In conclusion, in the majority of patients, the V/Q scan diagnosis is usually intermediate and such patients require further investigational studies, including angiography. However, among the few patients who demonstrated a high probability lung scan, there was a high positive predictive value for PE effectively avoiding the need for further studies. In those patients with low probability or near normal/normal V/Q scans, the negative predictive value was not lower than the general hospital population.     

A comparative study of intravenous digital subtraction angiography and ventilation-perfusion scans in suspected pulmonary embolism

We observed 102 patients suspected of having pulmonary emboli (PE) who underwent ventilation-perfusion (V/Q) lung scintigraphy and IV digital subtraction angiography (DSA). Only five DSA studies were inadequate for interpretation. In 81 of the remaining 97 patients (83.5 percent) the results of both studies correlated regarding the probability of PE. In 50 patients the results of both studies were highly suggestive of PE; in 31 patients DSA and V/Q were normal or classified as low probability of PE. There was disagreement in 3/97; in 13/97 one or both studies were nondiagnostic. The clinical data of these 16 patients are given. Conventional catheter pulmonary angiography was indicated in 11/102 patients to establish a firm diagnosis of PE. The results of V/Q and DSA correlated in 83 percent (49/59) of patients without chronic obstructive pulmonary disease (COPD) and in 84 percent (32/38) of the patients with COPD.     

Diagnostic utility of cardiac troponin-I levels in patients with suspected pulmonary embolism

Although positive troponin-I (TnI) assays have been reported in patients with pulmonary embolism (PE), TnI levels in patients with suspected PE have not been evaluated systematically. The purpose of this study was to evaluate the diagnostic utility of TnI measurements in patients with suspected PE. Consecutive patients with suspected PE were identified in whom nuclear ventilation/perfusion (V/Q) scans were performed and TnI levels were measured. TnI levels in patients with and without positive V/Q scans were compared by use of t tests. After categorizing TnI levels as positive (TnI-pos, > or = 0.40 ng/mL) or negative, chi-square tests were used to relate these values to V/Q scan results. Separate comparisons were made for subjects with high-probability V/Q scans (V/Q-high, > or = 90% likelihood of PE) and intermediate- or high-probability V/Q scans (V/Q-pos, > or = 50% likelihood of PE). The mean TnI level in the 10 subjects with V/Q-high scans was 0.39 +/-0.79 ng/mL. The mean TnI level in the 81 subjects without V/Q-high scans was 0.36 +/-0.66 ng/mL (p=0.89). TnI levels did not differ between the 22 V/Q-pos subjects and the 69 subjects with negative V/Q scans (p = 0.86). A positive TnI in the setting of V/Q-pos had a sensitivity of 32%, specificity of 71%, positive predictive value of 26%, and a negative predictive value = 77% (chi-square = 0.06, p = 0.80). Elevated TnI levels are not associated with positive V/Q scans. The TnI assay is not a useful test in patients suspected of having PE, unless used to exclude myocardial ischemia or infarction.     

Normal D-dimer levels in patients with pulmonary embolism.

BACKGROUND: Pulmonary embolism (PE) is frequently evaluated in acute care settings. Despite this, the clinical diagnosis of PE is difficult. Results of ventilation-perfusion (V/Q) scans may be inconclusive, and pulmonary angiograms (PAGs) are cumbersome, involve risk, and are often unavailable. Using PAG as the standard criterion, we evaluated the relationship between PE, V/Q scans, and semiquantitative latex agglutination (LA) D-dimer levels. METHODS: Ninety-eight patients who underwent V/Q scanning for suspected PE were enrolled; based on the results of the scans, the patients were scheduled for PAG. Blood samples were drawn for LA D-dimer assays during the PAGs at Saint Joseph Hospital, Denver, Colo, from January 1, 1996, to February 1, 1997. A detailed medical record review was performed for all enrollees. RESULTS: The mean+/-SEM patient age was 56.6+/-1.9 years; 52 (53%) were men, 13 (13%) had cancer, 23 (23%) had undergone surgery within 30 days of their PAG, and 13 (13%) were receiving warfarin sodium. There were no differences in warfarin therapy, hypercoaguable state, or cancer prevalence between patients with negative and positive PAGs (P = .53). Ventilation-perfusion scan results were available for all study patients. Eight (27%) of 30 patients who had positive angiogram results had LA D-dimer levels less than 250 ng/mL. Patients with positive PAGs (n = 30) had the following V/Q scan results: normal, 0; low probability, 7; intermediate or indeterminate probability, 22; and high probability, 1. In patients with low-probability V/Q scan results (n = 34), a positive D-dimer result for PE (>250 ng/mL) had a sensitivity of 71.4% (95% confidence interval, 0.29-0.97) and a negative predictive value of 87.5% (95% confidence interval, 0.62-0.98). We found a significant difference in D-dimer levels in patients with an abnormal angiogram result (mean, 750 ng/mL) compared with patients with a normal angiogram result (mean, 250 ng/mL) (P= .01, chi2 test). CONCLUSIONS: Eight patients had normal D-dimer levels with angiographic evidence of PE. Algorithms in acute care settings have been proposed; they exclude PE with normal D-dimer levels using the enzyme-linked immunosorbent assay technique. These cannot be extrapolated to the more widely used LA assays. A normal LA D-dimer level alone or with V/Q scan results is not recommended to preclude the treatment of PE.     

Diagnosing acute pulmonary embolism: effect of chronic obstructive pulmonary disease on the performance of D-dimer testing, ventilation/perfusion scintigraphy, spiral computed tomographic angiography, and conventional angiography. ANTELOPE Study Group. Advances in New Technologies Evaluating the Localization of Pulmonary Embolism

In patients with chronic obstructive pulmonary disease (COPD), differentiating a pulmonary embolism (PE) from an exacerbation of COPD can be difficult, since clinical signs and symptoms of the two conditions overlap. Development of reliable noninvasive or minimally invasive techniques for the diagnosis of PE is, especially in these patients, necessary. In this study we assessed the effect of COPD on the accuracy of the clinical probability estimate (CPE), spiral computed tomographic angiography (SCTA), D-dimer analysis, ventilation perfusion (V/Q) scintigraphy, and pulmonary angiography for the diagnosis of PE. From May 1997 through March 1998, 627 consecutive patients with suspected PE were investigated in six teaching hospitals. In these patients, D-dimer testing, CPE, V/Q scintigraphy, and SCTA and/or pulmonary angiography were performed according to a strict diagnostic protocol. The patients were also independently categorized as having COPD or not. A diagnosis of COPD was established in 91 patients (15%). The prevalence of PE was similar in patients with and without COPD (29% and 31%, respectively), notwithstanding the larger proportion of nondiagnostic V/Q scan results in patients with COPD (46% versus 21%, p < 0.001). The distribution of CPEs, diagnostic value of the D-dimer assay and SCTA, and reproducibility of pulmonary angiography were comparable among patients with and without COPD. The presence of COPD does not affect the diagnostic performance of CPE, D-dimer testing, SCTA, or pulmonary angiography. Furthermore, although more nondiagnostic V/Q scan results can be expected in the presence of COPD, V/Q scintigraphy remains a valuable screening test in patients with COPD.     

Urinary fibrinopeptide A in evaluation of patients with suspected acute pulmonary embolism. A prospective pilot study

This pilot study assessed the urinary fibrinopeptide A (uFPA) levels and the combination of uFPA test plus ventilation/perfusion (V/Q) scan in the diagnostic evaluation of acute pulmonary embolism (PE). One hundred consecutive patients were studied prospectively. Twenty-nine patients fulfilled diagnostic criteria defined in this study (seven with and 22 without PE). The uFPA concentration was significantly higher in patients with than without PE (41.1 +/- 2.6 vs 4.8 +/- 2.5 ng/mg of creatinine, p less than 0.0001). In all patients with PE, the uFPA levels were higher than threshold value derived by adding 2 standard deviations to the mean uFPA concentration of patients without PE. In patients without PE, the V/Q scan was negative in 16, the uFPA test was negative in 18, and at least one of the tests was negative in 21. These preliminary data suggest that a negative uFPA test may be helpful in excluding PE and that uFPA in combination with V/Q lung scans may correctly exclude PE in more patients than either test alone. Further studies in a large unselected population are needed to confirm these results.     

Objective analysis of tomographic ventilation-perfusion scintigraphy in pulmonary embolism

RATIONALE: Ventilation-perfusion scintigraphy is highly sensitive for pulmonary embolism (PE), but its clinical usefulness is limited by its nondiagnostic rate. Objective analysis of single photon emission computed tomography (SPECT) three-dimensional scintigraphy may improve its diagnostic performance compared with subjective interpretation. OBJECTIVES: To determine the diagnostic accuracy of objective SPECT analysis in PE. METHODS: We determined the ventilation/perfusion (V(.)/Q(.)) relationship using SPECT scintigraphy in a retrospective cohort of 73 patients. Measures of V(.)/Q(.) heterogeneity (logSD(Q(.)), logSD(V(.)), logSD(VQR)), including a novel parameter, the weighted median V(.)/Q(.) value, were calculated. Using receiver operating characteristic (ROC) analysis, each parameter's diagnostic accuracy was determined. The weighted median V(.)/Q(.) value was then assessed prospectively in a second cohort of 50 patients. MEASUREMENTS AND MAIN RESULTS: In cohort 1, all parameters of V(.)/Q(.) heterogeneity were higher in patients with PE (p < 0.002). The weighted median V(.)/Q(.) had the highest area under the ROC curve (0.93; 95% confidence interval, 0.87-0.98). When applied to the prospective cohort, the area under the ROC curve was 0.87 (95% confidence interval, 0.75-0.99), with diagnostic cutoff values having negative and positive predictive values of 96 and 83%, respectively. In the retrospective and prospective cohorts, 82 and 73% of initially reported intermediate or low probability scans had diagnostic weighted median V(.)/Q(.) values, with 90 and 100% accuracy, respectively. CONCLUSIONS: Objective analysis of SPECT scintigraphy has a high diagnostic accuracy in patients with suspected PE. Objective analysis has the potential to reduce the number of nondiagnostic scan results, and may be useful for quantifying V(.)/Q(.) mismatch in other pulmonary disorders.     

Clinical outcome of patients with a 'low probability' of pulmonary embolism on ventilation-perfusion lung scan

Lung ventilation and perfusion (V/Q) scintigraphy is usually indicated when pulmonary embolism (PE) is a suspected diagnosis. Typically, V/Q scintigraphic interpretation is reported as a "normal," "low," "intermediate," or "high probability" of PE. Although a "low probability" interpretation does not exclude the diagnosis of PE, it significantly reduces the likelihood. We retrospectively analyzed up to one year of follow-up in 90 patients who were clinically suspected of having PE, but in whom V/Q scintigraphy implied a low probability of PE. None of the 90 patients demonstrated clinical evidence of PE subsequent to the V/Q scan. Our findings suggest that significant pulmonary embolism is uncommon and that the clinical course appears to be predictable in patients with a low probability V/Q scan.     

Assessment of deep vein thrombosis or pulmonary embolism by the combined use of clinical model and noninvasive diagnostic tests

Deep vein thrombosis (DVT) and pulmonary embolism (PE) are relatively common diseases and are amenable to therapy but with a potentially fatal outcome if untreated. The diagnosis can be made in most patients with use of the noninvasive imaging tests, but limitations exist. The standard first choice of investigation in patients with suspected DVT is compression ultrasonography (CUS). As with all tests, there is a potential for false-positive and false-negative results. The latter are especially an issue for calf vein thrombi, and this in part has led to the concept of serial CUS testing of the proximal venous system and not imaging of the calf. The premise of the repeat (serial) CUS test is that only thrombi that extend to the proximal system are clinically relevant, and these thrombi will be detected during subsequent testing. However, despite the safety of the serial CUS testing concept, it is inconvenient and expensive. The standard first choice of investigation in patients with suspected PE, the ventilation-perfusion (V/Q) lung scan is nondiagnostic in most cases. In the past few years, the diagnostic process has improved because of the validation of clinical models that accurately categorize patients as having low (5%), moderate (20% to 30%), or high probability (>60%) for venous thromboembolic disease. Among the improvements this provides is the elimination of serial CUS testing if the ultrasound results are normal and the clinical probability is low in patients with suspected DVT. In patients with suspected PE in whom further testing is necessary, determination of clinical probability allows selection of invasive (angiography) or noninvasive testing (serial ultrasound) in patients with non-high-probability V/Q scans. The fibrin degradation product D-dimer has had a high negative predictive value; negative results with enzyme-linked immunosorbent assay (ELISA) tests effectively rule out DVT or PE. In addition, a negative result with less-sentive D-dimer testing and a low clinical probability excludes DVT or PE.     

The effect of imaging modality on patient management in the evaluation of pulmonary thromboembolism.

A retrospective medical record review was performed to study the differences in clinical risk profiles and the relationships between test results versus management for suspected pulmonary thromboembolism (TE) in patients undergoing either radionuclide ventilation perfusion (V/Q) scans or pulmonary computed tomographic angiography (CTA), as the initial test. Data of 138 consecutive V/Q patients were compared with that of 149 consecutive CTA patients during equivalent 6-month intervals before and after the introduction of CTA. Information on risk factors, signs and symptoms, all diagnostic test results, and the relationships between the test results and ultimate physician management were collected and analyzed. V/Q results predicted physician management in all patients with high probability scans and 91% with normal to low probability scans. There were 35 patients with indeterminate V/Q scans--43% of these patients were managed without any other diagnostic test. CTA results predicted management in all patients with positive studies and 99% of patients with negative studies. In contrast to the V/Q cohort, only seven CTA studies were inconclusive--additional diagnostic tests determined management in all but one case. Compared with V/Q, CTA has fewer indeterminate results, is more directly reflective of management, and reduces the number of patients managed with inconclusive data.     

"High probability" perfusion lung scans in pulmonary venoocclusive disease

"High-probability" ventilation/perfusion (V/Q) lung scans generally indicate proximal pulmonary arterial occlusion by thromboemboli or, rarely, other processes such as tumors, fibrosing mediastinitis, or vasculitis. In this report we describe three patients with high probability V/Q scans in whom pulmonary angiography failed to demonstrate arterial occlusion. All three patients were determined to have pulmonary venoocclusive disease (PVOD). In two patients, a tissue diagnosis of PVOD was made, in one case with explanted tissue taken after a successful heart-lung transplant and in the other case with tissue taken at autopsy. PVOD in the third patient was diagnosed with pulmonary venography. A potential explanation for the discrepancy between perfusion lung scan and pulmonary angiographic findings in PVOD is discussed.     

Helical CT pulmonary angiography predictors of in-hospital morbidity and mortality in patients with acute pulmonary embolism

PURPOSE: To determine if CT variables predict in-hospital morbidity and mortality in patients with pulmonary embolism (PE). MATERIALS AND METHODS: CT scans and charts of 173 patients with CT scans positive for PE were reviewed. CT scans were reviewed for leftward ventricular septal bowing, increased right ventricle (RV) to left ventricle (LV) diameter ratio, clot burden, increased pulmonary artery to aorta diameter ratio, and oligemia. Charts were reviewed for severe morbidity and mortality outcomes: death from pulmonary emboli or any cause, and cardiac arrest. Charts were also reviewed for milder morbidity outcomes: intubation, vasopressor use, or admission to an intensive care unit (ICU) and for multiple comorbidities. RESULTS: No CT predictor was significantly associated with severe morbidity or mortality outcomes. Ventricular septal bowing and increased RV/LV diameter ratio were both associated with subsequent admission to an ICU (P = 0.004 and P = 0.025, respectively). Oligemia (either lung) was associated with subsequent intubation; right lung oligemia was associated with the subsequent use of vasopressors. After controlling for history of congestive heart failure, ischemic heart disease, and pulmonary disease, both septal bowing and an increased RV/LV diameter ratio remained associated with admission to an ICU. CONCLUSION: No CT variables predicted severe in-hospital morbidity and mortality (death from pulmonary embolism, death from any cause, or cardiac arrest) in patients with PE. However, ventricular septal bowing and increased RV/LV diameter ratio were both strongly predictive of less severe morbidity, namely, subsequent ICU admission, and oligemia was associated with subsequent intubation and vasopressor use.     

Review of 6-month mortality following low-probability lung scans

BACKGROUND: Ventilation perfusion lung scanning is widely used as a diagnostic method for evaluating patients suspected of having pulmonary embolism (PE). While lung scan interpretation is traditionally performed in terms of probability of PE (usually low, moderate or intermediate, and high), in recent years concern has been raised that the term low probability may be misleading because adverse and even fatal sequelae of PE occasionally occur in such patients. To assess these concerns, a review of mortality in a large series of patients following low-probability lung scans was performed. OBJECTIVE: To determine the 6-month mortality in a consecutive series of patients following low-probability ventilation perfusion (V/Q) lung scans. METHODS: Records of all patients who had low-probability V/Q scans during a 9-year period (1987-1995) were reviewed. Causes of mortality for those patients who died during the 6-month period after the index scan were established from patients' charts, autopsy reports, and computer record data. RESULTS: Of the total 536 evaluable patients, 83 (15%) died within 6 months of the date of the lung scan; 73 (88%) died while inpatients at the Seattle Veterans Affairs Medical Center, Seattle, Wash, and the other 10 (12%) died at other facilities or at home. Pulmonary embolism was not reported as a suspected or probable contributing factor in any of the 83 deaths. Sixty-three patients (76%) who died had a diagnosis of either cancer (n = 32) or advanced cardiovascular disease (n = 31) at the time of their lung scans. Twenty-six patients (31%) underwent autopsies, and PE was not identified on examination of the lungs in any of them. Of the 27 patients who died within 1 month of the scan date, 17 (63%) underwent autopsies. CONCLUSION: Review of data from all patients with low-probability V/Q scans and a follow-up of 6 months showed no documentation to attribute any deaths to PE.     

Hypoxemia in acute pulmonary embolism

Most patients with severe, acute pulmonary embolism (PE) have arterial hypoxemia. To further define the respective roles of ventilation to perfusion (VA/Q) mismatch and intrapulmonary shunt in the mechanism of hypoxemia, we used both right heart catheterization and the six inert gas elimination technique in seven patients with severe, acute PE (mean vascular obstruction, 55 percent) and hypoxemia (mean PaO2, 67 +/- 11 mm Hg). None had previous cardiopulmonary disease, and all were studied within the first ten days of initial symptoms. Increased calculated venous admixture (mean QVA/QT 16.6 +/- 5.1 percent) was present in all patients. The relative contributions of VA/Q mismatching and shunt to this venous admixture varied, however, according to pulmonary radiographic abnormalities and the time elapsed from initial symptoms to the gas exchange study. Although all patients had some degree of VA/Q mismatch, the two patients studied early (ie, less than 48 hours following acute PE) had normal chest x-ray film findings and no significant shunt; VA/Q mismatching accounted for most of the hypoxemia. In the others a shunt (3 to 17 percent of cardiac output) was recorded along with radiographic evidence of atelectasis or infiltrates and accounted for most of the venous admixture in one. In all patients, a low mixed venous oxygen tension (27 +/- 5 mm Hg) additionally contributed to the hypoxemia. Our findings suggest that the initial hypoxemia of acute PE is caused by an altered distribution of ventilation to perfusion. Intrapulmonary shunting contributes significantly to hypoxemia only when atelectasis or another cause of lung volume loss develops.     

Diagnostic imaging and risk stratification of patients with acute pulmonary embolism

Pulmonary embolism (PE) is the third most common acute cardiovascular disease after myocardial infarction and stroke. The prompt diagnosis, risk stratification, and treatment of patients with acute PE can reduce mortality. Multidetector row computed tomography pulmonary angiography (CTPA) is the most common study used to make the diagnosis of acute PE. CTPA may additionally identify right heart dysfunction or alternative diagnoses. There is a growing body of evidence that computed tomography signs of right heart failure predict patients at higher risk of mortality. At the same time, CTPA has about a 6-fold greater whole body effective dose than ventilation-perfusion (V/Q) scintigraphy, and a much higher dose to breast tissue in particular. V/Q scintigraphy should be considered for patients with contraindications to iodinated contrast or for patients with normal chest radiographs, especially young women. Compression ultrasonography of the proximal lower extremities, an imaging study without ionizing radiation, should be considered for patients suspected of acute PE with signs of lower extremity deep venous thrombosis or for patients with negative CTPA or V/Q scan with discordant clinical probability. This article reviews factors affecting the selection of the best imaging test for a particular patient suspected of acute PE, performance characteristics of diagnostic imaging tests, and imaging findings that correlate with higher mortality.     

Diagnosis of pulmonary embolus using ventilation/perfusion lung scintigraphy: more than 0.5 segment of ventilation/perfusion mismatch is sufficient

Background: To determine the optimal diagnostic cut‐off point using a simplified criterion for the detection of pulmonary embolus (PE) and to evaluate the criterion’s utility and reporter reproducibility. Methods: Lung scintigraphy was carried out in 924 patients for the diagnosis of PE. This group consisted of 316 men and 608 women with median age of 63 years (range 18–94 years). Ventilation imaging was carried out with Tc‐99m Technegas followed by perfusion imaging using 190 MBq Tc‐99m macroaggregated albumin. Studies were classified using a 6‐category probability criterion of incremental ventilation/perfusion (V/Q) mismatch: A, normal; B, low (minor matched V/Q defects or segmental matched V/Q defects without opacity on chest X‐ray); C, low‐moderate (a partial segment of V/Q mismatch); D, moderate (1 segment of mismatch); E, moderate‐high (1–2 segments of V/Q mismatch) and F, high probability (=2 segments of V/Q mismatch). Clinical end‐points at 3 and 6 months were death by PE or PE treated with anticoagulation therapy. Three‐reporter reproducibility was determined by kappa statistic on a subgroup of patients (53/924). Results: A total of 122 patients (13%) had a confirmed diagnosis of PE at 3 months and no additional cases were registered at 6 months. The lung scintigraphy probability classification showed: normal 152 (16%), low 620 (67%), low‐moderate 20 (2%), moderate 28 (3%), moderate‐high 24 (3%) and high 80 (9%). The respective sensitivities and specificities, where the diagnostic cut‐offs were established at F, high; E, moderate‐high; D, moderate and C, low‐moderate probability, were F, 64 and 100%; E, 82 and 99%; D, 95 and 98% and C, 98 and 96%. The respective false‐negative cases for F, E, D and C cut‐offs were 44, 22, 7 and 3. Using the revised Prospective Investigation of Pulmonary Embolism Diagnosis reporting classification reporter agreement showed kappa values of 0.31–0.48. Using a simplified 2‐category (>0.5 segment of V/Q mismatch positive, all others negative) criterion resulted in a higher reporting agreement (kappa 0.74–0.83). There were only 3% of indeterminate cases if this was defined by the D category and a maximum of 8% if categories C, D and E were included. Conclusions: Using a simplified diagnostic criterion where all studies showing >0.5 segments of V/Q mismatch are regarded as positive and all others as negative, lung scintigraphy, incorporating Tc‐99m Technegas ventilation imaging or its equivalent, can achieve a very high diagnostic accuracy for the detection of PE. Using this technique, less than 5% of scans are indeterminate. A simplified, unambiguous approach to reporting is recommended.     

Pulmonary embolism: imaging modalities--V/Q scan, spiral (helical) CT, and MRI

Ventilation-perfusion (V/Q) imaging has been used as the screening test for pulmonary embolism (PE) for many years with diagnostic algorithms developed as a result of the Prospective Investigation of Pulmonary Embolism Diagnosis study. The primary conclusions were that high probability V/Q scans were reliable indicators for PE and normal or near-normal scans were reliable in the exclusion of PE. With the increasing availability of spiral (helical) computed tomography (CT) and many studies showing a high degree of accuracy for PE, there is much support for the replacement of V/Q by spiral CT. This article reviews the literature concerning V/Q scanning, spiral (helical) CT, and the future potential for magnetic resonance in the diagnosis of PE.     

The bedside investigation of pulmonary embolism diagnosis study: a double-blind randomized controlled trial comparing combinations of 3 bedside tests vs ventilation-perfusion scan for the initial investigation of suspected pulmonary embolism

BACKGROUND: We sought to determine whether using combinations of 3 bedside tests (7-variable clinical model, non-enzyme-linked immunosorbent assay D-dimer test, and alveolar dead-space fraction) to exclude pulmonary embolism (PE) before diagnostic imaging was as safe as a standard strategy of starting with ventilation-perfusion (V/Q) scan. METHODS: In this double-blind, randomized, controlled equivalency trial, patients were randomized to initial bedside tests or to initial V/Q scan without bedside tests. Patients assigned to the bedside test group had a sham V/Q scan performed if at least 2 of 3 bedside test results were negative; otherwise, they underwent an actual V/Q scan. Further diagnostic management was determined by a blinded physician after V/Q scan. The primary outcome measure was recurrent venous thromboembolic events during 3 months among patients who were not taking anticoagulant agents after the initial investigations were completed. RESULTS: Four hundred fifty-eight consecutive adults with suspected PE were eligible for the study; 398 of 399 consenting and randomized patients completed the study. The follow-up venous thromboembolic event rate was 2.4% in the bedside test group vs 3.0% in the V/Q scan group (P = .76). Pulmonary embolism was excluded in 34% (67/199) of the bedside test group patients with at least 2 negative results on 3 bedside tests vs 18% (35/199) excluded using only the 7-variable clinical model and the D-dimer test. CONCLUSION: Excluding PE with at least 2 negative results on 3 bedside tests safely eliminates the need for diagnostic imaging in 34% of patients with suspected PE.     

Assessment of cardiac stress from massive pulmonary embolism with 12-lead ECG

BACKGROUND: Massive pulmonary embolism (PE) that causes severe pulmonary hypertension can produce specific ECG abnormalities. We hypothesized that an ECG scoring system would vary in proportion to the severity of pulmonary hypertension and would help to distinguish patients with massive PE from patients with smaller PE and those without PE. METHODS: A 21-point ECG scoring system was derived (relative weights in parentheses): sinus tachycardia (2), incomplete right bundle branch block (2), complete right bundle branch block (3), T-wave inversion in leads V(1) through V(4) (0 to 12), S wave in lead I (0), Q wave in lead III (1), inverted T in lead III (1), and entire S(1)Q(3)T(3) complex (2). ECGs obtained within 48 h prior to pulmonary arteriography were located for 60 patients (26 positive for PE, 34 negative for PE) and for 25 patients with fatal PE. RESULTS: Interobserver agreement (11 readers) for ECG score was good (Spearman r = 0.74). The ECG score showed significant positive relationship to systolic pulmonary arterial pressure (sPAP) in patients with PE (r = 0.387, p < 0.001), whereas no significant relationship was seen in patients without PE (r = - 0.08, p = 0.122). When patients were grouped by severity of pulmonary hypertension (low, moderate, severe), only patients with severe pulmonary hypertension from PE had a significantly higher ECG score (mean, 5.8 +/- 4.9). At a cutoff of 10 points, the ECG score was 23.5% (95% confidence interval [CI], 16 to 31%) sensitive and 97.7% (95% CI, 96 to 99%) specific for the recognition of severe pulmonary hypertension (sPAP > 50 mm Hg) secondary to PE. In 25 patients with fatal PE, the ECG score was 9.5 +/- 5.2. CONCLUSIONS: The derived ECG score increases with severity of pulmonary hypertension from PE, and a score > or = 10 is highly suggestive of severe pulmonary hypertension from PE.     

Lung tissue density measured by low-dose CT during pulmonary perfusion SPECT/CT as a tool for differentiation pulmonary embolism from chronic obstructive pulmonary disease – A pilot study

ObjectiveInterpretation of lung perfusion scintigraphy in patients with suspected pulmonary embolism (PE) is difficult, especially in the presence of chronic obstructive pulmonary disease (COPD) and most often has to be combined with pulmonary ventilation scintigraphy. We investigated the data from the CT portion of pulmonary perfusion SPECT/CT for possible resolution of this problem.MethodsWe assessed data from 12 patients (4 male, 8 female, mean age 68 y) with perfusion defects, 6 with PE, 6 with COPD. Final interpretation was based on ventilation/perfusion (V/Q) scintigraphy (mismatch or match). Lung tissue density was measured from the CT portion of pulmonary perfusion SPECT/CT. We analyzed 32 areas in mismatch defects (PE), 25 areas in match defects (COPD), and 17 areas without perfusion defects. Perfusion defects cause easily identifiable on X-ray (e.g. effusion) were excluded from the analysis. Data were compared with ANOVA test and Bonferroni post-hoc analysis, p<0.05 was considered statistically significant.ResultsThe mean lung tissue density in areas without perfusion defects was ?758 HU, in V/Q mismatch defects (PE) ?695 HU, and in V/Q match defects (COPD) ?900 HU. The differences of lung tissue density was statistically significant (p=0.000).ConclusionLung tissue density measured by CT is significantly lower in perfusion defects caused by COPD than in those caused by PE. We believe this data could be used as an adjunct in interpretation of pulmonary perfusion studies and potentially help avoid the performance of ventilation scintigraphy in patients with suspected PE.