Pulmonary embolism: role of ventilation-perfusion scintigraphy

Risk of Acute Kidney Injury after Intravenous Contrast Media Administration in Patients with Suspected Pulmonary Embolism: A Propensity-Matched Study

BACKGROUND

 Although computed tomography pulmonary angiography (CTPA) is the preferred diagnostic procedure in patients with suspected pulmonary embolism (PE), some patients undergo ventilation/perfusion (V/Q) lung scan due to concern of contrast-associated acute kidney injury (AKI).

METHODS

 The study used a cohort of 4,565 patients with suspected PE. Patients who received contrast during CTPA were compared with propensity score-matched unexposed control patients who underwent V/Q lung scanning. AKI was defined as ≥50% increase in serum creatinine during the first 72 hours after either CTPA or V/Q lung scan.

RESULTS

 Classification and regression tree analysis demonstrated that baseline creatinine was the strongest determinant of the decision to use CTPA. Propensity-score matching yielded 969 patient pairs. There were 44 AKI events (4.5%) in patients exposed to contrast media (CM) and 33 events (3.4%) in patients not exposed to CM (risk difference: 1.1%, 95% confidence interval [CI]: -0.6 to 2.9%; odds ratio [OR]: 1.39, 95% CI: 0.86-2.26; p = 0.18). Using different definitions for AKI and extending the time window for AKI diagnosis gave similar results. In a sensitivity analysis with the inverse probability weighting method, the OR for AKI in the CTPA versus V/Q scan was 1.14 (95% CI: 0.72-1.78; p = 0.58).

CONCLUSION

 Intravenous contrast material administration was not associated with an increased risk of AKI in patients with suspected PE. Given the diagnostic superiority of CTPA, these results are reassuring with regard to the use of CTPE in patients with suspected PE perceived to be at risk for AKI.

The diagnostic accuracy of prospective investigative study of acute pulmonary embolism diagnosis criteria for the detection of acute pulmonary thromboembolism in acutely ill patients

The practical diagnostic performance of Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISAPED) criteria for the detection of acute pulmonary thromboembolism (APTE) in hospitalized patients is not yet well determined. This is the report of the initial results of our recently implemented protocol to employ PISAPED. One hundred and forty-seven pulmonary perfusion scans with 1–3 mCi ^99mTc-MAA of patients of a single pulmonologist were included. Patients with suspicious perfusion defects underwent single-photon emission computed tomography. Interpretations were done by consensus of two nuclear medicine specialists. Comparisons were done with chest X-ray or chest computed tomography when available. The interpreters had access to the clinical records. The scans were reported based on the PISAPED criteria as negative or positive for APTE or indeterminate. Patients were followed up for 6.2 ± 5.3 months when the final diagnosis confirming or excluding APTE was achieved. Patients aged 55.9 (17.2) years; 78 (53.1%) of them were female and 64 (43.8%) had high Wells’ score. The scans were positive, negative, and indeterminate in 17 (11.6%), 126 (85.7%), and 4 (2.7%) patients, respectively. In 6 out of 147 patients, follow-up was not completed and the final diagnosis was not achieved. APTE was finally diagnosed in 21 (14.3%) patients; 12 (57.1%) of them had positive scans. APTE was excluded in 116 (78.9%) patients; 112 (96.5%) of them had negative scans. The accuracy of the test for the diagnosis of APTE was 87.9%. Lung metastasis was the most frequent reason among false-negative cases. The lung perfusion scan using PISAPED criteria could be used with good accuracy in inpatient settings.

Imaging of suspected pulmonary embolism and deep venous thrombosis in obese patients

Obesity is a growing problem around the world, and radiology departments frequently encounter difficulties related to large patient size. Diagnosis and management of suspected venous thromboembolism, in particular deep venous thrombosis (DVT) and pulmonary embolism (PE), are challenging even in some lean patients, and can become even more complicated in the setting of obesity. Many obstacles must be overcome to obtain imaging examinations in obese patients with suspected PE and/or DVT, and to ensure that these examinations are of sufficient quality to diagnose or exclude thromboembolic disease, or to establish an alternative diagnosis. Equipment limitations and technical issues both need to be acknowledged and addressed. Table weight limits and scanner sizes that readily accommodate obese and even morbidly obese patients are not in place at many clinical sites. There are also issues with image quality, which can be substantially compromised. We discuss current understanding of the effects of patient size on imaging in general and, more specifically, on the imaging modalities used for the diagnosis and treatment of DVT and PE. Emphasis will be placed on the technical parameters and protocol nuances, including contrast dosing, which are necessary to refine and optimize images for the diagnosis of DVT and PE in obese patients, while remaining cognizant of radiation exposure. More research is necessary to develop consistent high-level evidence regarding protocols to guide radiologists, and to help them effectively utilize emerging technology.

Pathogenesis, Diagnosis, and Treatment of Venous Thromboembolism in Older Adults

Older adults have a significantly greater risk of venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, than younger adults. The cause of this greater risk is thought to be multifactorial, including age-related changes in hemostatic factors and greater comorbid conditions and hospitalizations, but is not completely understood. Moreover, VTE remains underrecognized in older adults and may present atypically. Thus, a low index of clinical suspicion is essential when evaluating older adults with possible VTE. Despite this underrecognition in older adults, the diagnostic approach remains similar for all age groups and includes estimation of pretest probability, measurement of the D-dimer, and imaging. Antithrombotic agents are the mainstay of VTE treatment and, when used appropriately, substantially reduce VTE recurrence and complications. The approval of novel oral anticoagulants (NOACs), including dabigatran, rivaroxaban, apixaban, and edoxaban, provide clinicians with new therapeutic options. In some individuals, NOACs may offer advantages over warfarin, including fewer drug interactions, more-predictable anticoagulation, and lower risk of bleeding. Nevertheless, anticoagulation of VTE in older adults should always be performed cautiously, because age is a risk factor for bleeding complications. Identifying modifiable bleeding risk factors and balancing the risks of VTE recurrence with hemorrhage are important considerations when using anticoagulants in older adults.

Lung or liver: An imaging dilemma on Tc-99m macroaggregated albumin lung perfusion scintigraphy

We present a 10-year-old boy having the bronchiectasis who was subjected to lung perfusion scintigraphy before lung resection surgery to assess the lung parenchymal function. It revealed unusual tracer distribution in right upper body that was mimicking to be liver. It was unusual unless there were some shunts bypassing the lung uptake or faulty radiopharmaceutical preparation. However by bringing down the image window, it became clear that radiopharmaceutical distribution was in thorax only correlating with lung uptake, and not in the liver. Corresponding X-ray chest and computed tomography thorax demonstrated multiple cystic lesions in left lung parenchyma.

The accuracy of V/Q SPECT in the diagnosis of pulmonary embolism: a meta-analysis

BACKGROUND

Ventilation perfusion single photon emission computed tomography (V/Q SPECT) and CT pulmonary angiography have all been used in the diagnosis of acute PE. Previous studies have shown higher sensitivity and specificity and a marked decrease in the non-diagnostic rate of V/Q SPECT than planar scan.

PURPOSE

To systematically review and perform a meta-analysis of published data on the performance of V/Q SPECT in the diagnosis of acute PE.

MATERIAL AND METHODS

A comprehensive computer search was conducted on literature published through 31 December 2013 in an effort to find relevant articles on the diagnostic performance of V/Q SPECT in the diagnosis of PE patients. Pooled sensitivity, specificity, negative likelihood ratio (LR), and positive LR, the area under the receiver-operating characteristic (ROC) curve of V/Q SPECT in the diagnosis of PE patients were calculated.

RESULTS

Nine studies, comprising a total sample size of 3454 patients, were included in our meta-analysis. The pooled sensitivity, specificity of V/Q SPECT in the diagnosis of acute PE patients, calculated on a per-patient-based analysis, was 96% (95% confidence interval [CI], 95-97%), 97% (95% CI, 96-98%). The pooled negative LR, positive LR of V/Q SPECT in acute PE patients was 0.06 (range, 0.02-0.19) and 16.64 (range, 9.78-31.54). The area under the ROC curve of V/Q SPECT in the diagnosis of acute PE patients was 0.99 on a per-patient-based analysis.

CONCLUSION

V/Q SPECT is an accurate method in acute PE patients with high sensitivity and high specificity in the diagnosis of PE.

Contribution of V/Q SPECT to planar scintigraphy in the diagnosis of pulmonary embolism

AIM

To evaluate the feasibility of V/Q SPECT and analyze its contribution to planar V/Q lung scintigraphy in the diagnosis of pulmonary embolism (PE).

MATERIAL AND METHODS

A total of 109 patients with suspected PE showing Wells score>2 and elevated D-dimer were studied. The V/Q could not be completed in 7 patients, so they were excluded. Ventilation and perfusion scans were done using Technegas and (99m)Tc-MAA. Planar study included 8 projections on a 256×256 matrix and 128 projections on a 128×128 matrix were acquired for the SPECT study, applying an iterative method. Planar images were interpreted according to modified PIOPED criteria, and SPECT by the guidelines of the EANMMI. The results with both techniques were compared.

RESULTS

V/Q planar scintigraphy and SPECT could be performed in 102 patients. V/Q planar scintigraphy was considered "diagnostic" in 39 of the 102 patients, and "non-diagnostic" in 63. Of the 39 "diagnostic" studies, 31 were reported as high probability of PE and 8 as normal. Of the 63 "non-diagnostic", 26 corresponded to intermediate, 29 to low, and 8 to very low probability. The SPECT study was "diagnostic" in 97 and indeterminate in only 5. All patients with a high probability planar scintigraphy had a positive SPECT. In the 8 patients with a normal planar scintigraphy SPECT was negative in 5 and positive in 3. In the 63 patients with a "non-diagnostic" planar scintigraphy SPECT was "diagnostic" in 58 of them, positive in 17 and negative in 41.

CONCLUSION

V/Q SPECT is a feasible technique as it was performed in 102 of the 109 patients who were enrolled in the study (94%). The addition of V/Q SPECT to planar V/Q decreases the number of "non-diagnostic" reports from 62% in planar scintigraphy to 4.9% in SPECT. Therefore, V/Q SPECT should be included in the diagnosis approach of PE due to its high diagnostic yield.

CT pulmonary angiography: increasingly diagnosing less severe pulmonary emboli

Background

It is unknown whether the observed increase in computed tomography pulmonary angiography (CTPA) utilization has resulted in increased detection of pulmonary emboli (PEs) with a less severe disease spectrum.

Methods

Trends in utilization, diagnostic yield, and disease severity were evaluated for 4,048 consecutive initial CTPAs performed in adult patients in the emergency department of a large urban academic medical center between 1/1/2004 and 10/31/2009. Transthoracic echocardiography (TTE) findings and peak serum troponin levels were evaluated to assess for the presence of PE-associated right ventricular (RV) abnormalities (dysfunction or dilatation) and myocardial injury, respectively. Statistical analyses were performed using multivariate logistic regression.

Results

268 CTPAs (6.6%) were positive for acute PE, and 3,780 (93.4%) demonstrated either no PE or chronic PE. There was a significant increase in the likelihood of undergoing CTPA per year during the study period (odds ratio [OR] 1.05, 95% confidence interval [CI] 1.04–1.07, P<0.01). There was no significant change in the likelihood of having a CTPA diagnostic of an acute PE per year (OR 1.03, 95% CI 0.95–1.11, P = 0.49). The likelihood of diagnosing a less severe PE on CTPA with no associated RV abnormalities or myocardial injury increased per year during the study period (OR 1.39, 95% CI 1.10–1.75, P = 0.01).

Conclusions

CTPA utilization has risen with no corresponding change in diagnostic yield, resulting in an increase in PE detection. There is a concurrent rise in the likelihood of diagnosing a less clinically severe spectrum of PEs.