Computed tomography pulmonary angiogram diagnosis of pulmonary embolism

Ethnicity as an independent predictive factor for the results of computed tomography pulmonary angiography and ultrasonography of the lower limbs

BACKGROUND

Asians, Pacific Islanders and Maori have significantly lower rates of venous thromboembolism (VTE) compared to Europeans, but its clinic implication regarding diagnosis and prevention is unclear.

AIMS

To investigate if ethnicity affects the yield of computed tomography pulmonary angiography (CTPA) and ultrasonography of the lower limbs.

METHODS

Data previously collected for 523 patients from another study were used to analyse the effect of ethnicity on the results of CTPA; 1587 consecutive ultrasonography of lower limbs was retrospectively analysed according to ethnicity. The Wells score was retrospectively calculated to determine the pretest probability of VTE.

RESULTS

The positive rates of CTPA were 23.3% for European patients and 9.3% for non-European patients. The rate ratio was 2.50 (confidence interval [CI] 1.27-4.95). European patients were 2.5 times more likely to have a positive scan result than non-Europeans, given same pretest probability. There was a larger difference among patients with low and moderate pretest probability with a rate ratio of 4.27 (CI 1.62-11.3). The positive rates of ultrasound scans (USS) among European patients were 16.6 and 9.0% for non-European patients. Rate ratio was 1.85 (CI 1.27-4.95). The difference was also more significant amongst patients with low and moderate pretest probability. The rate ratio was 2.31 (CI 1.38-3.86) for European patients compared to non-European patients.

CONCLUSION

Given the same pretest probability according to the Wells score, European patients had significantly higher positive rates of CTPA and ultrasonography of the lower limbs than non-European patients. Further prospective studies are required to confirm our findings and establish an appropriate pretest assessment tool for non-European patients.

A cohort study on the incidence and outcome of pulmonary embolism in trauma and orthopedic patients

BACKGROUND

This study aims to determine the incidence of pulmonary embolism (PE) in trauma and orthopedic patients within a regional tertiary referral center and its association with the pattern of injury, type of treatment, co-morbidities, thromboprophylaxis and mortality.

METHODS

All patients admitted to our institution between January 2010 and December 2011, for acute trauma or elective orthopedic procedures, were eligible to participate in this study. Our cohort was formed by identifying all patients with clinical features of PE who underwent Computed Tomography-Pulmonary Angiogram (CT-PA) to confirm or exclude the clinical suspicion of PE, within six months after the injury or the surgical procedure.Case notes and electronic databases were reviewed retrospectively to identify each patient's venous thromboembolism (VTE) risk factors, type of treatment, thromboprophylaxis and mortality.

RESULTS

Out of 18,151 patients admitted during the study period only 85 (0.47%) patients developed PE (positive CT-PA) (24 underwent elective surgery and 61 sustained acute trauma). Of these, only 76% of the patients received thromboprophylaxis. Hypertension, obesity and cardiovascular disease were the most commonly identifiable risk factors. In 39% of the cases, PE was diagnosed during the in-hospital stay. The median time of PE diagnosis, from the date of injury or the surgical intervention was 23 days (range 1 to 312). The overall mortality rate was 0.07% (13/18,151), but for those who developed PE it was 15.29% (13/85). Concomitant deep venous thrombosis (DVT) was identified in 33.3% of patients. The presence of two or more co-morbidities was significantly associated with the incidence of mortality (unadjusted odds ratio (OR) = 3.52, 95% confidence interval (CI) (1.34, 18.99), P = 0.034). Although there was also a similar clinical effect size for polytrauma injury on mortality (unadjusted OR = 1.90 (0.38, 9.54), P = 0.218), evidence was not statistically significant for this factor.

CONCLUSIONS

The incidence of VTE was comparable to previously reported rates, whereas the mortality rate was lower. Our local protocols that comply with the National Institute for Health and Clinical Excellence (NICE) guidelines in the UK appear to be effective in preventing VTE and reducing mortality in trauma and orthopedic patients.

The effect of left-sided versus right-sided contrast infusion on attenuation of the main pulmonary artery when performing computed tomography angiograms of the chest

OBJECTIVE

This study assesses if the arm of contrast infusion influences attenuation of the main pulmonary artery in computed tomography (CT) angiograms to evaluate for pulmonary emboli.

METHODS

Four hundred seven consecutive CT angiograms performed to exclude pulmonary emboli were reviewed. Patient characteristics, study details, and interpretation results were collected. After exclusion criteria, 100 studies from each scanner (4, 16, and 64 slice) remained. A reader, blinded to injection side, measured the attenuation of the main pulmonary artery.

RESULTS

The average attenuation in the main pulmonary artery was similar if infused through the right (275.4 HU) or left (275.0 HU) arm when controlling for confounders with a multiple regression analysis (P = 0.82). There was no statistical difference (P > 0.05) in the number of scans with attenuation less than 250 (45.9% right, 42.9% left), 200 (25.3% right, 29.2% left), or 150 HU (11.6% right, 12.3% left) and interpreted as indeterminate (1.4% right, 3.9% left) or nondiagnostic (2.7% right, 2.6% left).

CONCLUSIONS

Main pulmonary artery attenuation is independent of the arm of infusion when evaluating mean attenuation, attenuation beneath 250, 200, or 150 HU, or indeterminate or nondiagnostic interpretations for patients undergoing CT angiograms of the chest to rule out pulmonary emboli.