New PIOPED recommendations for the diagnosis of pulmonary embolism

Evaluation of autologous blood clot subsegmental pulmonary thromboembolism in minimally invasive experimental canine model

The incidence and significance of subsegmental pulmonary (SSP) thromboembolism is currently under investigation. We aimed to evaluate the clinical and diagnostic features of SSP thromboembolism in an experimental canine model. Obstruction of pulmonary arterial branches was induced in three beagle dogs by intravenous injection of a barium-coated autologous blood clot (size, approximately 1.7 × 5 mm). The clinical signs, haemodynamic changes (blood pressure, electrocardiogram, echocardiography), coagulation (aPTT, PT, FDPs and D-dimer test) and cytokine variations (TNF-a, IL-4, IL-6, and IL-10) were evaluated over a 24-hour period. Multidetector computed tomography (MDCT) with contrast was conducted to evaluate the pulmonary obstruction, and histopathological confirmation was performed. Pulmonary artery pressure gradient (PAPG) was increased 12 h after the autologous blood clot injection (14.2 ± 2.8 mmHg to 23.6 ± 1.7 mmHg, P = 0.003) and normalized 24 h later (P < 0.01). Infused radiopaque clots were confirmed with MDCT and histopathological examination. Pulmonary parenchymal changes such as arterial dilation and inflammatory reactions were also confirmed in histopathological examinations and were barely observable in MDCT. Usually small emboli are not easily detected through CT imaging, and the clinical relevance of these emboli is controversial. In this experimental study, we made radiopaque small emboli and induced SSP thromboembolism. Thus, we infer that obstruction of the small segmental and subsegmental pulmonary arteries does result in a pulmonary thromboembolism (PTE) and PTE-related pulmonary parenchymal changes which could be clinically significant.

Computed tomography for pulmonary embolism: assessment of a 1-year cohort and estimated cancer risk associated with diagnostic irradiation

BACKGROUND

The principal concern of any radiation exposure in computed tomography (CT) is the induction of stochastic risks of developing a radiation-induced cancer. The results given in this manuscript will allow to (re-)calculate yield of chest CT.

PURPOSE

To demonstrate a method to evaluate the lifetime attributable risk (LAR) of cancer incidence/mortality due to a single diagnostic investigation in a 1-year cohort of consecutive chest CT for suspected pulmonary embolism (PE).

MATERIAL AND METHODS

A 1-year cohort of consecutive chest CT for suspected PE using a standard scan protocol was analyzed retrospectively (691 patients, 352 men, 339 women). Normalized patient-specific estimations of the radiation doses received by individual organs were correlated with age- and sex-specific mean predicted cancer incidence and age- and sex-specific predicted cancer mortality based on the BEIR VII results. Additional correlation was provided for natural occurring risks.

RESULTS

LAR of cancer incidence/mortality following one chest CT was calculated for cancer of the stomach, colon, liver, lung, breast, uterus, ovaries, bladder, thyroid, and for leukemia. LAR remains very low for all age and sex categories, being highest for cancer of the lungs and breasts in 20-year-old women (0.61% and 0.4%, respectively). Summation of all cancer sites analyzed raised the cumulative relative LAR up to 2.76% in 20-year-old women.

CONCLUSION

Using the method presented in this work, LAR of cancer incidence and cancer mortality for a single chest CT for PE seems very low for all age groups and both sexes, but being highest for young patients. Hence the risk for radiation-induced organ cancers must be outweighed with the potential benefit or a treatment and the potential risks of a missed and therefore untreated PE.

Prophylaxis of deep-vein thrombosis in fractures below the knee: a prospective randomised controlled trial

The incidence of deep-vein thrombosis and the need for thromboprophylaxis following isolated trauma below the knee is uncertain. We have investigated this with a prospective randomised double-blind controlled trial using low molecular weight heparin with saline injection as placebo in patients aged between 18 and 75 years who had sustained an isolated fracture below the knee which required operative fixation. All patients had surgery within 48 hours of injury and were randomised to receive either the placebo or low molecular weight heparin for 14 days, after which they underwent bilateral lower limb venography, interpreted by three independent radiologists. Further follow-up was undertaken at two, six, eight and 12 weeks. A total of 238 patients fulfilled all the inclusion criteria, with 127 in the low molecular weight heparin group and 111 in the placebo group, all of whom underwent bilateral venography. There was no statistically significant difference in the incidence of deep-vein thrombosis between those patients treated with low molecular weight heparin or the placebo (p = 0.22). The number of deep-vein thromboses in the two groups was 11 (8.7%) and 14 (12.6%), respectively. Age and the type of fracture were significantly associated with the rate of deep-vein thrombosis (p = 0.001 and p = 0.009, respectively) but gender, comorbidities and the body mass index were not. The overall incidence of deep-vein thrombosis in this series was 11%. There was no clinical or statistical significant reduction in the incidence of deep-vein thrombosis with the use of thromboprophylaxis. However, we accept that owing to a cessation of funding, recruitment to this trial had to be ended prior to establishing the necessary sample size. Our results cannot, therefore, categorically exclude the possibility that low molecular weight heparin treatment could be beneficial. We recommend a further multicentre trial be undertaken to resolve this matter.