British Thoracic Society Standards of Care Committee Pulmonary Embolism Guideline Development Group. British Thoracic Society guidelines for the management of suspected acute pulmonary embolism

ECG Score Predicts Those With the Greatest Percentage of Perfusion Defects Due to Acute Pulmonary Thromboembolic Disease

BACKGROUND

More aggressive management may be warranted for patients with acute pulmonary embolism (PE) and the greatest pulmonary vascular obstruction. We hypothesized that a scoring system based on the ECG might identify such patients.

METHODS

Consecutive patients investigated for PE at Christchurch Hospital between 1997 and 2002 with high-probability ventilation/perfusion (V/Q) scan findings were studied. The ECG obtained closest to and within 48 h of the scan was scored by two independent observers, and the mean ECG score was calculated. V/Q scan findings were categorized into those with < 30%, 30 to 50%, and > 50% perfusion defect by two independent observers experienced in V/Q interpretation. A consensus score was taken when disagreement occurred.

RESULTS

Two hundred twenty-nine patients were included in the study. The interobserver agreement for ECG score was 0.96 (Cronbach alpha) and V/Q score was 0.55 (kappa). The ECG predicted those with the greatest amount of perfusion defects. Mean ECG score was 2.6 (SD 2.8) in patients with < 30% perfusion defect, 3.2 (SD 2.9) in patients with 30 to 50% perfusion defect, and 5.3 (SD 3.7) in patients with > 50% perfusion defect. The area under the receiver operating characteristic curve for ECG score and those with > 50% perfusion defect was 0.71 (SE 0.04). An ECG score of > or = 3 predicted those with > 50% perfusion defect with a sensitivity of 70% (95% confidence interval [CI], 59 to 81%), and a specificity of 59% (95% CI, 51 to 67%).

CONCLUSION

An ECG score, simple to derive, predicts those with the greatest percentage of perfusion defect. Using the ECG for management warrants prospective evaluation.

The Added Value of Spiral Computed Tomographic Angiography After Lung Scintigraphy for the Diagnosis of Pulmonary Embolism

OBJECTIVES

The objectives of this study were to evaluate the added clinical value of spiral computed tomographic angiography (CTA) after ventilation-perfusion lung scintigraphy (V/Q) for the management of patients with suspected pulmonary embolism (PE).

METHODS

Of 987 patients who had V/Q during 2001, 64 patients (6%) had CTA performed for further evaluation. V/Q and CTA findings were retrospectively analyzed by 2 clinicians who were blinded to the patients' outcome. Patient management was determined based on clinical and V/Q data and was reassessed after the addition of CTA data.

RESULTS

CTA was performed in 2 patients with normal V/Q, 16 patients with low probability, 28 patients with intermediate, 4 patients with high probability, and 14 patients with nonconclusive V/Q. Three patients (19%) with low probability, 9 (32%) with intermediate probability, 4 (29%) with nonconclusive, and 4 (100%) with high probability V/Q had PE diagnosed by CTA. CTA findings changed the management in 2 patients (13%) with low probability, 15 (54%) with intermediate probability, and 4 (29%) with nonconclusive V/Q.

CONCLUSION

In our institution, V/Q remains the main imaging modality for evaluation of patients with clinically suspected PE. CTA was performed after V/Q in 6% of patients. Patients with intermediate probability and those with nonconclusive V/Q, and to a much lesser extent, patients with low probability V/Q could benefit from the addition of CTA after V/Q. In patients with normal V/Q and those with high-probability V/Q, the addition of CTA does not seem to influence patient management.

CT venography in suspected pulmonary thromboembolism

Pulmonary embolism (PE) and deep venous thrombosis (DVT) are a continuum and are difficult to diagnose clinically. Combined CT venography and pulmonary angiography (CTVPA) is a single examination that combines multidetector CT pulmonary angiography (CTPA) and CT venography (CTV) of the abdomen, pelvis, and lower extremities, providing "one-stop shopping" for venous thromboembolism without additional venipuncture or i.v. contrast, and it adds only a few additional minutes to scanning time. CTVPA rapidly and accurately examines the deep veins, reveals the presence, absence, and extent of deep venous thrombosis, serves as a baseline, and helps guide patient management. Multiple investigators have reported a high degree of accuracy when CTV is compared with venous ultrasound. There are some pitfalls in image interpretation, especially with regard to mixing artifacts, and there are continuing controversies as to exactly which parts of the abdomen, pelvis, and legs should be scanned routinely, the ideal timing of CTV acquisition relative to contrast injection, and the slice thickness and gap, if any, that should be used.

Frequency of venous thromboembolism in low to moderate risk long distance air travellers: the New Zealand Air Traveller's Thrombosis (NZATT) study

BACKGROUND

The frequency and role of risk factors for venous thromboembolism related to air travel is uncertain. We aimed to establish the frequency of this disorder in a group of long distance air travellers and to investigate the role of potential risk factors.

METHODS

We designed a prospective study into which we recruited individuals aged between 18 and 70 years, travelling for 4 h or more by aircraft. D-dimer measurement was done before and after travel. Participants with a negative D-dimer (<500 ng/L) before travel were included in the study. Those who became D-dimer positive or developed high clinical probability symptoms during the 3 months after travel were investigated with bilateral compression ultrasonography and CT pulmonary angiography. Suspected clinical and thrombophilic risk factors, and use of prophylactic measures, were assessed.

FINDINGS

1000 individuals were recruited, with 878 meeting inclusion criteria and completing the study. All participants travelled at least 10 h, with a mean total duration of air travel of 39 h (SD 12.5). 112 patients underwent radiological assessment on return. Frequency of venous thromboembolism associated with travel was 1.0% (9/878, 95% CI 0.5-1.9), which included four cases of pulmonary embolism and five of deep venous thrombosis. Six patients with venous thromboembolism had pre-existing clinical risk factors, two had a recognised thrombophilic risk factor, two travelled exclusively in business class, five used aspirin, and four wore compression stockings.

INTERPRETATION

Our results suggest an association between multiple long distance air flights and venous thromboembolism, even in individuals at low to moderate risk. The role of traditional risk factors and prophylactic measures in air travel-related venous thromboembolism needs further investigation.

Effect of coronary blood flow on glycolytic flux and intracellular pH in isolated rat hearts

The rate of coronary blood flow was varied in isolated working rat heart preparations to determine its influence on the rate of glocose utilization, tissue high-energy phosphates, and intracellular pH. A 60% reduction in coronary blood flow resulted in a 30% reduction in oxygen consumption, an accelerated rate of glusoe utilization, lower tissue levels of high-energy phosphate, and higher tissue levels of lactate and H+. Ventricular performance deteriorated as reflected by a decrease in heart rate and peak systolic pressure. Further reductions in coronary blood flow resulted in inhibition of glycolysis, a greater decrease in tissue levels of high-energy phosphates, and higher tissue levels of both lactate and H+. These changes in glycolytic flux, tissue metabolites, and ventricular performance were proportional to the degree of restriction in coronary blood flow. The importance of coronary blood flow and washout of the interstitial space in the maintenance of accelerated glycolytic flux in oxygen-deficient hearts is emphasized. It is concluded that acceleration of ATP production from glycolysis can occur only in the marginally ischemic tissue in the peripheral area of tissue supplied by an occluded artery. The central area of tissue which receives a low rate of coronary blood flow will have a reduced rate of ATP production due to both a lack of oxygen and an inhibition of glycolysis.