Reappraisal of duplex criteria to assess significant carotid stenosis with special reference to reports from the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial.

PURPOSE: Duplex examination is today the principal initial method of assessing extracranial carotid or vertebral artery disease. However, varying haemodynamic criteria have been described to categorize the degree of internal carotid artery stenosis, and similarly the degree of stenosis detected with angiography has been assessed with different methods as highlighted in studies performed by the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. This study looks at the correlation between two commonly used methods of assessing carotid artery stenosis with duplex criteria and the two methods of angiographic interpretation used in these trials. Duplex parameters are also identified to determine the greater than 70% stenosis group identified as at risk in these studies. METHODS: A total of 120 carotid bifurcations were studied in patients who underwent both carotid duplex and angiography. Correlations of duplex with angiography were assessed with duplex criteria described by Zwiebel and by Strandness and the angiographic methods used in studies performed by the North American Symptomatic Carotid Endarterectomy Trial and the European Carotid Surgery Trial. Receiver operator curves were constructed from the duplex data for the detection of stenosis greater than 70% based on the angiographic assessment used in the study performed by the North American Symptomatic Carotid Endarterectomy Trial. RESULTS: The duplex criteria described by Zwiebel and Strandness differed in their accuracy depending on which of the two methods was used to report the angiograms. Zwiebel's criteria agreed more with the angiographic method used in the study performed by the European Carotid Surgery Trial (sensitivity 98%, specificity 81%, accuracy 88%), whereas Strandness' criteria agreed more with the angiographic method used in the study performed by the North American Symptomatic Carotid Endarterectomy Trial (sensitivity 96%, specificity 85%, accuracy 89%). For the detection of a stenosis greater than 70%, a peak systolic velocity greater than 270 cm/sec and end diastolic velocity greater than 110 cm/sec provided a sensitivity of 96%, specificity of 91%, and accuracy of 93%. CONCLUSIONS: The accuracy of duplex studies compared with angiography in the assessment of extracranial vascular disease depends on the method of angiographic determination of carotid stenosis. Vascular laboratories should validate the duplex criteria they use against a standard method of angiographic assessment of carotid artery stenosis, with special reference to the recently reported studies noting the significance of a stenosis greater than 70% in patients with symptoms.

Duplex ultrasound diagnosis of lower limb deep venous thrombosis.

To compare a non-invasive technique with contrast venography in the diagnosis of lower limb deep venous thrombosis (DVT), 355 patients (380 limbs) were examined over 15 months, using Duplex ultrasound. During this period, ascending venograms were performed in 53 of these patients (56 limbs) and the results were compared. Duplex detection of intraluminal thrombus was based on venous compressibility, Doppler-derived flow spectra, and visualization of thrombus within the lumen. Venography was designated the 'gold standard'. Duplex scanning had a sensitivity of 90.9%, and specificity of 91.3% in diagnosing DVT anywhere in the lower limb. Sensitivity, specificity, and accuracy were best in the femoral segment (95.2%, 100%, 98.2%, respectively), and fell slightly in the more distal limb: popliteal segment (90.4%, 97.1% and 94.6%), and calf veins (88.8%, 92.0% and 90.4%). These results indicate that duplex scanning produces sufficiently accurate data in the diagnosis of lower limb DVT to warrant its clinical use. It provides both the facility for diagnosis without the risks of contrast venography, and permits repeated imaging to follow the immediate progression of disease and efficacy of treatment.

Aluminum toxicity and albumin.

During a study of priming solutions for extracorporeal membrane oxygenation (ECMO) in the intensive care nursery, it was discovered that those solutions using certain brands of 25% albumin contained aluminum levels within the toxic range. When the brand was changed to a brand known to have a lower aluminum (Al) content, a marked drop in priming solution Al levels was measured. The heat exchanger was examined as a possible source of soluble Al. No evidence of elevated Al levels was found in fluids perfusing this heat exchanger when compared with a stainless steel heat exchanger. The Al content of various blood products was evaluated along with various brands of 5% albumin and 25% albumin.