The role of the vascular laboratory in clinical decision-making

Doppler ultrasonographic features of thoracic limb arteries in clinically normal horses

OBJECTIVES

To determine blood flow velocities and indices from spectral waveforms obtained by use of Doppler ultrasonography of thoracic limb arteries of horses and to assess interobserver and patient variability associated with the technique.

ANIMALS

9 clinically normal adult horses.

PROCEDURE

Left thoracic limb arteries of 8 nonsedated horses were examined at 5 sites by use of pulsed-wave Doppler ultrasonography to determine a range of values for peak systolic, end diastolic, and mean velocities and resistive and pulsatility indices. Interobserver and patient variabilities were determined by 2 operators repeating similar measurements on 1 horse 8 times at weekly intervals.

RESULTS

A range of values for each variable measured at the 5 selected sites was obtained. For each variable, strong positive correlations (R > or = 0.7) were detected for > 70% of the site-to-site comparisons made (excluding the coronary band). Among horses, resistive index varied least, whereas over time, mean velocity varied least. Waveform characteristics were consistent with resistive (n = 5) or nonresistive (4) patterns. In the single-horse experiment, waveform characteristics were consistent throughout the 8 weeks, and operator effects were not detected.

CONCLUSIONS AND CLINICAL RELEVANCE

Doppler ultrasonography of no one site resulted in more reliable measurements of blood flow characteristics in thoracic limb arteries of horses. Mean velocity and resistive index were the least variable measurements made. Pulsed-wave Doppler ultrasonography may be a useful technique for evaluating diseases that alter normal thoracic limb arterial blood flow in horses.

Vascular surgery without arteriography: use of Duplex ultrasound

Although contrast arteriography has served as the historical 'gold standard' for diagnosis of arterial disease, recent improvements in noninvasive diagnostic methods have made it possible to plan surgical treatment without subjecting patients to this invasive procedure. This approach avoids both the risks and costs associated with arteriography. Duplex scanning has become the standard noninvasive test for extracranial carotid artery disease, and it can also be used to directly evaluate the lower extremity arteries. In addition to the standard duplex criteria for classification of carotid stenosis, new criteria are available that reflect the stenosis thresholds identified in randomized clinical trials. Clinical experience has clearly shown that carotid endarterectomy can be performed safely based on the duplex scan alone in the majority of patients: however, arteriography is still indicated in selected cases. The evaluation of lower extremity arterial disease requires examination of multiple arterial segments, and most vascular surgeons still rely on the anatomic detail provided by arteriography for preoperative planning. Still, it may be possible to avoid formal preoperative arteriography in selected patients by using a combination of lower extremity duplex scanning and intraoperative arteriography. Further developments in noninvasive testing will continue to reduce the need for diagnostic arteriography prior to direct arterial surgery.

Duplex Doppler endosonography in the diagnosis of splenic vein, portal vein, and portosystemic shunt thrombosis

BACKGROUND/AIMS

Endoscopic ultrasonography is a promising procedure for imaging mesenteric vascular structures.

METHODS

Duplex and color Doppler endosonography were used to prospectively evaluate 20 asymptomatic paid volunteers. Subsequently, 11 patients with nondiagnostic transabdominal ultrasound and suspected thrombosis of the splenic and/or portal veins or a portosystemic shunt were evaluated with duplex endosonography. The final diagnosis was based on CT, angiography, and/or surgery or autopsy findings in 9 of 11 patients.

RESULTS

In normal volunteers, mesenteric vessel flow velocities and diameters were similar to previously described values. In 10 of the 11 patients with failed transabdominal ultrasound, duplex endosonography was able to provide the correct diagnosis (accuracy of ultrasound 0% versus EUS 91%, p < .001). Mean portal vein diameter was greater in the patient group than in the normal volunteers (18.5 mm versus 10.7 mm, p < .001) and all of the normal volunteers had a portal vein diameter less than 13 mm. No complications were experienced.

CONCLUSION

Duplex endosonography allows visualization of the intra-abdominal vasculature and can be considered when transabdominal ultrasound is nondiagnostic in patients with suspected thrombosis of their splenic vein, portal vein, or portosystemic shunt. EUS is able to identify indirect findings of portal hypertension including portal vein enlargement and venous collaterals.