Visualization of the azygos arch valves on multidetector-row computed tomography

Abstract

To evaluate the frequency and appearance of the azygos arch valves on chest examinations using multidetector-row computed tomography (MDCT), we retrospectively reviewed findings from 194 contrast-enhanced MDCT examinations of the chest. Rate of injection of 300 mgI/ml contrast materials was low (2.0 ml/s) and high (3.0 ml/s). Scanning delay was 80 s on examination on low-rate injection of contrast material and 20 s on high-rate injection of contrast material. The presence of residual contrast material in the azygos arch valves and reflux of contrast material into the azygos arch were recorded. The Cochran-Armitage trend test was used to compare the frequency of residual contrast material in the azygos arch valves and reflux of contrast material into the azygos arch in both groups. Of 92 examinations of high-rate injection of contrast material, 63 (68.5%) demonstrated residual contrast material in the azygos arch valves and 71 (77.2%) demonstrated reflux of contrast material into the azygos arch. A significantly higher frequency of reflux of contrast material into the azygos arch and residual contrast material in the azygos arch valves was seen in the high-rate injection group than in the low-rate injection group (P < 0.05). Residual contrast material in the azygos arch valves was demonstrated more frequently when contrast material was administered in the right side of the arm than in the left side of the arm (P < 0.05). Reflux of contrast material into the azygos arch was common in the high-injection-rate group and residual contrast material in the azygos arch valves was far more frequently seen in the high-injection-rate group than in the low-injection-rate group on MDCT.

Identification of efferent flow in the superior vena cava and azygos vein confluence using cine phase-contrast MRI: speculation of the role of the azygos arch valves

“…Past reports have revealed that reflux of contrast material into the azygos arch is commonly seen in CT images, especially when the injection rate was high [3,4]. The findings of the present study indicate that the reason for this is that the contrast material clashes with the efferent blood flow in the SVC during the diastolic phase and refluxes into the azygos vein.…”

“…The findings of the present study indicate that the reason for this is that the contrast material clashes with the efferent blood flow in the SVC during the diastolic phase and refluxes into the azygos vein. If the injection rate is high, the degree of reflux becomes more pronounced as indicated in previous reports [3,4]. Then, the reflux of contrast material will generally be dammed by the azygos arch valves.…”

“…In patients with high central venous pressure, such as from cardiac tamponade, the azygos arch valves are sometimes detected by computed tomography (CT) due to the reflux of contrast material into the azygos vein beyond the valves [5]. Even without such high central venous pressure, these valves are commonly observed, due to the development of multi-detector computed tomography (MDCT), especially following high rate injection of contrast material [3,4,6]. However, the reason why such reflux into the azygos vein occurs has not been fully explained and the role and significance of the azygos arch valves remain to be elucidated.…”

“…It is known that bicuspid valves exist in the azygos arch [3,4]. In patients with high central venous pressure, such as from cardiac tamponade, the azygos arch valves are sometimes detected by computed tomography (CT) due to the reflux of contrast material into the azygos vein beyond the valves [5].…”

Blood Brain Barrier Compromise with Endothelial Inflammation may Lead to Autoimmune Loss of Myelin during Multiple Sclerosis

“…Similar valves have been also found in the terminal segments of vertebral veins (Scapinelli, 2000) and in the azygous arch (Yeh et al, 2004;Ichikawa et al, 2008). These proximally situated valves may play a role in avoiding or limiting the venous refluxes.…”