12.1.8\ Carotid Body Stimulation

12.1.8.1\ Discussion

Electrical stimulation of the carotid sinus can be used to treat systemic hypertension that is unresponsive to medical therapy. The phenomenon is effectuated by initiating the baroreceptor reflex and decreasing sympathetic tone. Implanted carotid sinus stimulation systems comprise a pulse generator and bilateral perivascular carotid sinus leads (Fig. 12.34). Insertion of these devices does not appear to cause carotid artery injury or other major side effects.

12.1.9\ Adjustable Vascular Clamp

12.1.9.1\ Discussion

Adjustable vascular clamps were first introduced in the 1950s for treating carotid system aneurysms. Several varieties of metallic extracranial carotid vascular clamps have been developed, including the Selverstone, Crutchfield, Poppen-­ Blaylock, Salibi, and Kindt. The principle behind such vascular clamps is to reduce blood flow and to promote clotting of the aneurysm. If collateral circulation via the circle of Willis is inadequate, the clamps can be loosened. Gradual, graded occlusion of the carotids would yield better results than immediate occlusion. Over time, however, carotid revascularization can occur through the clamp and regular follow-up is recommended. On imaging, the clamps are recognized as rectangle-shaped metallic parts with central openings of variable sizes (Fig. 12.35). The lumen distal to the clamp becomes diffusely narrowed and usually remains as such even after the clamp is removed.

Fig. 12.35  Selverstone clamp. The patient has a history of right carotid body paraganglioma status post radiation and right common carotid artery aneurysm status post application of vascular clamp. Axial CT image (a) dem-

onstrates a right common carotid artery clamp (arrow). Doppler ultrasound (b) shows paucity of flow in the common­ carotid artery distal to the clamp

Fig. 12.36  Aberrant right subclavian artery reconstruction. Curved planar reformatted image shows a right axillary to right common carotid artery bypass (arrow) with retrograde opacification of the proximal axillary and distal right subclavian arteries. The proximal right subclavian artery has been sacrificed. There is also a left common carotid to subclavian artery bypass and an aortic endograft. There is artifactual duplication of the proximal left subclavian artery

12.1.10  Reconstruction of the Great

Vessels

12.1.10.1\ Discussion

Reconstruction of the great vessels may be performed for treatment of steno-occlusive lesions of congenital aberrations. The surgical maneuvers can be complicated and involve reimplantation of normal vessels onto others (Fig. 12.36) and/or the use of bypass grafts, such as collagen-­ impregnated Dacron and polytetrafluoroethylene (Figs. 12.37 and 12.38), each with different imaging appearing. Postoperative MRA, CTA, Doppler ultrasound, or catheter angiography can be used to evaluate suspected restenosis or occlusion (Fig. 12.39).

Fig. 12.37  Dacron graft. The patient has a history of symptomatic right common carotid and innominate artery occlusive disease. The patient is status post recent aorta to right common carotid/right subclavian artery bypass from the ascending aorta utilizing a 10 mm Hemashield graft. The innominate artery underwent endarterectomy and end-to-end anastomosis with the 10 mm Hemashield, which in turn was anastomosed to the ascending aorta,

also end to end. Catheter angiogram (a) shows a widely patent Hemashield graft (arrow) and distal vessels (arrowhead). CT angiography curved vessel trace (b) and 3D volume rendering (c) show patency of the aorta to right common carotid bypass components. The Hemashield graft (arrowheads) is a short bulbous segment connected to the stump of the innominate artery (arrows)

Fig. 12.39  Thrombosed graft. The patient is status post aortic repair and subclavian injury followed by placement of a right carotid to axillary bypass graft with 6 mm externally supported polytetrafluoroethylene. Axial CTA image (a) shows lack of enhancement within the artificial graft

(arrow), which is suggestive of thrombosis. There is also poor opacification of the distal right common carotid artery. Doppler ultrasound (b) of the distal graft anastomosis site reveals paucity of flow through the graft (GFT)