Carotid angioplasty and stenting
Carotid angioplasty and stenting is done when there is a critical narrowing of the common carotid or internal carotid artery with recurrent symptoms. The status of intervention for an asymptomatic critical stenosis is still investigational. When done in an experienced center, the results are comparable to carotid endarterectomy, with a much lesser discomfort associated with the procedure.
Use of distal protection devices is the standard of care in carotid angioplasty as it prevents the complications due to distal embolization. Sometimes when the plaque load is too much, there is still a chance of filter getting clogged and leading to slow flow. Repeat angiography including that of intracranial vessels is needed after the procedure to document good flow. If any distal, but accessible embolic occlusions are noted, it may be worthwhile trying to open them out as well, though the results may be suboptimal.
Carotid angioplasty procedures are usually done without sedation so that the operator can assess any potential neuro embolic manifestations quickly. The approach is usually through the femoral artery. Either a long sheath or a guide catheter is placed in the carotid ostium after conventional percutaneous femoral access is obtained. Careful monitoring of anticoagulation and meticulous attention to avoid air and thrombus in the system is needed. Once the initial check angiograms are obtained, a guide wire is introduced and the lesion crossed. The distal protection device is passed over the guide wire, across the lesion, ideally without predilatation. If the lesion is very tight, predilatation with a 1.5 or 2 mm coronary balloon may be needed. Once the filter with covering sheath is well beyond the lesion, usually as high in the extracranial portion of the internal carotid as possible, to prevent interference with stent delivery, the sheath of covering the filter is withdrawn, to open up the filter. The primary guide wire is removed prior to that. The sheath of the filter is then removed out of the system so that the pre dilation balloon can be introduced. Predilation is done cautiously, watching for bradycardia and hypotension which can occur due to stimulation of the carotid sinus. A temporary pacing wire is kept in the right ventricle with the pacer in stand by mode to pace in case of bradycardia.
After predilatation, the balloon is removed and the self expanding stent system is introduced over the filter guide wire. Once the position of the stent has been checked by angiograms, usually in lateral view, the proximal unlocking system is released and the sheath of the stent withdrawn. The expansion of the stent is checked on fluoroscopy. Most often there will be a residual narrowing which requires post dilatation. Post dilatation under high pressures is likely to bring on bradycardia and hypotension in most cases. In some cases it may required prolonged inotropic support. Once a good result is obtained, the balloon is removed and the filter sheath re-introduced. The sheath is pushed up to cover the filter and then the whole system is withdrawn. A diagnostic catheter is used to do a final check angiogram, including the intracranial circulation. Sometimes there may be proximal spasm of the carotid at the site of guide deployment, which may respond to local nitroglycerin.