Carotid Artery Stents
During the first attempts at CAS, the embolic stroke rate was higher than standard CEA. Attempts at reducing this risk were first trialed with distal protecting devices. Initially, a balloon was inflated downstream to the carotid lesion which would prevent emboli from traveling onward to the brain. However once the balloon was deflated there still posed a stroke risk.
In an effort to continue to improve results, a filter was used in place of a balloon. While the filters provided somewhat better protection, they can miss microembolization and also create microemboli upon deployment and removal. This realization soon gave way to the flow reversal system, which has proven to have a very high stroke protection. Overall, CAS has proven to be non inferior to CEA and is incredibly useful in poor surgical CEA candidates.
Carotid Artery Revascularization
Since the advent of CEA in 1953, minimally invasive efforts have been developed using carotid artery stents. Carotid artery stenting (CAS) was initially developed for patients who were at high risk for stroke and were poor surgical candidates. Early attempts at carotid angioplasty were seen in the late 1990’s, and as technology has improved, it is being trialed in increasing patients.
It usually involves access through a transfemoral approach and is performed with local anesthesia with or without sedation. Most carotid artery stents use either a cobalt-chromium or nickel titanium stent. However, a slightly increased risk in periprocedural stroke and mortality with CAS has led to other minimally invasive options, such as the transcarotid approaches for carotid artery revascularization.
Stroke is the fifth leading cause of death in the United States, with well over 100,000 deaths annually. Approximately 87% of strokes are caused by a lack of blood flow to the brain, these are termed ischemic strokes. The main causes of ischemic strokes are fatty deposits (plaques) lining the brain’s blood vessels restricting flow (cerebral thrombus) or fatty deposits that break off from arteries in another location and travel to the brain inhibiting blood flow (cerebral emboli).
The carotid artery is the main artery supplying blood to the brain. Plaque has a tendency to build up at the carotid artery bifurcation and can break off, causing a stroke. Approximately one third of strokes are due to cerebral emboli from carotid arteries. Thus, carotid artery narrowing (stenosis) is closely measured in those patients at risk for a stroke or who have had stroke like symptoms. Once the narrowing reaches 50% in patients with stroke symptoms or 70% in patients without symptoms, it is recommended to undergo surgery to clean the artery (carotid endarterectomy [CEA]).
The EnRoute Carotid Stenting system is a technology developed by Silk Road Medical which is used in the transcarotid approach to CAS. The Enroute system not only reverses the flow but allows the operator to control for the speed of blood flow. It harnesses the high pressure system of the artery and connects it with the low pressure system of the femoral vein in the leg—causing a reversal of blood flow in the arteries shunting blood to the vein.
The TransCarotid Artery Revascularization (TCAR) procedure is performed using the EnRoute transcarotid neuroprotection and stent system under sedation with a vascular surgeon. It involves making a small incision just above the collar bone to access the affected carotid artery. The EnRoute system is then inserted into the carotid artery and the other end is inserted into the common femoral vein. The flow reversal system is initiated, and the stent deployed into the carotid. After CAS, patients are usually observed overnight in the hospital.